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Journal of Electroceramics (v.23, #2-4)

Analytical estimation of high-frequency properties of RF micro-inductors prepared by direct-write techniques by Eui-Jung Yun; Jae-Wook Kim; Won-Gook Lee; Young-Jin Kim; Hyeong-Sik Park (pp. 103-109).
In this work, the high-frequency characteristics of micron size, square spiral-type RF thin film air-core inductors prepared by direct-write supersonic jet deposition of laser ablated nanoparticle were estimated by a software package. The important parameters that are determined by direct-write process, such as the materials, the cross-section shape, the thickness, and the conductivity of the coil, were varied systematically to estimate the trend of the inductors’ performances. The area dimensions of RF inductors utilized and the number of coil turns were 1.3 mm × 1.3 mm and 3, respectively. The 96 wt% Al2O3, SiO2-coated Al2O3, and SiO2-coated Si wafers were used as the substrate material. The high-frequency characteristics of the inductance (L) and quality factor (Q) of the utilized inductors were simulated using a Maxwell three-dimensional field simulator (HFSS 8.5), which employs the finite element method. The used inductors, which have silver metal (Ag) coils, the trapezoid shaped cross-section of the coil, the coil thickness of 30 μm, and the coil conductivity of 70% of Ag bulk value, exhibit L of 8 to 9 nH. They also exhibit a maximum Q of 35.5 near the frequency of 750 MHz and a self-resonant frequency of 5.14 GHz. The simulated high-frequency data of the inductors were agreed well with those obtained from the equivalent circuit model of the utilized inductors.

Keywords: RF micro-inductors; Square spiral-type; Direct-write process; High-frequency structure simulator

Novel hydrophobic coating process for gas diffusion layer in PEMFCs by Gug-Ho Yoon; Sung Bum Park; Eun Hyung Kim; Myung-Hoon Oh; Kyeong-Sik Cho; Soon Wook Jeong; Sungjin Kim; Yong-il Park (pp. 110-115).
The behavior of water and gas distribution in the gas diffusion layers (GDLs) of proton exchange membrane fuel cells (PEMFCs) were investigated analytically. In order to prevent the flooding phenomenon of the electrodes by the product water, gas diffusion layer is usually hydrophobed. Formerly, gas diffusion layer was partially coated with PTFE (polytetrafluroethylene) suspension but flaking-off of PTFE particles were observed. In this study, gas diffusion layer is coated with HTTS ((hepradecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane)-derived layers having hydrophobic functional group. The influence of the HTTS coating on gas permeability and hydrophobicity of gas diffusion layer are analyzed and discussed.

Keywords: Proton exchange membrane fuel cell; Gas diffusion layer; (Hepradecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane

Microwave dielectric properties of Mg4Nb2O9 ceramics produced by hydrothermal synthesis by Sung-woo Lim; Jaecheol Bang (pp. 116-120).
Mg4Nb2O9 ceramics have been prepared by a hydrothermal synthesis in order to reduce the sintering temperature. The sintering and microwave dielectric properties of the hydrothermally processed Mg4Nb2O9 were studied under various sintering temperatures ranging from 900 to 1300°C. The highest Q×f o value of 26,069 GHz was obtained at the sintering temperature of 1300°C and is attributed to the increased density and appropriate grain growth. τ f value of −17.1 ppm/°C was improved by the addition of TiO2 and τ f value of 6.7 ppm/°C was obtained at 20 wt% TiO2. Chemical compatibility of Mg4Nb2O9 with Ag was tested to identity the possibility of using Mg4Nb2O9 for an LTCC application. Since any secondary phase was not observed in the XRD pattern of the mixtures of Mg4Nb2O9 and Ag powder heat treated at 900°C, it was considered that the Mg4Nb2O9 system is applicable to the multilayer microwave devices using Ag as an electrode.

Keywords: Hydrothermal synthesis; Mg4Nb2O9 ; Microwave dielectric properties; Sintering; LTCC

Investigation of phase distribution in nanoscale BaTiO3 powders prepared by hydro-thermal synthesis by S.-M. Moon; N.-H. Cho (pp. 121-126).
Nanoscale BaTiO3 powders were prepared by hydro-thermal synthesis; a mixture of H2O and EtOH was used as solvent and the phase distribution of the powders was investigated in terms of the ratio (R) of DI water, H2O/(H2O+EtOH). The size of the powders was varied in the range of 20∼100 nm depending on the solvent condition. X-ray diffraction and Raman spectroscopy were applied to investigate the variation in the relative volume fraction of the tetragonal phase; most of the powders contain both tetragonal and cubic phases. The results obtained by the two different analysis methods appear to be very close to each other, and it was found that the maximum volume fraction of the tetragonal phase was 23∼26% when the synthesis was performed at R = 0.25∼0.5.

Keywords: Nano-BaTiO3 powder; Size control; Phase analysis

Crystallization behavior and microwave dielectric characteristics of ZnO-(La, Nd)2O3-B2O3-based dielectrics by Deuk Ho Yeon; Yeon Hwa Jo; Viswanathan S. Saji; Dong Heon Kang; Yong Soo Cho (pp. 127-132).
Crystallizable zinc borate glasses modified with different contents of La2O3 or Nd2O3 were investigated as a potential low loss dielectric with respect to their crystallization behavior and microwave dielectric characteristics. The glasses were admixed with Al2O3 filler and fired at 850°C for 30 min in air to prepare low temperature dielectrics. Crystallization behavior and microwave dielectric properties of the resulting samples strongly depended on the relative content of La2O3 or Nd2O3 in the glass. As a promising result, the composition of 0.15ZnO-0.25Nd2O3-0.6B2O3 exhibited k ∼ 6.5 and Q ∼ 1194 at the resonant frequency of 18.9 GHz. Near zero temperature coefficient of frequency (TCF) was obtained by additional modification of the composition with ∼10 wt.% of TiO2 filler. Crystallization kinetics of the samples was studied based on the differential thermal analysis (DTA) curves obtained with different heating rates. Correlation of the observed dielectric properties to the crystallization behavior is the main subject of this work.

Keywords: Dielectric; Glass; LTCC; Borate

Chemical development of preceramic polyvinylsilazane photoresist for ceramic patterning by Yi-He Li; Xiao-Dong Li; Dong-Pyo Kim (pp. 133-136).
In order to develop a preceramic photoresist for the fabrication of non-oxide SiCN ceramic microstructures by a mold-free photocuring shaping process, UV sensitive acrylate functional groups were successfully grafted onto the backbone of polyvinylsilazane by its reaction with ethyl-4-bromocrotonate via a high efficiency allyl bromide electrophilic substitution process. The as-modified polymer was characterized by 1H Nuclear Magnetic Resonance (1H-NMR) and 2D-1H-1H-NMR (COSY) spectroscopy, and its UV sensitivity was investigated by Differential PhotoCalorimetry (DPC) and Fourier Transform InfraRed (FT-IR) spectroscopy. The reaction mechanism was discussed in detail and the results showed that the as-modified polyvinylsilazane (m-PVSZ) is a promising preceramic photoresist.

Keywords: Preceramic polymer; Polyvinylsilazane; Modification; UV sensitivity

Application of HfO2 high-k gate insulator for excimer laser annealed poly-Si TFT by Woo-Hyun Lee; Soon-Young Oh; Chang-Geun Ahn; Won-Ju Cho (pp. 137-140).
The electrical characteristics of polycrystalline silicon (poly-Si) thin film transistor (TFT) crystallized by excimer laser annealing (ELA) method with high-k gate dielectrics were evaluated. Because a high thermal budget is inevitable for conventional fabricating process of poly-Si TFTs, an amorphous silicon film on a buried oxide was crystallized by annealing with a KrF excimer laser (248) to fabricate a poly-Si film at low temperature. Furthermore, the high permittivity HfO2 film with a thickness of 20 nm as the gate-insulator was deposited by atomic layer deposition (ALD) to low temperature process. In addition, the solid phase crystallization (SPC) was compared to the ELA method as a crystallization technique of amorphous-silicon film. As a result, the crystallinity and surface roughness of poly-Si crystallized by ELA method was superior to the SPC method. Also, we obtained excellent device characteristics from the poly-Si TFT fabricated by the ELA crystallization method.

Keywords: Poly-Si TFT; Excimer laser anneal; Solid phase crystallization; High-k; HfO2

Filler effect of low loss dielectricity in printed circuit board material by Jiae Lee; Hyosoon Shin; Jonghee Kim; Hogyu Yoon (pp. 141-145).
Dielectric properties of low-loss dielectric materials are investigated with variation of silica filler which is known to be general filler in PCB composite. With comparison of dielectric losses of various filler materials in use of BCB resin, it could be known that crystalline cristobalite was superior to other crystalline or amorphous silica-base materials and reduced dielectric losses in the composite with resin. And dielectric properties of composite with the variation of filler quantity showed that amorphous silica and quartz increased dielectric loss as their quantities increased, while cristobalite increased little. As quantity of crystalline cristobalite phase increases in cristobalite/quartz intermediates, dissipation factor decreases.

Keywords: Filler; Low loss dielectric; PCB

Fabrication of MgO-coated TiO2 nanotubes and application to dye-sensitized solar cells by Hun Park; Dae-Jin Yang; Ho-Gi Kim; Seong-Je Cho; Su-Chul Yang; Hyunjung Lee; Won-Youl Choi (pp. 146-149).
Dye-sensitized solar cells (DSCs) are more spotlighted than conventional photovoltaic devices due to their relatively low cost, easy fabrication and high efficiency. However, there are limitations to increase the conversion efficiency of DSCs. The limiting factors are the quantity of dye adsorption and charge recombination between TiO2 electrode and electrolyte. Coating other materials such as high energy band gap insulators or semiconductors on the TiO2 electrode enhances dye adsorption and reduces charge recombination. We fabricated DSCs based on bare TiO2 nanotube arrays and 0.02 and 0.04 M MgO coated TiO2 nanotube arrays. MgO layer increased the photovoltage and photocurrent. The overall conversion efficiency of DSCs using 0.02 M MgO coated TiO2 nanotubes was 1.61%. MgO formed insulating layers between TiO2 nanotube array electrode and electrolyte. Charge recombination was inhibited at the interfaces of TiO2 nanotube array electrode and electrolyte by MgO insulating layers. MgO coating also improved dye adsorption because iso-electric point (IEP) of MgO was larger than TiO2. When the IEP of coating material is larger than TiO2, the chemical attraction between the electrode surface and Ru-based dye molecule is increased.

Keywords: TiO2 ; Nanotube; Anodic oxidation; Dye-sensitized solar cells; MgO

Enhanced of electrical characteristics of nano-crystal floating gate memory with In2O3 nano-particles embedded in polyimide by Hyun-Mo Koo; Won-Ju Cho; Dong Uk Lee; Seon Pil Kim; Eun Kyu Kim (pp. 150-153).
We fabricated the nano-floating gate memory (NFGM) with In2O3 nano-particles embedded in polyimide gate insulators. Self-assembled In2O3 nano-particles were created by chemical reaction between the polymer precursor and the indium film. The particle size and density of In2O3 nano-particles were about 7 nm and 6 × 1011 cm−2, respectively. The electrical characterization of the NFGM with In2O3 nano-particles embedded in polyimide layer were measured and the memory window larger than 3.8 V was obtained from the fabricated NFGM devices due to the charging effects of In2O3 particles. Subthreshold swing, output current characteristics and retention time of fabricated NFGM devices were considerably improved by the post-annealing process in 3% hydrogen diluted H2/N2 ambient.

Keywords: Nano-floating gate memory; In2O3 metal nano-particles; Annealing effect; Post-annealing

Investigation of microwave dielectric properties in the BaO–Nb2O5–P2O5 system by In-Sun Cho; Jeong Seop Lee; Shin-Tae Bae; Jeong-Ryeol Kim; Kug Sun Hong (pp. 154-158).
BaNb2P2O11 and Ba3Nb2P4O18 compounds with corner-sharing NbO6 octahedra and PO4 tetrahedra were prepared by a conventional solid-state reaction method. The crystal structure and microstructure were investigated by X-ray powder diffraction and field emission scanning electron microscope, respectively. The microwave dielectric properties were measured using a network analyzer. Both ceramics were sintered at a relatively low temperature of 1150 °C and had a relative density of ∼96%. Compared to Ba3Nb2P4O18, BaNb2P2O11 had a higher permittivity of 31.7. However, the quality factor of BaNb2P2O11, was smaller than Ba3Nb2P4O18. Furthermore, the effect of the crystal structure on the microwave dielectric properties was investigated.

Keywords: BaO–Nb2O5–P2O5 ; Dielectric properties; BaNb2P2O11 ; Ba3Nb2P4O18 ; Bond strength

Fabrication of a patterned TiO2 nanotube arrays in anodic oxidation by Dae-Jin Yang; Hun Park; Ho-Gi Kim; Seong-Je Cho; Won-Youl Choi (pp. 159-163).
In general, the fabrication of self-ordered TiO2 nanotube arrays, under conventional constant-voltage anodization, results in only straight nanotube arrays. In the present work, we report on variation of nanotube morphology by modifying the anodization conditions. This approach offers substantial advantages over conventional anodization processes in terms of the fabrication of flexible dimensional architectures. We could see small variation of the nanotube diameter in the experiments using rocking voltage applied anodization in the ethylene glycol based electrolyte. Applying of abruptly increased voltage induced to separate into two nanotube segments having different diameters. We suggest that these new types of nanotube array architecture will be useful for new base materials for the development of nano-scale devices.

Keywords: Self-organization; Titanium oxide; Anodic oxidation; Nanoporous

Low-temperature sintering and dielectric properties of the Bi(Nb1−x Ta x )O4 system by Dae Min Kim; Shin Kim; Kwan Soo Kim; Sang Ok Yoon; Jong Guk Park (pp. 164-168).
Low-temperature sintering and dielectric properties of the Bi(Nb1−x Ta x )O4 (x = 0.1, 0.3, and 0.5) system was investigated as a function of the zinc borosilicate (ZBS) glass content with a view to applying this system to LTCC technology. The addition of 7 wt% ZBS glass ensured a successful sintering below 900°C. The complete solid solution of Bi(Nb, Ta)O4 with an orthorhombic structure was formed and the high temperature form of Bi(Nb, Ta)O4 with a triclinic structure was not observed. The second phase of Bi2SiO5 was observed for all compositions. The non-relative liquid phase sintering (NLPS) occurred and the one-stage sintering was conducted. The Q × f values were improved by the addition of Ta. Bi(Nb0.7Ta0.3)O4 with 7 wt% ZBS glass sintered at 900°C demonstrated 35.8 in the dielectric constant (ɛ r), 2,200 GHz in the quality factor (Q × f 0), and −48 ppm/°C in the temperature coefficient of resonant frequency (τ f).

Keywords: BiNbO4 ; Bi(Nb1−x Ta x )O4 ; LTCC; Zinc-borosilicate; Dielectrics

Effects of oxygen partial pressure on the preferential orientation and surface morphology of ITO films grown by RF magnetron sputtering by Jae-Hyung Kim; Joon-Hyung Lee; Young-Woo Heo; Jeong-Joo Kim; Ju-O Park (pp. 169-174).
In this study, effects of oxygen pressure in the sputtering ambient on the preferential orientation and resultant surface morphology of ITO films grown by RF magnetron sputtering were investigated. ITO film grown with pure Ar gas shows a preferential (400) plane orientation parallel to the substrate surface and a sawteeth-shaped rough surface. ITO film grown in the sputtering ambient of Ar and oxygen mixtures shows a preferential (222) plane orientation and a flat and smooth surface. The differences in the growth rate, surface morphology, and roughness between the preferentially orientated films were discussed in terms of the surface energy of planes. The electrical and optical properties of the films were examined.

Keywords: ITO; RF magnetron sputtering; Surface morphology; Oxygen partial pressure

Charge storage at the Pt/YSZ interface by György Fóti; Arnaud Jaccoud; Cyril Falgairette; Christos Comninellis (pp. 175-179).
The electrochemical behavior of Pt/YSZ electrodes in oxygen containing atmosphere at 450 °C has been investigated by double-step chronoamperometry and programmed linear sweep cyclic voltammetry. The response of the O2(g),Pt/YSZ system in these experiments could be separated into a time dependent and a steady state contribution, the former being dominated by pseudocapacitive processes. It is proposed that Pt–O type species were stored via different processes at three different locations in the O2(g),Pt/YSZ system: (1) Build-up of a platinum oxide monolayer at the Pt/YSZ binary interface. (2) Formation of Pt-O species at the triple phase boundary and their spreading-out along the Pt/gas interface. (3) Growth of the platinum oxide layer from the binary Pt/YSZ interface toward the bulk of the platinum electrode.

Keywords: Platinum electrode; YSZ; Charge storage; Pseudocapacitance

Influence of ion beam bombardment on characteristic of InGaN/GaN single quantum well grown by metal–organic chemical vapor deposition by Seung-Kyu Choi; Jae-Min Jang; Sung-Hak Yi; Jung-A Kim; Woo-Gwang Jung (pp. 180-184).
The influence of ion beam bombardment on sapphire substrate was investigated on the electrical and optical characteristics of Indium–Gallium–Nitride/Gallium–Nitride (InGaN/GaN) single quantum well (SQW) structure. Ion bombardment of N+, He+, H+ ions were made on single crystal substrate of sapphire with dose of 1 × 1014–17 ions/cm2. The InGaN/GaN SQW was fabricated on the ion beam bombarded sapphire substrate in two-flow Metal Organic Chemical Vapor Deposition (MOCVD) equipment. The thickness of InGaN/GaN SQW was about 20 nm and the composition of InGaN/GaN SQW was found to be In0.1Ga0.9N. In PL spectra, it is found that InGaN/GaN SQW was emitted from 441.1 to 446.6 nm (2.8–2.7 eV). The highest mobility value of 118 cm2/V–S and the lowest carrier concentration of 3.41 × 1017/cm2 was found for N of 1016 ions/cm2 ion beam bombarded sample. The optimal condition for InGaN/GaN SQW on sapphire substrate of ion beam bombardment was deduced to be N+ ion dose of 1016 ions/cm2.

Keywords: GaN; InGaN; Ion beam bombardment; Single quantum well; N+ ; He+ ; H+

Effects of various oxide fillers on physical and dielectric properties of calcium aluminoborosilicate-based dielectrics by Ik Jin Choi; Yong Soo Cho (pp. 185-190).
Physical and dielectric properties of LTCC (low temperature co-fired ceramics) materials based on a typical calcium aluminoborosilicate glass and various fillers such as Al2O3, BaTiO3, CaTiO3, TiO2, ZrO2, MgO and SiO2 were investigated. Densification, crystallization and thermal and dielectric properties were found to strongly depend on the type of filler. The XRD patterns of Al2O3, BaTiO3, CaTiO3 and MgO samples demonstrated crystalline phases, CaAl2Si2O8, BaAl2Si2O8, CaTiSiO5 and CaMgSi2O6, respectively, as a result of firing at 850 °C. For the sample containing CaTiO3 filler, specifically, dielectric constant increased drastically to approximately 19.9. A high quality factor of >210 and a high TCE (temperature coefficient of expansion) of >8.5 ppm/°C were obtained for the composition containing MgO or SiO2. Near zero TCF (temperature coefficient of frequency) was obtained for the samples containing TiO2. The purpose of this work is to investigate the effects of various ceramic fillers on physical and dielectric properties and ultimately to provide the technical guidelines for the proper choice of filler in various LTCC systems.

Keywords: LTCC; Dielectrics; Dielectric constant; Glass; Filler

Control of magnetic anisotropy in Fe–Co–B soft magnetic underlayer for perpendicular magnetic recording media by Kyung-Hwan Kim; Sok-Hyun Kong; Shigeki Nakagawa (pp. 191-195).
Anisotropic residual stress induced in the Fe–Co–B/Ni–Fe layers causes high anisotropy field H k in the films induced by magnetoelastic effect. The origin of residual stress in Fe–Co–B/Ni–Fe layers was investigated. The direction of magnetic anisotropy of Fe–Co–B/Ni–Fe layers was formed in the direction corresponding to the incident direction of sputtered particles reached substrate. The magnitude of the H k depended strongly on the condition of argon gas pressure. An incident direction of sputtered particles, which has an important effect on the direction of H k, seemed to be dispersed under high Ar gas pressure condition because of the increase of collision number between sputtered particles and Ar particles. However, a low gas pressure condition of 1 mTorr in which sputtered particles have a long mean free path led to restrain the dispersion of H k direction. As a soft magnetic underlayer of high H k, the noise level of the media with Fe–Co–B/Ni–Fe decreased about 4 dB compared to that with the layer of low H k in low frequency.

Keywords: Fe–Co–B/Ni–Fe layer; High H k ; Incident direction of sputtered particles; Low gas pressure; Residual stress

CO gas sensing properties in Pd-added ZnO sensors by Won-Taek Moon; Youn-Ki Jun; Hyun-Su Kim; Won-Sik Kim; Seong-Hyeon Hong (pp. 196-199).
Unadded and 0.5 mol% Pd-added ZnO bulk and thin films were prepared by sintering and sputtering, respectively, and their CO gas sensing properties were investigated. The effects of Pd addition, sensing temperature (100–500 °C), and humidity on the CO gas response were discussed. In the bulk sensors, Pd-addition lowered the temperature for the maximum CO gas response (sensitivity) from 400 to 300 °C, whereas the thin film sensors (unadded and Pd-added) exhibited maximum gas response at 200 °C. The Pd-addition enhanced the CO gas response in thin film sensors, and it was also effective for reducing the interference from humidity in both bulk and thin film sensors.

Keywords: CO gas sensor; ZnO; Pd-addition; Bulk; Thin film

Phase evolution and Sn-substitution in LiMn2O4 thin films prepared by pulsed laser deposition by Dong Wook Shin; Ji-Won Choi; Yong Soo Cho; Seok-Jin Yoon (pp. 200-205).
LiMn2O4 thin films prepared on a Pt/Ti/SiO2/Si(100) substrate by pulsed laser deposition were studied with focusing on the effects of different processing conditions and Sn substitution on phase evolvement and surface microstructure. Major experimental parameters include substrate temperature up to 770 °C and working oxygen pressure of 50–250 mTorr. LiMn2O4 thin films became highly crystallized with increased grain sizes as the substrate temperature increased. Second phases such as LiMnO2 and Li2Mn2O4 were found at the temperature of 300 and 770 °C, respectively. As an optimum condition, films grown at 450 °C showed a homogeneous spinel phase with well-defined crystallinity and smooth surface. A high pressure of oxygen tended to promote crystallization and grain growth. Working pressure did not affect significantly the phase formation of the thin films except that unexpected LiMn3O4 phase formed at the lowest oxygen pressure of 50 mTorr. Tin-substituted thin films showed lower Mn–O stretching vibrations, which suggests that more Li-ions can be inserted into vacant octahedral sites of the spinel structure.

Keywords: LiMn2O4 thin films; Spinel; Pulsed laser deposition; Sn substitution

Dependence of hole mobility on channel surface of ultrathin-body silicon-on-insulator pMOSFETs by Kwan-Su Kim; Sang-Mo Koo; Won-Ju Cho (pp. 206-208).
We investigated the characteristics of ultrathin-body (UTB) silicon-on-insulator (SOI) p-type metal–oxide–semiconductor field-effect transistors pMOSFETs with channel thickness less than 10 nm regime. At the same time, the dependence of electrical characteristics on the silicon surface orientations with (100) or (110) were also investigated. As a result, it is found that the electrical characteristics of (100)-surface UTB-SOI pMOSFETs were superior to those of (110)-surface. Moreover, the SOI thickness from 3 to 5 nm, the increase of effective hole mobility at the effective field of 0.3 MV/cm was observed for both (100) and (110) surfaces. The mobility enhancement ratio of (110) surface was larger than that of (100) surface.

Keywords: Ultrathin-body; SOI; Hole mobility enhancement; Subband modulation

Thermal and dielectric properties of glass-ceramics sintered based on diopside and anorthite composition by Jinho Kim; Seongjin Hwang; Wookyung Sung; Hyungsun Kim (pp. 209-213).
To develop a low dielectric constant of LTCC substrate, we studied the effect of the sintering and crystallization behavior on the dielectric properties of a sintered body by mixing a CaO–Al2O3–SiO2 frit and a CaO–MgO–SiO2 frit for a low dielectric constant of LTCC substrates. In this work, the two glass frits were mixed at different proportions and sintered at 860~920°C. After sintering at 900oC for 1h, the glass frits crystallized into diopside and anorthite. The sintered bodies exhibited dielectric properties, ɛ r = 6~8.6 at 1 GHz, which is an essential condition for a substrate in microwave devices. The results suggest that the glass-ceramic can be applied to low dielectric LTCC materials in the electronics packaging industry.

Keywords: LTCC; Dielectric properties; Glass-ceramic; Crystallization

LiCoO2 thin film cathodes grown by sol–gel method by Vaishali Patil; Arun Patil; Ji-Won Choi; Yoon-Pyo Lee; Young Soo Yoon; Hyun-Jai Kim; Seok-Jin Yoon (pp. 214-218).
Lithiated layered transitional metal oxide materials of the LiMO2 type and especially LiCoO2 presents interesting specific properties as high energy density, long cycle life and constant discharging properties in a wide range of working conditions as well as a good safety. These properties made these materials excellent candidates as active compounds for high capacity cathode materials for rechargeable lithium batteries. LiCoO2 is the most common lithium storage material for lithium rechargeable batteries, used widely to power portable electronic devices. Operation of lithium rechargeable batteries is dependent on reversible lithium insertion and extraction processes into and from the host materials of lithium storage. In this study, LiCoO2 thin films were prepared by the sol–gel spin coating technique using metal acetate and citric acid as starting materials. Citric acid acts as a chelating agent, which promotes the preliminary reaction between lithium and cobalt and suppresses the precipitation of acetates. The sol–gel method is well known as one of promising thin-film preparation methods, which has good advantages such as low fabrication cost, relatively easy stoichiometry control, high deposition rate and also known as a low-temperature synthesis method for various ceramics. In addition, the crystal phases involved in the thin film can also be controlled by changing the chemical compositions of the sol. The crystallinity, microstructure and electrochemical properties of final films are also studied by XRD, SEM, AFM and galvanostatic charge/discharge cycling test. Films heat-treated under appropriate conditions exhibit high capacity and good crystallinity so those films are considered to be candidates as cathodes for thin-film micro batteries.

Keywords: LiCoO2 thin films; Sol–gel; Characterization

Electrochemical characteristics of LiFePO4/LiCoO2 mixed electrode for Li secondary battery by Hyun-Soo Kim; Mingzhe Kong; Ketack Kim; Ick-Jun Kim; Hal-Bon Gu (pp. 219-224).
LiFePO4 cathode active material was synthesized using a solid state method and a mixed cathode was prepared by adding LiCoO2. A coin cell was prepared using the mixed cathode and its electrochemical performances were evaluated. The LiFePO4 material improved both in thermal stability and rate capability. The discharge capacity of the 5 wt.% LiCoO2-added LiFePO4 material was 139.4 mAh/g at 0.2 C rate, and it showed a capacity retention of 64.2% even at 5 C rate in comparison to 0.2 C rate. The cycle performance of the bare LiFePO4 material was excellent, but the capacity fading of 20 wt.% LiCoO2-added LiFePO4 material became significant during charge/discharge cycle. However, 5∼10 wt.% LiCoO2-added LiFePO4 material showed good thermal stability, high rate capability and good cycle performances.

Keywords: LiFePO4/LiCoO2 ; Cathode material; Rate-capability; Capacity retention; Thermal stability

Silicon radical effect coated on alumina powder layer in junction between different materials for LTCC by Ui-Kyeong Jang; Hyo-Soon Shin; Dong-Hun Yeo; Jong-Hee Kim (pp. 225-229).
Several studies are reported on the possibility of reliable bonding alumina and barium titanate with derivation from the glass infiltration method for zero-shrinkage substrates, but infiltration into alumina was not satisfactory, compared with the case of barium titanate. In this study, silicon radical, which is main component of glass, is coated on alumina powder in order to improve glass infiltration effect in bonding alumina and barium titanate with use of common glass in low temperature cofired ceramic composite. As a result, it is verified that infiltration effect on large-sized alumina powder layer was improved to the level of barium titanate which is fully glass infiltrated and bonding barium titanate and alumina was possible.

Keywords: LTCC; Glass infiltration; Bonding

Structural and electrochemical properties of Nichrome anode thin films for lithium battery by Arun Patil; Vaishali Patil; Ji-Won Choi; Hyun-Jai Kim; Bong-Hee Cho; Seok-Jin Yoon (pp. 230-235).
Low cost anode materials having a high electrochemical efficiency have been critical in the success of thin film batteries that are applicable in ubiquitous environments as a portable energy source. Nichrome thin films are ideally suited for use in hybrid assemblies but their applications include precision integrated circuits in fields of telecommunications, instrumentation, power supplies, military and medical equipment where low noise and good power dissipation are required. With such a wide spectrum of applications, it is important to understand the electric behavior of the Nichrome alloy thin films by their microstructure. In this work, nanocrystalline films of nickel chromium alloys were deposited on alumina substrate by radio frequency (RF) magnetron sputtering technology. High purity nickel and chromium sputtering target were used for the deposition. First, aluminum was deposited on ceramic substrate acts as a current collector and over that NiCr was deposited by RF sputtering method. Both the layers were analyzed for structural and electrical properties using X-ray diffraction (XRD), energy dispersive X-ray analysis (EDS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry. The XRD peak confirms that deposited NiCr and Aluminum have tetragonal and cubic structures, respectively. The crystallite size was determined by full width at half maximum of XRD peaks. Structure, composition and the properties of the film are the major focus of this paper. Composition ratio between nickel and chrome obtained by EDS is 1:1. Particle size and microstructure of the film have been studied by SEM and AFM. Electrochemical properties of the films were analyzed. Reaction mechanism for the insertion and excretion is reported. After Lithium insertion and extraction the effect on the surface and structure of the thin film has been studied. The composition of equilibrium phases of NiCr as useful as attracting anode for the thin film battery. Nichrome on aluminum thin films as an anode has been attracted because it provides practical advantages including low cost production and competitive electrical performance.

Keywords: Ni-Cr alloy; Thin film; Anode; Secondary lithium batteries

Size control of Pb-based glass powders between 38 and 84 nm in the flame spray pyrolysis by Jung Sang Cho; Dae Soo Jung; Seung Kwon Hong; Yun Chan Kang (pp. 236-241).
Nano-sized Pb-based glass powders with different mean size, ranging from 38 to 84 nm were prepared by flame spray pyrolysis. The mean sizes of the glass powders were controlled by changing the concentration of spray solution. The glass powders prepared by flame spray pyrolysis from the spray solutions with different concentration had broad peaks at around 28° in the XRD patterns. The dielectric layers formed from the glass powders with the mean size of 38 nm had dense inner structures at firing temperatures of 480 and 520°C. On the other hand, the dielectric layer formed from the glass powders with the mean size of 84 nm had some voids inside the layer. The transmittances of the dielectric layer formed from the glass powders with the mean sizes of 38 and 84 nm were each 91% and 74% at firing temperature of 480°C.

Keywords: Glass powder; Spray pyrolysis; Nano powder; Dielectric material

A newly designed chopper for pyroelectric infrared sensor by using a dome-shaped piezoelectric linear motor (DSPLM) by Yoon Man-Soon; Heo Sung-Moo; Ur Soon-Chul (pp. 242-247).
In an attempt to develop a compact and simple structured chopper for a PIR (Pyroelectric Infrared Ray) sensor, a smart ultrasonic linear motor was introduced for a new solid state chopper. The actuating component contains a dome-shaped monolithic piezoelectric ceramic fabricated using PIM. Dome-shaped piezoelectric actuator (DSPA) parts having two different diameters, 5 mm and 8 mm, each with the same curvature radius of 10 mm, were fabricated using powder injection molding (PIM). Dynamic characteristics of the linear motors were evaluated. As a result, it was found that the maximum tip displacements in the Φ 8 and Φ 5 samples were 700 and 300 nm, respectively. To measure the output characteristics as a function of chopping period, the changes of output signals at various chopping periods (1 to 3 s) were observed by applying stationary infrared rays. The observed pulse signal voltages were a value of 1.7 to 2.2 V. As the intermitting period increased, output signals decreased as much as 0.5 V. When the DSPLM chopper is operated at room temperature after removing the IR source, the average noise output voltage was 0.3V, resulting in a one-sixth lower value compared with the output voltage when the infrared rays were incident. These results indicated that the signal-to-noise ratio has available values within 5.4 to 7.2. Moreover, it was shown that the power consumption was less than 1 watt when the DSPLM was in operation. Therefore, a module of the continuously detectable PIR sensor that was compact in size with reduced power consumption and high reliability was successfully realized using the DSPLM chopper.

Keywords: Dome-shaped; Piezoelectric; Pyroelectric; Infrared; Sensor

Carbon film covering originated from fullerene C60 on the surface of lithium metal anode for lithium secondary batteries by Arenst Andreas Arie; Oleg M. Vovk; Jin O. Song; Byung Won Cho; Joong Kee Lee (pp. 248-253).
Carbon films from fullerene C60 were coated on the surface of lithium metal for the anode of lithium secondary battery. In order to investigate the relationship between the electrochemical characteristics of the carbon films and deposition technique, three different vacuum techniques were employed such as RF (radio frequency)—magnetron sputtering of C60, plasma assisted thermal evaporation of C60 and ion beam assisted thermal evaporation of fullerene C60. From the physical and chemical characterization tests, we found that the carbon films produced by those above techniques mainly consist of sp2/sp3 hybridized amorphous carbons. Electrochemical tests implied that the cyclic performance was enhanced by the fullerene C60 coating on lithium metal anode in comparison to the pure lithium metal one. This enhanced performance is due to the formation of thin carbon film on the surface of lithium metal anode which plays a role as a passive layer against the side reaction between lithium metal and the electrolyte.

Keywords: Fullerene C60 ; Vacuum deposition techniques; Carbon films; Anode

Improving the rate performance of LiCoO2 by Zr doping by Seon Hye Kim; Chang-Sam Kim (pp. 254-257).
Zr-doped LiCoO2 cathode materials for lithium ion batteries were synthesized by an ultrasonic spray pyrolysis method. The synthesized powders with less than 1 mol% Zr had a single phase layered structure while those with 5 mol% Zr had a little secondary phase, Li2ZrO3. The cycle stabilities of Zr-doped and undoped LiCoO2 were compared at various charge–discharge rates. The Zr-doped LiCoO2 showed much improved cycle stability compared to the undoped, especially at a high C-rate of 3C (4.2 mA/cm2). To investigate the reasons of the improvement, changes of the lattice parameters and the interatomic distances of Co–Co and Co–O of the doped and the undoped powders were analyzed using XRD and EXAFS. The lattice parameters, a and c, increased in the powders with less than 1 mol% Zr, but decreased in the powder with 5 mol% Zr. On the other hand, the interatomic distances of Co–Co and Co–O did not change with Zr doping. From these results, the improved cycle stability is thought to be due to the expanded inter-slab distance, which enhances Li-ion mobility during charge/discharge processes.

Keywords: Lithium ion battery; Zirconium-doping; Rate performance; Slab distance; EXAFS

A study on the characteristics of hydrated La2O3 thin films with different oxidation gases on the various annealing temperature by Hyo June Kim; Jin Hyung Jun; Doo Jin Choi (pp. 258-261).
In order to investigate the structural and electrical properties of La2O3 films deposited by O2 and O3, films were hydrated in DI-water and annealed at 600 and 900 °C. La2O3 films deposited by O3 showed better hydration resistance than those deposited by O2. The thickness of both hydrated films decreased after annealing at 600 °C and increased after annealing at 900 °C. The dielectric constants of the La2O3 films deposited by O3 were greater than films deposited by O2 after annealing at 600 °C and slightly less after annealing at 900 °C. The leakage current density of the La2O3 films deposited by O3 was lower than those by O2 after annealing at 900 °C. To this end, La2O3 films deposited by O3 showed better dissolution resistance than O2 for hydration experiment as a function of dipping time.

Keywords: High-k material; La2O3 ; dielectric properties; Hydration; Gate oxide

Operating frequency tracking of single phase driving type piezoelectric motors by Burhanettin Koc (pp. 262-271).
We developed a multi (or mixed) mode excitation type piezoelectric motor that uses a rectangular bar type piezoelectric multilayer stator as the vibrating element. The stator has a first longitudinal vibration mode in a direction of longest length and second flexural mode in a direction of thickness. During operation of the motor, these two modes are coupled so at the two end surfaces, elliptical motions are generated. The elliptical motion at one end of the stator is transferred to a moving element through frictional contact. This paper introduces structure and operating principal of the piezoelectric multilayer stator. An equivalent circuitry model for the free stator and a frequency tracking method to operate the motor at its optimum operating frequency are also proposed. The frequency tracking method not only finds the best operating frequency, it also tracks the frequency variations from sample to sample and operating frequency shift due to temperature change.

Keywords: Piezoelectric; Multilayer; Multi-mode; Motor; Equivalent circuitry; Frequency tracking

Dielectric properties of zinc titanate thin films prepared by Rf magnetron sputtering by Jin Suk Jung; Young Ho Kim; Sang Keun Gil; Dong Heon Kang (pp. 272-276).
Zinc titanate thin films of ~500 nm in thickness were synthesized by an RF magnetron sputtering using a sintered ceramic target. After annealing in temperature ranges of 300–800 °C, their phase transition and dielectric properties were investigated as a function of annealing temperature. Crystalline ZnTiO3 phase was first detected at the annealing temperature of 500 °C within XRD detection limit though the sputtered film was mainly amorphous. ZnTiO3 still remained as a main phase although the slight decomposition of ZnTiO3 into Zn2TiO4 and TiO2 occurred in association with the increase of annealing temperature. Dielectric properties were apparently improved with increase of annealing temperature and showed maximum value at 650 °C. Further higher temperature annealing caused inferior dielectric property. These results were explained in terms of the presence of TiO2 (rutile) phase, resulting from the decomposition of ZnTiO3 phase, and the morphology of the thin film.

Keywords: Zinc titanate; Thin film; RF sputtering; XRD; Dielectric property

Physical and dielectric properties of BaTiO3–fluoride–glass systems for nitrogen-fireable embedded capacitors by Byeong Kon Kim; Dong Joo Shin; Ik Jin Choi; Jong Won Lee; Jun Chul Kim; Nam Kee Kang; Jun Kwang Song; Yong Soo Cho (pp. 277-283).
BaTiO3-based dielectrics containing the selective additive combinations from Pb-free glasses and fluoride compounds such as AlF3, BaF2, CaF2, LiF and ZnF2 were studied mainly for a potential N2-fireable embedded capacitor in printed circuit board with Cu metallization. The physical and dielectric properties, such as dielectric constant (k), loss tangent (tanδ) and T c, strongly depended on the choice of additive combination. A bismuth borosilicate glass was most promising in terms of the degree of densification and dielectric constant. The samples containing LiF and ZnF2 and sintered at 950 °C looked most beneficial in that these additives produced high k of >1,200 and low tanδ of < 0.022 at room temperature regardless of sintering atmosphere. As an example, the 95BaTiO3–2LiF–3(Bi borosilicate) sample exhibited k ~ 1,340 and tanδ ~ 0.022 at room temperature when fired at 950 °C in N2.

Keywords: Embedded capacitor; BaTiO3 ; Fluoride; Dielectrics; High k ; PCB

Fabrication and characterization of Au/SBT/LZO/Si MFIS structure by Jong-Hyun Im; Ho-Seung Jeon; Joo-Nam Kim; Jeong-Hwan Kim; Gwang-Geun Lee; Byung-Eun Park; Chul-Ju Kim (pp. 284-288).
Ferroelectric SrBi2Ta2O9 (SBT) films on a p-type Si (100) wafer with a LaZrO x (LZO) buffer layer have been fabricated to form a metal-ferroelectric-insulator–semiconductor (MFIS) structure. The LZO thin film and SBT films were deposited by using a sol–gel method. The equivalent oxide thickness (EOT) value of the LZO thin film was about 8.83 nm. Also, the leakage current density of the LZO thin film is about 3.3 × 10−5 A/cm2 at bias sweeping voltage of ±5 V. SBT films were crystallized in polycrystalline phase with highly preferred (115) orientation. Also, the intensity of each pick slightly increased as thickness of SBT films increased. The CV characteristics of Au/SBT/LZO/Si structure showed clockwise hysteresis loop. The memory window width increased as the thickness of SBT films increased. The leakage current density of Au/SBT/LZO/Si structure decreased as thickness of SBT films increased.

Keywords: SrBi2Ta2O9 ; LaZrO x ; MFIS; Sol–gel

Thermal stability and performance studies of LiCo1/3Ni1/3Mn1/3O2 with phosphazene additives for Li-ion batteries by Seyoung Ahn; Hyun-Soo Kim; Sunhye Yang; Jung Yun Do; Byung Hwa Kim; Ketack Kim (pp. 289-294).
Phosphazene derivatives as flame retardant (FR) additives were investigated to evaluate their thermal stability and performance in Li-ion batteries. Hexamethoxy-cyclo-tri-phosphazene (HMTP) and hexaethoxy-cyclo-tri-phosphazene (HETP) were added to the electrolytes of the test cells. Thermal stability and the performance influenced by the additives were evaluated using cathodes prepared with LiCo1/3Ni1/3Mn1/3O2. Concentration dependence on FR properties, rate capabilities, and cycle life was analyzed. The additives formed a surface layer on the cathode. The layer on the cathode reduced electrochemical reaction resistance, which improved the performance of the cells. Optimization studies show that HETP has better FR properties than does HMTP.

Keywords: Li-ion batteries; LiCo1/3Ni1/3Mn1/3O2 ; Flame retardant additives; Electrolytes; Thermal stability; Phosphazenes

Piezoelectric microspeakers with high compressive ZnO film and floating electrode by SeungHwan Yi; ManSoon Yoon; SoonChul Ur (pp. 295-300).
This paper describes micromachined piezoelectric microspeakers that can produce an audible signal supplied from an MP3 player through the use of 5Vpeak-to-peak signal amplification circuit modules. The Sound Pressure Level (SPL) of the fabricated microspeakers is higher than that of previous results even though the input voltage is reduced. The success of this technology is based upon two distinct features; one is the use of a high quality compressive ZnO thin film, the other is the implementation of a floating electrode beneath the piezoelectric ZnO film in order to induce more strain in the diaphragm of the microspeaker when two top electrodes are biased with different polarities. A high quality piezoelectric ZnO film is achieved using an Ar/O2 gas ratio of 4:1, an R.F. power of 1,500W, a substrate temperature of 150°C, and a chamber pressure of 23mTorr. In this condition, the deposited ZnO film shows a compressive residual stress of −1.3GPa. The fabricated piezoelectric microspeakers were tested over a frequency range of 400Hz to 12kHz with a 5Vpeak-to-peak input signal, the maximum SPL of the fabricated microspeakers was shown to be more than 97.2dB at 7.1kHz with a distance of 3mm between the fabricated microspeakers and the reference microphone (B&K type 2,669 and 4,192L).

Keywords: Micromachined piezoelectric microspeaker; Sound pressure level (SPL); Piezoelectric ZnO film; Composite residual stress; Floating electrode

Multilayer piezoelectric energy scavenger for large current generation by Hyun-Cheol Song; Hyung-Chan Kim; Chong-Yun Kang; Hyun-Jai Kim; Seok-Jin Yoon; Dae-Yong Jeong (pp. 301-304).
Piezoelectric energy harvesting system is promising to the energy source of wireless sensor nodes for ubiquitous sensor networks. The piezoelectric material has been usually considered as a high voltage and low current source. When charging current into the thin film battery or supercapacitor, a larger current is needed to shorten the charging time. In order to increase the current in the piezoelectric energy harvesting, multilayer ceramics were fabricated. N-layer multilayer ceramics decreased the voltage but increased the current N times. The impedance of the multilayer ceramics are matched to 1 kΩ which is similar to the impedance of general electrical devices. The multilayer piezoelectric generator could be directly employed for electrical device without the additional electrical circuit to improve efficiency.

Keywords: Piezoelectric; Energy harvesting; Multilayer; Current; Impedance matching

FeWO4Cl as cathode material for lithium rechargeable battery by Sookhyeon Im; Jinhee Park; Heesung Oh; Jinho Choy; Claude Delmas; Kyooseung Han (pp. 305-311).
Lithium has been electrochemically and chemically intercalated into layered FeWO4Cl. The discharge curve between FeWO4Cl and Li2FeWO4Cl is constituted by three potential plateaux and two domains where the cell voltage decreases rapidly upon the intercalation of lithium ions. A wide bi-phase domain is obtained for x in Li x FeWO4Cl ranging between 0.0 and 0.85. The limit of a solid solution extends in the vicinity of the LiFeWO4Cl composition. The theoretical and practical discharge capacities for Li1 − xFeWO4Cl are 79.03 mAh/g and 78.45 mAh/g respectively. The structures of FeWO4Cl and LiFeWO4Cl were determined: from single crystal analysis and by Rietveld refinement of the powder X-ray diffraction pattern respectively. The modifications of the Fe–O bond lengths emphasize the iron reduction during the discharge process. Moreover, the strong change of Fe–Cl distance suggests a reversible framework modification.

Keywords: FeWO4Cl; Lithium rechargeable battery; Cathode; Intercalation

Structures and luminescence properties of Eu2+- doped α-sialon phosphors for UV-LED by Bo Yun Jang; Joo Seok Park; Joon Soo Kim; Seong Ok Han; Hong Soo Kim; Young Soo Ahn; Soon Jae Yoo (pp. 312-316).
Eu2+-doped α-sialon phosphor was synthesized and structures and various luminescence properties were studied. High crystalline Ca0.8Al2.8Si9.2O1.169N14.94 phase was successively obtained for undoped and Eu2+-doped samples. Eu2+-doped α-sialon phosphor exhibited wide absorption in ultra violet (UV) and visible range, and high broad emission band peaking at from 570 to 582 nm. The optimum compositions and process conditions was obtained from 0.75 mol% Eu2+–doped Ca0.8Al2.8Si9.2O1.169N14.94 fired at 1650 °C for 2 h in 30% H2–70% N2 atm. In addition, fabrication of UV-light emitting diode (LED) lamp using this phosphor was conducted and the optical properties were measured. Relative quantum efficiency of the phosphor and luminous efficiency of the lamp were 83.66% and 35.28 lm/W, respectively. Those results indicated that Eu2+-doped α-sialon phosphor in this study was a good candidate for UV-LED light source.

Keywords: Eu2+ ; α-Sialon; Phosphor; UV-LED; Structures; Luminescence properties; Process conditions

Motional characteristics of thin piezoelectric rotary motor using cross shaped stator by Taegone Park; Hyonho Chong; Seongsu Jeong; Kenji Uchino (pp. 317-321).
New type of cross shaped ultrasonic rotary motor was designed and fabricated using a thin brass plate. Cross shaped stator was comprised by attaching ceramic plates on both sides of thin brass plate. When two harmonic voltages which have 90o phase difference were applied to ceramics, the symmetric and anti-symmetric displacements were generated at inside tips to make the elliptical motion. The finite element analysis (ATILA) was used for simulating the motional pattern of contact tips of the stator. Elliptical motions of the contact tips of the stator were consistently obtained at off resonance frequencies. From a prototype motor, speed of 500 rpm was obtained at 16 (V rms).

Keywords: Thin ultrasonic rotary motor; Cross shaped stator; Four contact tips; Elliptical motion; FEM

Characteristics on electrical resistance change of Ag doped chalcogenide thin film application for programmable metallization cell by Hyuk Choi; Ki-Hyun Nam; Yong-Woon Koo; Hong-Bay Chung (pp. 322-325).
Programmable Metallization Cell (PMC) Random Access Memory is based on the electrochemical growth and removal of nanoscale metallic pathways in thin films of solid electrolyte. This paper investigates the resistance change characteristics with applied voltage bias on Ag/Ge–Se and Ag/As–Se chlacogenide thin film structure and describes the electrical characteristics of PMC-RAM made from these materials following annealing at 150 °C. As a result, it was obtained that R reverse/R forward ratio which represent by reversible resistance change was about 106, which ratio value can be get a high sensing margin when PMC-RAM detect the data. PMC-RAM technology promises to be non-volatile, low current and potentially, low cost for the next generation of nonvolatile memory application such as RFID chip to replace EEPROM.

Keywords: PMC (Programmable Metallization Cell); ReRAM; Ag-doped; Chalcogenide; Amorphous

Deposition of Europium Oxide on Si and its optical properties depending on thermal annealing conditions by Young Chul Shin; Shi Jong Leem; Chul Min Kim; Su Jin Kim; Yun Mo Sung; Cheol Koo Hahn; Jong Hyeob Baek; Tae Geun Kim (pp. 326-330).
We investigate the influence of the ambient gas during thermal annealing on the photoluminescence (PL) properties of europium compound thin films on Si substrates. The films were deposited by radio-frequency magnetron sputtering and subsequently annealed in N2 or O2 ambient gas by rapid thermal annealing (RTA). The results of X-ray diffraction indicate that the resulting europium compound annealed in N2 ambient have several silicate phases such as EuSiO3 and Eu2SiO4 compared to those annealed in O2 ambient. The spectral results revealed that a broad luminescence associated with Eu2+ ions, with a maximum intensity at 600 nm and a FWHM of 110 nm, was observed from the thin film annealed at 1000 °C in N2 ambient. However, a series of narrow PL spectra from Eu3+ ions were observed from the film annealed in O2 ambient.

Keywords: Europium silicate; RF-sputtering; Rapid thermal annealing; Photoluminescence

Negative thermal quenching in undoped ZnO and Ga-doped ZnO film grown on c-Al2O3 (0001) by plasma-assisted molecular beam epitaxy by W. K. Choi; H. C. Park; B. Angadi; Y. S. Jung; J. W. Choi (pp. 331-334).
Negative thermal quenching (NTQ) was observed in bound exciton emission line in undoped ZnO and the donor-to-valence-band emission in heavily Ga-doped ZnO thin films grown on c-Al2O3 (1000) through low temperature photoluminescence spectra. In both cases, the enhanced feature of PL peak intensity occurred in the temperature range of 35–45 K corresponding to the energies of either excitation to the vibrational/rotational resonance states or the involvement of B-valence band considering the activation energy of about 5 meV.

Keywords: Negative thermal quenching; ZnO; Ga-doped ZnO; B-valence band; Vibrational/rotational resonance states

Application of piezoelectric multi-layered actuator to floating mass transducer for implantable middle ear hearing devices by Eung-Pyo Hong; Il-Yong Park; Ki-Woong Seong; Chang-Woo Lee; Myoung-Nam Kim; Jin-Ho Cho (pp. 335-340).
Implantable middle ear hearing devices (IMEHDs), which have been developed since the 1970s, directly stimulate the middle ear and can realize a high efficiency of sound transmission with better sound fidelity. For such kinds of IMEHDs, this paper presents the design and application of a piezoelectric floating mass transducer (PFMT) using a PMN-PT multi-layered actuator as a new type of vibrating transducer. The proposed PFMT consists of only three components of a multi-layered piezoelectric actuator, a metal case, and a clamping clip. The actuator’s one side is connected with the metal case and the other side is linked to the clamp for the attachment to an incus long process of middle ear ossicles. The vibration displacement of the PFMT attached to the incus is studied theoretically by simplified kinetic model between the PFMT and the incus. Through an in-vitro experiment using a human temporal bone, it has been verified that the proposed PFMT can generate the vibration force equivalent to the sound pressure of about 100 dB SPL. Therefore, the proposed PFMT is expected to be used as an IMEHD transducer with the advantages such as simple surgical implantation, no interference from external electromagnetic fields, and improved productivity.

Keywords: Piezoelectric multi-layered actuator; Piezoelectric floating mass transducer; Implantable middle ear hearing devices

Study on the electrical and optical properties of ITO and AZO thin film by oxygen gas flow rate by Sang-Mo Kim; You-Seung Rim; Min-Jong Keum; Kyung-Hwan Kim (pp. 341-345).
Transparent conductive oxide (TCO) thin films such as tin doped indium oxide (ITO), zinc doped indium oxide (IZO) and Al doped zinc oxide (AZO) have been widely used as transparent electrode for display. ITO and AZO thin films for display was prepared by the facing targets sputtering (FTS) system. The FTS method is called a plasma-free sputter method because the substrate is located apart from plasma. This system can deposit the thin film with low bombardment by high energetic particles in plasma such as γ-electrons, negative ions and reflected Ar atoms. ITO and AZO thin films were deposited on glass substrate at room temperature with oxygen gas flow rate and input power. And the electrical, structural and optical properties of the thin films were investigated. As a result, the resistivity of ITO, AZO thin film is 6 × 10−4 Ω cm, 1 × 10−3 Ω cm, respectively. And the optical transmittance of as-deposited thin films is over 80% at visible range.

Keywords: AZO; ITO; FTS; TCO

Development of a piezoelectric pump using hinge-lever amplification mechanism by Young-Bog Ham; Woo-Suk Seo; Won-Young Cho; Dong-Won Yun; Jung-Ho Park; So-Nam Yun (pp. 346-350).
This paper presents the design, fabrication, and tests of a piezoelectric pump using hinge-lever amplification mechanism. The proposed hinge-lever amplification mechanism consists of a base frame, a lever with contact steel ball, and a multilayer piezoelectric actuator. The lever is in contact with the piezoelectric actuator through hinged steel ball. The extended piezoelectric actuator pushes the contact steel ball; therefore, a small displacement of piezoelectric actuator can be amplified through the movement of the lever. The amplified displacement of 683 μm was measured at the applied voltage of 100 V. These results show the fact that the proposed hinge-lever mechanism can be obtained the amplification ratio of up to ten times. The piezoelectric pump using hinge-lever amplification mechanism was fabricated and pumping performance was experimentally investigated. The pump achieved no-load flow rate, maximum output pressure of 600 ml/min and 6.8 kPa, respectively, at the applied voltage of 100 V and driving frequency of 250 Hz.

Keywords: Multilayer PZT; Displacement amplification; Hinge-lever mechanism; Piezo-electric pump

Sintering behavior of silver conductive thick film with frit in information display by Seongjin Hwang; Sangwook Lee; Hyungsun Kim (pp. 351-355).
A silver conductive thick film with a frit was examined for its potential applications in the plasma display panel industry. A low melting glass frit (firing temperature, less than 600 °C) was used in the conductive thick film for this work. The thermal behavior of the silver, frit and mixing powder was studied using hot stage microscopy. During the sintering of the silver conductive thick film with the frit, the frit melted, which was followed by accelerated densification. However, the increase in spreading rate with frit affected the microstructure, which has 1.9% porosity and the geometry of the silver conductive thick film. These results suggest that the content of the frit, firing temperature and the thermal properties of the frit in the silver conductive thick film influence the level of shrinkage, conductivity, and shape of the thick film.

Keywords: Silver powder; Shrinkage; Thick film; Bulk resistivity; Frit

Electrical and optical studies of transparent conducting ZnO:Al thin films by magnetron dc sputtering by Vinh Ai Dao; Tran Le; Tuan Tran; Huu Chi Nguyen; Kyunghae Kim; Jaehyeong Lee; Sungwook Jung; N. Lakshminarayan; Junsin Yi (pp. 356-360).
Transparent conducting aluminium-doped Zinc oxide (ZnO:Al) films have been deposited on glass substrates by magnetron dc sputtering using a ceramic target (ZnO with 2 wt% Al2O3). The dependence of the electrical and optical properties of these films on substrate temperature, sputtering pressure of Ar and location of substrates were investigated in detail. Target is perpendicular with substrate and we controlled the distance ‘x’ of target and substrate. Optimized films with resistivity of 3.7 × 10−4 Ω cm, an average transmission in the visible range (300–800 nm) of greater than 85% and the reflectance in the infrared range being greater than 85% have been formed. Substrate temperature, distance ‘x’, and working pressure are optimized for lower resistivity and high concentration of carriers.

Keywords: Transparent conductive oxide films; Energetic oxygen atoms; ZnO:Al

Electrical, optical, and structural properties of ITO co-sputtered IZO films by dual target magnetron sputtering by Jin-A Jeong; Kwang-Hyuk Choi; Jung-Hyeok Bae; Jong-Min Moon; Soon Wook Jeong; Insoo Kim; Han-Ki Kim; Min-Su Yi (pp. 361-366).
We have investigated electrical, optical, and structural properties of indium tin oxide (ITO) co-sputtered indium zinc oxide (IZO) film prepared by a dual target direct current (DC) magnetron sputtering at room temperature in pure Ar ambient. It was shown that the resistivity and sheet resistance of ITO co-sputtered IZO films monotonically increased with increasing DC power of ITO target at constant DC power of IZO target. Synchrotron X-ray scattering and scanning electron microscope examination results show that addition of ITO in the IZO film lead to crystallization of IZTO film due to low transition temperature of the ITO from amorphous to crystalline. However, ITO co-sputtered IZO film (ITO/IZO power = 100 W:100 W) exhibit higher work function than those of pure IZO and ITO film. It was found that the work function as well as the electrical, optical, and surface properties of the IZTO film could be controlled by varying the DC power of IZO and ITO targets, respectively.

Keywords: Co-sputtered IZO; ITO; IZTO; Work function; DC magnetron sputter

Self-constrained sintering of Al2O3/glass/Al2O3 ceramics by glass infiltration by Jung-Hun You; Dong-Hun Yeo; Hyo-Soon Shin; Jong-Hee Kim; Ho-Gyu Yoon (pp. 367-371).
Though need for precise alignment of interlayer patterning in LTCC application, there have been few reports about zero-shrinkage sintering techniques. In this study, ceramic substrate with minimal xy shrinkage was prepared by glass infiltration method with ‘Al2O3/glass/Al2O3’ structure. Glass infiltration into alumina particle layer was observed with variation of both sintering temperature (700 ≤ T sint. ≤ 900 °C) and alumina particle size distribution (0.5 ≤ D 50 ≤ 1.8 μm). Since glass had low viscosity enough to infiltrate at 700 °C, infiltration started at that temperature and infiltrated up to 20 μm or so with temperature increase, but infiltration depth did not increase noticeably above 750 °C. Based on these results, when sintered at 900 °C with controlled sheet thickness of both glass and alumina, the shrinkage in xy direction was calculated as less than 0.2%, with 40% in z direction. Dielectric constant (ɛ r) measured 6.19 with quality factor (Q) of 552 at 1 GHz of frequency. From these results, it is thought that zero-shrinkage ceramic substrates would be obtained without de-lamination.

Keywords: LTCC; Zero shrinkage; Infiltration; Al2O3/glass/Al2O3 structure

Lead-free NKN-5LT piezoelectric materials for multilayer ceramic actuator by Min-Soo Kim; Sohyun Jeon; Dae-Su Lee; Soon-Jong Jeong; Jae-Sung Song (pp. 372-375).
As a candidate for lead-free piezoelectric materials, Li2O excess 0.95(Na0.5K0.5)NbO3–0.05LiTaO3 (NKN-5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding Li2O as a sintering aid. Abnormal grain growth in NKN-5LT ceramics was observed with varying Li2O content. In the 1 mol% Li2O excess NKN-5LT samples sintered at 1000°C for 4 h in air, electromechanical coupling factor and piezoelectric constant of NKN-5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively. Lead-free piezoelectric ceramic, Li2O excess NKN-5LT, multilayer ceramic actuators (MLCA) were fabricated. 10 × 10 × 1 mm3 size MLCAs were fabricated by conventional tape casting method. The displacement of Li2O excess NKN-5LT MLCA with 3 mm thickness was ~1 μm at 150 V.

Keywords: Lead-free; Piezoelectric; Actuator

Electrochemical characteristics of phosphorus doped silicon and graphite composite for the anode materials of lithium secondary batteries by Myung-ho Kong; Jae-hyun Noh; Dong-jin Byun; Joong-kee Lee (pp. 376-381).
Poly-crystalline silicon particles with a diameter of 80∼100 nm were synthesized by the plasma arc discharge method. Natural graphite, poly-crystalline silicon, poly-crystalline silicon/graphite composite and phosphorus doped poly-crystalline silicon/graphite composite particles were used as the anode materials of lithium secondary batteries and their electrochemical performances were compared. The phosphorus component on the surface and internal structure of the silicon particles were observed by XPS and SIMS analyses, respectively. In our experiments, the phosphorus doped silicon/graphite composite electrode exhibited better cycle performance than the intrinsic silicon/graphite composite electrode. The discharge capacity retention efficiency of the intrinsic silicon/graphite composite and phosphorus doped silicon/graphite composite electrodes after 20 cycles were 8.5% and 75%, respectively. The doping of phosphorus leads to an increase in the electrical conductivity of silicon, which plays an important role in enhancing the cycle performance. The incorporation of silicon into graphite has a synergetic effect on the mitigation of the volume change and conducting medium in the composite electrode during the charge–discharge reaction.

Keywords: Lithium secondary battery; Phosphorus doping; Silicon; Anode; Composite

Electrochemical evaluation of La1 − x Ca x CoO3 cathode material for zinc air batteries application by Seung-Wook Eom; Se-Young Ahn; Ik-Jun Kim; Yang-Kook Sun; Hyun-Soo Kim (pp. 382-386).
We synthesized nano-sized La1 − x Ca x CoO3 (x = 0.1–0.4) cathode catalysts for zinc air secondary batteries by the citrate method, and measured electrochemical characteristics of the cathodes according to the cathode catalyst’s calcium content. We heat treated the prepared precursor at a calcination temperature of 700°C, and examined it by XRD analysis and electrochemical evaluation. We examined the prepared La1 − x Ca x CoO3 catalyst powder’s oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and cycle-stability performance. When we consider ORR, OER and cycle-stability performance simultaneously, La0.9Ca0.1MnO3 catalyst showed the best performance because of its lowest voltage deference between charge and discharge, and its lowest degradation according to cycle.

Keywords: Zinc air batteries; Oxygen reduction; Oxygen evolution; Cathode

Piezoelectric and dielectric characteristics of low-temperature-sintering Pb(Mg1/2W1/2)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 ceramics according to the amount of PNN substitution by Yeongho Jeong; Kyungjin Yoo; Juhyun Yoo (pp. 387-391).
In this study, in order to develop low-temperature-sintering ceramics for multilayer piezoelectric actuator, Pb(Mg1/2W1/2)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 (abbreviated as PMW–PNN–PZT) ceramics were fabricated using Li2CO3 and CaCO3 as sintering aids and their dielectric and piezoelectric properties were investigated with the amount of Pb(Ni1/3Nb2/3)O3 (abbreviated as PNN) substitution. PMW–PNN–PZT composition ceramics could be sintered up to 870°C by adding sintering aids. At the sintering temperature of 900°C, electromechanical coupling factor (k p), piezoelectric constant (d 33) and Curie temperature (Tc) in the composition ceramics with 9 ;mol% PNN substitution showed the optimal value of 0.64 517 ;pC/N and 317°C, respectively for multilayer actuator application.

Keywords: Low-temperature-sintering; Piezoelectric constant; Electromechanical coupling factor (k p); Piezoelectric constant (d 33); Curie temperature (Tc); Sintering aids

Piezoelectric properties of textured Bi3.25La0.75Ti2.97V0.03O12 ceramics fabricated by reactive templated grain growth method by Chang Won Ahn; Euh Duck Jeong; Young Hyeok Kim; Jae Shin Lee; Gwiy Sang Chung; Jae Young Lee; Ill Won Kim (pp. 392-396).
We have fabricated Bi3.25La0.75Ti2.97V0.03O12 (BLTV) ceramics by reactive templated grain growth method using a Bi4Ti3O12 template and investigated the electromechanical coupling coefficient (k) and temperature coefficient of a resonant frequency as a function of temperature. The highly preferentially [00l] oriented BLTV ceramics were obtained and the grain-orientation factor (Lotgering factor) was 83%. The electromechanical coupling coefficient of the longitudinal vibration mode (k 33) and the temperature coefficient of resonant frequency of textured BLTV ceramics were enhanced compared to those of nontextured BLTV ceramics.

Keywords: Lead-free; Reactive templated grain growth; Piezoelectricity; Bismuth titanate

Photoluminescence characteristics of Y3Al5O12:Tb3+ phosphors synthesized using the combustion method by Hyun-ho Kwak; Se-Jun Kim; Hyon-Hee Yoon; Sang-Joon Park; Hyung-wook Choi (pp. 397-401).
For this study, terbium-doped yttrium aluminum garnet (YAG:Tb) phosphor powders were prepared via the combustion process using the 1:1 ratio of metal ions to reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and photoluminescence. Single-phase cubic YAG:Tb crystalline powder was obtained at 800 °C by directly crystallizing it from amorphous materials, as determined by XRD techniques. There were no intermediate phases such as yttrium aluminum perovskite (YAlO3) and yttrium aluminum monoclinic (Y4Al2O9) observed in the sintering process. The SEM image showed that the resulting YAG:Tb powders had uniform sizes and good homogeneity. With the increase in the sintering temperature, the grain size increased. The photoluminescence spectra of the YAG:Tb nanoparticles were investigated to determine the energy level of electron transition related to luminescence processes. There were three peaks in the excited spectrum, and the major one was a broad band of around 274 nm. Also, the YAG:Tb nanoparticles showed two emission peaks in the range of 450 × 500 and 525 × 560 nm, respectively, and had maximum intensity at 545 nm.

Keywords: YAG; Combustion; Phosphor; Luminescence

The effect of Bi4Ti3O12 particles addition in lead-free Bi0.5(Na0.75K0.25)0.5TiO3 ceramics by Chang Won Ahn; Euh Duck Jeong; Young Hyeok Kim; Jae-Shin Lee; Hai Joon Lee; Ill Won Kim (pp. 402-405).
We studied the effect of Bi4Ti3O12 (BiT) platelet addition in Bi0.5(Na0.75K0.25)0.5TiO3 (BNKT) ceramics by preparing two kinds of BNKT ceramics. One type of BNKT ceramic was fabricated by a conventional solid state reaction method (normal sample), while the other by addition of 15 wt% BiT platelets to BNKT powders (BiT-added sample). In the case of BiT-added BNKT ceramics, plate like grains were formed by the reaction of BiT platelets with Na2CO3, K2CO3, and TiO2 during the sintering process. The grain size of BiT-added BNKT ceramics was 10 times larger than that of normal BNKT ceramic. The piezoelectric strain and d33 values of BiT-added BNKT ceramics were 0.135% and 225 pm/V, respectively. These values were 35% higher than those of normal BNKT ceramics. The piezoelectric properties of BiT-added BNKT ceramics were enhanced by the higher domain activity due to a decrease in domain density at larger grain sizes.

Keywords: Bismuth sodium potassium titanate; Piezoelectric; Grain size; Strain

Effects of Mg dopant on the degradation of InGaN multiple quantum wells in AlInGaN-based light emitting devices by Sung-Nam Lee; H. S. Paek; J. K. Son; H. Kim; K. K. Kim; K. H. Ha; O. H. Nam; Y. Park (pp. 406-409).
We investigated the effects of Mg dopant on the degradation of AlInGaN-based light emitting diodes (LEDs) and laser diodes (LDs) with InGaN multi-quantum wells (MQWs). Photoluminescence (PL) intensity of InGaN MQWs was significantly decreased with increasing the Mg intentional doping process in InGaN active region, indicating that Mg dopant could degrade the optical quality of InGaN MQWs. From secondary ion mass spectroscopy (SIMS) analysis of AlInGaN-based LDs grown on GaN/sapphire and GaN substrate with different dislocation densities, we found that Mg concentration of LD on GaN/sapphire was higher than that of LD on GaN substrate at the InGaN MQWs regions. Additionally, we observed that Mg atoms were significantly diffused from p-type layer to InGaN MQWs region in the LD structure after aging evaluation. From these results, we could conclude that Mg diffusion along threading dislocations is one of the major gradual degradation mechanisms of AlInGaN-based LD/LEDs during the device operation under high voltage condition.

Keywords: GaN; LD; LED; Degradation

Morphology and luminescence properties of BaMgAl10O17:Eu2+ blue phosphors by Aerosol Flame Deposition by Sang Won Ko; Dongwook Shin (pp. 410-414).
BaMgAl10O17:Eu2+ (BAM:Eu) is widely used as a blue phosphor for fluorescent lamps and plasma display panels (PDP). The improvement of the luminescence efficiency is a significant issue for applications in plasma display panels. In this study, the Aerosol Flame Deposition (AFD) was applied to fabricate BaMgAl10O17:Eu2+ (BAM:Eu) particles with spherical shape and fine size in order to improve their luminescence. The sub-micrometer powder was synthesized in spherical shape in an oxy-hydrogen flame and deposited on a substrate in the form of porous film. The particle size of as-prepared powder increased with increasing the concentration of precursor solution and the heat treatment under reducing atmosphere increased particle size additionally with surface roughening due to the needle-like crystallized phases. Photoluminescence spectrum was observed at about 450nm due to the 5d–4f transition of Eu2+ and the intensity of phosphor was as high as 70% of that of the commercial phosphor.

Keywords: PDP; Phosphor; BAM; BaMgAl10O17:Eu2+ ; Aerosol Flame Deposition

Effect of fluorine doping on the properties of ZnO films deposited by radio frequency magnetron sputtering by D. Y. Ku; Y. H. Kim; K. S. Lee; T. S. Lee; B. Cheong; T.-Y. Seong; W. M. Kim (pp. 415-421).
ZnO films with varying fluorine content were prepared on Corning glass by radio frequency magnetron sputtering of ZnO target containing ZnF2 at room temperature, and the compositional, electrical, optical, and structural properties of the as-grown films together with the vacuum-annealed films were investigated. The fluorine content in the fluorine doped ZnO (FZO) films increased almost linearly with increasing ZnF2 content in sputter target, and the highest atomic concentration was 7.3%. Vacuum-annealing caused a slight reduction of fluorine content in the films. The resistivity of the as-grown FZO films deposited showed a typical valley-like behavior with respect to the fluorine content in film, i.e. having minimum resistivity at intermediate fluorine content. Despite high fluorine content in the FZO films, the carrier concentration remained below 1.2 × 1020 cm−3, leading to very low doping efficiency level. Upon vacuum-annealing, the resistivity of FZO films decreased substantially due to increase in both the carrier concentration and the Hall mobility. From the structural analysis made by X-ray diffraction study, it was shown that addition of small amount of fluorine enhanced the crystallinity of FZO films with (002) preferred orientation, and that large amount of fluorine addition yielded disruption of preferred orientation. It was also shown that doping of fluorine rendered a beneficial effect in reducing the absorption loss of ZnO films in visible range, thereby substantially enhancing the figure of merit.

Keywords: Fluorine doped ZnO film; Transparent conducting oxide; Magnetron sputtering; Vacuum-annealing

Enhanced photovoltaic properties of overlayer-coated nanocrystalline TiO2 dye-sensitized solar cells (DSSCs) by Jin Young Kim; Sangwook Lee; Jun Hong Noh; Hyun Suk Jung; Kug Sun Hong (pp. 422-425).
TiO2 dye-sensitized solar cells (DSSCs) coated with various oxide layers were fabricated via a screen printing method and the effects of the oxide layers on the photovoltaic properties were systematically investigated. The open circuit voltage (V oc) was closely dependent to the conduction band (CB) edge position and the band gap energy (E g) of the oxide layers, while the short circuit current density (J sc) was related to the iso-electric point (IEP). V oc showed an increasing behavior with the CB edge position of the oxide layers, which could be explained by the blocking effect of the insulating layers. Although J sc was basically proportional to the IEP and the resulting dye adsorption, there were other factors like the resistance of oxide layers. The cell efficiency could be enhanced by 60% when the cells were coated with the oxide layers of high E g and IEP.

Keywords: TiO2 ; Dye-sensitized solar cell (DSSC); Oxide coating layer; Band gap energy (E g); Iso-electric point (IEP)

Piezoelectric characteristics of low temperature sintering Pb(Ni1/3Nb2/3)O3–Pb(Zr1/2Ti1/2)O3 ceramics as a function of Pb(Mn1/3Sb2/3)O3 substitution by Sangho Lee; Juhyun Yoo; Insung Kim; Jaesung Song (pp. 426-431).
In this study, in order to develop the composition ceramics for multilayer ceramic for ultrasonic nozzle and ultrasonic actuator application, Pb(Mn1/3Sb2/3)O3 (abbreviated as PMS) substituted Pb(Ni1/3Nb2/3)O3–Pb(Zr,Ti)O3 (abbreviated as PNN-PZT) ceramics were fabricated using two-stage calcinations method and Li2CO3, Na2CO3 and ZnO as sintering aids, and their piezoelectric and dielectric characteristics were investigated. With the increase of the amount of PMS substitution, electromechanical coupling factor (k p), and mechanical quality factor (Q m) of specimens showed the maximum value at 3 mol% substituted specimen while dielectric constant (ɛ r) was decreased. At the sintering temperature of 900 °C, the density, ɛ r, k p, and Q m of 3 mol% PMS substituted PNN-PZT composition ceramics showed the optimal values of 7.92 [g/cm3], 959, 0.584, and 1003, respectively, for low loss multilayer piezoelectric actuator application.

Keywords: Multilayer ceramic; Ultrasonic nozzle and ultrasonic actuator; Electromechanical coupling factor; Mechanical quality factor; Sintering aids

Piezoelectric properties of MnO2 doped low temperature sintering Pb(Mn1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr0.50Ti0.50)O3 ceramics by Juhyun Yoo; Sangho Lee (pp. 432-436).
In this study, in order to develop the composition ceramics for low loss and low temperature sintering multilayer piezoelectric actuator, Pb(Mn1/3Nb2/3)O3–Pb(Ni1/3Nb2/3)O3–Pb(Zr0.50Ti0.50)O3 (abbreviated as PMN-PNN-PZT) ceramics were fabricated using Li2CO3 and Na2CO3 as sintering aids, and their piezoelectric and dielectric characteristics were investigated according to the amount of MnO2 addition. At the 0.2 wt% MnO2 doped specimen sintered at 900 °C, density and mechanical quality factor (Q m) showed the maximum values of 7.81[g/cm3]and 1186, respectively. And also, at 0.1 wt% MnO2 doped specimen, electromechanical coupling factor (k p), piezoelectric constant (d 33) of specimen showed the maximum values of 0.608 and 377[pC/N], respectively. Dielectric constant (ɛ r) slightly decreased with increasing MnO2. Taking into consideration the density of 7.81[g/cm3], electromechanical coupling factor (k p)of 0.597 the mechanical quality factor (Q m) of 1,186, and piezoelectric constant (d 33) of 356[pC/N], it could be concluded that 0.2 wt% MnO2 doped composition ceramics sintered at 900 °C was best for low loss and low temperature sintering multilayer piezoelectric actuator application.

Keywords: Low loss multilayer piezoelectric actuator; Low temperature sintering; Mechanical quality factor; Electromechanical coupling factor

Spherical shape Ba-based glass powders prepared by spray pyrolysis for MLCCs by Seung Kwon Hong; Dae Soo Jung; Yun Chan Kang (pp. 437-441).
Spherical shape BaO–B2O3–SiO2 glass powders were directly prepared by high temperature spray pyrolysis at >1000 °C. The thermal and morphological characteristics of the prepared glass powders were investigated. The glass powders prepared at temperature of 1000 °C had spherical shape and hollow inner structure. On the other hand, the powders prepared at high temperature of 1300 °C had complete spherical shape and dense inner structure by complete melting. The mean size of the glass powders was 0.9 μm. The glass transition temperatures (T g) of the glass powders obtained by spray pyrolysis at preparation temperatures between 1000 and 1300 °C were 601.1 °C regardless of the preparation temperatures. The specimen of the glass powders obtained by spray pyrolysis at the preparation temperature of 1300 °C had small number of voids even at low sintering temperature of 700 °C. In addition, the specimen sintered at temperature of 800 °C had dense microstructure without voids.

Keywords: Glass power; Spray pyrolysis; MLCC; Fluxing agent

Effects of Mg doping concentration on the band gap of ZnO/Mg x Zn1−x O multilayer thin films prepared using pulsed laser deposition method by Ja Young Cho; In Ki Kim; In Ok Jung; Jong-Ha Moon; Jin Hyeok Kim (pp. 442-446).
Epitaxial ZnO/Mg x Zn1-x O multilayer thin films (x = 0~0.15) were prepared on c-Al2O3 substrates by pulsed laser deposition and their crystallinity and optical properties were investigated using X-ray diffraction, TEM, and UV-Vis spectroscopy. ZnO/Mg x Zn1-x O multilayer thin films were grown by stacking alternate layers of ZnO and Mg x Zn1−x O with laser fluence of 3 J/cm2, repetition rate of 5 Hz, substrate temperature of 600 °C, and oxygen partial pressure of 5 × 10–4 Torr. The thickness of individual ZnO and Mg x Zn1−x O layers was maintained at 3 and 6 nm, respectively, and the total thickness of the films was kept in 300 nm. X-ray diffraction results showed that the multilayer thin films were grown epitaxially on c-Al2O3 substrates with an epitaxial orientation relationship of $$left. {left( {0001} ight)left[ {10ar 11} ight]_{{ ext{multilayer}}} } ight|left( {0001} ight)left[ {10ar 11} ight]_{{ ext{Al}}_{ ext{2}} { ext{O}}_{ ext{3}} } $$ . Cross-sectional TEM micrographs showed alternating layers of bright and dark contrast, indicating the formation of ZnO/Mg x Zn1−x O multilayer thin films. The 2θ value of Mg x Zn1−x O (0002) peak increased from 34.30° at x = 0 to 34.67° at x = 0.15 with increasing Mg doping concentration in the multilayer thin films. The absorption edge in the UV-Vis spectra shifted to shorter wavelength from 360 at x = 0 to 342 nm at x = 0.15 and the band gap energy increased from 3.27 eV at x = 0 to 3.54 eV at x = 0.15.

Keywords: ZnO; MgO; Zn x Mg1−x O; PLD; UV-detector; Multilayer

Synthesis and electrochemical properties of LiNi1−y Zn y O2 by Bok-Hee Kim; Jong-Hwan Kim; Sang-Jae Han; Su-Jin Hong; Myoung-Youp Song (pp. 447-451).
Zn doped LiNi1−y Zn y O2 (0.00 ≤ y ≤ 0.100) composition was synthesized by an emulsion method. The emulsion-derived powder was calcined at the temperature range of 650 ∼ 800 °C for 12 ∼ 48 h. A single phase of LiNi1−y Zn y O2 was obtained at 700 °C. The optimum condition for the synthesis of LiNi1−y Zn y O2 was to be calcined at 750 °C for 36 h in oxygen stream. The composition of LiNi0.995Zn0.005O2 showed the largest discharge capacity and improved cycle life. The initial and final discharge capacities were 163 and 154.5 mAh/g, respectively. The fading rate in discharge capacity after 20 cycles was only 5.2%.

Keywords: Powder synthesis; Discharge capacity; LiNi1−y Zn y O2 ; Cathode material; Emulsion method

Inorganic cryogels for energy saving and conversion by Oleg A. Shlyakhtin; Young-Jei Oh (pp. 452-461).
Cryogels are usually obtained by freezing and thawing or freeze drying of gels and residues. Essential morphological features of the cryogels are bimodal pore size distribution, nanosize of the primary particles (crystallites) and their low agglomeration. Widely used for a decades in the polymer science and technology, cryogels find now a growing number of applications in the electroceramic materials. Freeze casting technique based on the freeze gelation effect is proved to be useful forming method in the production of complex-shaped SiO2-containing electroceramics. Directed modification of the micromorphology by using solvent exchange schemes allows to obtain SiO2 cryogel monoliths with density ≤ 0.05 g cm−3 and specific surface area 700–800 m2 g−1 suitable for cryogenic thermal insulation of the superconducting devices. Excellent electrocatalytic activity of the macro/mesoporous PtRu/C cryogels in the methanol oxidation reaction makes them perspective anode materials of direct methanol fuel cells. Application of the cryogel-derived starting powders promoted substantial reduction of the sintering temperatures for a number of electroceramic materials. MnO2- and V2O5-based cryogels are efficient cathode materials for secondary lithium batteries with specific capacity up to 300 mAh g−1. Recent studies demonstrated also a feasibility of cryochemical approaches to the synthesis of complex oxide-based nanocrystalline electrode materials for electrochemical supercapacitors with high specific capacity at current densities up to 50 mA cm−2.

Keywords: Cryogel; Freeze drying; Nanocrystalline materials; Sol–gel synthesis; Mesoporous materials

Surface modification of stainless steel bipolar plates for PEMFC (proton exchange membrane fuel cell) application by Young-Hoon Yun; Sung-Churl Choi (pp. 462-467).
Stainless steel 316 and 304 plates were deposited with a metallic film (top layer) and a conductive oxide film (intermediate layer) by a sputtering method and an E-beam method, respectively. The conductive oxide film was formed on the stainless steel plates in the range of thickness of 200, 400, and 600 nm. The XRD patterns of the conductive oxide films showed a typical indium-tin oxide (ITO) crystalline phase. The metallic films of 100 nm thickness were subsequently formed on the surface region of the bare stainless steel plates and the stainless steel plates deposited with ITO thin film. Surface morphologies of the stainless steel bipolar plates deposited with conductive film and metallic film were observed by AFM and FE-SEM. The metallic films on the stainless steel plates represented the microstructural morphology of the fine columnar grains of 10 nm diameter and 60 nm length. The electrical resistivity and contact angle of the stainless steel bipolar plates modified were examined as a function of the thickness of the conductive oxide film.

Keywords: Proton exchange membrane fuel cell (PEMFC); Bipolar plate; Conductive oxide film; Metallic film; Resistivity

Effect of heat treatment of sputter deposited ZnO films co-doped with H and Al by S. H. Lee; T. S. Lee; K. S. Lee; B. Cheong; Y. D. Kim; W. M. Kim (pp. 468-473).
ZnO films co-doped with H and Al (HAZO) were prepared by sputtering ZnO targets containing Al2O3 dcontent of 1 (HA1ZO series) and 2 wt.% (HA2ZO series) on Corning glass (Eagle 2000) at substrate temperature of 150 °C with Ar and H2/Ar gas mixtures. The effects of hydrogen addition to Al-doped ZnO (AZO) films with different Al contents on the electrical, optical and structural properties of the as-grown films as well as the vacuum- and air-annealed films were examined. For the as-deposited films, the free carrier number in both series of HAZO films increased with increasing H2 content in sputter gas. HA2ZO film series prepared from target containing 2 wt.% Al2O3 showed better crystallinity and higher carrier concentration than HA1ZO film series deposited using target containing 1 wt.% Al2O3. The crystallinity and the Hall mobility of HA2ZO film series decreased with increasing H2 content in sputter gas, while those of HA1ZO film series showed a reversed behavior. Although HA2ZO film series yielded lower resistivity than HA1ZO film series due to higher carrier concentrations, the higher figure of merit (expressed as 1 / ρα, where ρ and α represents the resistivity and absorption coefficient, respectively) was observed for HA1ZO film series because of substantially low absorption loss in these films. When annealed in air ambient, HA1ZO film series showed much stronger stability than HA2ZO film series. Vacuum-annealing resulted in drop of the carrier concentrations as well as large shrinkage in lattice constant, which indicated that the hydrogen dopants are in relatively volatile state and can be removed easily from the films upon annealing.

Keywords: Hydrogen doping; ZnO; Transparent conducting oxide; Magnetron sputtering; Annealing

Polymer modified hematite nanoparticles for electrophoretic display by Mi Ah Lee; Bong Jun Park; In-Joo Chin; Hyoung Jin Choi (pp. 474-477).
Hematite nanoparticles (Fe2O3) as a red inorganic pigment were encapsulated with poly (methyl methacrylate-co-acrylamide) (PMMA-co-AAM) for application in the electronic paper display. Since the Fe2O3 nanoparticle has relatively high density (ρ = 5.07 g/cm3), it usually causes severe sedimentation problem in the suspending medium. In order to reduce density mismatch between inorganic pigment and dielectric medium, the Fe2O3 nanoparticles were modified by dispersion polymerization method. Zeta potential and electrophoretic property of the inorganic pigment coated with copolymers in a low dielectric medium were investigated by using electrophoretic light scattering. The surface morphology and molecular structure of the fabricated particles were measured via SEM and FT-IR, respectively. The amount of polymeric coating was also examined by using TGA.

Keywords: Electrophoretic; Inorganic pigment; Zeta potential; Electronic paper

Fabrication of a superconducting flux flow transistor with a serial-channel structure by an AFM lithography method by Seokcheol Ko; Seong-Jong Kim; Byoung-Sung Han (pp. 478-483).
Atomic force microscopy (AFM) has become an attractive technique to fabricate nano devices since the observing mechanism is different from fabricating one. We have fabricated the superconducting flux flow transistor (SFFT) with a serial-channel structure using the AFM lithography analyzed the modified surface by the AFM image. We investigated the induced voltage in a serial-channel terminals dependence on the gate current by the IV measurement system. We performed the numerical simulation to get the theoretical characteristics of the SFFT controlled by the gate current via the modified channel. The transresistance was 0.006 Ω for Id=51 mA at Ig=5 mA. It is very low transresistance in comparison with SFFTs fabricated by the other processes, however our results show that the SFFT with a serial-channel structure is effectively fabricated by an AFM lithography method.

Keywords: SFFT; AFM lithography; Serial-channel; Transresistance

Nitrogen impurity effects of W–B–C–N quaternary thin film for diffusion barrier for Cu metallization by Soo In Kim; Chang Woo Lee (pp. 484-487).
To investigate the thermal stability of nitrogen stuffing effect of tungsten–boron–carbon–nitrogen (W–B–C–N) thin diffusion barrier, the binding energy shift was studied for various annealing temperature. The X-ray diffraction patterns, the deposition rates and the resistivities of W–B–C–N thin film were measured as a function of nitrogen gas ratios for various annealing temperatures and the binding energy between tungsten and nitrogen was determined by the X-ray photoemission spectroscopy. The interface of Cu/W–B–C–N/Si multilayer was characterized for various nitrogen impurity concentration. Our experimental results indicate that W–B–C–N thin films are effective diffusion barriers to prevent the interdiffusion between Cu and Si interface after annealing up to 850 °C for 30 min.

Keywords: W–B–C–N thin film; Diffusion barrier; Copper metallization

Impurity behaviors of nitrogen in W–C–N thin diffusion barriers for Cu metallization schemes by Soo In Kim; Chang Woo Lee (pp. 488-491).
To investigate the effect of nitrogen impurities in the tungsten–carbon thin films, the electrical and structural properties of W–C–N thin films deposited with rf magnetron sputtering method were measured. Interface characteristics of W–C–N/Si were studied with resistivity and crystal structure as a function of nitrogen impurity concentrations of as-deposited and annealed state for various annealing temperature. We also investigate the interface of Cu/W–C–N/Si for various nitrogen concentration by using XRD pattern and Nomarski microscope. Our experimental results indicate that nitrogen impurity provides stuffing effect for preventing the interdiffusion between Cu and Si interface after annealing up to 800°C for 30 min, because W–C–N thin films serve as a good diffusion barrier and this may be due to the role of nitrogen and carbon inside the W–C–N film not as bonded state but impurities

Keywords: W–C–N thin film; Diffusion barrier; Copper metallization

Synthesis and characterization of Eu doped Y2O3 particles by a glycothermal processing by Sung Kang; Hoy-Yul Park; Dong-Sik Bae (pp. 492-496).
Eu doped Y2O3 particles were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. The Eu doped Y2O3 particles were obtained at 270°C. The average particle size of synthesized powders was below 1 um. The X-ray diffraction pattern shows that the synthesized particles were crystalline. This study has shown that the synthesis of Eu doped Y2O3 crystalline particles is possible under glycothermal conditions in ethylene glycol solution. The effects of synthesis parameters, such as the concentration of starting solution, pH of starting solution, reaction temperature and time, are discussed.

Keywords: Eu doped Y2O3 particles; Glycothermal processing

Electrical and optical properties of epitaxial and polycrystalline undoped and Al-doped ZnO thin films grown by pulsed laser deposition by Jun Hong Noh; Jae-Sul An; Jin Young Kim; Chin Moo Cho; Kug Sun Hong; Hyun Suk Jung (pp. 497-501).
Undoped and Al-doped (1.6%) ZnO films were prepared on (0001) sapphire and fused silica substrates using a pulsed laser deposition technique. The ZnO films on sapphire substrates were epitaxially grown, while the ZnO films on fused silica substrates were texturally grown. The films on sapphire substrates were ordered along the in-plane direction and had grains in which the c-axis was well aligned normal to the substrate. However, the films on fused silica were randomly oriented along the in-plane direction and had poor c-axial aligned grains. The structure analyses showed that the epitaxial ZnO films had low-angle grain boundaries, while the textured polycrystalline ZnO films had high-angle tilt and twist grain boundaries. The nature of the grain boundaries influenced the electrical and optical properties of the undoped and Al-doped ZnO films. Resistivity, Hall mobility, carrier concentration, and near band edge emission of the films were measured at room temperature and discussed in connection with the nature of grain boundaries.

Keywords: Al-doped ZnO; Thermal stability; Epitaxial; Polycrystalline; Grain boundary; Transparent conducting oxide

Synthesis and piezoelectric properties of (1 − x)(Na0.5K0.5)NbO3x(Ba0.95Sr0.05)TiO3 ceramics by Mi-Ro Kim; Hyun-Cheol Song; Ji-Won Choi; Yong-Soo Cho; Hyun-Jai Kim; Seok-Jin Yoon (pp. 502-505).
(1 − x)(Na0.5K0.5)NbO3x(Ba0.95Sr0.05)TiO3 [(1 − x)NKN–xBST] ceramics were synthesized by the conventional solid-state sintering, and their microstructure and piezoelectric properties were investigated. The sintering temperature of the specimens was 1075 °C in air atmosphere and a morphotropic phase boundary (MPB) was observed in the specimens with 0.03 ≤ x ≤ 0.05. Compared with the piezoelectric properties of the NKN ceramics, the enhanced d 33 value of 136 pC/N and ɛ 3 T /ɛ o value of 671 were obtained for the (1 − x)NKN–xBST specimens with x = 0.03.

Keywords: Piezoelectric properties; Lead-free; (Na0.5K0.5)NbO3 ; Perovskite structure

Electrical and optical properties of fluorine-doped tin oxide (SnOx:F) thin films deposited on PET by using ECR–MOCVD by Ji Hun Park; Dong Jin Byun; Joong Kee Lee (pp. 506-511).
The electrical, optical, structural and chemical bonding properties of fluorine-doped tin oxide (SnOx:F) films deposited on a plastic substrate prepared by Electron Cyclotron Resonance–Metal Organic Chemical Vapor Deposition (ECR–MOCVD) were investigated with special attention to the process parameters such as the H2/TMT mole ratio, deposition time and amount of fluorine-doping. The four point probe method, UV visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic emission spectroscopy (AES), X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the films. Based on our experimental results, the characteristics of the SnOx:F thin films were significantly affected by the process parameters mentioned above. The amount of fluorine doping was found to be one of the major parameters affecting the surface resistivity, however its excess doping into SnO2 lead to a sharp increase in the surface resistivity. The average transmittance decreased with increasing film thickness. The lowest electrical resistivity of 5.0 × 10−3 Ω.cm and highest optical transmittance of 90% in the visible wavelength range from 380 to700 nm were observed at an H2/TMT mole ratio of 1.25, fluorine-doping amount of 1.3 wt.%, and deposition time of 30 min. From the XRD analysis, we found that the SnOx:F films were oriented along the (2 1 1) plane with a tetragonal and polycrystalline structure having the lattice constants, a = 0.4749 and c = 0.3198 nm.

Keywords: SnOx:F; PET; Electrical conductivity; Optical transmittance; ECR–MOCVD

Effects of sputtering pressure and thickness on properties of ZnO:Al films deposited on polymer substrates by Jae-Hyeong Lee (pp. 512-518).
Highly conducting and transparent aluminum doped zinc oxide (ZnO:Al) thin films have been deposited on polyimide substrate by r.f. magnetron sputtering at room temperature. The influence of sputter pressure and thickness on the structural, electrical, and optical properties of ZnO:Al films deposited on polyimide substrate is reported. The crystallinity and degree of orientation was increased by decreasing the sputter pressure. For higher sputtering pressures an increase on the resistivity was observed due to a decrease on the mobility and the carrier concentration. As the film thickness was increased, the crystallite sizes were increased, but the average transmittance in the wavelength range of the visible spectrum was decreased. The electrical performances of the ZnO:Al films deposited on glass substrates are slightly worse than the ones of the films deposited on polyimide substrates with same thickness. The lowest resistivity of 8.6 × 10−4 Ω cm can be obtained for films deposited on glass substrate with the thickness of 800 nm.

Keywords: Al-doped ZnO (ZnO:Al); Sputtering; Polymer substrate; Sputter pressure, thickness; Solar cell

Piezoelectric and dielectric properties of low temperature sintering Pb(Mn1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3–Pb(Zr0.48Ti0.52)O3 ceramics with variation of sintering time by Juhyun Yoo; Ilha Lee; Dong Soo Paik; Yong-Wook Park (pp. 519-523).
Pb(Mn1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3–Pb(Zr0.48Ti0.52)O3 (abbreviated as PMN–PZN–PZT) ceramics containing Li2CO3, Bi2O3 and CuO as sintering aids were fabricated using two-stage calcinations method in order to develop low temperature sintering ceramics for multilayer piezoelectric actuators. Their dielectric and piezoelectric properties were investigated according to the variation of sintering time. All the specimens sintered at 930°C for 60~150 min showed tetragonal phases without secondary phases. Electromechanical coupling factor (kp), dielectric constant (ε r) and piezoelectric constant (d 33) increased with the increase of the sintering time. The mechanical quality factor (Qm) exhibited maximum of 1,815 with the increase of sintering time for 120 min and then slightly decreased. At the sintering temperature of 930°C and the sintering time of 120 min, the optimal values such as the density of 7.69 g/cm3, kp of 0.516, ε r of 1158, Qm of 1815, and d 33 of 287 pC/N were found for multilayer piezoelectric actuators.

Keywords: Two-stage calcination; Sintering aids; Sintering time; Multilayer piezoelectric actuators

Silicon nanodot arrays patterned using diblock copolymer templates by Gil Bum Kang; Seong-Il Kim; Young Hwan Kim; Yong Tae Kim; Jung Ho Park (pp. 524-529).
Dense and periodic arrays of holes and Si nano dots were fabricated on silicon substrate. The holes were approximately 20–40 nm wide, 40 nm deep and 40–80 nm apart. To obtain nano-size patterns, self-assembling resists were used to produce layer of hexagonally ordered parallel cylinders of polymethylmethacrylate (PMMA) in polystyrene (PS) matrix. The PMMA cylinders were degraded and removed with acetic acid rinse to produce a PS. 10 nm-thick Au thin film was deposited by using electron beam evaporator. PS template was removed by lift-off process. Arrays of Au nano dot were transferred by using fluorine-based reactive ion etching. Au nano dots were removed by sulfuric acid. Si nano dots size and height were 24–70 nm and 20–30 nm respectively. Sequential oxidation-wet etching method reduced size of Si nano dots. Reduced sized silicon nano dots diameter and height were 18 nm and 12 nm, respectively. Nanopatterned holes sizes were observed by field emission scanning electron microscope (FESEM) and atomic force microscopy.

Keywords: Diblock copolymer; Copolymer lithography; Reactive ion etching; Si nano dot; Nanotemplate

Piezoelectric actuator for mobile auto focus camera applications by Hyun-Phill Ko; Hoseop Jeong; Burhanettin Koc (pp. 530-535).
Recently, various multimedia devices such as MP3 player, camera and even TV are integrated into a mobile phone. Consumer demands image cameras in mobile phone to have similar quality and performance as those of dedicated digital cameras. For a good image quality, increasing of resolution requires optical auto focusing, where a small lens group needs to be moved in a limited volume. Due to the efforts for reducing the size of each component in mobile phone, many types of motors have been investigated to achieve AF or zooming functions. However, a motor should be able to provide high controllability and performance to perform auto-focus (AF) camera function. One of the important features that piezoelectric motors have is the ability to maintain moving element position when the motor is not electrically excited. For mobile device application where power consumption is critical, this feature is fitting very well for lens positioning application in phone cameras. In this paper, we have applied our own development of piezoelectric motor for auto focus phone cameras. During auto focusing, we have measured total motor operating time that is less than one percent of total auto focusing time. Average instantaneous power, which is about 65 mWatts, is consumed only when the motor operates, which make piezoelectric motors to be superior over electromagnetic counterparts in terms of energy efficiency.

Keywords: Piezoelectric; Actuator; Auto focusing; Camera module

Physical properties of transparent conducting indium doped zinc oxide thin films deposited by pulsed DC magnetron sputtering by Young Ran Park; Donggeun Jung; Ki-Chul Kim; Su Jeong Suh; Tae Seok Park; Young Sung Kim (pp. 536-541).
Transparent conducting In-doped (1at.%) zinc oxide (IZO) thin films are deposited on glass substrate by bipolar pulsed DC magnetron sputtering. We have investigated the effect of pulse frequency on the physical properties of the IZO films. A highly c-axis oriented IZO thin films were grown in perpendicular to the substrate. At optimal deposition conditions, IZO films with a smoothest surface roughness of ∼3.6 nm, a low-resistivity of 5.8 × 10−3 Ωcm, and a high mobility of 14 cm/Vs were achieved. The optical spectra showed a high transmittance of above 85% in the UV–visible region and exhibited the absorption edge of near 350 nm. In micro-Raman, we observed the three phonon modes of host ZnO, which are E 2 low, E 2 high, and A 1 modes, and the three additional modes. The origin of three additional modes is attributed to the host lattice defect due to the effect of In dopant and increasing the pulse frequency.

Keywords: Pulse DC magnetron sputtering; Semiconductor; In doped ZnO (IZO); Transparent conducting oxide (TCO); Raman spectra

One step synthesis and densification of nanocrystalline TaSi2–Si3N4 composite from mechanically activated powders by high-frequency induction-heated combustion by Hyun-Kuk Park; Jeong-Hwan Park; Jin-Kook Yoon; Ki-Tae Lee; In-Jin Shon (pp. 542-547).
Dense nanocrystalline 4TaSi2–Si3N4 composite was synthesized by high-frequency induction-heated combustion synthesis (HFIHCS) method within 1 min in one step from mechanically activated powders of TaN and Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of an induced current and mechanical pressure. Highly dense 4TaSi2–Si3N4 composite with relative density of up to 99% was produced under simultaneous application of a 60 MPa pressure and the induced current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated.

Keywords: High-frequency induction heated combustion; Composite materials; Sintering; Nanophase; Mechanical properties; TaSi2–Si3N4

Effect of a hydrogen ratio in electrical and optical properties of hydrogenated Al-doped ZnO films by S. J. Tark; Y.-W. Ok; M. G. Kang; H. J. Lim; W. M. Kim; D. Kim (pp. 548-553).
This study examined the effect of the hydrogen ratio on the electrical and optical properties of hydrogenated Al-doped zinc oxide (AZO) thin films deposited by rf magnetron sputtering using a ceramic target (98 wt% ZnO, 2 wt% Al2O3). Various AZO films on glass were prepared by changing the H2/(Ar + H2) ratio at room temperature. The AZO/H films showed a lower resistivity and a higher carrier concentration and mobility than the AZO films. However, the resistivity and mobility of the AZO/H films increased and decreased with increasing H2 flow ratio, respectively. As a result, the AZO/H films grown with 2% H2 addition showed excellent electrical properties with a resistivity of 4.98 × 104 Ωcm. The UV-measurements showed that the optical transmission of the AZO/H films was >85% in the visible range with a wide optical band gap. In addition, the effect of H2 flow ratio on the structure and composition of hydrogenated AZO thin films have also been studied.

Keywords: ZnO; Al doping; Hydrogenated; rf magnetron sputtering

Effects of substrate temperature on electrical and optical properties ITO films deposited by r.f. magnetron sputtering by Jae-Hyeong Lee (pp. 554-558).
Indium tin oxide (ITO) films have been prepared by r.f. magnetron sputtering using powder target. X-ray diffraction analysis indicates that the deposited films were polycrystalline and retained a cubic bixbite structure. The ITO films deposited at low substrate temperature (T s) exhibit a (411) preferred orientation but the films deposited at high T s prefer a (111) orientation. The substrate temperature was found to significantly affect the electrical properties. As the T s was increased, the conductivity of ITO films was improved due to thermally induced crystallization. The lowest resistivity (8.7 × 10−4 Ω-cm) was obtained from ITO films deposited at 450 °C. However, optical properties of the films were somewhat deteriorated. The infrared (IR) reflectance of the film increases with increasing the substrate temperature.

Keywords: ITO film; Sputtering; Powder target; Substrate temperature

Control of shrinkage on the behavior of co-firing of ferrite and varistor multi-layers composite with organic content by Ik Hyun Han; Young Hyun Lee; Seong Jae Myoung; Myoung Pyo Chun; Jeong Ho Cho; Byung Ik Kim; Duck Kyun Choi (pp. 559-563).
When make multi-layer ceramics device such as EMI filter, there are a lot of process problems. Specially, crack, camber and delamination should be controlled surely by different sinter shrinkage rate of interface of two materials. The purpose of this work was to co-fire defect-free ferrite/varistor ceramic multi-layers fabricated via a calcination temperature and organic vehicle contents of ferrite. Sintering shrinkage of both calcined ferrite and varistor materials were measured using dilatometer. X-ray diffraction analysis indicated that no significant phase change occurred in the materials under investigation as a result of the sintering process. Crack and delamination of each interface were observed by scanning electron microscopy and optical microscope. We obtained the defect-free and co-fired ferrite/varistor ceramic multi-layer by controlling calcinations temperature.

Keywords: Ferrite; Varistor; Co-firing; Multi-layer; Shrinkage

Effects of co-doped CaO/MnO on the piezoelectric/dielectric properties and phase transition of lead-Free (Bi0.5Na0.5)0.94Ba0.06TiO3 piezoelectric ceramics by Man-Soon Yoon; Young-Geun Lee; Soon-Chul Ur (pp. 564-571).
The piezoelectric properties of (1−x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramics were reported and their piezoelectric properties reach extreme values near the MPB (about x = 0.06). The X-ray analysis of (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics for all compositions exhibited a pure perovskite structure without any secondary phase. Within a certain ratio of contents, the co-doped ceramics enhanced piezoelectric coefficient (d 33 ), lowered the dielectric loss, and increased the sintered density. The temperature dependence of relative dielectric permittivity (K 33 T ) reveals that the solid solutions experience two phase transitions, ferroelectric to anti-ferroelectric and anti-ferroelectric to relaxor ferroelectric, which can be proven by P-E hysteresis loops at different temperatures. In addition, the specimen containing 0.04/0.01 wt.% CaO/MnO showed that the coercive field E c was a minimum value of 26.7 kV/cm, while the remnant polarization P r was a maximum value of 38.7 μC/cm2, corresponding to the enhancement of piezoelectric constant d33 of 179 pC/N, electromechanical coupling factor k p of 37.3%, and relative dielectric permittivity K 33 T of 1137. (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics co-doped with CaO/MnO were considered to be a new and promising candidate for lead-free piezoelectric ceramics owing to their excellent piezoelectric/dielectric properties, which are superior to an un-doped BNBT system.

Keywords: BNBT; Co-doping; CaO/MnO; Piezoelectric; Dielectric; Phase transition

Effect of CuO addition on sintering temperature and piezoelectric properties of 0.05Pb(Al0.5Nb0.5)O3−0.95Pb(Zr0.52Ti0.48)O3+0.7 wt.% Nb2O5 + 0.5 wt.% MnO2 ceramics by Ju-Young Lee; Ji-Won Choi; Min-Gyu Kang; Sang-Jong Kim; Tae-Kuk Ko; Seok-Jin Yoon (pp. 572-575).
Effect of CuO addition on piezoelectric properties of 0.05Pb(Al0.5Nb0.5)O3−0.95Pb(Zr0.52Ti0.48)O3+0.7 wt.% Nb2O5 + 0.5 wt.% MnO2 (PAN-PZT) ceramics was studied to decrease the sintering temperature below 900°C for LTCC. The PAN-PZT ceramics sintered at 1200°C had piezoelectric properties of d 33 = 340 pC/N, k p = 61.6%, Q m = 1,725, and density of 7.5 g/cm3. The addition of CuO significantly decreased the sintering temperature due to the formation of liquid phase containing a binary combination of PbO and CuO in grain boundary. Piezoelectric properties of d 33 = 361 pC/N, k p = 57%, Q m = 145, and density of 7.8 g/cm3 were achieved at sintering temperature of 900°C. The CuO doped PAN-PZT ceramics show high density and d 33 at low sintering temperature though its electromechanical quality factor abruptly decreases due to the CuO additive effect.

Keywords: 0.05Pb(Al0.5Nb0.5)O3−0.95Pb(Zr0.52Ti0.48)O3+0.7 wt.% Nb2O5 + 0.5 wt.% MnO2 ceramics; Piezoelectric properties; Low temperature sintering; CuO

Chemical development of preceramic polyvinylsilazane photoresist for ceramic patterning by Yi-He Li; Kuk-Ro Yoon; Xiao-Dong Li; Dong-Pyo Kim (pp. 576-576).
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