Journal of Materials Science: Materials in Electronics (v.23, #12)

Surface state dependence of PbS and PbSe infrared noise and detectivity by S. Kouissa; A. Djemel; M. S. Aida (2083-2088).
It is established that the surface state is one of the most important mechanisms limiting the performance of photoconductors. In a previous work, we have presented the theoretical platform of surface state model exhibiting the analysis of the space charge region at the free surface of semiconductors. To know that recombination effects directly influence the quantum efficiency of detector, the dependence of some detector parameters on surface defect densities and the comparison of this model with experimental data of responsivity are evaluated. The present papers use this model to explore the dependence of surface parameters on signal, noise and detectivity. The results of the model are compared with the experimental results for p-PbS case.

A series of surface modified titanium dioxide (TiO2)/polyarylene ether nitriles (PEN) composite films with different modified TiO2 contents were prepared by solution casting method combined with ultrasonic dispersion technology. TiO2 particles were successfully surface modified by PEN–COOH polymer previously, which was confirmed by transmission electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. Besides, SEM images of composite films revealed that the interfacial adhesion between surface modified TiO2 particles and the PEN matrix was effectively improved because of their common cyano groups and similar structure units. Furthermore, thermal, mechanical and dielectric characterizations showed that the composite films possess excellent thermal properties and flexibility as well as good dielectric properties, their glass transition temperatures were as high as 223 °C and the initial decomposition temperatures were all above 480 °C. In addition, it was found that the tensile strength of modified TiO2/PEN composites was better than raw TiO2/PEN composites. More importantly, the dielectric constant of composite films increases linearly with increment of the surface modified TiO2 particles content. When the mass fraction of modified TiO2 particles reached 40 %, the dielectric constant of the composite film increased to 7.9 (1 kHz), while the dielectric loss is just 0.028 (1 kHz).

Magnetoelectric effect of the multilayered CoFe2O4/BaTiO3 composites fabricated by tape casting by Dongxiang Zhou; Liangbin Hao; Shuping Gong; Qiuyun Fu; Fei Xue; Gang Jian (2098-2103).
This paper presents the structural, ferroelectric, ferromagnetic, resonance and magnetoelectric (ME) properties of multilayered ME composites fabricated using tape casting method. The compositions corresponding to CoFe2O4 (CFO) with particle size of ~150 nm and BaTiO3 (BTO) with particle size of ~100 nm were chosen as ferromagnetic and ferroelectric phases, respectively. Delamination was found at the interface between CFO and BTO layers, which was related to the residual stress due to the difference in thermal expansion coefficient between the two layers. The largest direct magnetoelectric and converse magnetoelectric coefficients of the multilayered ME composite were, respectively, 36 μV/cm Oe at a bias magnetic field of 2,800 Oe and 1.16 × 10−3 G/V at a frequency of 30 kHz. In addition, the corresponding interfacial coupling coefficient was calculated to be 3.2 × 10−5. For the multilayered ME composite, a resonance frequency of 4.96 MHz and a bandwidth of 40 kHz were obtained using capacitance-frequency spectrum method.

Polyaniline–CdS nanocomposites: effect of camphor sulfonic acid doping on structural, microstructural, optical and electrical properties by B. T. Raut; M. A. Chougule; A. A. Ghanwat; R. C. Pawar; C. S. Lee; V. B. Patil (2104-2109).
Nanocomposites of CdS nanocrystals with conducting polyaniline doped with camphor sulfonic acid (CSA) have been prepared by spin coating technique and investigated by X-ray diffraction, field emission scanning electron microscopy (FESEM), fourier transform infra red spectroscopy (FTIR), UV–visible spectroscopy and electrical transport method. The X-ray diffraction patterns showed broad peaks due to formation of nanoparticles of CdS in polyaniline matrix. FESEM showed that the transformation of morphology from agglomeration to nanopetals. The FTIR spectra confirmed the interaction between CSA and polyaniline (PANi)–CdS nanocomposite. The UV–visible spectrums revealed the enhancement of doping level for the PANi–CdS nanocomposites which is assigned to the existence of greater number of charges on the polymer backbone. DC electrical conductivity studies showed an increase in conductivity of PANi–CdS nanocomposites from 6.9 × 10−6 to 3.14 × 10−4 due to addition of CSA (10–50 %).

Composition, microstructure, and surface morphology of Ni–Cu alloy films electrodeposited at different deposition potentials have been investigated. The microstructural analysis carried out by using X-ray diffraction (XRD) confirmed that all Ni–Cu films are polycrystalline in nature and possess face-centered cubic structure. XRD analysis also revealed that the (111) peak of the Ni–Cu alloy films splits into two as Cu-rich and Ni-rich peaks and the peak intensities change depending on the deposition potential and hence the film composition. Compositional analysis of Ni–Cu films carried out by energy dispersive X-ray spectroscopy showed that Ni content within the films increases as the deposition potential becomes more negative. The morphological analysis performed by using a scanning electron microscopy and an atomic force microscopy revealed that the surface morphology changes significantly with applied deposition potential. Furthermore, a direct correlation is observed between the surface roughness and lattice strain.

PAN-based carbon fibers/PMMA composites: thermal, dielectric, and DC electrical properties by Z. M. Elimat; W. T. Hussain; A. M. Zihlif (2117-2122).
The study deals with thermal, dielectric, and DC electrical properties of polyacrylonitrile (PAN)-based carbon fibers/poly(methyl methacrylate) composites. The polymer composites contain 0, 5, 10, 20 and 30 wt.% PAN-based carbon fibers. The thermal conductivity was studied as a function of filler content and temperature. It was found that the thermal conductivity is enhanced by addition of carbon fibers concentration and temperature. The dielectric properties were determined using impedance measurements. The results showed that the dielectric constant and dielectric loss are decreased with frequency, and increased with both temperature and fibers content. The DC electrical conductivity, temperature coefficient of resistance, and activation energy were studied as a function of fibers concentration in the temperature ranges 30–110 °C. It was found that the composites exhibit negative temperature coefficient of resistivity and enhancement of electrical conductivity with increasing temperature and carbon fibers concentration. The observed increase in the DC conductivity was explained according to the approach of conductive paths and connections between the carbon fibers.

Mechanical characterization of glass–ceramics substrate with embedded microstructure by Eszter Horváth; Gábor Hénap; Ádám Török; Gábor Harsányi (2123-2129).
One of the biggest challenge in the microfluidic channel fabrication in glass–ceramics or so called low temperature co-fired ceramics (LTCC) is the elimination of channel deformation during lamination. In this paper the expected deformation of the substrate and the sacrificial layer (starch powder and 3D printed UV polymerized material) during the lamination process of microfluidic structure fabrication is described. The choice of sacrificial volume material (SVM) plays an important role in channel deformation. Two types of SVM were investigated considering the width of the channel and the applicability. Uniaxial compression and Jenike shear test was used to obtain the mechanical parameters of starch SVM. To determine the stress–strain characteristics of LTCC uniaxial compression experiment was conducted. The shape of the laminated LTCC containing embedded channel was modeled by finite element method using the mechanical parameters obtained by the measurements. A design rule is given considering the channel width and the choice of SVM based on the simulation results.

Microstructure and dielectric properties of glass/Al2O3 composites with various low softening point borosilicate glasses by Ming Liu; Hongqing Zhou; Haikui Zhu; Zhenxing Yue; Jianxin Zhao (2130-2139).
The effects of various low softening point borosilicate glasses on both the sintering behavior and dielectric properties of glass/Al2O3 composites were investigated by FTIR, DSC, XRD, SEM and EDS. Results show that the addition of alkali oxides and PbO can decrease the glass softening temperature. While, the addition of Al2O3 and more SiO2 content in the glass can increase the continuity of glass network and further increase the glass softening temperature of samples. Glass with lower softening temperature has more time to flow to finish the densification of samples, and that can contribute to get better sintered composites. By contrast, CaO–PbO–B2O3–SiO2–Na2O–K2O glass/Al2O3 composites sintered at 875 °C for 15 min exhibit better properties of a bulk density of 3.06 g/cm3, a porosity of 0.17 %, a λ value of 2.47 W/m K, a ε r value of 8.05 and a tan δ value of 8.8 × 10−4 at 10 MHz.

A micro initiator realized by reactive Ni/Al nanolaminates by Xiaotun Qiu; Rui Tang; Ranran Liu; Hai Huang; Shengmin Guo; Hongyu Yu (2140-2144).
This study described a micro initiator realized by reactive Ni/Al nanolaminates. A self-propagating reaction can be triggered in the Ni/Al film by applying a DC voltage of 1.5 V. This exothermic reaction can raise the temperature of the film (10 μm in thickness) surface to as high as 622 K. The measured ignition power to start the self-propagating reaction in the film was 3 mW with an ignition delay of around 0.63 s. The small ignition energy required and the large energy output make the Ni/Al film superior to the current resistive heater based initiators. Numerical simulation results demonstrated that different temperatures can be achieved by simply alternating the film thickness and the localization of high temperature exposure was realized to avoid unintentional fire of adjacent initiators. These findings were confirmed by the experiment using thermal indicators.

In the paper, the formation mechanism for pure phase BiFeO3 (BFO) in an EDTA-assisted hydrothermal process with the presence of NaNO2 was investigated in detail. The analysis revealed that the hydrothermal decomposition of Fe-EDTA complexes with the presence of NaNO2 intensely influenced both the crystal structure and morphology of BFO powders. Moreover, pure BFO particles exhibited efficient photocatalytic activity under visible-light irradiation, suggesting their promising applications as photocatalysts.

Diffusion mechanism in the gold-copper system by R. Ravi; A. Paul (2152-2156).
Interdiffusion study is conducted in the Au–Cu system, which has complete solid solution in the higher temperature range and ordered phases in the lower temperature range. First experiments are conducted at higher temperatures, where atoms can diffuse randomly. Higher values of interdiffusion coefficients are found in the range of 40–50 at.% Cu. This trend is explained with the help of thermodynamic factor and possible concentration of vacancies. Following an experiment is conducted at 623 K (350 °C), where the ordered phases are grown. The interdiffusion coefficients at this temperature are compared after extrapolating the data calculated at higher temperatures.

Multiferroic BiFe0.95Co0.05O3 thin films were fabricated on Pt/Ti/SiO2/Si substrates at various temperatures by pulsed laser deposition. It was found the deposition temperature had great effects on phase purity, orientation, microstructure and multiferroic properties of these films. The optimized deposition temperature was close to 600 °C. Polarization–electric field (P–E) and magnetization–magnetic field (M–H) hysteresis loops at room temperature were observed simultaneously in the films fabricated at 600 °C. The remnant polarization, coercive electric field (P r , E c ) and the remnant magnetization, coercive magnetic field (M r , H c ) of the films deposited at 600 °C were (0.95 μC/cm2, 31 kV/cm) and (0.59 emu/cm3, 130 Oe), respectively. These results might have implications for further investigations on high quality BiFe0.95Co0.05O3 multiferroic films.

Sintering and electrical properties of Nb5+ doped 0.63Bi(Mg1/2Ti1/2)O3–0.37PbTiO3 piezoelectric ceramics by Xun Ji; Ruzhong Zuo; Wenwu Zuo; Xiaohui Wang; Longtu Li (2162-2166).
Nb5+ doped 0.63Bi(Mg1/2Ti1/2)O3–0.37PbTiO3 (0.63BMT–0.37PT + xNb5+) ceramics have been fabricated by means of citrate sol–gel method and ordinary sintering. Effects of Nb5+ doping on the densification and various electrical properties were studied. The results indicated that the addition of a small amount of Nb5+ gradually changes the crystal structure from a typical rhombohedral-tetragonal coexisted structure to a nearly pure rhombohedral structure. A slight amount of secondary phases start to appear as the doping content of Nb5+ is more than 1.5 mol%, indicating that the solubility limit of Nb5+ in the matrix composition is reached. Moreover, electrical properties of the sintered ceramics were obviously changed based on the effect of densification and ionic substitution. 0.63BMT–0.37PT + 0.005Nb5+ ceramics sintered at 1,020 °C exhibit optimum properties of piezoelectric constant d33 ~ 245 pC/N, planar electromechanical coupling factor kp ~ 30 %, $$ varepsilon_{33}^{ ext{T}} /varepsilon_{ ext{o}} $$  ~ 1,220, and Tc ~ 460 °C.

Ho2O3 (0–0.7 wt%)-doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 (BNKT18) lead-free piezoelectric ceramics were synthesized by a conventional solid-state reaction method. The effects of Ho2O3 on the microstructure and electrical properties were investigated. X-ray diffraction data shows that Ho2O3 in an amount of 0.1–0.7 wt% can diffuse into the lattice of the BNKT18 ceramics and form the pure perovskite phase. Scanning electron microscope (SEM) images indicate that the grain sizes of BNKT18 ceramics decrease with the increase of Ho2O3 content; in addition, the modified ceramics have the clear grain boundary and a uniformly distributed grain size. At room temperature, the electrical properties of the BNKT18 ceramics have been improved with the addition of Ho2O3, and the BNKT18 ceramics doped with 0.3wt.% Ho2O3 have the highest piezoelectric constant (d 33 = 137 pC/N), the highest remnant polarization (P r = 26.9 μC/cm2), the higher relative dielectric constant (ε r = 980) and lower dissipation factor (tanδ = 0.046) at a frequency of 10 kHz. The BNKT18 ceramics doped with 0.1 wt% Ho2O3 have the highest planar coupling factor (k p = 0.2426).

In this study, n-type porous silicon (PS) layers are formed in the dark with the assistance of a low mechanical pressure during electrochemical etching process. Pressure-induced stress/strain modifies the resistivity of the silicon substrate to enhance the etching process. Under the same equivalent etching condition, pressure-assisted etching can yield PS layer with stronger room temperature photoluminescence intensity than the layer formed by ordinary electrochemical etching. The porosity of pressure-assisted etched PS layers is found to be much higher than that of ordinary etched layer. Fourier transformation infrared absorption spectroscopy and grazing incidence X-ray diffraction measurements and analysis show that application of the pressure during electrochemical etching promotes the degree of oxidation and reduces the crystallites size of the PS layer. The effect of the pressure during etching process on the surface topography of PS is revealed by scanning electron microscopy imaging.

AlN-W composite ceramics were prepared by spark plasma sintering using AlN powder and tungsten powder. Effect of size and content of tungsten particles on the densification, electrical and dielectric properties of AlN ceramic was studied. The result indicates that AlN ceramic with fine tungsten powder is easy to obtain higher densification. The dielectric constant and loss of the composites obviously increased with the increase of content and size of tungsten below the percolation threshold. When R c (the mean size of AlN powder) equals approximately R i (the mean size of tungsten powder), the composites obtain the highest percolation threshold (22vol. %), dielectric constant ε r and tgδ are 110.90 and 0.02, respectively.

In this paper, it is demonstrated that Sn and Au–Sn alloys can be electrodeposited from a single non-cyanide electrolyte. This electrolyte consists of KAuCl4 · xH2O, SnCl2 · 2H2O, sodium sulfite (Na2SO3), tri-ammonium citrate and Triton X-100. The Sn is electrodeposited at a current density of 4 mA/cm2 or higher, while the Au-rich intermetallic (Au5Sn) is electrodeposited at lower current densities (0.8–1.5 mA/cm2). Microstructural analysis shows that the deposits are uniform and smooth. If the deposits are plated at current densities from 2 to 4 mA/cm2, which corresponds to a composition range of 30–80 at% Sn, multiple phases co-exist in the deposits.

In this work are reported properties of polyaniline processed from trifluoroacetic acid. Films obtained by simple drop casting were smooth and defectless. Features like absorption in range of UV–vis-NIR, mid-IR and electrical conductivity are discussed. The highest electrical conductivity of such films was found equal to 65 S/cm. It was observed a striking feature—successive colour transition from cyan to deep green when the solvent was dried out from the cast film.

The effects of the Nb-dopant content and the sintering conditions on the electrical properties and the positive temperature coefficient of resistance (PTCR) effect of Ba1.005(Ti1−xNbx)O3 (BTN) ceramics were investigated, which were sintered at 1,070–1,220 °C for 0.5–6 h in a reducing atmosphere and then re-oxidized at 600–750 °C for 1 h. The results indicated that both the sintering temperature and sintering time affected the electrical properties and the PTCR effect of the multilayer BTN samples, whose room-temperature (RT) resistance first reduced and then increased as a function of the donor–doped concentration at all sintering temperature; moreover, the higher the sintering temperature was, the lower the critical dopant concentration. The BTN ceramics showed a remarkable PTCR effect, with a resistance jump greater by 3.3 orders of magnitude, along with a low RT resistance of 0.3 Ω at a low reoxidated temperature of 600 °C after sintering in a reducing atmosphere.

Microwave-assisted synthesis and thermoelelectric properties of CoSb3 compounds by Yunguang Zhu; Honglie Shen; Hao Guan (2210-2215).
Using CoCl2 and SbCl3 as precursors and NaBH4 as reducing agent, we obtained nano CoSb3 particles of about 10 nm with the assistance of microwave radiation. Different Sb/Co ratio and different microwave radiation time were used to prepare CoSb3. The results show that single CoSb3 phase was synthesized successfully under the condition of Sb/Co ratio with 5:1 and microwave radiation time with 5 min. The samples with microstructure and nanostructure were synthesized respectively by cold isostatic pressing and sintering method, and their thermoelectric properties were studied. Due to its powder preparation method and its small grain size, the sample with nanostructure has lower electrical resistivity and thermal conductivity than the sample with microstructure. The maximum ZT value was found to be 0.11 at 650 K in the sample with nanostructure, which is about 10 times higher than that of the sample with microstructure.

Residual stress of AlN films RF sputter deposited on Si(111) substrate by Hui Zhong; Zhanfei Xiao; Xiangquan Jiao; Jie Yang; Hualei Wang; Rui Zhang; Yu Shi (2216-2220).
AlN films with (002) crystal orientation are widely used in various resonator-based applications. Low intrinsic stress is one of the important requirements for the thin film stacks employed in electroacoustic devices. In this paper, AlN films were deposited by reactive radio frequency (RF) sputtering with various conditions. The effects of N2 concentrations, sputtering pressure, substrate temperature, and RF power on the microstructure and stress of AlN films were investigated. The X-ray diffraction, atomic force microscopy, and field emission scanning electron microscopy were utilized to investigate the orientation and surface morphology of AlN films. A systematic study of the stress of AlN was done as a function of the deposition parameters. As the nitrogen concentration decreased, the sputtering pressure increased. The residual stress has a change tendency from compressive to tensile. The substrate temperature and RF power affect stress slightly. The N2 concentrations is the major fact that influences on stress of sputtering AlN films.

Observation of the solidification microstructure of Sn3.5Ag droplets prepared by CDCA technique by Jin Zhao; Yulai Gao; Weipeng Zhang; Tingting Song; Qijie Zhai (2221-2228).
The Sn3.5Ag droplets in various sizes have been prepared by the consumable-electrode direct current arc technique. The cooling rates of the droplets have been evaluated based on Newton’s cooling law and it shows that the cooling rates of the droplets increase dramatically from 6.84 × 102 to 2.52 × 105 K/s as the droplet size decreases from 830 to 43 μm. The range of cooling rate is close to that of laser soldering (up to 104 K/s). It has been found that the β-Sn dendrites are refined as the cooling rate increase, and when the cooling rate is 1.30 × 105 K/s, which corresponding to the size scale smaller than 60 μm, the dendrites nearly disappear in the droplets. In addition, it has been observed that the high cooling rate could successfully avoid the precipitation of plate-like Ag3Sn and promote the formation of nanoparticles which are desirable in practical application. These nanoparticles uniformly distribute in the Sn matrix and the average size of nanoparticles in different droplets is 46.4 nm (in 380–830 μm droplets), 57.2 nm (in 150–250 μm droplets), 60.6 nm (in 96–150 μm droplets), 63.2 nm (in 43–60 μm droplets) and 65.3 nm (in droplets of <43 μm), respectively. According to the dispersion-strengthening effect, the existence of nanoparticles would be beneficial to improve the mechanical property of the Sn3.5Ag solder alloy.

Thermoelectric properties of Ti-doped WO3 ceramics by Haiqing Wang; Yingjie Gan; Xiang Dong; Shujie Peng; Liang Dong; Yu Wang (2229-2234).
The influences of titanium dioxide (TiO2) on thermoelectric properties of tungsten trioxide (WO3) ceramics were investigated. In the sintered samples, the grain size of the ceramics was evidently reduced while the dense of the ceramics was improved due to the addition of TiO2. Doping WO3 with TiO2 obviously raised the electrical conductivity (σ) of the ceramics by about two orders of magnitude. The absolute value of Seebeck coefficient (|S|) of the doped samples was enhanced because of the small grain size. Thus, the magnitude of the power factor (σS 2) was uplifted strongly by adding TiO2. In addition, there existed an optimum doping concentration of TiO2 in WO3 to obtain a better power factor.

A study of chemical reactions of silver and indium at 180 °C by Yuan-Yun Wu; Wen P. Lin; Chin C. Lee (2235-2244).
The silver-indium system has become important in electronic packaging applications. The In-3.5 % Ag eutectic alloy has been used for laser diode attachment since 1980. The Ag-rich alloys were less studied but have received significant attention recently for producing high temperature joints at low bonding temperature. In multilayer Ag-rich bonding structure design, typical bonding temperature is 180 °C and the process can be made entirely fluxless. The melting temperature of joints fabricated is higher than 695 °C. Despite success in several bonding processes, the chemical reactions of Ag and In at 180 °C were little known. In this study, we performed systematic experiments to investigate these reactions. In experimental design, copper (Cu) substrates were electroplated with 40 μm Ag layer, followed by indium layers of 1, 3, 5, 10, and 15 μm, respectively. Thick Ag layer was chosen to prevent In from reacting with the Cu substrate. The samples were annealed at 180 °C in 0.1 torr vacuum for 5 min to emulate the bonding conditions. The microstructure and composition on the surface of the samples were evaluated using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) as well as X-ray diffraction. They were then cut in cross section, polished, and examined by SEM/EDX. The results show that, for samples with 1 μm thick In, the In layer converts to Ag2In entirely after annealing. For samples with In thickness of 3 and 5 μm, AgIn2, Ag2In, and solid solution (Ag) all form after annealing. No indium was identified. For samples having 10 and 15 μm thick In, In covers almost over the entire sample surface after annealing. The effect of annealing Ag layer was investigated. After Ag plating, samples were annealed at 450 °C for 3 h to grow Ag grains. This was followed by plating 10 μm In and annealing at 180 °C. The result shows that, by annealing Ag before plating In, more In is kept in the structure during annealing at 180 °C. In theory, this effect is caused by larger Ag grains and thus fewer grain boundaries resulting from annealing the Ag layer. Other than scientific values, the results of this investigation are useful in designing better bonding structures.

The potential dependence of Co–Cu alloy thin films electrodeposited on n-Si(100) substrate by M. R. Khelladi; L. Mentar; A. Azizi; L. Makhloufi; G. Schmerber; A. Dinia (2245-2250).
The aim of this work is to study the effect of the deposition potential on the properties of Co–Cu alloy thin films on n-type Si substrate. Voltammetric measurements showed that the potential dissolution of Co and consequently the composition of the films depend greatly on the applied potentials. The compositional measurement, which was made using an atomic absorption spectroscopy (AAS), demonstrated that the Co content of the films considerably increases as the applied potentials tend toward negative values. SEM micrographs revealed a transition of branched dendritic structures to well covered, agglomerated and compact alloy morphology with increased Co concentrations in the deposits. X-ray diffraction analysis showed that the films crystallize in varieties of phases; a mixture of Co fcc and hcp, and Cu fcc structures, greatly related to applied potential. The increase of the applied potential induces a decrease in the grain size and the lattice constant. The magnetization of the alloys was found to be enhanced for high Co concentrations and consequently at high deposition potential.

In this study, the Ca3−xSbxCo4O9 (x = 0.0, 0.5, 0.75 and 1.0) system was fabricated using solid-state reaction technique. From the XRD analysis, it was found that increase of the Sb concentration in the system caused formation of impurity phases and therefore a distortion in the main lattice. The SEM-EDX results showed that the grain size reduced with increasing Sb in the Ca3Co4O9 system. The resistivity, ρ, value increased with increasing the Sb-content and insulating behavior was obtained as the temperature was decreased. The samples fabricated have positive thermoelectric power, S, value, suggesting that holes are dominant charge carriers in the samples. S value decreased with decreasing the temperature. The Fermi energy, E F , and the carrier concentration, n, decreased by the Sb-substitution. The Sb-substitution caused a decrease of thermal conductivity, κ which is due to reduction of the phonon thermal conductivity, κ ph, in the system. Figure of merit, ZT, value decreased significantly due to strongly increase in ρ. The impurities, defects and distortion with substitution of Sb are responsible for large variation on electrical and thermal transport properties.

La(OH)3 nanorods of length varying between 30 and 50 nm with aspect ratio of 2–5 were synthesized in aqueous solution using hydrazine hydrate in presence of mixture of cationic N-cetyl-N,N,N,trimethylammonium bromide (CTAB) and tetra-n-butylammonium bromide (TBAB) surfactants. The resultant product was characterized for its morphology and structure using XRD, TEM and FT-IR. Thermal stability studied using TGA indicated good stability. Surfactants in reaction mixture reduces the surface tension of the solution which lowers the energy needed to form a new phase, resulting in the formation of La(OH)3 crystals of anisotropic shape with low aspect ratio. The A.C. conductivity was found to be of the order of nano-seimen (ns), which non-linearly increases with the increase in frequency (102–106 Hz) The capacitance behaviour was observed in pF in mid frequency region, which can be useful as low loss dielectric material. Nano rods may work as standard materials to monitor conductivity levels in biofluid proteins.

UV irradiated wet chemical deposition and characterization of nanostructured tin sulfide thin films by A. J. Ragina; K. V. Murali; K. C. Preetha; K. Deepa; T. L. Remadevi (2264-2271).
Tin sulfide (Sn2S3) films were synthesized both by chemical bath deposition method without (CBD) and with simultaneous irradiation of UV light (UV–CBD). The influence of UV illumination on the synthesis of Sn2S3 thin films were investigated through the structural, compositional, morphological, optical and electrical studies. CBD films were Sn2S3 having orthorhombic structure with some impurities while that of UV–CBD films exhibit excellent crystallinity of pure single phase Sn2S3 having the same structure. Morphology of CBD films was spherical grains of different sizes while that of UV–CBD films was uniformly distributed thin long nanoworms. Optical properties of the films were different and the optical band gap for CBD and UV–CBD films was 1.20 and 1.57 eV respectively. Refractive index of the films lies in 1.84–2.02 in the 700–1,500 nm wavelength range. Electrical resistivity of the CBD and UV–CBD films was 104 and 103 Ωcm for respectively. UV irradiation during the synthesis of tin sulfide films had highly enhanced the properties demanded by various optoelectronic applications. UV–CBD is a novel, simple and cost effective approach, having the potential to stimulate new research in the study of tin sulfide thin films and other metal chalcogenides.

Charge dynamic in disordered organic semiconductors is often described in terms of transport sites and trap states. The process can be refined to include site energy distribution and hopping energetic. In turn, these will affect transport properties such as the carrier mobility and the thermal conductivity. As is well known, ZT in thermoelectric also depends on these parameters. This work attempts to analyze the relationship between site energy distribution and hopping mobility in oxidized Poly(3,4-ethylenedioxythiophene-tosylate) (PEDOT.Tos) (an organic thermoelectric known to have both high carrier density and low thermal conductivity). To understand the charge transport in oxidized PEDOT.Tos, we examined the thermoelectric data reported in the literature and used them to evaluate site parameters such as the escape frequency, the localization length and the width of the DOS (density of states). These results were used to compute the carrier mobility using the gaussian disorder model and the correlated disorder model We then used the computed parameters to assess the optimal value of ZT in PEDOT.Tos. Our simulations suggested that major improvement in ZT is achieved by increasing the localization length and to a lesser extent by reducing the bandwidth of the DOS. For the somewhat narrow bandwidth found in PEDOT.Tos (

Bismuth ferrite BiFeO3 (BFO) powders with various morphologies were successfully prepared via a sol–gel–hydrothermal synthesis process. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Microspheres and microcubes were obtained as Bi–Fe–glycerol sol was used as precursor, and submicrometer-sized particles could be prepared by using Bi–Fe–glycerol gel. Possible formation mechanism of BFO microcrystals was proposed in this work. Moreover, the results of UV–vis diffuse reflectance spectroscopy reveal that BFO powders can be used as an effective photocatalyst under visible light in addition to its ferroelectric and magnetic applications.

Electrical characterization of a pre-ceramic polymer modified Ag/poly(hydridocarbyne)/p-Si Schottky barrier diode by Necati Başman; Orhan Uzun; Songül Fiat; Cemil Alkan; Güven Çankaya (2282-2288).
In this study, poly(hydridocarbyne) (PHC), a pre-ceramic polymer that can be converted to ceramic upon heating, was used to fabricate Ag/PHC/p-Si metal-interlayer-semiconductor (MIS) diode. The diode obtained by easy processing steps presented a good rectifying behavior and a sufficient reverse bias saturation. By using the forward bias IV characteristics, the ideality factor (n) and barrier height (Φ b ) of Ag/PHC/p-Si MIS structure were found as 1.93 and 0.94 eV, respectively. The non-ideal IV behavior with the value of ideality factor greater than unity was attributed to series resistance. The Φ b value of 0.94 eV obtained for Ag/PHC/p-Si MIS diode was larger than value of 0.84 of conventional Ag/p-Si Schottky diode. This was ascribed to PHC interlayer influencing the space-charge region of Si. The interface state density of MIS diode was determined, and it was found that the interface state density of Ag/p-Si junction significantly changed by PHC organic layer inserted into metal and semiconductor. Furthermore, Cheung’s and Norde’s functions were used to extract barrier height and series resistance values, and the obtained results were compared.

Zn doped BaMn2Sb2 single crystals were synthesized by a Sn-flux method using nominal compositions of BaMn2−xZnxSb2 (x = 0.0, 0.3, 0.5, 0.7, and 1.0). The products were characterized by powder X-ray diffraction and scanning electron microscopy equipped with electron energy dispersive spectroscopy, respectively. A pure phase of BaMn2Sb2 for x = 0, a mixture of Zn doped BaMn2Sb2 and Sn for x = 0.3–0.7, and a mixture of Zn doped BaMn2Sb2, Sn and ZnSb for x = 1 were obtained. The electrical conductivity and Seebeck coefficient of the crystals from room temperature to 773 K were measured. The electrical conductivity of all the crystals increased with increasing temperature, while the Seebeck coefficient decreased with increasing temperature and approached negative values at high temperatures. The Zn doped BaMn2Sb2 crystals showed significantly higher Seebeck coefficient at low temperatures (T < 550 K) and lower electrical conductivity at higher temperatures (T > 550 K) than the BaMn2Sb2 single crystal.

Transparent amorphous La- and Sm-codoped organo-silicate hybrid material has been synthesized, in the form of bulk samples, via an alkoxide sol–gel route. Thermal behavior of the synthesized glass was investigated using differential thermal analysis (DTA) coupled with thermogravimetry (TGA). From the DTA–TGA analyses, it can be concluded that the organic component constitutes ≈8 weight percentage (wt%) of the as prepared La–Sm-codoped hybrid organo-silica glass; and this glass contains about 29.3 wt% structural water in the form of hydroxyl groups. Fourier transform infrared (FTIR) and ultraviolet–visible-near infrared (UV–Vis-NIR) spectroscopic analyses were used for structural characterization of the prepared hybrid sol–gel glass. FTIR spectroscopy reveals functional groups, specifically –CH2, C–O–C, Si–O–C and Si–O–Si bonds, which indicate the formation of covalent bonds between the organic and inorganic components in the produced polyethylene glycol (PEG)-silica hybrid network. UV–Vis-NIR spectrum exhibits well defined absorption bands of Sm3+ ions due to 4f–4f transitions. The evolution of Sm3+ photoluminescence in the La–Sm-codoped hybrid organo-silica glass was investigated at room temperature. A strong reddish-orange emission, attributed to the 4G5/2 → 6H7/2 electronic transition in 4f5 configuration of Sm3+ ions, was observed. Semiconducting characteristics have been also reported and interpreted.

Interfacial polarization arising from two contributions in glass added barium titanate ceramics by Yong Zhang; Xiangrong R. Wang; Xiaozhen Z. Song; Tao Ma; Qian Zhang (2301-2305).
The glass added barium titanate ceramics were prepared and their dielectric properties have been investigated as a function of temperature, frequency, bias voltage, and specimen thickness. The XRD result indicated that the specimen exhibits a single perovskite structure without any detectable secondary phases. And microstructural observation showed that the average grain size was about 1 μm and there was no apparent abnormal grain growth. In addition, the dielectric temperature curve revealed an extremely high dielectric peak with strong frequency dispersion. The bias voltage dependence of the impedance and modulus spectra demonstrated that this increase in dielectric permittivity in the ferroelectric regime was related to the interfacial polarization at both the electrode/ceramic and the grain/glass interfaces. Moreover, the remarkable thickness dependence of dielectric response demonstrated the existence of the interfacial polarization at the electrode/ceramic interfaces. The two deduced contributions to the interfacial polarization were qualitatively discussed to complement the proposed formation mechanism.

Diffusion and growth mechanism of phases in the Pd-Sn system by Raju Ravi; Aloke Paul (2306-2310).
Growth mechanism of phases and atomic mechanism of diffusion are discussed in the Pd-Sn system. The Kirkendall marker plane location indicates that the PdSn4 phase grows because of diffusion of Sn. Atomic arrangement in the crystal indicates that Sn can diffuse through its own sublattice but Pd cannot diffuse unless antisites are present. The negligible diffusion of Pd indicates the absence of Pd antisites. The activation energy value indicates that the contribution from grain boundary diffusion cannot be neglected although experiments were conducted in the homologous temperature range of 0.7–0.79.