Thin Solid Films (v.518, #19)
Characterization of Cl-doped n-type Cu2O prepared by electrodeposition
by Xiaofei Han; Kunhee Han; Meng Tao (pp. 5363-5367).
N-type doping of cuprous oxide (Cu2O) films by chlorine (Cl) during electrodeposition was reported by the authors recently. A more detailed study on the effects of doping conditions on electrical properties of Cl-doped Cu2O is presented in this paper. The resistivity of Cl-doped Cu2O is affected by doping conditions, including Cu and Cl concentrations, different Cu and Cl precursors, complexing agent concentration, solution pH, and deposition temperature. It is believed that these conditions control the amount of Cl incorporated into the Cu2O films, thus the doping level. The lowest resistivity obtained so far is 7Ω-cm, suitable for solar cell applications. Photocurrent-potential measurements verify the n-type conductivity of Cl-doped Cu2O. Scanning electron microscopy indicates a small grain size of around 100nm in Cl-doped Cu2O. X-ray diffraction confirms Cu2O as the only detectable phase in the film.
Keywords: Doping; Copper oxide; Electrodeposition; N-type; Chlorine
Heteroepitaxial silicon film growth at 600°C from an Al–Si eutectic melt
by P. Chaudhari; Heejae Shim; Brent A. Wacaser; Mark C. Reuter; Conal Murray; Kathleen B. Reuter; Jean Jordan-Sweet; Frances M. Ross; Supratik Guha (pp. 5368-5371).
A method for growing heteroepitaxial Si films on sapphire was developed using a 6nm thin Al layer at substrate temperature of 600°C. Subsequently, the growth of Si nanowires was demonstrated on these films at 490°C without breaking vacuum. We characterized the properties of the Si films by Raman scattering, X-ray diffraction and transmission electron microscopy and show that the crystal quality and dopant control are promising for photovoltaic applications.
Keywords: Silicon; Nanowires
Synthesis and characterization of hard ternary AlMgB composite films prepared by sputter deposition
by Ce Yan; Z.F. Zhou; Y.M. Chong; C.P. Liu; Z.T. Liu; K.Y. Li; I. Bello; O. Kutsay; J.A. Zapien; W.J. Zhang (pp. 5372-5377).
Hard and superlight thin films laminated with boron carbide have been proposed as candidates for strategic use such as armor materials in military and space applications. Aluminum magnesium boride (AlMgB) films are excellent candidates for these purposes. We prepared AlMgB films by sputter deposition using multiple unbalanced planar magnetrons equipped with two boron and one AlMg targets. The film morphology changed and the film's root mean square (rms) roughness varied from 1.0 to 18nm as the power density of the AlMg target increased from 0.2 to 1.0W/cm2 while the power density of each boron target was maintained at 2W/cm2. Chemical analyses show dominating Al, Mg, B and trace elements of oxygen, carbon and argon. The film composition also varies with altering the power density supplied to the AlMg target. The film with an atomic ratio of Al:Mg:B=1.38:0.64:1 exhibits the highest hardness (~30GPa). This value surpasses the hardness of hydrogenated diamond-like carbon films (24–28GPa) prepared by plasma enhanced chemical vapor deposition.
Keywords: Thin films; Hard coatings; Magnetron sputtering; Spectroscopy; Structural properties; Mechanical properties
Raman study of stress effect on Ge nanocrystals embedded in Al2O3
by S.R.C. Pinto; A.G. Rolo; A. Chahboun; R.J. Kashtiban; U. Bangert; M.J.M. Gomes (pp. 5378-5381).
Ge nanocrystals (NCs) embedded in Al2O3 were grown by RF-sputtering. X-ray diffraction, high resolution transmission electron microscopy, and Raman spectroscopy techniques were used to characterize the stresses on the NCs. While small NCs (<10nm) have been observed to be spherical and fully relaxed in the matrix, the larger ones (>17nm) demonstrated a compressive stress effect. This could be linked to the crystal structure of the adjacent Al2O3 matrix.
Keywords: Germanium; Aluminium oxide; Nanocrystals; Stress; Raman spectroscopy; Transmission electron microscopy
Embedding of reduced pressure-chemical vapor deposition grown Ge nanocrystals in a high quality SiO2 matrix for non-volatile memory applications
by L. Masarotto; K. Yckache; A. Fanton; F. Aussenac; F. Fillot (pp. 5382-5386).
We have obtained thanks to reduced pressure-chemical vapor deposition germanium nanocrystals in a high quality SiO2 matrix. A perfect control of (i) the tunnel and control oxide layer thicknesses and (ii) the germanium nanocrystals' density and diameter has been achieved. Scanning electron microscopy was used to (i) determine the nucleation and growth rate of the germanium nanocrystals and (ii) evaluate their morphological stability during their embedding. We have also studied the influence of thin selectively grown Si films in order to passivate the surface of the germanium nanocrystals. X-ray photoelectron spectroscopy has shown that the germanium nanocrystals' surface properties are better with a Si capping. The polycrystalline state of the nanocrystals has been evaluated with X-ray diffraction. Transmission electron microscopy image reveals the lack of germanium diffusion and precipitation in the SiO2 matrix.
Keywords: Germanium; Nanocrystals; Reduced pressure-chemical vapor deposition; Scanning electron microscopy; X-ray diffraction; Scanning transmission electron microscopy; X-ray photoelectron spectroscopy; Non Volatile Memory
Multiple dip deposition of CdS films prepared by oscillating chemical bath
by C.D. Gutiérrez-Lazos; E. Rosendo; A.I. Oliva; M. Ortega; Bartolo-Perez P. Bartolo-Pérez; Juarez H. Juárez; Diaz T. Díaz; Garcia G. García; Rubin M. Rubín (pp. 5387-5390).
Highly oriented CdS thin films with thicknesses greater than 1μm were deposited using the oscillating chemical bath deposition technique with multiple dips at 75°C, and from 15 to 75min as deposition times. Samples with different thicknesses were deposited by repeating the chemical deposition process one, two and three times. All CdS films present the α-greenockite hexagonal structure with (002) as the preferential orientation. Band-gap energy values ranged from 2.35 to 2.42eV, being the smaller value for the two dip processes. Energy dispersion spectroscopy measurements show good stoichiometry of the CdS films with 4.3at.% as the maximum Cd variation.
Keywords: Cadmium sulfide; Thin films; Chemical bath deposition; X-ray diffraction
Localized high-rate deposition of zinc oxide films at atmospheric pressure using inductively coupled microplasma
by Sven Stauss; Yasuo Imanishi; Hiroyuki Miyazoe; Kazuo Terashima (pp. 5391-5395).
Linear transparent zinc oxide films were fabricated using an inductively coupled microplasma jet generated in argon under atmospheric conditions. The films were formed by the sputtering and melting of a zinc filament placed inside the plasma. Film growth rates varied between 10 to 30nm/s for input powers between 20 and 30W. Film roughness below 20nm and optical transmittances up to 90% in the visible were obtained while the sheet resistances ranged between 2×104 and 1×105Ω/□. The presented technique may allow high-rate, localized, fabrication of functional ZnO films for optoelectronic applications.
Keywords: Zinc oxide; Plasma processing and deposition; Sputtering
Growth and characteristics of ZnO films on growth side of freestanding diamond substrate dependent on buffer layer thickness
by Shiyong Gao; Hongdong Li; Junwei Liu; Yingai Li; Lu Xianyi Lü; Xuxin Yang; Shiyuan Ren; Guangtian Zou (pp. 5396-5399).
We report the growth and properties of highly c-axis oriented ZnO films, by radio-frequency magnetron sputtering, on the growth side of freestanding chemical vapor deposited diamond film-substrate. Low-temperature ZnO buffer layer is required for the formation of continuous ZnO films. The morphology, structure, and optical properties of the ZnO films deposited are strongly dependent on the thickness of the buffer layer. The optimized thickness of ZnO buffer layer is about 10nm to realize high-quality ZnO films having small compressive stress and high intensity ultraviolet emission. The ZnO/diamond (growth side) system is available for the applications in numerous fields, especially for high performance surface acoustic wave devices.
Keywords: Zinc oxide thin films; Diamond; Buffer layer; Magnetron sputtering; X-ray diffraction; Photoluminescence
Atomic layer deposition of ZnS via in situ production of H2S
by J.R. Bakke; J.S. King; H.J. Jung; R. Sinclair; S.F. Bent (pp. 5400-5408).
Atomic layer deposition (ALD) of ZnS films utilizing diethylzinc and in situ generated H2S was performed over a temperature range of 60°C–400°C. This method for generating H2S in situ was developed to eliminate the need to store high pressure H2S gas. The H2S precursor was generated by heating thioacetamide to 150°C in an inert atmosphere, producing acetonitrile and H2S as confirmed with mass spectroscopy. ALD behavior was confirmed by investigation of growth behavior and saturation curves. The properties of the films were studied with X-ray diffraction, transmission electron microscopy, ellipsometry, atomic force microscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy. The results show a growth rate that monotonically decreases with temperature, and films that are stoichiometric in Zn and S. The root mean square roughness of the films increases with temperature above 100°C. A change in crystal phase begins at ∼300°C. The band gap is dependent on the crystal phase and is estimated to be 3.6–4eV.
Keywords: Zinc sulfide; Atomic layer deposition; Hydrogen sulfide; Band gap; Stacking fault; Zincblende; Wurtzite; Transmission electron microscopy
Influence of the plasma expansion dynamics on the structural properties of pulsed laser ablation deposited tin oxide thin films
by S. Trusso; B. Fazio; E. Fazio; F. Neri; F. Barreca (pp. 5409-5415).
Tin oxide thin films were deposited by pulsed laser ablation at different oxygen partial pressures and substrate temperatures. Information on the structural and morphological properties of the deposited thin films has been obtained by means of X-ray photoelectron, Fourier transform infrared absorption spectroscopies and scanning electron microscopy. The expansion of the laser generated plasma has been studied by means of time resolved fast photography. Different expansion regimes were observed: in vacuum the plasma follows a free expansion one while the raise of the background oxygen pressure leads to the development of a shock wave. It was found that only at 13.3Pa of oxygen gas, in the presence of a shock wave, the deposition of stoichiometric films, at relatively low substrates temperature, is attainable. The correlation between the observed dynamics of the plasma expansion and the structural properties of the deposited films is presented and discussed.
Keywords: Tin oxide; Pulsed laser ablation; Plasma expansion
Preparation and characterization of transparent semiconductor RuO2–SiO2 films synthesized by sol–gel route
by Jiann-Shing Jeng; Yun-Ting Lin; J.S. Chen (pp. 5416-5420).
RuO2–SiO2 thin films with different Si/Ru molar ratios were prepared by the sol–gel method, using the hydrate ruthenium (III) chloride (RuCl3·3.5H2O) and tetraethylorthosilicate as precursors. The crystal structure, resistivity, chemical bonding configuration, transmittance, carrier concentration, and mobility of the RuO2–SiO2 films were investigated before and after annealing in N2 ambient at 400–700°C. The resistivity of the RuO2–SiO2 films with different Si/Ru molar ratios decreased abruptly after annealing at 400–700°C. On the other hand, RuO2 phase precipitated in the RuO2–SiO2 films with different Si/Ru molar ratios after annealing. Fourier transform infrared spectroscopy spectra indicated that the water absorption occurs for as-deposited RuO2–SiO2 films with different Si/Ru molar ratios. The transmittance of all RuO2–SiO2 films presented transmittance maximums after annealing at 700°C. The carrier concentration and mobility of RuO2–SiO2 films are related to the Si/Ru molar ratios and the annealing temperature. This study discusses the connection among the material properties of the RuO2–SiO2 films and how they are influenced by the Si/Ru molar ratios and the annealing temperatures of RuO2–SiO2 films.
Keywords: Sol–gel; RuO; 2; –SiO; 2; Precipitation; Mobility; Transparent semiconductors
Enhanced conductivity in iodine doped polyaniline thin film formed by thermal evaporation
by S. Adhikari; P. Banerji (pp. 5421-5425).
Thermal evaporation technique was employed to deposit pristine and iodine doped polyaniline (PANI) thin films on glass substrates. PANI was synthesized by the chemical oxidation method. Iodine doping was carried out by evaporation. The polymer synthesized was characterized by Thermo Gravimetric Analysis (TGA), Fourier Transform Infra Red (FTIR) and Ultraviolet–Visible (UV–VIS) spectroscopy. The evaporation temperature was optimized from TGA measurements. The thin film was deposited in vacuum at 1.33×10−4Pa by thermal evaporation of PANI. The polymer film was characterized by FTIR and UV–VIS spectroscopy. The surface morphology of the films was studied by field emission scanning electron microscopy. The resistivity was measured by van der Pauw technique. The conductivity of the doped films was seen to increase with the iodine concentration and many fold increase in conductivity was observed in comparison to the pristine films. The increase in conductivity is due to the generation of polaron band in the band gap upon iodine doping.
Keywords: Polyaniline; Thin films; Thermal evaporation; Iodine; Doping; Conductivity
Conformal ZnO nanocomposite coatings on micro-patterned surfaces for superhydrophobicity
by Adam Steele; Ilker Bayer; Stephen Moran; Andrew Cannon; William P. King; Eric Loth (pp. 5426-5431).
A conformal coating process is presented to transform surfaces with inherent micro-morphology into superhydrophobic surfaces with hierarchical surface structure using wet chemical spray casting. Nanocomposite coatings composed of zinc oxide nanoparticles and organosilane quaternary nitrogen compound are dispersed in solution for application. The coating is applied to a micro-patterned polydimethylsiloxane substrate with a regular array of cylindrical microposts as well as a surface with random micro-structure for the purpose of demonstrating improved non-wettability and a superhydrophobic state for water droplets. Coating surface morphology is investigated with an environmental scanning electron microscope and surface wettability performance is characterized by static and dynamic contact angle measurements.
Keywords: Superhydrophobicity; Wettability; Nanocomposite; Zinc oxide; Polydimethylsiloxane; Spray deposition; Micro-molding
Design of magnetic akaganeite-cyanobacteria hybrid biofilms
by Si Amar Dahoumane; Chakib Djediat; Yepremian Claude Yéprémian; Coute Alain Couté; Fievet Fernand Fiévet; Roberta Brayner (pp. 5432-5436).
Common Anabaena cyanobacteria are shown to form intra-cellularly akaganeite β-FeOOH nanorods of well-controlled size and unusual morphology at room temperature. High-resolution transmission electron microscopy showed that these nanorods present a complex arrangement of pores forming a spongelike structure. These hybrid akaganeite-cyanobacteria were used to form “one-pot” hybrid biofilms. The hybrid biofilm presents higher coercivity ( Hc=44.6kAm−1 (560Oe)) when compared to lyophilized akaganeite-cyanobacteria powder ( Hc=0.8kAm−1 (10Oe)) due to the quasi-assembly of the cells on the glass substrate compared to the lyophilized randomly akaganeite-cyanobacteria powder.
Keywords: Akaganeite; Cyanobacteria; Biofilm
Compositional dependence on the optical properties of amorphous As2− xS3− xSb x thin films
by Ramakanta Naik; R. Ganesan; K.S. Sangunni (pp. 5437-5441).
In this paper, we report results of the optical properties of thermally deposited As2− xS3− xSb x thin films with x=0.02, 0.07, 0.1 and 0.15. We have characterized the deposited films by Fourier Transform Infrared, Raman and X-ray photoelectron spectroscopy (XPS). The relationship between the structural and optical properties and the compositional variation were investigated. It was found that the optical bandgap decreases with increase in Sb content. The XPS core level spectra show a decrease in As2S3 percentage with increase in Sb content. This is confirmed from the shifting of the Raman peak from AsS3 vibrational mode towards SbS3 vibrational mode.
Keywords: Chalcogenides; Optical properties; X-ray photoelectron spectroscopy; X-ray diffraction; Raman spectroscopy; Amorphous
Synthesis and characterization of HfO2 and ZrO2 thin films deposited by plasma assisted reactive pulsed laser deposition at low temperature
by W.T. Tang; Z.F. Ying; Z.G. Hu; W.W. Li; J. Sun; N. Xu; J.D. Wu (pp. 5442-5446).
A plasma assisted reactive pulsed laser deposition process was demonstrated for low-temperature deposition of thin hafnia (HfO2) and zirconia (ZrO2) films from metallic hafnium or zirconium with assistance of an oxygen plasma generated by electron cyclotron resonance microwave discharge. The structure and the interface of the deposited films on silicon were characterized by means of Fourier transform infrared spectroscopy, which reveals the monoclinic phases of HfO2 and ZrO2 in the films with no interfacial SiO x layer between the oxide film and the Si substrate. The optical properties of the deposited films were investigated by measuring the refractive indexes and extinction coefficients with the aid of spectroscopic ellipsometry technique. The films deposited on fused silica plates show excellent transparency from the ultraviolet to near infrared with sharp ultraviolet absorption edges corresponding to direct band gap.
Keywords: Hafnia; Zirconia; Thin films; Optical property; Plasma assisted deposition; Low-temperature preparation
Structural and textural characterization of LiFePO4 thin films prepared by pulsed laser deposition on Si substrates
by C. Legrand; L. Dupont; K. Tang; H. Li; X.J. Huang; E. Baudrin (pp. 5447-5451).
LiFePO4 thin films were grown on silicon (100) substrates by pulsed laser deposition using Traditional Geometry (TG) and Off-Axis Geometry (OAG) deposition chambers. We examined and compared the structure and composition of the so formed thin films. The nails observed on the OAG-film present an amorphous “body” and a crystallized “head”. The Fe/P ratio determined using energy dispersive spectrometry combined with high angle annular dark field images reveals a metallic iron heart surrounded by LiFePO4 shell. On the other hand, the protuberances on TG-film are pure iron. The focused ion beam prepared cross-section of the film suggests the presence of iron particles and iron dendritic like filaments inside the LiFePO4 layer.
Keywords: Lithium iron phosphate; Thin films; Batteries; Pulsed laser deposition; Transmission electron microscopy
Synthesis and characterization of plasma assisted chemically vapor deposited tantalum
by Y. Suh; W. Chen; S. Maeng; S. Gu; R.A. Levy; H. Thridandam (pp. 5452-5456).
This study focuses on the synthesis of tantalum (Ta) coatings on high strength steel by plasma assisted chemical vapor deposition using tantalum pentachloride (TaCl5) as a preferred precursor and hydrogen (H2) as a reducing agent. The interrelationships governing the growth kinetics, compositions, and coating properties are discussed as a function of deposition temperature, total pressure, and gas composition. The synthesized tantalum coatings are shown to be essentially pure with trace amounts of oxygen, carbon, and chlorine. The coatings are found to be dense and to exhibit conformal coverage. Preferential formation of the α-Ta phase is noted to occur when coatings are grown sequentially and in-situ on a TaN x seed layer.
Keywords: Tantalum; Plasma Assisted Chemical Vapor Deposition; Scanning Electron Microscopy; X-ray diffraction; Auger Electron Spectroscopy
Structural and electrochromic properties of TiO2 thin films prepared by metallorganic chemical vapor deposition
by Z.S. Khalifa; H. Lin; S. Ismat Shah (pp. 5457-5462).
Titanium dioxide thin films were deposited by Metallorganic Chemical Vapor Deposition at substrate temperatures ranging from 250°C to 450°C over soda lime glass and indium tin oxide coated glass substrates. X-ray diffraction studies show that films have a crystalline anatase structure at all the deposition temperatures. Particle size decreases and texture changes with the increase in substrate temperature. X-ray photoelectron spectroscopy confirms the appearance of a new well resolved state in the core level of Ti 2p spectrum shifted by 1.16eV to lower binding energy due to the reduction of Ti+4 to Ti+3 upon litheation. Chronoamperometery, cyclic voltammetery and in situ UV–Vis spectrophotometeric studies were carried out on the prepared samples. Particle size and crystallinity control the electrochromic performance. The 350°C film shows the highest ion storage capacity and the highest optical modulation along with an appreciable band gap broadening.
Keywords: Metallorganic Chemical Vapor Deposition; Photochromic property; Thin films; Titanium dioxide; Voltammetry; X-ray diffraction
Comparison of some coating techniques to fabricate barrier layers on packaging materials
by Terhi Hirvikorpi; Vaha-Nissi Mika Vähä-Nissi; Ali Harlin; Maarit Karppinen (pp. 5463-5466).
Atomic layer deposition (ALD), electron beam evaporation, magnetron sputtering and a sol–gel method were used to deposit thin aluminum oxide coatings onto two different fiber-based packaging materials of commercial board grades coated with synthetic and biodegradable polymers. Significant decreases in both the water vapor and oxygen permeation rates were observed. With each technique the barrier performance was improved. However, among the techniques tested ALD was found to be most suitable. Our results moreover revealed that biodegradable polylactic acid-coated paperboard with a 25-nm thick layer of aluminum oxide grown by ALD on top of it showed promising barrier characteristics against water vapor and oxygen.
Keywords: Barrier coating; Atomic layer deposition; Electron beam evaporation; Magnetron sputtering; Sol–gel; Aluminum oxide
Broad band optical characterization of sol–gel TiO2 thin film microstructure evolution with temperature
by Sarika Phadke; Judith D. Sorge; Sherwood Hachtmann; Dunbar P. Birnie, III (pp. 5467-5470).
Titanium dioxide (TiO2) thin films have been produced by spin coating a titanium isopropoxide sol on silicon wafer substrates. The structural evolution of the thin films in terms of decomposition, crystallization and densification has been monitored as a function of annealing temperature from 100 to 700°C using optical characterization and other techniques. The effect of annealing temperature on the refractive index and extinction coefficient of these TiO2 thin films was studied in the range of 0.62 to 4.96eV photon energy (250–2000nm wavelength) using spectroscopic ellipsometry. Thermal gravimetric analysis and atomic force microscopy support the ellipsometry data and provide information about structural transformations in the titania thin films with respect to different annealing temperatures. These data help construct a coherent picture of the decomposition of the sol–gel precursors and the creation of dense layers of TiO2. It was observed that the refractive index increased from 2.02 to 2.45 at 2.48eV (500nm) in sol–gel spin coated titania films for annealing temperatures from 100°C to 700°C.
Keywords: Optical properties; Titanium dioxide; Spectroscopic ellipsometry
Growth and characterization of (Pb,La)(Zr,Ti)O3 thin film epilayers on SrTiO3-buffered Si(001)
by Ørnulf Nordseth; Chang Chuan You; Erik Folven; Stefano Gariglio; Alessia Sambri; Jean-Marc Triscone; James W. Reiner; Charles H. Ahn; Thomas Tybell; Jostein K. Grepstad (pp. 5471-5477).
Ferroelectric Pb0.92La0.08Zr0.4Ti0.6O3 (PLZT) thin films were deposited on SrTiO3-buffered Si(001) substrate by on-axis radio frequency magnetron sputtering. X-ray diffraction analysis revealed epitaxial growth of monocrystalline PLZT films, with an (001) rocking curve full width at half maximum of ∼0.3°. φ-scans showed 45° in-plane orientation of the perovskite unit cell relative to that of silicon. The elemental composition of the thin film heterostructure was examined by Auger sputter depth profiling measurements. The recorded profiles suggest that the SrTiO3 buffer layer serves not only as a template for epitaxial growth, but also as a barrier suppressing Pb–Si interdiffusion between the PLZT layer and the Si substrate. The surface roughness of the PLZT layer was measured at ∼4nm for films with ∼500nm thickness. Wavelength dispersions for the refractive index ( n) and the extinction coefficient ( k) were obtained from spectroscopic ellipsometry measurements, withn ∼2.48 at the main communication wavelength λ=1550nm and k<0.001 for λ>650nm. Recorded polarization vs. electric field loops for the PLZT epilayer, with a SrRuO3 electrode layer interposed between PLZT and SrTiO3, showed a remnant polarization Pr≈40µC/cm2 and coercive field Ec≈100kV/cm. These findings suggest that the sputter-deposited PLZT thin films retain the functional properties critical to ferroelectric and electro-optic device applications, also when integrated on a semiconductor substrate.
Keywords: (Pb,La)(Zr,Ti)O; 3; Sputter deposition; X-ray diffraction; Electron spectroscopy; Depth profiling
Polyelectrolyte multilayer films containing silver as antibacterial coatings
by Xingjie Zan; Zhaohui Su (pp. 5478-5482).
A facile approach to fabrication of transparent antimicrobial coatings based on polyelectrolyte multilayers (PEMs) is presented. Counterions existing in PEMs were utilized via ion exchange and in situ reduction to incorporate into the films silver ions and nanoparticles, and the antibacterial efficacy of the films against E. coli was assessed by the Kirby–Bauer method. The PEMs containing silver in the ionic form exhibited high activities in short terms, and the antibacterial effects depended on the ionic strength in the polyelectrolyte solutions used for the PEM fabrication. The PEMs loaded with silver nanoparticles showed lower initial bactericidal effects, but remained active after long periods of time, and the antimicrobial performance can be improved by increasing the silver loading through repeating the ion-exchange/reduction cycle for multiple times. The films were transparent in the visible region. Coatings containing multiple antimicrobial agents for possible synergistic effects can be fabricated in a single process using this method.
Keywords: Antibacterial coating; Counterions; Ion exchange; Polyelectrolyte multilayers; Silver
Characterisation of size-controlled and red luminescent Ge nanocrystals in multilayered superlattice structure
by B. Zhang; S. Shrestha; P. Aliberti; M.A. Green; G. Conibeer (pp. 5483-5487).
Ge nanocrystals (Ge NCs) embedded in a multilayered superlattice structure have been fabricated and investigated. The presence of Ge NCs was confirmed by Raman scattering and X-ray diffraction measurements. The average size of Ge NCs was modulated by the sputtering time of Ge-rich layer and possible mechanisms have been proposed. The blue shift of optical absorption edge was observed with the decrease of nanocrystal size. The photoluminescence showed broad bands centred at ∼1.77eV and ∼2.01eV for 3.9nm and 3.0nm nanocrystals, respectively, which are consistent with the theoretical calculation in literature. The properties of shifted optical absorption and red luminescence are tentatively explained by quantum confinement in the Ge NCs.
Keywords: Ge; Nanocrystal; Multilayer; Size-control; Photoluminescence
Tris(8-hydroxyquinoline)aluminum (III) (Alq3) nanowires templated from an eggshell membrane
by Tu Lee; Shih Chia Chang; Jen Fan Peng (pp. 5488-5493).
One to 2-µm long, ≤400-nm wide amorphous tris(8-hydroxyquinoline)aluminum (III) (Alq3) nanowires (NWs) grown from the 15-min boiled outer shell membrane (OSM) of the hen's egg and from the OSM solution cast film via thermal evaporation with a source temperature of 260°C and a substrate temperature of 138°C under 6.7×10−2Pa gave about 1.4 to 1.7 times more photoluminescence emission than the control Alq3 sample did, which was grown from the plain glass surface. The characteristic bonding energies of C 1s X-ray photoelectron signal at 282eV, O 1s signal at 529eV and N 1s signal at 397eV suggested that the relatively high NW density for the 15-min boiled OSM and the OSM solution cast film, was mainly caused by the formation of the O═C–O–C═O anhydride moiety and the C═N group in the proteinaceous OSM at high temperature of 90°C to 100°C. Therefore, we proposed that the 15-min boiled OSM and the OSM solution cast film apparently served as good templates by providing nano-regions of high concentration of the O═C–O–C═O anhydride groups and the C═N groups for nesting the Alq3 gas molecules to form nano-conical Alq3 nuclei for the growth of long and narrow NWs.
Keywords: Tris(8-hydroxyquinoline)aluminum (III); Nanowires; Eggshell membrane; Photoluminescence
Tunable properties of wide-band gap p-type BaCu(Ch1− xCh x′)F (Ch = S, Se, Te) thin-film solid solutions
by A. Zakutayev; D.H. McIntyre; G. Schneider; R. Kykyneshi; D.A. Keszler; C.-H. Park; J. Tate (pp. 5494-5500).
Thin-film solid solutions of BaCu(Ch1− xCh x′)F (Ch, Ch′ = S, Se, or Te) wide-band gap p-type semiconductors are obtained by pulsed laser deposition at elevated substrate temperatures from alternating layers of BaCuChF and BaCuCh′F. Adjusting the thickness of the component layers varies the relative chalcogen content, which allows tunability of the film transparency and results in a conductivity change of more than three orders of magnitude. The tunability of the physical properties makes these chalcogen-based semiconductors potentially useful for optoelectronics applications. Lattice parameters of BaCuChF calculated using density functional theory agree with those previously reported for the powders. Deviations from Vegard's law are observed in BaCu(S1− xSe x)F thin films with large sulfur content.
Keywords: p-Type transparent conductor; Wide-band gap semiconductor; Mixed-anion compound; BaCuSF; BaCuSeF; BaCuTeF; Pulsed laser deposition; 1111 compounds
Preparation of solar selective absorbing coatings by magnetron sputtering from a single stainless steel target
by Rei-Cheng Juang; Yung-Chin Yeh; Bing-Hung Chang; Wen-Chieh Chen; Tsair-Wang Chung (pp. 5501-5504).
This paper presents a method to prepare solar selective absorbing coatings by radio frequency magnetron reactive sputtering using a single stainless steel target. Stainless steel/stainless steel nitride (SS/SS-N) ceramic–metal composite (cermet) thin films were produced under varied nitrogen gas flow ratios. The solar selective absorbing films have good solar absorptance of 0.91 and thermal emittance of 0.06 at 82°C. The refractive index ( n) and extinction coefficient ( k) of the cermet composite layers prepared in nitrogen and argon atmospheres were determined by spectroscopic ellipsometry. The films were also analyzed by different oscillator models. The results showed a significant transformation from metal to cermet as the nitrogen gas flow ratio was increased to 10%. As the nitrogen gas flow ratio was increased to 17.5%, the film became a dielectric layer that could be used as an anti-reflection layer, suitable as the outermost layer of the solar selective absorbing coatings. A theoretical solar absorptance of 0.92 was achieved by selecting an appropriate combination of three solar absorbing layers. The experimental results agreed well with the theoretical calculations. This study proved the possibility of preparing solar selective absorbing coatings with high solar absorptance by using a single stainless steel target.
Keywords: Reactive sputtering; Stainless steel nitride; Cermet film; Solar absorber
Influence of vanadium concentration on the microstructure and magnetic properties of V-doped ZnO thin films
by Ts. Naydenova; P. Atanasov; M. Koleva; N. Nedialkov; J. Perriere; D. Defourneau; H. Fukuoka; M. Obara; Ch. Baumgart; Sh. Zhou; H. Schmidt (pp. 5505-5508).
Vanadium doped ZnO thin films (Zn1− xV xO, where x=0.05 or x=0.13) were grown on c-cut sapphire substrates using pulsed laser deposition technique. Their structure and magnetic properties were examined in relation to the doping concentration. All deposited films were highly oriented along the c-axis and exhibited ferromagnetic behavior with a Curie temperature up to 300K. The crystal structure was found to be better for layers with lower vanadium concentration. The films had a porous fine-grained microstructure and a column-like character as the V concentration was reduced. A weak dependence of magnetization on temperature was observed. The saturation magnetization was found to be strongly dependent on the crystal structure, grain size and V-ion concentration.
Keywords: ZnO; Vanadium doping; Thin films; PLD; DMS
Combined ellipsometry and X-ray related techniques for studies of ultrathin organic nanocomposite films
by Kramer Markus Krämer; Katy Roodenko; Beatrix Pollakowski; Karsten Hinrichs; Jörg Rappich; Norbert Esser; Alex von Bohlen; Hergenroder Roland Hergenröder (pp. 5509-5514).
Ultrathin nanocomposite films of nitrobenzene on silicon were analyzed by Infrared Spectroscopic Ellipsometry (IRSE), X-ray reflectivity (XRR) and X-ray standing waves (XSW) before and after evaporation of gold. Infrared Spectroscopic Ellipsometry measurements were performed for identification of adsorbates and for investigation of the molecular orientation. Results for film thickness were correlated with XRR measurements. Further, XSW measurements of elements incorporated in nitrobenzene (C, N, and O) were performed with soft X-rays. The combination of the different methods allowed to confirm a model for the electrochemically deposited nitrobenzene films before and after gold evaporation. The characterization by XRR and XSW scans using hard X-rays showed that gold had penetrated into the nitrobenzene film and thus changed density and optical properties of this layer significantly. A depth profile correlated to the electron density is deduced from the XRR measurements. This profile allows to localize—in vertical direction—gold islands within the composite film.
Keywords: Optical simulations; Infrared spectroscopic ellipsometry; Synchrotron; X-ray standing waves; Surface modification
Effect of triethanolamine and sodium dodecyl sulfate on the formation of CuInSe2 thin films by electrodeposition
by Rui Yu; Tong Ren; Can Li (pp. 5515-5519).
In this paper, we describe the development of a bath comprising triethanolamine and sodium dodecyl sulfate for electrodeposition of CuInSe2 thin films, by which long-term bath stability was found to be improved and near-stoichiometric CuInSe2 films with smooth surface morphology were obtained. Scanning electron microscopy studies reveal a dramatic improvement of the crystalline quality of CuInSe2 films with the addition of sodium dodecyl sulfate. X-ray diffraction results and Raman spectra confirm that the improvement of the film growth is attributed to the synergistic effect of triethanolamine and sodium dodecyl sulfate. The addition of anionic surfactant sodium dodecyl sulfate can significantly improve the adherence between the CuInSe2 layer and the substrate.
Keywords: Electrodeposition; Copper indium selenide; Raman spectroscopy; Scanning electron microscopy; Sodium dodecyl sulfate; Triethanolamine; Thin films; Solar cells
Control of epitaxial growth orientation in ZnO nanorods on c-plane sapphire substrates
by Hou-Guang Chen; Zheng-Wei Li; Hong-De Lian (pp. 5520-5524).
This paper presents a study on low temperature hydrothermal growth of ZnO nanorods (NRs) on pre-seeded (0001) sapphire substrates. Prior to hydrothermal growth of ZnO NRs, epitaxial ZnO seeds were grown by metal-organic chemical vapour deposition under various process conditions. Findings show that the majority of ZnO NRs inclined at a specific angle of about 38° to the direction perpendicular to the substrate surface and exhibited a preferential in-plane alignment, besides other NRs growing vertically from the sapphire surface. X-ray diffraction φ-scan measurements reveal that the ZnO nanorods displayed two distinct epitaxial relationships with sapphire which were (0001)ZnO//(0001)sapphire and (0001)ZnO//(101̅4)sapphire, respectively. Reduced lattice mismatch between ZnO and sapphire is responsible for the inclined ZnO NRs growth. The growth direction of ZnO NRs is remarkably dependent on the growth conditions of ZnO seeds and sapphire substrate pre-treatment. The epitaxial orientations of ZnO seeds grown on the sapphire substrate dominate the subsequent ZnO NRs growth and can be controlled through adjusting growth conditions.
Keywords: Zinc oxide; Nanorods; Epitaxial growth; Sapphire; X-ray diffraction; Metal-organic chemical vapor deposition; Hydrothermal growth; Scanning electron microscopy
Femtosecond laser deposition of TiO2 by laser induced forward transfer
by M. Sanz; M. Walczak; M. Oujja; C. Domingo; A. Klini; E.L. Papadopoulou; C. Fotakis; M. Castillejo (pp. 5525-5529).
Femtosecond lasers have been used for laser induced forward transfer (LIFT) of TiO2, a wide-band semiconductor with many industrial and research applications. TiO2 polycrystalline thin films on quartz (obtained by pulsed laser deposition) were used as donors and both quartz and fluorine-doped tin dioxide coated glass substrates as acceptors. LIFT was performed at the laser wavelengths of 248 and 800nm with pulses of 450 and 300fs respectively. The transferred material was characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction and micro-Raman spectroscopy to determine the composition and crystalline quality, and by scanning electron microscopy and atomic force microscopy to assess the surface morphology. The relation between these properties and the laser transfer conditions, including wavelength, pulse energy and acceptor substrate, are presented.
Keywords: TiO; 2; Laser deposition; Laser induced forward transfer; Nanostructures; Titanium dioxide; Scanning electron microscopy; X-ray diffraction; Raman spectroscopy
Study of the fabrication of infrared-transparent dielectric aspheric deposits by continuous-wave laser deposition
by Gonzalez-Leal J.M. González-Leal; J.A. Angel; Rubio-Pena L. Rubio-Peña; J. Valverde; Gamez A. Gámez (pp. 5530-5534).
The fabrication of dielectric aspheric deposits with optical refractive functionality by a continuous-wave laser deposition technique is reported for the particular case of an amorphous As–S alloy. The influence of both the laser power and fabrication times in the deposit thickness profile is studied from the measurements performed by a mechanical profilometer. The use of press-powder tablets as starting material have been found to have a significant effect in the deposition efficiency, and indications of a transition from a discrete to a continuous nature of the target, have also been observed. A notable reproducibility has been found both in the material stoichiometry and thickness profiles. The optical function of the fabricated refractive aspheric deposits has been measured to be similar to one performed by axicon lenses.
Keywords: Optical materials; Laser deposition; Optical design; Lenses; Pulse laser deposition; Optical transmission
Controlled stepwise growth of siloxane chains using bivalent building units with different functionalities
by Nils Salingue; Dominic Lingenfelser; Pavel Prunici; Peter Hess (pp. 5535-5541).
Organic/inorganic hybrids of silicon and their subsequent chemical modification are of interest for tailoring and structuring surfaces on the nanoscale. The formation of organic (sub)monolayers on hydroxylated silicon surfaces was employed to synthesize molecular siloxane chains by stepwise wet-chemical condensation reactions. Functionalizations with small alkyl-monochlorosilanes, yielding dimethylsilyl, diisopropylsilyl, di- tert-butylsilyl terminations, and with an aryl-monochlorosilane, providing diphenylsilyl groups, were studied. The SiH moiety of these end groups could be selectively oxidized to the corresponding silanol. The reactivity of this group opened the possibility of bonding additional species step by step in bottom-up growth reactions. In particular, dimethylsiloxane units were studied as possible molecular building blocks. By repeating the oxidation and condensation reactions the stepwise growth of one-dimensional siloxane chains was demonstrated. The ongoing chain growth was characterized by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry (NIR–UV), and contact-angle experiments.
Keywords: Organic (sub)monolayers; Bottom-up synthesis; Siloxane chains; Attenuated total reflection spectroscopy; X-ray photoelectron spectroscopy; Silicon hybrids
Preparation and application in p–n homojunction diode of p-type transparent conducting Ga-doped SnO2 thin films
by Tieying Yang; Xiubo Qin; Huan-hua Wang; Quanjie Jia; Runsheng Yu; Baoyi Wang; Jiaou Wang; Kurash Ibrahim; Xiaoming Jiang; Qing He (pp. 5542-5545).
The direct preparation of p-type transparent conducting Ga-doped SnO2 thin films and their fundamental application in transparent p–n homojunction diode were realized. The films were grown in an active oxygen ambient using reactive rf magnetron sputtering without post-deposition annealing involved. This method improved the electrical properties of the films while maintaining their optical transparency. By growing a p-type thin film on commercial n-type SnO2:F-coated glass, transparent p–n homojunction diode was obtained. It exhibits a distinct current–voltage rectifying characteristic, manifesting this p-type thin film and the fabrication technology are suitable for industrial applications.
Keywords: p-Type transparent conducting oxide; Ga-doped SnO; 2; Thin films; p–n homojunction diode; Magnetron sputtering; X-ray diffraction; X-ray photoelectron spectroscopy
Influence of carbon chemical bonding on the tribological behavior of sputtered nanocomposite TiBC/a-C coatings
by M.D. Abad; Sanchez-Lopez J.C. Sánchez-López; M. Brizuela; Garcia-Luis A. García-Luis; D.V. Shtansky (pp. 5546-5552).
The tribological performance of nanocomposite coatings containing Ti–B–C phases and amorphous carbon (a-C) are studied. The coatings are deposited by a sputtering process from a sintered TiB2:TiC target and graphite, using pulsed direct current and radio frequency sources. By varying the sputtering power ratio, the amorphous carbon content of the coatings can be tuned, as observed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The crystalline component consists of very disordered crystals with a mixture of TiB2/TiC or TiBxCy phases. A slight increase in crystalline order is detected with the incorporation of carbon in the coatings that is attributed to the formation of a ternary TiBxCy phase. An estimation of the carbon present in the form of carbide (TiBxCy or TiC) and amorphous (a-C) is performed using fitting analysis of the C 1s XPS peak. The film hardness (22 to 31GPa) correlates with the fraction of the TiBxCy phase that exists in the coatings. The tribological properties were measured by a pin-on-disk tribometer in ambient conditions, using 6mm tungsten carbide balls at 1N. The friction coefficients and the wear rates show similar behavior, exhibiting an optimum when the fraction of C atoms in the amorphous phase is near 50%. This composition enables significant improvement of the friction coefficients and wear rates ( μ∼0.1; k<1×10−6mm3/Nm), while maintaining a good value of hardness (24.6GPa). Establishing the correlation between the lubricant properties and the fraction of a-C is very useful for purposes of tailoring the protective character of these nanocomposite coatings to engineering applications.
Keywords: Titanium boron carbide; Nanocomposites; Amorphous carbon; X-ray photoelectron spectroscopy; Raman; Wear; Friction; Hardness
Low friction CrN/TiN multilayer coatings prepared by a hybrid high power impulse magnetron sputtering/DC magnetron sputtering deposition technique
by J. Paulitsch; M. Schenkel; A. Schintlmeister; H. Hutter; P.H. Mayrhofer (pp. 5553-5557).
High power impulse magnetron sputtering (HIPIMS) has gained increasing scientific and industrial attention as it allows high plasma densities without the drawback of droplet formation. Recently, we showed that by a combination of HIPIMS with dc magnetron sputtering the properties of the coatings are comparable to those prepared solely with HIPIMS, but with the advantage of increased deposition rate.Here, we show that for CrNHIPIMS/TiNDCMS multilayered coatings the friction coefficient µ decreases from 0.7 to 0.35 (with an almost constant hardness H around 25GPa, and modulus of indentation around 375GPa) when decreasing the bilayer period λ from 7.8 to 6.4nm, while keeping the CrNHIPIMS layer thickness constant at 3.2nm. A further reduction of the friction coefficient at room temperature dry-sliding testing to ∼0.25 or 0.05 is obtained when an additional HIPIMS cathode equipped with a Cr or Ti target material, respectively, is added to the process. Contact angle measurements of distilled water drops on as deposited film surfaces were carried out to investigate their wettability. The measurements show, that with increasing contact angle from 70° to 90°, for the individual coatings prepared, also their friction coefficient increases from ∼0.05 to ∼0.8. The depositions of all coatings were achieved with two- and threefold substrate rotation, which meet the industrial requirements of uniform deposition on complex shaped specimens.
Keywords: TiN/CrN; HPPMS; Low friction coefficient; Wear resistance; BOD
Structure and properties of high power impulse magnetron sputtering and DC magnetron sputtering CrN and TiN films deposited in an industrial scale unit
by J. Paulitsch; M. Schenkel; Zufrass Th. Zufraß; P.H. Mayrhofer; Munz W.-D. Münz (pp. 5558-5564).
Deposition of complex shaped or round-symmetric samples requires multi-fold substrate rotations during deposition or multiple cathode arrangements. The present paper investigates the influence of the high power impulse magnetron sputtering (HIPIMS) and DC magnetron sputtering (DCMS) process on the mechanical and tribological properties as well as the resulting structure of CrN and TiN coatings using static (0-fold) and dynamic (1-, 2- and 3-fold) depositions in an industrial scale unit. Furthermore, to increase the deposition rate without losing the high ion density in the plasma a hybrid HIPIMS/DCMS deposition technique is investigated. The results demonstrate the advantage of the HIPIMS technique when using multi-fold substrate rotation during deposition as it enables depositions of CrNHIPIMS and TiNHIPIMS coatings with hardness values around 23 and 35GPa, respectively, compared with around 15GPa for CrNDCMS and TiNDCMS coatings. Hardness values of 35GPa for TiNDCMS coatings prepared with substrate rotations could only be obtained when introducing an additional anode or using a multilayered CrNHIPIMS/TiNDCMS base layer as a template.Based on our results we can conclude that especially for up-scaling and multi-fold substrate rotations the HIPIMS process offers an improved performance as compared to DCMS.
Keywords: TiN; CrN; Hybrid HIPIMS/DCMS; Planetary rotation; Up-scaling
Thin film hardness determination using indentation loading curve modelling
by D. Chicot; L. Gil; K. Silva; F. Roudet; E.S. Puchi-Cabrera; M.H. Staia; D.G. Teer (pp. 5565-5571).
A methodology for determining the thin film hardness from a microindentation loading curve is proposed. The loading curve is modelled to compute the dynamic Martens hardness using the indentation depth reached during the test. Moreover, the indentation size effect is taken into account by applying the strain gradient plasticity theory. Then, the dynamic Martens hardness and the hardness length-scale factor are used to express the applied load as a function of the indentation depth. The proposed model involves three parameters: ( i) the dynamic Martens macro-hardness, equivalent to the hardness obtained for an infinite applied load, ( ii) the hardness length-scale factor, which represents the material resistance to plastic deformation under indentation and ( iii) a corrective load, considering the rounded tip effect of the indenter and the zero shift. The model is validated on a 316L stainless steel which subsequently is used as a substrate material for two different Diamond Like-Carbon thin films. The coated systems involved both a hydrogen-free mostly amorphous carbon–chromium (a-C) film of ∼2.6μm in thickness and a hydrogenated, amorphous carbon (a-C:H) solid lubricant of ∼2μm.
Keywords: Depth-sensing microindentation; Modelling; Strain gradient plasticity; Diamond like-carbon; Thin films
Double subband occupation of the two-dimensional electron gas in In xAl1− xN/AlN/GaN/AlN heterostructures with a low indium content (0.064≤ x≤0.140) barrier
by S.B. Lisesivdin; P. Tasli; M. Kasap; M. Ozturk; E. Arslan; S. Ozcelik; E. Ozbay (pp. 5572-5575).
We present a carrier transport study on low indium content (0.064≤ x≤0.140) In xAl1− xN/AlN/GaN/AlN heterostructures. Experimental Hall data were carried out as a function of temperature (33–300K) and a magnetic field (0–1.4T). A two-dimensional electron gas (2DEG) with single or double subbands and a two-dimensional hole gas were extracted after implementing quantitative mobility spectrum analysis on the magnetic field dependent Hall data. The mobility of the lowest subband of 2DEG was found to be lower than the mobility of the second subband. This behavior is explained by way of interface related scattering mechanisms, and the results are supported with a one-dimensional self-consistent solution of non-linear Schrödinger–Poisson equations.
Keywords: Indium aluminum nitride; Metal organic chemical vapor deposition; Two dimensional electron gas; Hall effect
Nickel dissolution into AuGe in alloyed AuGe/Ni/Au Ohmic contacts on GaAs/AlGaAs multilayer structures
by T.S. Abhilash; C.H. Ravi Kumar; G. Rajaram (pp. 5576-5578).
Magnetic properties of alloyed Ohmic contacts of the type AuGe/Ni/Au on GaAs/AlGaAs multilayers with n+ cap layer with different AuGe compositions and Ni-layer thicknesses are examined. Magnetization data indicate that the annealed structures are non-magnetic, at room temperature for commonly used anneal temperatures (∼400–430°C) and Ni-layer thicknesses (10–100nm). The transformation of Ni to non-magnetic phase begins at ∼100°C, well below temperatures at which extensive alloying with the GaAs substrate takes place. The fraction of Ni transformed to non-magnetic phase on annealing appears to scale with AuGe layer thickness, has a quadratic dependence on anneal temperature and is time independent for time scales of minutes. The data indicate that the Ni layer dissolves into the AuGe layer at temperatures well below that at which alloying between AuGe and GaAs substrate takes place. The dissolved Ni concentration is limited by a solubility that increases with anneal temperature and decreases with decreasing Ge content from that of the AuGe eutectic composition.
Keywords: GaAs/AlGaAs; Multilayer; Ohmic contacts; AuGe/Ni/Au; Semiconductor; Magnetic properties; Sensors
Trapping properties of sputtered hafnium oxide films: Bulk traps vs. interface traps
by E. Verrelli; G. Galanopoulos; I. Zouboulis; D. Tsoukalas (pp. 5579-5584).
The purpose of this work is to investigate the influence of the spatial distribution of traps on the electrical characteristics of hafnium oxide films deposited by physical vapor deposition. Samples were Al gated metal-oxide-semiconductor capacitors with hafnium oxide films deposited on SiO2 layer thermally grown on Si. During capacitance–voltage measurements large hysteresis, up to 10V, are observed in all samples. It is shown that depending on the hafnium oxide deposition conditions, the spatial distribution of the traps responsible for the hysteresis can be either two dimensional (interface/border traps) or three dimensional (bulk traps).
Keywords: Hafnium oxide; Electrical characterization; High dielectric constant; Non-volatile memory; Bulk trap; Interface trap; Charge retention; Charge distribution; Sputtering
Third-order optical nonlinear absorption in Bi1.95La1.05TiNbO9 thin films
by Hengzhi Chen; Bin Yang; Mingfu Zhang; Feiyan Wang; Kokwai Cheah; Wenwu Cao (pp. 5585-5587).
Single phase Bi1.95La1.05TiNbO9 (LBTN-1.05) thin films with a layered aurivillius structure have been fabricated on fused silica substrates by pulsed laser deposition at 700°C. The X-ray diffraction pattern revealed that the films are single-phase aurivillius. The band gap, linear refractive index and linear absorption coefficient were obtained by optical transmittance measurements. The film exhibits a high transmittance (>70%) in visible-infrared region and the dispersion relation of the refractive index vs. wavelength follows the single electronic oscillator model. The nonlinear optical absorption property of the film was determined by the single beam Z-scan method using 800nm with a duration of 100fs. A large positive nonlinear absorption coefficient β=5.95×10−8m/W was determined experimentally. The results showed that the LBTN-1.05 is a promising material for applications in absorbing-type optical devices.
Keywords: Nonlinear optical absorption; Bi; 1.95; La; 1.05; TiNbO; 9; Optical properties
Investigation of emission location in top-emitting green organic light-emitting devices by optical analysis
by Ji-Hwan Yoon; Hee-Seong Jeong; Il-Soo Park (pp. 5588-5592).
A series of top-emitting organic light-emitting devices with different thicknesses of carrier transporting layers (N,N′-di(1-naphtyl)-N,N′-diphenylbenzidine, tris(8-hyroxyquinloine) aluminum (Alq3)) and emitting layer (EML, 10-(2-Benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyropyrano(6,7-8-i,j)quinolizin-11-one (C545T)-doped Alq3) were fabricated. C545T-doped Alq3 was found to bring about double recombination peaks in EML. As the distance between EML and reflective anode was increased, the outcoupling efficiency greatly deviated from optically-simulated values due to charge imbalance in EML and optical loss at the EML/Alq3 interface. The device with 30nm of EML exhibited maximized outcoupling efficiency and further increase of EML thickness brought about decrease in efficiency due to decrease in hole–electron recombination at the EML/Alq3 interface.
Keywords: Microcavity; Top emission; Organic light-emitting devices; Outcoupling efficiency
Shelf-life time test of p- and n-channel organic thin film transistors using copper phthalocyanines
by Nenon Sébastien Nénon; Daiki Kanehira; Noriyuki Yoshimoto; Frédéric Fages; Christine Videlot-Ackermann (pp. 5593-5598).
P- and n-type channel thin film transistors (OTFTs) were fabricated by using hexadecahydrogen copper phthalocyanine (H16CuPc) and hexadecafluoro copper phthalocyanine (F16CuPc) molecules, respectively. Top-contact and bottom-contact source-drain configurations were used for both semiconductors. Furthermore, the temperature and film thickness dependences on the mobility values were measured in the saturation regime of source-drain current. Unipolar mobilities in such single-layer OTFTs were correlated to thin film morphology by X-ray diffraction analysis and atomic force microscopy measurements. Shelf-life time tests of p-type and n-type OTFTs are detailed as OTFT configuration and substrate temperature dependence over a time period of 100days.
Keywords: Organic semiconductor; Copper phthalocyanine; Fluorinated copper phthalocyanine; Thin films; Morphology; Thin film transistor; Stability; X-ray diffraction; Atomic force miscoscopy; Charge carrier mobility
Mobility of holes in a Si/Si0.8Ge0.2/Si metal oxide semiconductor field effect transistor
by Ghassem Ansaripour (pp. 5599-5603).
Using all standard scattering mechanisms the hole mobility in a metal oxide semiconductor field effect transistor SiGe conduction channel at 17K and room temperature was calculated. The mobility measurements were performed at different bath temperatures in the range of 4–300K. The 4K peak mobility at a sheet carrier concentration, n h, of 2.1×1011cm−2 is 5100cm2V−1s−1 while the 300K mobility has a peak value of 350cm2V−1s−1. By comparing between theory and measurements it is shown that the interface impurities and surface roughness more strongly limit the mobility than alloy scattering does.
Keywords: Hole mobility; SiGe; Scattering; Interface impurities; Surface roughness
Low temperature growth and properties of Cu–In–Te based thin films for narrow bandgap solar cells
by Takahiro Mise; Tokio Nakada (pp. 5604-5609).
Cu–In–Te based thin films were grown onto soda–lime glass (SLG) substrates at 200°C by co-evaporation using a molecular beam epitaxy system. The microstructural properties were examined by means of scanning electron microscopy, X-ray diffraction and Raman scattering. The crystalline quality of Cu–In–Te based thin films with high Cu/In ratios is superior to that of films with low Cu/In ratios. The films with Cu/In ratios of 0.69±0.04 exhibited a single chalcopyrite phase with random orientation, whereas a defect chalcopyrite phase with a preferred (112) orientation was obtained for thin films with Cu/In ratios of 0.26±0.02. However, the films with high Cu/In ratios of 0.69±0.04 showed nearly constant low resistivity (∼10−2Ωcm) at temperatures from 80 to 400K due to high hole concentration (>1019cm−3), resulting in semi-metallic behavior. The hole conduction mechanism of the film (Cu/In atomic ratios=0.26±0.02) with semi-conductive properties was found to be variable-range-hopping of the Mott type in the wide range of 80–300K. The optical bandgaps of Cu–In–Te based thin films are determined to be 0.93–1.02eV at 300K from transmission and reflection measurements. A solar cell with a ZnO/CdS/CuIn3Te5/Mo/SLG structure showed a total area (0.50cm2) efficiency of 5.1% under AM1.5 illumination (100mW/cm2) after light soaking. The conduction band offset at the CdS/CuIn3Te5 interface was estimated to be −0.14eV from X-ray photoelectron spectroscopy analysis.
Keywords: CuInTe; 2; CuIn; 3; Te; 5; Chalcopyrite compound; Co-evaporation; Narrow bandgap; Solar cell; Band offset
Rotating polarizer-analyzer scanning ellipsometer
by Taher M. El-Agez; Ahmed A. El Tayyan; Sofyan A. Taya (pp. 5610-5614).
A spectroscopic ellipsometer in which the polarizer and the analyzer are rotating synchronously in opposite directions at the same speed is proposed. The light intensity involves four components, one dc and three cosine terms, with frequencies of ω, 2 ω, and 3 ω. The main advantage of the proposed ellipsometer is that: it is feasible to extract the ellipsometric parameters ψ and Δ from the even Fourier coefficients without relying on the dc component which is considered to be a serious problem in rotating-analyzer or -polarizer ellipsometer. This allows measurements in semi-dark room without worrying about stray light problems, dark currents in detectors, and long term fluctuations in light sources. The calculations of the optical parameters of c-Si, Au, and GaAs are in excellent agreement with the published data.
Keywords: Rotating polarizer-analyzer; Ellipsometry; Pseudodielectric function; Optical constants
A comparative study of two advanced spraying techniques for the deposition of biologically active enzyme coatings onto bone-substituting implants
by Lise T. de Jonge; J. Ju; S.C.G. Leeuwenburgh; Y. Yamagata; T. Higuchi; J.G.C. Wolke; K. Inoue; J.A. Jansen (pp. 5615-5621).
Surface modification of implant materials with biomolecule coatings is of high importance to improve implant fixation in bone tissue. In the current study, we present two techniques for the deposition of biologically active enzyme coatings onto implant materials. The well-established thin film ElectroSpray Deposition (ESD) technique was compared with the SAW-ED technique that combines high-frequency Surface Acoustic Wave atomization with Electrostatic Deposition. By immobilizing the enzyme alkaline phosphatase (ALP) onto implant surfaces, the influence of both SAW-ED and ESD deposition parameters on ALP deposition efficiency and ALP biological activity was investigated. ALP coatings with preserved enzyme activity were deposited by means of both the SAW-ED and ESD technique. The advantages of SAW-ED over ESD include the possibility to spray highly conductive protein solutions, and the 60-times faster deposition rate. Furthermore, significantly higher deposition efficiencies were observed for the SAW-ED technique compared to ESD. Generally, it was shown that protein inactivation is highly dependent on both droplet dehydration and the applied electrical field strength. The current study shows that SAW-ED is a versatile and flexible technique for the fabrication of functionally active biomolecule coatings.
Keywords: Titanium; Coating; Alkaline phosphatase; Electrostatic deposition; Surface acoustic wave
Strain and temperature effects in indium–tin-oxide sensors
by Otto J. Gregory; Ximing Chen; Everett E. Crisman (pp. 5622-5625).
Indium–tin-oxide (ITO) thin films strain gages were prepared by reactive sputtering onto both high purity alumina and lanthanum stabilized zirconia substrates. We report the piezoresistive response of these ITO gages in the temperature range 350–1500°C up to 1000 microstrain (με). Strain response and gage factors are reported for ITO in both tension and compression. The data suggest that not only is there an annealing component but also a strain component of the piezoresistive change with time at temperature. The effects in both tension and compression are reported.
Keywords: Indium–tin-oxide (ITO); Thin films; Strain gage; High temperature; Sputtering
Effect of ionic liquid dispersion on performance of a conducting polymer based Schottky diode
by Jyoti Nayak; Suresha K. Mahadeva; Y. Chen; K.S. Kang; Jaehwan Kim (pp. 5626-5628).
The effect of ionic liquid (IL) dispersion on the performance of Schottky diode fabricated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been investigated. Two kinds of ILs including 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6, hydrophobic IL) and 1-butyl-3-methylimidazolium chloride (BMICL, hydrophilic IL) were dispersed to the PEDOT:PSS by mechanical stirring and sonication processes. Schottky diodes were fabricated with these mixtures. The forward current of Schottky diodes fabricated with PEDOT:PSS dispersed BMI PF6 (SD-BMIPF6)/BMICL (SD-BMICL) by mechanical stirring is slightly reduced compared with that of Schottky diodes fabricated with pristine PEDOT:PSS (SD-PEDOT). However, SD-BMIPF6 and SD-BMICL by sonication technique show higher forward current with respect to SD-PEDOT. Compared with SD-BMIPF6 and SD-BMICL, the forward current of SD-BMICL is much higher than that of SD-BMIPF6. Since the BMICL has hydrophilic nature, the enhancement of forward current might be due to the uniform dispersion of the BMICL on the PEDOT:PSS matrix.
Keywords: Schottky diodes; Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate); Room temperature ionic liquids; 1-Butyl-3-methylimidazolium chloride; 1-Butyl-3-methylimidazolium hexafluorophosphate; Scanning electron microscopy; Electrical properties and measurements