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Neodymium-doped GeO2/γ-glycidoxypropyltrimethoxysilane hybrid planar waveguide films were prepared by a low-temperature sol-gel technique from an organic-inorganic hybrid system for photonic applications. Optical properties such as refractive index, thickness, propagation modes, and attenuation coefficient of the hybrid planar waveguides were investigated by using a prism coupling technique. An intense room-temperature yellow-to-violet up-conversion emission at 397 nm (4D3/2→4I13/2) was measured from the hybrid planar waveguide film heated at a low temperature of 100 °C upon excitation with a xenon lamp at the wavelength of 580 nm. In addition to this intense violet emission, a relatively weak ultraviolet emission at 376 nm and a blue emission at 468 nm were also observed. The mechanism of the up-conversion emission is proposed, and they indicate that the excited-state absorption process originating from the long-lived 4F3/2 excited state should be responsible for the up-conversion process. [ABSTRACT FROM AUTHOR]

Presents a study which deposited diamond-like carbon films by a plasma chemical vapor deposition system. Properties of the carbon films; Results; Conclusions.

A sputtering gas-aggregation technique has been used to prepare FePt and FePt:Ag nanocluster films. The cluster size was controlled in a range from 3 to 6 nm. FePt cluster films were directly deposited onto Si substrate; FePt:Ag cluster films were fabricated by depositing a FePt cluster layer between a Ag underlayer and overlayer. Nanostructure and magnetic properties of the samples were characterized by x-ray diffraction, transmission electron microscopy, and magnetometry. The high magnetic anisotropy L1[SUB0] fct phase was realized in the films annealed at a temperature of 550°C and above. The orientation of clusters is random. The coercivity increases with an increase of annealing temperature; high in-plane and out-of-plane coercivities, exceeding 10 kOe, were achieved in both FePt and FePt:Ag cluster films after annealing. For FePt:Ag films, the coercivity increases with Ag underlayer thickness, t[SUBAg], and reaches about 17 kOe at room temperature for t[SUBAg] = 5 nm after annealing at 650°C for 10 min. The high coercivity is closely correlated with the degree of L1[SUB0] ordering and nanostructure of the films. [ABSTRACT FROM AUTHOR]

Abstract: The roughness evolutions of micro-crystalline silicon thin films (μc-Si:H) with different growth rates prepared by chemical vapor depositions have been investigated by atomic force microscopy. The growth exponent β was measured as 0.8±0.03, 1.1±0.07 and 0.75±0.02 for three sets of samples prepared by PECVD with and without hydrogen dilution ratio modulation and by HWCVD, respectively, and does not correlated with the deposition rate in a set. However, the root-mean-square roughness and lateral correlation length decrease with increasing the deposition rate for both PECVD and HWCVD process. We suggested that the nonstationary growth with large β is correlated with the shadowing effect. The influence of the deposition rate on the surface roughness could be related to the diminishing of the shadowing effect by surface species diffusion with higher mobility on an H-covered surface. The initial surface and nucleation condition play an important role in the surface roughness evolution. [Copyright &y& Elsevier]

GaFeO3 thin films were prepared on (111)-oriented SrTiO3:Nb substrates under various oxygen pressures from 0.1 to 10 Pa at 700 °C by using a pulsed laser deposition method. Effects of the oxygen pressures on the crystallinity, dielectric and ferroelectric properties of the thin films were investigated at room temperature. The results show that the GaFeO3 thin films exhibit ferroelectricity and the properties of the thin films are influenced markedly by the deposition oxygen pressures. [ABSTRACT FROM AUTHOR]

Abstract: The P-Ga codoping ZnO thin films have been prepared on sapphire substrates by magnetron sputtering. Structural, optical and electrical properties of ZnO film were investigated using X-ray diffraction meter, transmittance spectra and resistivity, respectively. The obtained films were polycrystalline with the hexagonal structure, and a preferred orientation (0002) with the c-axis perpendicular to the substrates. The ZnO thin films became P- type after annealing. We have observed a room resistivity of 0.37Ωcm and a carrier concentration of 1.6×1018 cm−3 in P-type ZnO film. [Copyright &y& Elsevier]

Abstract: Tetrahedral amorphous carbon (ta-C) film was coated on aligned carbon nanotube (CNT) films via filtered cathodic vacuum arc (FCVA) technique. Field electron emission properties of the CNT films and the ta-C/CNT films were measured in an ultra high vacuum system. The I–V measurements show that, with a thin ta-C film coating, the threshold electric field (E thr) of CNTs can be significantly decreased from 5.74 V/μm to 2.94 V/μm, while thick ta-C film coating increased the E thr of CNTs to around 8.20 V/μm. In addition, the field emission current density of CNT films reached 14.9 mA/cm2 at 6 V/μm, while for CNTs film coated with thin ta-C film only 3.1 V/μm of applied electric field is required to reach equal amount of current density. It is suggested that different field emission mechanisms should be responsible for the distinction in field emission features of CNT films with different thickness of ta-C coating. [Copyright &y& Elsevier]

The electrochemical behavior of heme proteins such as hemoglobin (Hb), myoglobin (Mb), and horseradish peroxidase (HRP) was studied in stable thin films composed of the proteins and a natural bacterial endotoxin (lipopolysaccharide, LPS). All three protein-LPS films exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks in pH 6.0 phosphate buffers. Moreover, hydrogen peroxide and trichloroacetic acid could be reduced catalytically by the proteins entrapped in the films. Electrochemical parameters, such as the apparent Michaelis-Menten constant ( K app m) and formal potentials ( E 0), were obtained. The positions of the Soret absorption band of the proteins suggested that the three proteins could keep their secondary structure in LPS films. [ABSTRACT FROM AUTHOR]

Efficient hydrogenated diamond-like carbon (DLC) film deposition in a plasma reactor that features both the capacitive and inductively coupled operation regimes is reported. The hydrogenated DLC films have been prepared on silicon wafers using a low-frequency (500 kHz) inductively coupled plasma (LF ICP) chemical vapor deposition (CVD) system. At low RF powers, the system operates as an asymmetric capacitively coupled plasma source, and the film deposition process is undertaken in the electrostatic (E) discharge regime. The films deposited in the electrostatic mode feature graphite-like structure. Above the mode transition threshold, the high-density inductively coupled plasma is produced in the electromagnetic (H) discharge regime. Raman spectrometry suggests the possibility to control relative proportions of sp² and sp³ hybridized carbon. Variation of the DC substrate bias results in dramatic modification of the film structure from the polymeric (unbiased substrates) to the diamond-like (optimized bias). It has been shown that the deposition rate and hardness of the DLC film are much higher in the H-mode deposition regime. For a 20 mTorr H-mode CH[sub 4]+Ar gas mixture discharge, the DLC film exhibits mechanical hardness of 18 GPa, Young's modulus of 170 GPa, and compressive stress of 1. [ABSTRACT FROM AUTHOR]

The unique electron field emission properties of carbon nanotube films are promising for fiat panel display application as the cold cathode. In this work, the multiwall carbon nanotube (10-10² nm in diameter, and 10³-10[sup 4] nm in length) film arrays (the pixel size: 50 µm × 50 µm) were deposited on the patterned Ni-Si substrate from hydrocarbon precursor (C[sub 2]H[sub 2]/H[sub 2]) by chemical vapor deposition at low temperature (550°C). The patterned films were characterized by scanning electron microscopy and Raman spectroscopy. The carbon nanotube film arrays exhibit good electron emission properties, e.g. low threshold emission field (below 2 V/µm), high emission current density (above 1 mA/cm² at 10 V/µm), and high emission luminance spot density on the phosphor coated-ITO(indium tin oxide)glass anode. These properties are good enough for high-resolution flat panel display application using carbon nanotube film arrays as the cathode. [ABSTRACT FROM AUTHOR]

Abstract. The nonlinear optical properties of a new polymeric material, the doped film of 4'-(2",4",6"-trichlorophenazoamino)-phenazo-4-nitrobenzene, was studied. Large nonresonant optical nonlinearity (chi[sup (3)] is greater than or equal to 10[sup -28]C[sup 4]m/J[sup 3] or 10[sup -9] esu) and fast response time (t < 20 ps) were measured by forward degenerate four-wave mixing experiment. Optical bistable behavior in a quasi-waveguide interferometer with the thin film of the material was observed. The potential of the material for optical switching was evaluated. [ABSTRACT FROM AUTHOR]

Conductive atomic force microscope had been applied to study the electrical transportation mechanism together with topographic information on a periodical silica nanotrench structure. The bottom of the trench is covered by a 4 nm silica thin film, while the ridges between the trenches are made up of 90 nm thick silica film. On the same bias, the current transport through the bottom is larger than the current transport through the ridges. In the bottom, rectifying characteristics are observed; the conduction mechanism can be ascribed as a Schottky emission. Strong inhomogeneous electrical properties are also observed. A high resolution with a lateral resolution below 6 nm is demonstrated in the conductive atomic force microscope study. [ABSTRACT FROM AUTHOR]

Abstract: Ordered 2D-arrays of nanoparticles were synthesised by a poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) block-copolymer templated sol–gel process within a thin polymer film. The order within the filled polymer films was found to depend on the sol–gel content during synthesis. Grazing incidence small angle X-ray scattering and scanning electron microscopy imaging proved that well-ordered structures were created over large areas of the thin hybrid film. [Copyright &y& Elsevier]

A polymer, poly(phenylcarbyne) (PPC), was converted to carbon film by ultraviolet pulsed-laser (KrF, λ=248 nm) irradiation in nitrogen atmosphere at room temperature. The irradiated PPC consisted of fine graphitic carbon particles of several tens of nm in size, and exhibited good field emission properties. Low turn-on emission field of 2 V/μm (at 1 nA/cm[sup 2]), high emission current density of 20 mA/cm[sup 2] (at 12 V/μm), and high emission luminescent spots density of 10[sup 4]/cm[sup 2] were observed for the polymer film irradiated by a pulsed-laser fluence of 40 mJ/cm[sup 2]. We demonstrate multiple-lines and 2x5 array field emission patterns using the laser irradiation of PPC. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We discuss how reactive and dissipative nonlinearities affect the intrinsic response of superconducting thin-film resonators. We explain how most, if not all, of the complex phenomena commonly seen can be described by a model in which the underlying resonance is a single-pole Lorentzian, but whose centre frequency and quality factor change as external parameters, such as readout power and frequency, are varied. What is seen during a vector-network-analyser measurement is series of samples taken from an ideal Lorentzian that is shifting and spreading as the readout frequency is changed. According to this model, it is perfectly proper to refer to, and measure, the resonant frequency and quality factor of the underlying resonance, even though the swept-frequency curves appear highly distorted and hysteretic. In those cases where the resonance curve is highly distorted, the specific shape of the trajectory in the Argand plane gives valuable insights into the second-order physical processes present. We discuss the formulation and consequences of this approach in the case of nonlinear kinetic inductance, two-level-system loss, quasiparticle generation, and a generic model based on a power-law form. The generic model captures the key features of specific dissipative nonlinearities, but additionally leads to insights into how general dissipative processes create characteristic forms in the Argand plane. We provide detailed formulations in each case, and indicate how they lead to the wide variety of phenomena commonly seen in experimental data. We also explain how the properties of the underlying resonance can be extracted from this data. Overall, our paper provides a self-contained compendium of behaviour that will help practitioners interpret and determine important parameters from distorted swept-frequency measurements. [ABSTRACT FROM AUTHOR]

Titanium-containing tetrahedral amorphous carbon (ta-C:Ti) films with different titanium content were deposited by a filtered cathodic vacuum arc technique. The microstructure of these films was confirmed to be of ta-C+TiC[sub x](x<1) nanocomposite by Rutherford backscattering spectroscopy, x-ray diffraction, and micro-Raman spectroscopy experiments. With the increase of titanium content, the titanium carbide content increased and the sp[sup 3] fraction in the residual ta-C phase decreased gradually. In the electron field emission tests, it was found that proper conditioning processes are necessary for all these films in order to get a steady reproducible emission behavior. After conditioning, the emission threshold field of the films is about the same value, around 10 V/μm, except for the film with the lowest titanium content (∼1.2 at%) of which the threshold field is much higher, around 17-18 V/μm. The optimum titanium concentration in the film for field emission, showing the highest emission current and emission site density, is about 12 at%. After field emission testing, graphitization was involved and the titanium carbide phase, at least some of the sub-stoichiometric TiC[sub x] phase, in the ta-C:Ti films decomposed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

L10-FePt thin films with linearly distributed anisotropy were fabricated by continuously varying substrate temperatures from 650 °C to 290 °C. An average ordering parameter S = 0.6 was obtained. The hysteresis loop has a clear bow-tie shape with low remanence and coercivity before patterning. The patterned nanopillar arrays exhibit an enhancement in both remanence and coercivity. Dynamic coercivity measurement shows that the nanopillar arrays with linearly graded anisotropy have a relatively small intrinsic coercivity and a relatively high value of the figure of merit. The switching field exhibits a narrow distribution, which indicates a strong coupling between soft and hard phases in nanopillar arrays with graded anisotropy. [ABSTRACT FROM AUTHOR]

Abstract: Titanium dioxide nanotubes were directly fabricated from commercial P25 TiO2 via alkali hydrothermal transformation. The prepared titanate nanotubes were successfully used as an electrode material for dye-sensitized solar cells (DSCs). A metal-free organic dye (indoline dye D102) was used as a sensitizer. The used indoline dye D102 is of high purity (⩾98%) and high absorption coefficient (67,500Lmol−1 cm−1 at 501nm). The TiO2 pastes were prepared with PEG (Mw 20,000) and as-made TiO2 nanotubes or P25 powders. Titania thin films were grown by screen printing method. High conversion efficiencies of light to electricity of around 9.8% and 7.6% under illumination of simulated AM1.5 sunlight (100mW/cm2) were achieved with P25 and TiO2 nanotube cells, respectively. The fill factor of DSCs based on TiO2 nanotubes increased in comparison with that of DSCs based on TiO2 nanoparticles. The electron transport and dye adsorption properties in both titanate nanotube and P25 electrodes were evaluated in terms of photovoltaic characteristics of the fabricated cells. The related mechanisms were discussed. The study provides a promising method for the development of high-efficiency and low-cost DSCs. [Copyright &y& Elsevier]

Ta-C and iron containing amorphous carbon (a-C:Fe) films were deposited by filtered cathodic vacuum arc technique. The influences of Fe contents on the wettability of the films were investigated in terms of surface energy. The surface energy of a-C:Fe films was determined by the contact angle measurement. Atomic force microscopy (AFM), Raman spectroscopy and X-ray induced photoelectron spectroscopy (XPS) were employed to analyze the origin of the variation of surface energy with various Fe content. It is found that the contact angle for water increases significantly after incorporating Fe into the films and the films become hydrophobic. The roughness of these films has a little effect on the contact angle. The surface energy is reduced after incorporating Fe into the a-C film which is due to the reduction of both dispersive and polar component. The reduction in dispersive component is ascribed to the decrease of atomic density of the a-C:Fe films due to the increase in sp² bonded carbon. The absorption of oxygen on the surface play an important role in the reduction of polar component for the a-C:Fe films. It is proposed that such network as (C[sub n]-O-Fe)-O-(Fe-O-C[sub n]) may be formed and responsible for the reduction of polar component. [ABSTRACT FROM AUTHOR]

Amorphous silicon-carbon alloy films have been successfully deposited by filtered cathodic vacuum arc technique. The structural and mechanical properties of the films were investigated by using x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, surface profiler and nano-indenter. The silicon content in the films determined by XPS measurement varies from 2.4 to 48 at.%. Both XPS and Raman spectroscopy show the existence of silicon carbide dusters in the films containing intermediate concentration of silicon. The silicon atoms predominately substitute the carbon atom into the carbon clusters at low silicon concentration, and form amorphous silicon carbide clusters or amorphous silicon clusters at high silicon concentration. The hardness of the films varies from 60 to 22 GPa while the stress reduces from 8.0 to 2.1 GPa. [ABSTRACT FROM AUTHOR]

Iron containing diamond-like amorphous carbon (a-C:Fe) films were deposited by filtered cathodic vacuum arc technique. The influences of Fe content and substrate bias on the surface energy of the films were investigated. The surface energy of a-C:Fe films was determined by the contact angle measurement. Atomic force microscopy, Raman spectroscopy, and x-ray induced photoelectron spectroscopy were employed to analyze the origin of the variation of surface energy with various Fe content and substrate bias. It is found that the contact angle for water increases significantly after incorporating Fe into the films and the films become hydrophobic. The roughness of these films has no effect on the contact angle. The surface energy is reduced from 42.8 to 25 dyne/cm after incorporating Fe into the a-C film (10% Fe in the target), which is due to the reduction of both dispersive and polar component. The reduction in dispersive component is ascribed to the decrease of atomic density of the a-C:Fe films due to the increase in sp[sup 2] bonded carbon. When sp[sup 2] content increases to some extent, the atomic density remains constant and hence dispersive component does not change. The absorption of oxygen on the surface plays an important role in the reduction of the polar component for the a-C:Fe films. It is proposed that such network as (C[sub n]-O-Fe)-O-(Fe-O-C[sub n]) may be formed and responsible for the reduction of polar component. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A new in-between shots evaporative lithium coating system has been successfully developed and implemented on the Experimental Advanced Superconducting Tokamak (EAST) for the 2017 campaign. This paper describes a novel technique for the introduction of lithium into the EAST vessel allowing evaporative coatings to be applied between discharges without requiring a significant amount of time to insert and retract the lithium source. This newly designed system utilizes a rotating axis driven by a vacuum dynamic sealing feedthough under remote control to open and close a shutter. A compression bellows, which drives the delivery tube, guarantees accurate position of the oven thus avoiding possible direct contact with the plasma. This allows the new evaporation system to be operated in two distinct modes. One mode is operated in-between shots to refresh pre-coated lithium film, the other is a real-time lithium vapor injection during plasma operations to provide active wall conditioning during long pulse plasma discharges. In this paper, operation of this new lithium deposition system in the in-between shots replenishment mode is described. Initial experiments show that this system worked well during the interval of discharges in EAST, and the in-between shots lithium coating effectively reduced the wall recycling and impurity concentrations. Moreover, the application of fresh lithium coating lead to sustain the plasma stored energy and confinement, as well as a reduction of impurity radiation. [ABSTRACT FROM AUTHOR]

Topological insulators and graphene present two unique classes of materials, which are characterized by spin-polarized (helical) and nonpolarized Dirac cone band structures, respectively. The importance of many-body interactions that renormalize the linear bands near Dirac point in graphene has been well recognized and attracted much recent attention. However, renormalization of the helical Dirac point has not been observed in topological insulators. Here, we report the experimental observation of the renormalized quasiparticle spectrum with a skewed Dirac cone in a single Bi bilayer grown on Bi2Te3 substrate from angle-resolved photoemission spectroscopy. First-principles band calculations indicate that the quasiparticle spectra are likely associated with the hybridization between the extrinsic substrate-induced Dirac states of Bi bilayer and the intrinsic surface Dirac states of Bi2Te3 film at close energy proximity. Without such hybridization, only single-particle Dirac spectra are observed in a single Bi bilayer grown on Bi2Se3, where the extrinsic Dirac states Bi bilayer and the intrinsic Dirac states of Bi2Se3 are well separated in energy. The possible origins of many-body interactions are discussed. Our findings provide a means to manipulate topological surface states. [ABSTRACT FROM AUTHOR]

Abstract: AA2099-T8 aluminium alloy was anodized at a current density of 5mA/cm2 to selected voltages in 0.1M ammonium pentaborate electrolyte at 293K. It was found that the growth of barrier-type anodic film on the alloy was accompanied by oxidation of intermetallics, formation and rupture of oxygen gas-filled voids in the anodic film and healing of the anodic film at the sites of rupture. It was revealed that the formation of oxygen gas-filled voids was related to the oxidation of copper-rich nanoparticles in the copper-enriched layer at the film/alloy interface, and that the oxidation process of copper-rich nanoparticles depended on grain orientation. Further, the significantly reduced Pilling–Bedworth ratio for formation of anodic lithium oxide compared with that for formation of anodic alumina resulted in the formation of fine voids at the alloy/film interface and sequentially, detachment of the anodic film from the alloy surface. [Copyright &y& Elsevier]

The amorphous gallium nitride thin films doped with Mn were deposited by Laser assisted Molecular Beam Epitaxy (LMBE). After annealing at different NH flow rates, the high-quality GaMnN crystalline films with different concentration of nitrogen vacancies ( V) were obtained, which were confirmed by the X-ray diffraction spectroscopy and Raman measurements. The magnetic behaviors of these films were also obtained to investigate the effects of nitrogen vacancies. It indicates that V play a significant role in the origin of ferromagnetism. The stronger room-temperature ferromagnetism is given with the higher V concentration when it is not beyond a critical concentration. Moreover, from our M( T) curves and Raman analysis, the films present high resistivity. The magnetism of films with high resistivity varies with concentration of nitrogen vacancies, which can be explained by the bound magnetic polarons (BMP) theory. [ABSTRACT FROM AUTHOR]

A simple and hydrazine-free solution-based approach for depositing (CZTS) and (CZTSSe) absorber layers is reported. The process involves incorporating metal salts and thiourea into a single pyridine-based solution, spin-coating a precursor film, and sulfurizing with sulfur powders or selenizing using pellets in an inert atmosphere, to form the desired CZTS or CZTSSe films. X-ray diffraction and Raman spectra studies show that kesterite CZTS and CZTSSe are formed after sulfurization and selenization, respectively. The selenized CZTSSe displays higher crystallinity than the sulfurized CZTS. Photovoltaic devices (glass//CZTSSe//i-/n-/A) employing the solution precursor selenized at 500°C have yielded power conversion efficiency of 1.44% under AM 1.5 illumination. [ABSTRACT FROM AUTHOR]

Abstract: Cu(In,Ga)Se2 (CIGS) surface was modified with Zn doping using a magnetron sputtering method. CuInGa:Zn precursor films targeting a CuIn0.7Ga0.3Se2 stoichiometry with increasing Zn content from 0 to 0.8at% were prepared onto Mo-coated glass substrates via co-sputtering of Cu–Ga alloy, In and Zn targets. The CuInGa:Zn precursors were then selenized with solid Se pellets. The structures and morphologies of grown Zn doped CIGS films were found to depend on the Zn content. At zinc doping level ranging between 0.2 and 0.6at%, the Zn doping improved the crystallinity and surface morphology of CIGS films. Compared with the performance of the non-doped CIGS cell, the fabricated CIGS solar cell displayed a relative efficiency enhancement of 9–22% and the maximum enhancement was obtained at a Zn content of 0.4at%. [Copyright &y& Elsevier]

Abstract: The influence of ammonia concentration on stoichiometric, surface morphological, and optical properties of chemical bath deposited cadmium sulphide thin films has been studied systemically. Chemical bath deposition (CBD) of CdS thin films was carried out via using cadmium acetate as the cadmium ion source, thiourea as the sulphur source and ammonia as the complexing agent. Ammonia concentration was changed from 0 to 2.5M. At ammonia concentration greater than or equal to 0.1M and lower than 0.6M, nanowires or flake-like structures were obtained. At ammonia concentration ranging from 0.8 to 2.0M, uniform, dense, and continuously coated films were obtained. The energy dispersive X-ray spectroscopy (EDXS) analysis revealed that as the ammonia concentration changed from 0.1 to 2.0M, the Cd/S ratio in the obtained film increased from 0.24 to 2.61. Not only typical cadmium-poor but also unusual sulphur deficiency phenomena were observed for CBD CdS thin films. The films deposited with ammonia concentration of 1.0M show the highest degree of crystallinity and closest stoichiometry Cd/S≅1, and have a preferred orientation. The direct band energy gaps of as-grown films were found to be 2.23–2.77eV. The formation mechanism of the films with various morphologies and cadmium and sulphur deficiencies are discussed. [Copyright &y& Elsevier]

Abstract: ZnS thin films have been prepared by chemical bath deposition (CBD) technique onto glass substrates deposited at about 80°C using aqueous solution of zinc sulfate hepta-hydrate, ammonium sulfate, thiourea, ammonia and hydrazine hydrate. Ammonia and hydrazine hydrate were used as complexing agents. The influence of the ratio of [Zn]/[S] on formation and properties of ZnS thin films has been investigated. The ratio of [Zn]/[S] was changed from 3:1 to 1:9 by varying volumes and/or concentrations of zinc sulfate hepta-hydrate and thiourea in the deposition solution. The structural and morphological characteristics of films have been investigated by X-ray diffraction (XRD), scanning electron microscope and UV–vis spectroscopic analysis. ZnS films were obtained with the [Zn]/[S] ratio ranged from1:1 to 1:6. In the cases of [Zn]/[S] ratio≥3:1 or ≤1:9, no deposition was found. Transparent and polycrystalline ZnS film was obtained with pure-wurtzite structure at the [S]/[Zn] ratio of 1:6. The related formation mechanisms of CBD ZnS are discussed. The deposited ZnS films show good optical transmission (80–90%) in the visible region and the band gap is found to be in the range of 3.65–3.74eV. The result is useful to further develop the CBD ZnS technology. [ABSTRACT FROM AUTHOR]

Single-phase CuInSe2 films were grown by high vapor selenization of CuIn alloy precursors within a partially closed graphite box. The CuIn precursors were prepared using CuxIny alloy targets with different composition rates under low vacuum level by a homemade sputtering system. The Cu and In composition rates of the used targets are 11:9, 10:10, and 9:11, respectively. The metallic precursor films were selenized using a two-step temperature profile, i.e. at 250°C and 400–500°C, respectively. The influence of the temperature at the second selenization step on the quality of the CIS absorbing layers was investigated. The CIS films were characterized by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. The deposited CIS absorbers selenized at a high temperature of 500°C for 30 min exhibited a single-phase chalcopyrite structure with a preferential orientation in the (112) direction. These layers display uniform, large, and densely packed crystals with a grain size of about 3–5 μm. Cadmium sulfide buffer layer was manufactured by chemical bath deposition method. Bilayers ZnO/ZnO:Al were prepared by RF magnetron sputtering deposition. CIS solar cells with an efficiency of about 6.5% were produced without antireflective films. The method to fabricate CIS solar cells by a combination of the low vacuum sputtering deposition and the graphite box selenization process has provided a simple control process and shown a promising potential for developing high efficient and low-cost CuInSe2 solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Indium tin oxide (ITO) films were grown without external heating in an ambient of pure argon by RF-magnetron sputtering method. The influence of argon ambient pressure on the electro-optical properties of as-deposited ITO films was investigated. The morphology, structural and optical properties of ITO films were examined and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and UV–VIS transmission spectroscopy. The deposited ITO films with a thickness of 300nm show a high transparency between 80% and 90% in the visible spectrum and 14–120Ω/□ sheet resistance under different conditions. The ITO films deposited in the optimum argon ambient pressure were used as transparent electrical contacts for thin film Cu(In,Ga)Se2 (CIGS) solar cells. CIGS solar cells with efficiencies of the order of 7.0% were produced without antireflective films. The results have demonstrated that the developed ITO deposition technology has potential applications in thin film solar cells. [Copyright &y& Elsevier]

An improved chemical bath deposition (CBD) technique has been provided to prepare zinc sulfide (ZnS) thin films on glass substrates deposited at 80–82°C using a mixed aqueous solution of zinc sulfate, ammonium sulfate, thiourea, hydrazine hydrate, and ammonia at the alkaline conditions. Both the traditional magnetic agitation and the substrates vibration by hand frequently were done simultaneously during the deposition. The substrates vibration reduced the formation and residence of gas bubbles on the glass substrates during growth and resulted in growth of clean ZnS thin films with high quality. Ammonia and hydrazine hydrate were used as complexing agents. It is found that hydrazine hydrate played an important role in growth of ZnS films. The structure and microstructure of ZnS films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-vis spectroscopic methods. The XRD showed a hexagonal structure. The formed ZnS films exhibited good optical properties with high transmittance in the visible region and the band gap value was estimated to be 3.5–3.70 eV. [ABSTRACT FROM AUTHOR]

Copper indium diselenide (CuInSe2) thin films were grown on indium–tin oxide (ITO)/soda-lime glass using a one-step cathodic electrodeposition process at potentials lower than -0.6 V vs SCE, and in the presence of a large excess of In3+. The source solution contained CuCl2, InCl3, and H2SeO3 complexed by citric acid. The concentration of InCl3 in the electrochemical bath affected the structure, composition, stoichiometric ratio, and morphological properties of electrodeposited films. CuInSe2 films with a chalcopyrite structure and quite good stoichiometry were directly electrodeposited from a solution of 20 mM InCl3, 5 mM CuCl2, and 8 mM H2SeO3. Annealing of these CuInSe2 films in the temperature range from 300°C to 500°C improves their crystallinity and increases their grain size. Good chalcopyrite CuInSe2 films with a (112) preferential orientation suitable for the production of efficient solar cells are obtained after annealing at 500°C. The formation mechanism of the ternary CuInSe2 compound during the electrodeposition process was discussed. [ABSTRACT FROM AUTHOR]

A simply modified bath deposition technique has been successfully used to deposit uniform CdS thin films using cadmium chloride or cadmium acetate as the cadmium ion source, and thiourea as the sulfur source on glass substrates. Both the traditional magnetic agitation and the frequent substrate vibration by hand were done simultaneously during the deposition. Various properties of the deposited films such as surface morphology, crystallinity, and optical properties were investigated. The CdS films deposited from cadmium acetate show a good crystallinity and exhibit a preferential orientation along the hexagonal (002) direction. Their surface morphologies are more homogeneous with smaller grains than those from cadmium chloride. The CdS films prepared from both cadmium ion sources present a high optical transmission (more than 80%) in the visible range with the band gap value of about 2.4 eV. The substrate vibration reduces the formation and residence of gas bubbles on the glass substrate during growth and resulted in deposition of CdS thin films with high quality. XRD, SEM, and UV–Vis measurements have provided the supported data. The fundamental CBD growth mechanisms involving different cadmium salts are discussed. [ABSTRACT FROM AUTHOR]

Intrinsic zinc oxide (i-ZnO) film was prepared for CuInSe2 (CIS) solar cell application [L. Stolt and J. Hedstrom, Appl. Phys. Lett.62 (1993) 8; D. Rudmann, Ph.D. Thesis, University of Basel, Basel, (2004)] on glass substrate by inductively coupled plasma (ICP)-assisted DC magnetron sputtering and under a quite low temperature of 50°C. The sputtering was done in an Ar and O2 gas mixture and a ceramic ZnO target was used. The microstructures of the film were investigated by X-ray diffractometer and scanning electron microscope. It was shown that all of the films had a c-axis preferred orientation perpendicular to the substrate. In our work, film with resistivity of 7 × 108Ω·cm and transmittance of about 80% in the visible range was prepared under the conditions of 4 mTorr working pressure and 50°C temperature. [ABSTRACT FROM AUTHOR]

The dynamics and the conditions of amorphous transitions induced in a Ge1Sb2Te4 system upon a single femtosecond (fs) pulse melting were studied by real-time reflectivity measurements. The system has a multilayer structure of 100 nm ZnS–SiO2/(15–100 nm) Ge1Sb2Te4/120 nm ZnS–SiO2/0.6 mm polycarbonate substrate. It is shown that under optimum conditions amorphization is completed within 900 ps. The thickness of the phase change layer plays an important role in controlling the heat flow conditions in the system upon a fs pulse irradiation. The use of the fs laser pulse leads to a situation in which the pulse energy is deposited within a very short time in a thin surface layer, leading to heating or melting. The so-generated steep temperature gradient is subsequently smoothed by heat diffusion toward the substrate. The relative thermal process and effects are estimated. The calculated results are consisted with those from real-time reflectivity measurements. The mechanism of crystalline to amorphous transition triggered by single fs laser pulses is discussed. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) thin films were prepared by radio frequency (RF) magnetron sputtering and under a quite low vacuum level of 2.3 × 10-3Pa. The sputtering was done in an Ar and O2 gas mixture at a temperature of 200°C. A ceramic In2O3:SnO2 target (10 wt% SnO2) was used. The microstructures of the films were investigated by a field emission scanning electron microscope (FESEM) and an X-ray diffractometer (XRD). X-ray photoelectron spectroscopy (XPS) was performed to characterize the composition of the films. ITO films with a high transparency in the visible wavelength range (80–95%) were obtained. The dependency of the electrical, optical and structural properties of ITO films on both the O2 flow ratio (O2/(O2 + Ar)) and the working pressure was investigated. In the case of low working pressure (1 Pa), the more highly transparent and conducting films were produced at the lower O2 flow ratio. High working pressure (2 Pa) gave rise to low quality, low transparency and amorphous films. Under RF sputtering at low vacuum level, the main contribution to the chamber atmosphere is due to water vapor. Oxygen originating from water vapor dissociation induced by plasma plays the same role as an oxygen or water vapor flux usually intentionally introduced in the system in order to have good quality films. [ABSTRACT FROM AUTHOR]

Abstract: Nd3+-doped GeO2–SiO2 thin films are prepared by a sol–gel spin-coating process for photonic applications. Acid-catalyzed solutions of γ-glycidoxypropyltrimethoxysilane mixed with gemanium isopropoxide are used as matrix precursors. Thermal gravimetric analysis, UV–visible spectroscopy, and Fourier transform infrared spectroscopy are used to study the structural and optical properties of the thin films. The results indicate that crack-free and high transparency in the visible and near infrared range thin films with a thickness of about 0.7μm can be obtained by a single spin-coating process after a heat treatment at 500°C. A strong UV absorption region at short wavelength ∼200nm, accompanied with a shoulder peak at ∼240nm due to the neutral oxygen monovacancies defects, is also identified. The effect of Nd3+ doping concentration on up-conversion emission of the thin films is studied. An intense room-temperature violet up-conversion emission at 397nm is observed from the thin film with an optimum Nd3+ concentration of 0.5mol% upon excitation with a xenon lamp at the wavelength of 586nm. In addition to this intense violet emission, a relative weak ultraviolet emission at 372nm and a blue emission at 469nm are also observed. [Copyright &y& Elsevier]

Hydrogenated tetrahedral amorphous carbon (ta-C : H) films prepared by filtered cathodic vacuum arc at different hydrogen partial pressures (0.0008- 0.5mTorr) were studied in terms of their structure and properties. It is shown that a single Breit-Wigner-Fano (BWF) line shape is appropriate to fit the Raman spectra acquired from the ta-C : H films deposited at a hydrogen partial pressure of 0.0008-0.08 mTorr. However, the single BWF fit shows a residual near 1350 cm-1 for the film deposited at a higher hydrogen partial pressure. This indicates the presence of graphitic clusters in the corresponding film. The data from infrared spectroscopy show that the hydrogen in the ta-C : H films is associated with triply bonded sp1, CH[sub n] sp2 and CH[sub n] sp3 bonding. The absorption for the CH[sub n] sp3 is maximum for ta-C : H at a hydrogen partial pressure of 0.008 mTorr. It was observed that the film hardness and compressive stress are about 70 GPa and 12 GPa respectively corresponding to the hydrogen partial pressure from 0.0008 to 0.02 mTorr. When the hydrogen partial pressure further increases from 0.02 to 0.5 mTorr, the hardness and compressive stress decrease to about 50 GPa and 8 GPa respectively. The optical bandgap is about 3.0 eV for the ta-C:H film deposited at hydrogen partial pressure of 0.008 mTorr compared with 2.7 eV for the hydrogen free ta-C films. A lower intraband absorption coefficient of the ta-C:H sample (hydrogen partial pressure, 0.008mTorr) indicates that the defect states are lower in this sample. [ABSTRACT FROM AUTHOR]

We report a bistable resistance switching behavior of CuO thin films. To understand the resistance switching mechanism, we have studied impedance spectroscopy and nanoscale electrical property. From the frequency-dependent impedance properties of CuO thin films in high resistance (ROFF) and low resistance (RON) states, we infer the formation of conducting paths generated by external bias as a possible origin of the bistable resistance states. In addition, the observation of inhomogeneous conducting path using a conducting atomic force microscope is also consistent with our inference. [ABSTRACT FROM AUTHOR]

Electrosorption of ions from aqueous solutions with carbon nanotubes and nanofibers (CNTs-CNFs) composite film electrodes has been demonstrated. The large area CNTs-CNFs film was directly grown on Ni plate by low pressure and low temperature thermal chemical vapor deposition. The CNTs-CNFs electrodes have great advantages such as low cost, easy operation, long-term reproducibility, and integrity of monolithic CNTs-CNFs film and current collector. Batch-mode experiments at low voltage (0.4–2 V) were conducted in a continuously recycling system to investigate the electrosorption process. Purification of water with good reproducibility was achieved because of optimal pore size distribution of CNTs-CNFs composite films. [ABSTRACT FROM AUTHOR]

A solution process was used to grow SrTiO3 (STO) buffer layers on LaAlO3 (LAO) and biaxially textured Ni substrates by spin coating technique. The epitaxial STO film obtained has strong cube texture and uniform microstructure. A metal organic decomposition process using trifluoroacetate precursors was applied to deposit YBa2Cu3O7-δ (YBCO) thin films on these buffer layers. The YBCO/STO/LAO was biaxially textured and the TConset and ΔTC is 90.1K and 2.7K, respectively. [ABSTRACT FROM AUTHOR]

Cobalt-containing amorphous carbon composite films have been prepared by the filtered cathodic arc technique using a cobalt-containing graphite target at room temperature. After heat treatment at 550 °C in a mixture of acetylene and nitrogen gases, the field emission properties were significantly improved. A threshold electric field of 1.7 V/μm and an emission site density of 10[sup 5]/cm[sup 2] were obtained without conditioning. The composite films, which can be deposited with a high rate at room temperature and require a relatively low temperature heat-treatment process to enhance electron emission, are promising for practical applications in field emission display. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]