Electrochemical synthesis and characterization of zinc selenide thin films

In this work, electrochemical deposition and characterization of zinc selenide (ZnSe) thin films is reported. ZnSe thin films were deposited onto tin oxide (SnO₂) coated conducting glass substrates from an aqueous solution bath containing ZnSO₄ and SeO₂. The effect of deposition parameters such as bath temperature, deposition time and electrolyte composition on the properties of the ZnSe films has been studied. Cyclic Voltammetric studies were carried out to optimize the deposition potential for the co-deposition of Zn and Se. Deposited ZnSe films have been characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscope (SEM) and optical techniques for their structural, compositional and optical properties and the results are discussed.     

Electrochemical synthesis of thin CdS films

Thin cadmium sulfide (CdS) films have been electrochemically synthesized on metal substrates and the related photosensitive surface barrier structures have been obtained. The proposed method can be used in the technology of thin-film photoelectric converters with large areas.     

Electrochemical deposition and characterization of cupric oxide thin films

Polycrystalline cupric oxide (CuO) thin films are deposited using an alkaline solution bath employing cathodic electrodeposition method. Thin films are electroplated at various bath temperatures onto conducting indium tin oxide coated glass substrates. The bath temperature effects on the structural, optical and morphological properties of copper oxide films are studied and reported. X-ray diffraction studies revealed mixed phases of monoclinic and cubic for films grown at lower bath temperatures and that the deposited films at temperatures optimized as 75 °C exhibited cubic structure with preferential orientation along a (111) plane. Texture coefficient (T_c) values are calculated for all diffraction lines and the films were highly textured (T_c > 1). The surface morphology and surface roughness are estimated using scanning electron microscopy and atomic force microscopy, respectively and a morphology made up of pyramid shaped grains is presented. Energy dispersive analysis by X-rays revealed that the near stoichiometric CuO thin films are obtained at optimized preparative parameters. The refractive index is calculated using the envelop method. Also, the optical constants of CuO thin films such as complex dielectric constant (ε) and extinction coefficient (k) are also evaluated and reported.     

Electrochemical synthesis of Tl-based highT c single-phase superconductor thin films

Co-deposition of the Tl-based superconductors using electrodeposition technique was successfully carried out. Different processing parameters such as deposition potential, current density, deposition period etc were studied. The Tl-based alloyed thin films were deposited at a constant potential of −1·25V with respect to SCE electrode onto silver substrates and oxidized at 850°C in oxygen atmosphere. The samples thus prepared showed superconducting behaviour below 122·5 K and the critical current density was 1·5×10³A/cm². Electrochemical synthesis of Tl-based highT _c single-phase superconductor thin films is also reported.     

Sol-gel synthesis of nickel oxide thin films and their characterization

Sol-gel method has been employed for the synthesis of nanocrystalline nickel oxide (NiO). The NiO powders were sintered at 400-700 °C for 1 h in an air. Thin films of sintered powders were prepared on glass substrate using spin coating technique and changes in the structural, morphological, electrical and optical properties were studied. The structural and microstructural properties of nickel oxide films were studied by means of X-ray diffraction and field emission scanning electron microscopy. Structural analysis shows that all the films are crystallized in the cubic phase and present a random orientation. Surface morphology of the nickel oxide film consists of nanocrystalline grains with uniform coverage of the substrate surface with randomly oriented morphology. The electrical conductivity showed the semiconducting nature with room temperature electrical conductivity increased from 10^− 4 to 10^− 2 (Ω cm) ^− 1 after sintering. The electron carrier concentration (n) and mobility (μ) of NiO films annealed at 400-700 °C were estimated to be of the order of 1.30 to 3.75 × 10¹⁹ cm^− 3 and 1.98 to 4.20 × 10^− 5 cm² V^− 1 s^− 1.The decrease in the band gap energy from 3.86 to 3.47 eV was observed for NiO sintered between 400 and 700 °C. These mean that the optical quality of NiO films is improved by sintering.     

Electrochemical synthesis of Hg-Ba-Ca-CuO superconducting thin films from a nonaqueous solution

Quaternary alloy thin films of Hg-Ba-Ca-Cu with the composition 1:2:2:3 were successfully synthesised from a dimethyl sulphoxide bath using the electrodeposition technique. Ba-Ca-Cu alloy films were first electrodeposited onto silver substrates at a deposition potential of −1.2 V versus SCE. These films where then oxidised at 600°C for 8 h and mercury electrodeposited on these films at a potential of −1.3 V versus SCE followed by an oxidation treatment at 200°C for 8 h. The films, after these treatments, were tested for their electrical properties and were found to show superconducting behaviour below T_c = 114 K.     

Electrochemical performance of diamond-like carbon thin films

Diamond-like carbon (DLC) thin films used in this study were intended for their electrochemical properties. The DLC films were deposited by a filtered cathodic vacuum arc (FCVA) process on p-type silicon (100) substrates biased at different pulse voltages (0-2000 V). The chemical bonding structures of the DLC films were characterized with micro-Raman spectroscopy and the electrochemical properties were evaluated by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The DLC films showed high impedance, high polarization resistance and high breakdown potential in a 0.5 M H₂SO₄ aqueous solution, which were attributed to the high sp³ content and uniformity of the films. The excellent chemical inertness of the DLC films made them promising corrosion resistant coating materials.     

Electrochemical fabrication of nanoporous polypyrrole thin films

Polypyrrole thin films with pores in nanometer scale were synthesized by direct electrochemical oxidation of pyrrole in a mixed electrolyte of isopropyl alcohol, boron trifluoride diethyl etherate, sodium dodecylsulfonate and poly(ethylene glycol) using well-aligned ZnO nanowires arrays as templates. The thin films exhibit high conductivity of ca. σ_rt ∼ 20.5  s/cm and can be driven to bend during redox processes in 1.0  M lithium perchlorate aqueous solution. The movement rate of an actuator based on this nanoporous film was measured to be over 90°/s at a driving potential of 0.8  V (vs. Ag/AgCl).     

Bi-Te-Se热电薄膜的电化学沉积

在含有Bi 3＋、HTeO2＋、Se4＋离子的水溶液中通过电化学方法实现了Bi2Te3-ySey热电薄膜沉积,研究了电沉积Bi2Te3-ySey的阴极极化曲线及热电薄膜的生长过程,通过电子显微镜（SEM）和能谱仪（EDS）等手段对热电薄膜进行了形貌、成分分析。结果表明电解液的离子组成、沉积电位对薄膜成分、形貌有较大影响。在-0.07V沉积电位下制备的热电薄膜Bi2Te2.75Se0.95晶粒大小均匀,结构致密。     

Photothermal characterization of thin films and coatings

The principles of non-destructive, non-contact characterization of coatings by means of photothermal measuring techniques are briefly explained. A method of quantitative interpretation is presented, which relies on the relative extrema of the calibrated thermal wave phase lags measured as a function of the heating modulation frequency for coatings deposited by reactive magnetron sputtering. The application potential of this interpretation method with respect to the on-line control of coating deposition processes is discussed.     

Tem characterization of nanodiamond thin films

The microstructure of thin films grown by microwave plasma-enhanced chemical vapor deposition (MPCVD) from fullerene C₆₀ precursors has been characterized by scanning electron microscopy (SEM), selected-area electron diffraction (SAED), bright-field electron microscopy, high-resolution electron microscopy (HREM), and parallel electron energyloss spectroscopy (PEELS). The films are composed of nanosize crystallites of diamond, and no graphitic or amorphous phases were observed. The diamond crystallite size measured from lattice images shows that most grains range between 3–5 nm, reflecting a gamma distribution. SAED gave no evidence of either sp²-bonded glassy carbon or sp³-bonded diamondlike amorphous carbon. The sp²-bonded configuration found in PEELS was attributed to grain boundary carbon atoms, which constitute 5–10% of the total. Occasionally observed larger diamond grains tend to be highly faulted.     

氧化锌薄膜溶胶-凝胶分析

应用sol-gel技术,在普通载玻片上制备出透明的ZnO薄膜。由于醋酸锌前驱体在醇中的溶解度小，因此刺备过程中，选用了质子化能很强的物质(如乙醇胺)改变了其在醇中的溶解度。本文还通过热分析、红外光谱等手段分析了不同温度下ZnO的sol-gel热分解过程。并应用AFM、X射线衍射和UV—Vis吸收光谱对sol-gel路线制得的薄膜进行表征。实验结果表明：二水醋酸锌-单乙醇胺-异丙醇体系sol-gel的热分解过程与纯二水醋酸锌过程的分解大相径庭。ZnO薄膜的sol-gel的分解趋于一步完成。预处理温度对ZnO薄膜的性能有显著影响。只有通过控制试验条件，才能保证ZnO薄膜的透光率。     

Electrochemical synthesis and characterization of hydroxyapatite powders

Electrochemical synthesis of hydroxyapatite powders was performed galvanostatically from homogeneous solution of Na₂H₂EDTA·2H₂O, NaH₂PO₄ and CaCl₂ at a concentration relationship Ca/EDTA/PO₄³⁻ of 0.25/0.25/0.15 M at current densities of 137 and 207 mA cm⁻² and pH values of 9.0 and 12.0. The hydroxyapatite powders were characterized by X-ray diffraction, size distribution measurements, transmission electron microscopy, scanning electron microscopy and thermogravimetric and differential thermal analysis. The influence of the electrochemical synthesis parameters, e.g. applied current density and pH value, on the phase composition, crystallite size, morphology and thermal characteristics of hydroxyapatite powders were investigated.     

Electrochemical corrosion behavior of amorphous carbon nitride thin films

The corrosion behavior along with biocompatibility and mechanical properties plays an important role in determining of biomedical implants feasibility. Diamond-like carbon seems to be the promising material in which all these three requirements can be achieved. In this study nitrogen doped amorphous carbon (a-C:N) films were deposited on silicon and medical CoCrMo alloy substrates by vacuum glow discharge sputtering technique using different deposition conditions from graphite target. Potentiodynamic polarization tests were employed to assess the corrosion performances of the films at room temperature in 0.89 wt. % NaCl solution. The influence of substrate bias on the electrochemical corrosion behavior was investigated. The highest value off E_corr for CoCrMo substrate was measured on the coating deposited with substrate bias around −0.6 kV. The shift of E_corr to more positive values was about 350 mV.     

Preparation and characterization of oxidized silver thin films

Silver reacts readily with atomic oxygen, which is present in oxygen plasmas and in low earth orbit. To study the oxidation process, silver films were deposited by r.f. sputtering or by thermal evaporation, then exposed to an oxygen plasma from an electron cyclotron resonance (ECR) source. In-situ spectroscopic ellipsometry (SE) was used to monitor deposition and oxidation, and determine final thicknesses and optical constants. SE indicated that oxidation began at the surface of the silver and proceeded downward, with a rough interface which increased steadily in thickness. Oxide films were nearly transparent over the visible spectrum, where the refractive index was above 2, and were strongly absorbing below 400 nm. Completely oxidized films were twice as thick as the original silver films. They appeared smooth to the eye, and were relatively stable in ambient air. Films that were not oxidized all the way through were much less stable in air, changing interference color and appearing rough within a few days. Oxide films deposited by reactive sputtering of silver in an O₂ background had higher refractive index ( > 2.5) than the ECR oxidized silver films. They were also relatively stable in air, unless deposited onto silver, in which case the samples changed color and appeared rough within a few days, similar to the partially oxidized silver films.     

Electrodeposition and characterization of CdSe semiconductor thin films

The electrodeposition of cadmium selenide alloy on glassy carbon and gold electrodes has been studied by electrochemical techniques. Potentiostatic I-t transients were recorded to obtain the nucleation mechanism, while cyclic voltammetry was used to characterize the system. Structural information on the electrodeposited layers was obtained by X-ray diffraction. The experimental results clearly show that the deposition of cadmium selenide alloy on glassy carbon and gold electrodes is a diffusion-controlled process. The nucleation is progressive, and the number of nucleation sites decreases with increasing bath temperature. The deposition of CdSe alloy results in well-defined crystals with hexagonal shape. The films were characterized by optical absorption and electrical resistivity measurements. Films showed a direct band gap of 3.56 eV.     

Optical and electrical characterization of CdS thin films

Thin CdS films have been grown by chemical bath (CdCl₂, thiourea, ammonia) deposition (CBD) on SnO₂ (TO)-coated glass substrate for use as window materials in CdS/CdTe solar cells. High-resolution transmission electron microscopy revealed grains with an average size of 10 nm. The structure was predominantly hexagonal with a high density of stacking faults. The film crystallinity improved with annealing in air. Annealing in a CdCl₂ flux increased the grain size considerably and reduced the density of stacking faults. The optical transmission of the as-deposited films indicated a band gap energy of 2.41 eV. Annealing in air reduced the band gap by 0.1 eV. Annealing in CdCl₂ led to a sharper optical absorption edge that remained at 2.41 eV. Similar band gap values were obtained by photocurrent spectroscopy and electroabsorption spectroscopy (EEA) using an electrolyte contact. EEA spectra were broad for the as-deposited and air-annealed samples, but narrower for the CdCl₂-annealed films, reflecting the reduction in stacking fault density. Donor densities of ca. 10¹⁷ cm ^–3 were derived from the film/electrolyte junction capacitance.     

电沉积技术制备钼酸钡薄膜及其特性表征

采用恒电流电沉积技术，在不同衬底（金属钼片、镀金的硅片、ITO导电玻璃）上，不同溶液酸碱性的条件下制备出了具有白钨矿结构的钼酸钡薄膜，利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、原子力显微镜（AFM）对制备的薄膜进行了分析表征。分析了利用电沉积方法制备的钼酸钡薄膜的成膜机制．实验结果表明：在室温环境下，利用电沉积技术，在不同材质的衬底（金属钼片、镀金的硅片和ITO导电玻璃）上，可以制备出具有白钨矿结构钼酸钡薄膜，不同材质的衬底会影响到薄膜晶粒的形状进而影响薄膜的表面形貌和致密性，用镀金的硅片（Au-Si片）作衬底时，制备的钼酸钡薄膜晶粒更加饱满，晶体生长呈四方锥形，晶界清晰。     

Growth and characterization of CuInSe2 thin films

Films of CulnSe₂ have been grown using a technique similar to close-spaced vapour transport. The effect of substrate temperature and the distance of the substrate from the source have been optimised to grow well-oriented chalcopyrite phase of CuInSe₂. D.c. conductivity and Hall coefficient studies have been made in the temperature range 77–300 K. The films grown at a substrate temperature of 350 °C have an electron mobility of 3.4×10³ cm²V^–1 s^–1 at 77 K.