Corrosion of bare Ag,Ni/Ag and Cu/Ag films on glass by wet HCl vapor

The chemical corrosion of bare Ag, Ni/Ag and Cu/Ag films on an aluminoborosilicate and a soda lime glass in wet HCl vapor at 30 and 50°C was investigated. Ni and Cu produce additional chemical reactions which adversely affect the reflective characteristics of Ag films. Ni provides more chemical protection than Cu, but neither of them is as surable as bare Ag films.     

Ethanol steam reforming and water gas shift over Co/ZnO catalytic honeycombs doped with Fe,Ni, Cu,Cr and Na

The effect of Fe, Ni, Cu, Cr, and Na (1%) addition over ZnO-supported Co (10%) honeycomb catalysts in the steam reforming of ethanol (ESR) and water gas shift reaction (WGS) for the production of hydrogen was studied. HRTEM and EEL spectroscopy revealed the formation of metal alloys between Co and Fe, Ni, Cu, and Cr. Catalysts promoted with Fe and Cr performed better in the ESR, and the sample promoted with Fe showed high activity for WGS at low temperature. As deduced from TPR and oxidation pulse experiments, alloy particles in catalysts promoted with Fe and Cr exhibited a rapid and higher degree of redox exchange between reduced and oxidized Co, which may explain the better catalytic performance.     

Electrical and optical properties of Al doped cadmium oxide thin films deposited by radio frequency magnetron sputtering

Cadmium oxide thin films with different percentages of aluminum doping have been synthesized via radio frequency magnetron sputtering technique. Thin films were deposited on glass and silicon substrates with different percentages of aluminum at a substrate temperature of 573 K and pressure of 0.1 mbar in Ar+O₂ atmosphere. The deposited films were characterized by studying their structural, electrical and optical properties. The X-ray diffraction pattern revealed good crystallinity with preferred (1 1 1) orientation in the films. Aluminum doping in CdO thin films were confirmed by X-ray photoelectron spectroscopic studies and actual doping percentages were also measured from it. The optical band gap was found to decrease first and then increase with increasing percentages of aluminum concentrations. The electrical conductivity was found to increase with increase of aluminum doping concentration up to 5% but for higher doping concentration (>5%) the conductivity was found to decrease.     

Synthesis of nano-crystalline Zr-M (M=Ni,Co, Fe,Cu) bilayer films and their thermodynamics of hydrogen uptake by resistance measurement

Nano-crystalline thin metal films for hydride formation for small amount of hydrogen storage is an emerging field of research for portable applications e.g. thin film fuel cells. Nano-crystalline films of Zr/ M (M = Ni, Co, Fe, Cu) bilayer systems were synthesized using ion beam sputtering technique in argon atmosphere which were characterized using GIXRD and AFM techniques. In thin film metal hydride it is difficult to measure P-C-T isotherm because of the small amount of hydrogen present and the same difficulty is to study thermodynamics of such systems. Hence in the present work change in electrical resistance with hydrogen pressure in temperatures range 298 to 573 K has been used to investigate thermodynamic properties and found that resistance of film increases with the absorption of hydrogen and decreases due to hydrogen desorption.     

Structural, electrical and optical properties of annealed Al/Sb multiayer films

The multilayer Al/Sb thin films were deposited on quartz glass substrates using magnetron sputtering method and annealed at high temperature to obtain AlSb films. The experimental conditions were optimized to obtain the AlSb single phase. XRD measurements indicate that high-temperature annealing is necessary to form AlSb and is helpful to the grain growth of AlSb polycrystalline. The average grain size of AlSb polycrystalline increases obviously with the increase in annealing temperature when higher than 500 °C. The electrical measurements show that the prepared AlSb films are p-type semiconductors with the conductivity activation energy of 0.21 and 0.01 eV. The optical band gap for a typical AlSb film is 1.76 eV. The obvious photovoltaic effect has been observed in TCO/CdS/AlSb/ZnTe:Cu/Au devices, which demonstrated the potential of AlSb film as the absorber layer in thin film solar cells.     

Potential PV materials-based InN thin films: fabrication, structural and optical properties

The fabrication details, as well as basic structural and optical properties, of low temperature plasma enhanced reactively sputtered InN thin films are presented. SEM and AFM studies of surface morphology, including a microstructural cross-section were performed. Optical absorption and reflectance spectra of InN textured films at room temperature in the visible and NIR regions were taken, to reproduce accurately the dielectric function as well as to determine the optical effective mass of electrons (0.11) and the direct band gap (2.03 eV). Some TO (445, 480 and 490 cm⁻¹) and also LO (570 cm⁻¹) phonon features of indium nitride polycrystalline films in the near infrared and Raman spectra are presented and discussed.These results, both as obtained now and a few years ago from identical samples just after preparation, are in good agreement. This demonstrates an extraordinary long-term stability of this compound, with respect to its optical and electrical characteristics. The attractive possibilities based on model calculations of InN/Si tandem film systems for potential applications in photovoltaic devices, including high efficiency thin film solar cells, are emphasized and discussed.     

Preparation of nanocrystalline metal (Cr,Al, Mn,Ce, Ni,Co and Cu) modified ferrite catalysts for the high temperature water gas shift reaction

Water gas shift reaction is an essential process of hydrogen production and carbon monoxide removal from syngas. Fe–Cr–Cu catalysts are typical industrial catalysts for high temperature water gas shift reaction but have environmental and safety concerns related to chromium content. In this work nanocrystalline metal (M)-modified ferrite catalysts (M = Cr, Al, Mn, Ce, Ni, Co and Cu) for replacement of chromium were prepared by coprecipitation method and the effects of promoters on the structural and catalytic properties of the iron based catalysts were studied. Prepared catalysts were characterized using X-ray diffraction (XRD), N₂ adsorption (BET), temperature-programmed reduction (TPR) and transmission electron microscopies (TEM) techniques. Temperature-programmed reduction measurements inferred that copper favors the active phase formation and significantly decreased the reduction temperature of hematite to magnetite. In addition, water gas shift activity results revealed that Fe–Al–Cu catalyst with Fe/Al = 10 and Fe/Cu = 5 weight ratios showed the highest catalytic activity among the prepared catalysts. Moreover, the effect of calcination temperature, GHSV and steam/gas ratio on the catalytic performance of this catalyst was investigated.     

Structural and optical properties of hot wall deposited CdSe thin films

Cadmium selenide (CdSe) films were prepared by hot wall deposition technique using optimized tube length under a vacuum of 6 mPa on to well-cleaned glass and ITO substrates. The X-ray diffraction analysis revealed that the films are polycrystalline in nature for lower thickness and at lower substrate temperatures, but with increasing thickness and increasing substrate temperature a more preferred orientation along (0 0 2) direction was observed. The crystallite size (D), dislocation density (δ) and strain () were calculated. An analysis of optical measurements revealed a sharp absorption around 700 nm and a direct allowed transition. The band gap was found to be around 1.7 eV. The effect of thickness and substrate temperature on the fundamental optical parameters like band gap, refractive index and extinction coefficient are studied.     

Studies on optical and electrical properties of SILAR-deposited CuO thin films

CuO thin films prepared by SILAR technique using aqueous solutions of various pH values and their characterization are presented in this report. The pH dependence on structural, morphological, optical and electrical properties of the prepared films is studied. Thickness of films is found to vary in between 0.52 and 0.82 µm. Microstructural parameters such as crystallite size, strain and dislocation density of the film have been evaluated. The crystallographic behaviour of the film has shown that all the coated thin films are in monoclinic structure with (002) preferred orientation. The size of the crystallites is found to increase with the pH values. Surface morphological behaviour of the films prepared using different pH values are analysed. Optical properties of the films were analysed from absorption and transmittance studies of CuO thin films. Band gap energy values of CuO thin films have been found to decrease from 2.12 to 1.91 eV with increasing pH values of the solution. The thin film formed at a solution pH 11 has shown least resistivity and high carrier concentration. The I-V characteristics of n-Si/p-CuO heterojunction under 200-watts halogen lamp illumination show open-circuit voltage of ~ 0.37 V and short-circuit current of ~1.02 × 10^?6 A.     

ZnO thin films,surface embedded with biologically derived Ag/Au nanoparticles,for efficient photoelectrochemical splitting of water

ZnO thin films, showing nano-ridges at the surface and the top layer embedded with metal (Ag/Au) nanoparticles (MNP), were obtained by sol-gel synthesis, using zinc acetate dihydrate [(CH₃.COO)₂Zn.2H₂O] as precursor. The method involved prior synthesis of Ag and Au nanoparticles via biological reduction of AgNO₃ and HAuCl₄, respectively, using algae Spirulina platensis. The XRD analysis indicated dominant evolution of wurtzite ZnO phase. Low-angle shift in peaks, seen with nanoparticles embedded films, indicated partial diffusion of metals into ZnO lattice. Band gap energy was least affected and lied in the expected range. AFM and SEM analysis revealed the surface topography and morphology, while EDX analysis confirmed the elemental stoichiometry and existence of Ag/Au nanoparticles in samples. Significant gain in photoelectrochemical current using MNP embedded films is largely accountable to the improvement in electrical conductance and the role played by metal nanoparticles in charge-carrier separation, collection and transport.     

The catalytic effect of Fe and Cr on hydrogen and deuterium absorption in Mg thin films

We examined the deuterium absorption and desorption of 55 nm thick Mg films alloyed with Fe and Cr using in-situ neutron reflectometry. The Mg alloy films were covered with bimetallic catalyst layers and could be fully absorbed at room temperature at a pressure of 8 mbar. The NR experiments revealed a deuterium gradient within the Mg alloy layers during absorption and a large deuterium uptake up to a D/M ratio of about 0.45 before the layer started to expand and form magnesium deuteride (MgD₂). Our NR data suggest that the catalytic effect of the Fe–Cr alloy is based on the avoidance of the formation of a blocking MgD₂ layer in the early stages of the absorption process leading to a fast hydrogen absorption kinetics.     

Effect of Au,Ag and Cu thin films' thickness on the electrical parameters of metal-porous silicon direct hydrogen fuel cell

The effect of the thickness of the gold, silver and cupper films on the electrical properties such as open circuit voltage (V_oc) and short circuit current (I_sc), in the direct hydrogen fuel cell, which uses water as a source of hydrogen, is studied by fabricating Metal/Porous Silicon/n-Silicon/Indium structures. The Porous Silicon (PS) layer on n-type (111) oriented silicon wafers were prepared by anodization. The thin films of Au or Ag or Cu with different thicknesses between 120 and 600 nm were deposited onto the PS surface by the electron-beam technique. The obtained results indicated that V_oc and I_sc, strongly depend on the Au, Ag and Cu layer thicknesses. The Au/PS/n-Si structure generated highest V_oc and I_sc values for all thicknesses of Au film. The best values of V_oc and I_sc were obtained at 325 nm as 0.89 V and 0.021 mA for Au, at 350 nm as 0.75 V and 0.017 mA for Ag, at 350 nm as 0.50 V and 0.010 mA, respectively.     

Structure and optical properties of M/ZnO (M=Au, Cu, Pt) nanocomposites

Metal (Au, Cu, Pt)/zinc oxide nanocomposite films were prepared with different metal contents by radio frequency co-sputtering technique. The films were annealed at different temperatures in an argon atmosphere for 2 h. Formation of metal nanoparticles was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). UV-Vis optical absorption spectroscopy was used for optical characterization of the samples. With the increase of annealing temperature, the size of the metal particles in the ZnO matrix varied. Surface plasmon resonance bands were observed in the Au/ZnO and Cu/ZnO composite films due to the formation of nanometer-size Au and Cu particles in the matrix. However, a similar behavior was not seen with Pt/ZnO composites. Upon incorporation of Pt nanoparticles in the ZnO matrix, the optical band gap of the matrix was drastically reduced.     

Ozone coloration of Ni and Cr oxide films

Films of Ni and Cr oxide were made by reactive DC magnetron sputtering. Ozone exposure, obtained by ultraviolet irradiation in the presence of oxygen, gradually induced coloration in the initially transparent films. Electrochemical measurements correlated the optical absorption with a charge deficiency in the film. Our results demonstrate a convenient technique for treating the counter electrode in a W-oxide-based electrochromic device prior to device assembly.     

Effect of the Cu underlayer on the optoelectrical properties of ITO/Cu thin films

Sn doped indium oxide (ITO) single layer films and ITO/Copper (Cu) bi-layer films were prepared on polycarbonate substrates by DC and RF magnetron sputtering without intentional substrate heating. In order to consider the influence of the Cu underlayer on the optoelectrical properties and microstructures of the films, the thickness of the Cu bottom layer in the ITO/Cu films was varied from 5 to 20 nm.Conventional ITO films had a constant optical transmittance of 74% and an electrical resistivity of 3.1 × 10⁻³ Ω cm, while ITO/Cu films had different optoelectrical properties that were influenced by the thickness of the Cu bottom layer. The lowest electrical resistivity, 5.7 × 10⁻⁵ Ω cm, was obtained from ITO 80 nm/Cu 20 nm films and the highest optical transmittance of 72%, was obtained from the ITO 95 nm/Cu 5 nm films. From the figure of merit (_TC) which is defined by _TC = T¹⁰/R_s, where T is the optical transmittance at 550 nm and R_s is the sheet resistance, it can be concluded that the most effective Cu thickness in the ITO/Cu films on the optoelectrical properties was 5 nm.     

Structural, morphological, optical and electrochromic properties of Ti-doped MoO3 thin films

Thin films of molybdenum trioxide (MoO₃) doped with titanium were prepared using a spray pyrolysis technique. Increasing Ti doping concentration was found to hamper the polycrystalline nature of undoped orthorhombic MoO₃ and undergo transformation from polycrystalline to amorphous structure with decrease in grain size. This was also reflected in scanning electron microscopy wherein transformation of thread-like reticulated morphology to spongy structures could be observed at higher Ti concentration (9 at% Ti). With increasing Ti concentration, the charge capacity, coloration efficiency, reversibility and electrochemical stability increased. This improvement could be ascribed to the amorphous spongy morphology of the doped samples that offers easy pathway for intercalation and deintercalation of the ions. Hence, 9 at% Ti-doped MoO₃ can act as an adequate host for electrochromic devices.     

Structural, compositional, and optical properties of electrochemically deposited stoichiometric CdSe thin films from non-aqueous bath

In the recent years, cadmium chalcogenide compounds have been extensively investigated because of their potential applications in solar energy conversion. Thin films of CdSe have been deposited onto the stainless steel and fluorine doped tin oxide (FTO) coated glass substrates using simple and inexpensive electrodeposition technique. The non-aqueous solvent ethylene glycol (CH₂OHCH₂OH) containing precursors of Cd and Se with ethylenediaminetetraacetic acid (EDTA) tetra sodium salt as a complexing agent is used to obtain stoichiometric deposits. Deposition potential was estimated from polarization curves and other preparative parameters such as bath temperature and concentration of solution were optimized. X-ray diffraction (XRD) analysis reveals that the films are polycrystalline with cubic structure. PEC study shows the CdSe films are photoactive. Optical absorption study shows the presence of direct transition with band gap energy 1.72 eV. The energy dispersive analysis by X-rays (EDAX) reveals that the substrate is well covered with large number of grains indicating compact structure. The average ratio of the atomic percentage of Cd:Se is 50.31:49.69, showing that the deposited films are almost stoichiometric.     

Structural, optical and electrical properties of indium tin oxide thin films prepared by spray pyrolysis

Spray pyrolysis process has been used to deposit highly transparent and conducting films of tin-doped indium oxide onto glass substrates. The electrical, structural and optical properties have been investigated as a function of various deposition parameters namely dopant concentrations, temperature and nature of substrate. The morphology of the surface as a function of the substrate temperature has been studied using atomic force microscopy. XRD has shown that deposited films are polycrystalline without second phases and have a preferred orientation (4 0 0). Indium tin oxide layers with low resistivity values around 4×10⁻⁵ Ω cm and transmission coefficients in the visible and near-infrared range of about 85–90% have been easily obtained.     

Hydrogenation effect on structural,electrical and optical properties of CdS thin films for solar cell

Adsorption effects would be expected to be of considerable importance with thin films because of the changes in electron location accompanying adsorption. The effects of hydrogenation on structural, optical and electrical properties of the CdS thin films have been reported. GIXRD patterns shows that films have polycrystalline nature with a hexagonal structure. The optical band gap increased after hydrogenation of the film. The variation of conductivity of CdS films have been investigated depending upon the applied voltage at room temperature. The resistivity increased after hydrogenation of the films. Hydrogenated thin films can be used in solar cells because hydrogen plays an important role to modify the physical properties.     

Structural and optical properties of sulfur-annealed CuInS2 thin films

CuInS₂ thin films were deposited by single source vacuum thermal evaporation method on substrates submitted to longitudinal thermal gradient. Some of these films were annealed in sulfur atmosphere and converted into CuInS₂ homogenous layers. Both of the as-deposited and sulfurated films were characterized by X-ray diffraction, optical transmission and reflection measurements. The optical band gap of films after sulfurization was 1.50 eV which is near the optimum value for photovoltaic energy conversion.