Polycrystalline Cadmium Sulfide Research Articles

無電解めっきによるカドミウム皮膜の形成

Electroless deposition of cadmium films was investigated using titanium trichloride as a reducing agent. Cadmium films were formed direcity on the surface of aluminum substrates activated with palladium. The deposition rate increased with increasing titanium trichloride concentration, bath temperature, and pH.Silver-like bright cadmium film was produced from a solution containing cadmium dichloride 0.08M, trisodium citrate 0.34M, disodium EDTA 0.08M, NTA 0.20M, and titanium trichloride 0.04M, at temperatures above 70°C and pHs above 9.5. Each complexing agent served as bath stabilizer as well as plating promoter. Intended thickness was obtained by renewing the bath at 30-minute intervals.Cadmium sulfide film was also electrolessly plated from the cadmium bath to which sodium thiosulfate was added. Films obtained at above pH 10.0 were of polycrystalline cadmium sulfide similar to chemically deposited films for solar cell applications.

Influence of laser treatment on the adsorption interaction of cadmium sulfide films with oxygen

During interaction of pulsed laser radiation with the surface of polycrystalline cadmium sulfide films an enrichment of sulfur vacancies near the surface was previously observed. In this paper, the adsorption-desorption sensitivity (ADS) of the cadmium sulfide film to oxygen was determined by the temperature dependence of the dark current. In this case, the sulfur vacancies serve as adsorption centers. The presence of surface and volume components of ADS was detected. Here the surface portion of ADS remains essentially unchanged, but the volume component grows with increase in the radiation dose.

Thickness dependent properties of electro-chemical-photovoltaic (ecpv) cells formed with chemically deposited CdS films

Thin polycrystalline cadmium sulphide photoelectrodes of various thicknesses have been deposited on polished stainless steel substrates by a chemical bath deposition technique. The electrochemical photovoltaic (ecpv) cells were formed with these photoanodes. Short circuit current (Isc) and open circuit voltage (Voc) are recorded under 100 mW/cm2 light intensity. It is found thatIsc increases with increase in thickness of the photoanode whereasVoc remains more or less constant. The other cell parameters, maximum power output (Pm) and efficiency (η) are found to improve with increasing thickness, while fill factor (f.f.) varies slightly with the photoanode thickness. The semiconductor-liquid space charge region capacitances in the dark were measured. The variation of 1/C 2 versus applied reverse biasV is nonlinear. The deviation from straight line behaviour is attributed to the existence of surface states and degeneracy of states. The flat band potential is determined from the extrapolation of the (1/C 2) −V plot to the voltage axis, and is found to vary with the thickness of the photoanode.

The mechanism of photoconductivity in polycrystalline cadmium sulphide layers

The mechanism of photoconductivity in polycrystalline CdS has been studied over the temperature range 100–300 K using Hall-effect and conductivity measurements in the dark and under white light illumination. Samples were prepared in thin film form by spray pyrolysis and as power-binder mixtures. Dark conductivities covered the range 10−9–101 Ω−1 cm−1. Dark conductivity is interpreted in terms of a two-dimensional version of the grain-boundary barrier model developed by Seto for polycrystalline Si. Except at very low carrier densities, Hall mobilities are found to be thermally activated, and intergrain barrier heights φb are derived for spray pyrolysis layers with doping levels covering the range N = 1014–1018 cm−3. A maximum barrier φbmax ≊0.2 Ev is found at a corresponding doping level, Nmax ≊2×1016 cm−3, which represents the situation where the barrier depletion layers just extend through the whole grain. From this we derive a mean grain diameter of 0.3 μm in good agreement with the result of transmission electron microscopy. For samples having N<Nmax the average free carrier density n̄≪N and photoconductivity occurs entirely through an increase in n̄ up to the point where the depletion regions begin to contract away from the center of the grains. For samples having N≳Nmax both μ and n̄ increase. The detailed variations of μ and n̄ are interpreted in terms of the Seto model with the added hypothesis that photogenerated holes are all trapped at grain boundaries. Hall-effect measurements are interpreted on the assumption that the Hall coefficient R measures the average carrier density in the grain, i.e., R = (n̄e)−1, and we note that n̄ may differ significantly from the doping level N, even when N⩾Nmax. Photo-Hall results provide evidence in support of this hypothesis.

Photoelectrochemical Cells with Polycrystalline Cadmium Sulfide as Photoanodes

AbstractA simple procedure for the fabrication of fairly efficient polycrystalline CdS electrodes from CdS powders is described (by coating a thin film of a paste formed with an aqueous solution of a surfactant and ZnCl2 on a Ti substrate and sintering at 670°C in Ar). Light conversion efficiencies of these thin film (‐20 μm) electrodes have been tested in two regenerative solar cells (with Fe(CN)63‐/4‐ and polysulfide redox systems) and ζsolar and ζ490nm have been found to be 0.37% and 4.4%, respectively for the former. The onset of the photoresponse was λ 520 nm with maximum efficiency at λ = 490 nm (2.53 eV). Photoelectrochemical cells of the type CdS/reductant//water/Pt for the visible light induced H2 generation from water have also been assembled and were found to produce H2 with a quantum yield of 5–16%.

The origin of the uncommon X-ray reflections of CdS:Mn, Cl polycrystalline thin films

A critical discussion of the unusual X-ray diffraction pattern of CdS:Mn, Cl thin films is given. None of the known chlorine or chlorine-rich phases can account for the observed system of additional reflections. The correlation between these reflections and the presence of a chlorine-rich phase was obtained by electron microprobe analysis. It os concluded that a new phase of crystallites is immersed in a polycrystalline cadmium sulphide matrix.

Deep level defects in polycrystalline cadmium sulfide

Properties of deep level defects in polycrystalline CdS junctions were investigated using transient capacitance spectroscopy. A total of seven electron traps and one hole trap was observed with activation energies of 0.16, 0.31, 0.38, 0.42, 0.53, 0.69, 0.96, and 0.32 eV, respectively. The emission rate, capture cross section and concentration of the traps are presented. The temperature dependence of the capture cross section for the electron traps at 0.53 and 0.69 eV are also given.

Stimulation of an anomalous temperature dependence of dark current in polycrystalline cadmium sulfide layers

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Apparatus for Measuring the Thermal Expansion of Optical Materials from 30°C to 250°C

An apparatus has been designed and constructed for measuring the coefficient of linear thermal expansion in the 30-250 degrees C temperature range for samples as small as 13 mm in length and 6 mm in diameter. Similarities between this apparatus and one previously built for measurements from room temperature down to 10 K are reviewed; important modifications appropriate to the high temperature range are discussed in detail. Measurements were made at 25 degrees C intervals on two infrared-transmitting optical materials: polycrystalline cadmium sulfide (Eastman Kodak Co.) and chalcogenide glass 20, composition Ge(33)Se(55)As(l2) (Texas Instruments, Inc.). Measurements were also made on a sample of Corning crown glass 8263; the results are compared with Corning data. Finally, it is shown that the thermal expansion coefficients determined with this high temperature apparatus are compatible with those obtained with the above-mentioned low temperature device.

Model for the blue photoluminescence of cadmium sulfide

A model for the blue luminescence of polycrystalline cadmium sulfide and cadmium sulfide single crystals is proposed on the basis of a joint study of the absorption, reflection, emission, and excitation spectra of this luminescence at 77 °K. The blue luminescence arises in the transition of an electron from the conduction band to the 5s2 1S0 ground level of a super-stoichiometric cadmium atom which has trapped a hole from the valence band. The width of the energy gap (2.614 eV) at κ = 0 is estimated on the basis of the oscillatory nature of the excitation spectrum for the blue luminescence, and the effective mass of heavy holes is estimated.

Mechanism for the optical absorption of cadmium sulfide

The optical transmission and reflection spectra of polycrystalline cadmium sulfide films heated in sulfur vapor have been measured at 77 and 300 °K. The absorption coefficient of the film is calculated for the range 2.25–3.5 eV. Analysis of the spectral dependence of the absorption coefficient shows indirect optical transitions of an electron from the upper valence band to the conduction band in the range 2.31–2.54 eV and direct substitutional transitions in the range 2.58–3.45 eV. Superimposed on this intrinsic absorption is selective absorption due to superstoichiometric atoms.

Model for the green photoluminescence of polycrystalline cadmium sulfide films

Model for the green photoluminescence of polycrystalline cadmium sulfide films

Photocurrent decay processes in hexagonal and cubic polycrystalline cadmium sulfide

Photocurrent decay in polycrystalline specimens of cadmium sulphide of the zincblend type is compared with the decay in the same specimens transformed to the Wurtzite type by hydrothermal treatment.

Photoluminescence of polycrystalline cadmium sulfide films at 77 �K

The absorption, reflection, emission, and luminescence spectra of polycrystalline cadmium sulfide films have been studied at 77 deg K at 4500–5500 A. The films were prepared by sublimination of the powder in argon, hydrogen sulfide, or vacuum, followed by crystallization on a heated or unheated substrate.

The effect of crystal structure on the photoelectric properties of thin cadmium sulfide layers

The results presented are of an investigation into the photoelectric properties of polycrystalline cadmium sulfide layers obtained by thermal evaporation in vacuum. In producing the layers the substrate temperature was varied over the range 80 °–500 ° C, and in addition the layers were heated in air. It was found that the spectral distribution of the photocurrent, the absolute and relative phbtosensitivity, and the relaxation time depend to a marked extent on the substrate temperature. These differences are connected with a change in the degree of defectiveness and phase compositions of the polycrystalline cadmium sulfide layers.

Conductivity induced by Radiation in Polycrystalline Cadmium Sulphide and Polyethylene

WHEN ionizing radiation falls on insulating or semiconducting solids, there is an increase in electrical conductivity resulting from the production of electron-hole pairs. If the source of ionizing radiation is removed, the conductivity decreases at a rate dependent upon the release of electrons from traps into the conduction band.