Properties of pulse electrodeposited copper gallium sulphide films

Copper gallium sulphide films were deposited for the first time by the pulse electrodeposition technique at different duty cycles in the range of 6–50 % at room temperature and at a constant current density of 1.0 mA cm^?2. The films exhibited single phase copper gallium sulphide. The grain size increased from 30 to 70 nm with increase of duty cycle. Optical band gap of the films varied in the range of 2.30–2.36 eV. The resistivity increased from 0.10 to 1.70 ohm cm with increase of duty cycle from 6 to 50 %. Preliminary studies on solar cells with p-CuGaS₂/n-CuInS₂ junction yielded an efficiency of 4.14 %. This is the first report on solar cells using CuGaS₂ with CuInS₂.     

Oxidation of thin films of tin at room temperature in hydrogen sulphide atmosphere

The oxidation of thin films of tin at room temperature in an atmosphere containing 10% H₂S and 90% air has been studied by measuring the changes in resistance of thin films. Morphological studies have also been carried out using optical and scanning electron microscopes. Reaction kinetics change from logarithmic law at ordinary atmospheres to a power law in the presence of H₂S. The basis of formation of sulphide along with the oxide is explained, the former growing on a lower layer and the latter on an upper layer.     

Thin films of tin sulphide for use in thin film solar cell devices

SnS is of interest for use as an absorber layer and the wider energy bandgap phases e.g. SnS₂, Sn₂S₃ and Sn/S/O alloys of interest as Cd-free buffer layers for use in thin film solar cells. In this work thin films of tin sulphide have been thermally evaporated onto soda-lime glass substrates with the aim of optimising the properties of the material for use in superstrate configuration device structures. The thin films were characterised using energy dispersive X-ray analysis (EDS) to determine the film composition, X-ray diffraction (XRD) to determine the phases present and structure of each phase, transmittance versus wavelength measurements to determine the energy bandgap and scanning electron microscopy (SEM) to observe the surface topology and topography. These properties were then correlated to the deposition parameters. Using the optimised conditions it is possible to produce thin films of tin sulphide that are pinhole free and conformal to the substrate that are suitable for use in thin film solar cell structures.     

Electrodeposition of nickel selenide thin films in the presence of triethanolamine as a complexing agent

Electrodeposition in the presence of triethanolamine in aqueous solution was found to offer some improvements in the synthesis of nickel selenide thin film. The presence of triethanolamine also showed its capacity for improving the longevity of the deposition as well as the adhesion of the deposited films on the titanium substrate. Photoelectrochemical analysis reveals outstanding photoactivity for the thin film deposited at –0.70 V, while the optical study shows an energy gap of about 2.0 eV. The film exhibited p-type semiconductor behavior. The scanning electron microscope results showed that the samle deposited in the presence of triethanolamine produced better and smoother surface coverage and bigger grain size.     

Preparation and characterization of chemically deposited tin(II) sulphide thin films

A chemical method was developed for the preparation of tin(II) sulphide (SnS) thin films on glass substrates at room temperature (300 K) using an Sn²⁺ salt solution, triethanolamine, ammonia and thioacetamide as the reagents. Chemical analysis, X-ray characterization, optical absorption and electrical measurements were performed to confirm the deposition of SnS. The films were found to be amorphous and n type with an optical energy gap of 2.42 × 10^-19 J (1.51 eV).     

Characteristics of pulse electrodeposited PbS thin films

PbS thin films were deposited for the first time using the pulse electrodeposition technique at different duty cycles in the range of 9 to 50% and at room temperature using lead nitrate and sodium thiosulphate. The thickness of the films increased from 0.5 to 1.0 μm with increase of duty cycle. The films were polycrystalline and exhibited cubic structure. The band gap of the films deposited at 50% duty cycle is 0.42 eV. The resistivities of the films decreased from 0.9 to 0.5 × 10⁵ ohm cm as the duty cycle increased. Films with grain size in the range of 20 to 35 nm were deposited. Films with refractive index varying in the range of 4.45–3.75 with increase of wavelength were obtained. Films with higher photosensitivity and higher detectivity compared to earlier reports were obtained.     

Electrical properties of electrodeposited CdTe thin films

The electrical properties of electrodeposited CdTe thin films have been studied. The temperature-dependent electrical conductivity data obtained have been used to determine the conductivity type and semiconductor parameters (E _g, B, and α) of the films.     

Assessment of the potential of tin sulphide thin films prepared by sulphurization of metallic precursors as cell absorbers

In this work, SnxSy thin films have been grown on soda-lime glass substrates by sulphurization of metallic precursors in a nitrogen plus sulphur vapour atmosphere. Different sulphurization temperatures were tested, ranging from 300 °C to 520 °C. The resulting phases were structurally investigated by X-Ray Diffraction and Raman spectroscopy. Composition was studied using Energy Dispersive Spectroscopy being then correlated with the sulphurization temperature. Optical measurements were performed to obtain transmittance and reflectance spectra, from which the energy band gaps, were estimated. The values obtained were 1.17 eV for the indirect transition and for the direct transition the values varied from 1.26 eV to 1.57 eV. Electrical characterization using Hot Point Probe showed that all samples were p-type semiconductors. Solar cells were built using the structure: SLG/Mo/SnxSy/CdS/ZnO:Ga and the best result for solar cell efficiency was 0.17%.     

Trap diagnostic of thin cadmium sulphide films

A simplified expression for the temperature dependence of trap depth was derived. This expression together with experimental observations confirmed the existence of a number of deep trap levels (0.9–1.02 eV) in CdS and it is suggested that with the knowledge of these trap levels a better correlation between experimental and theoretical results for tunnel-induced impact ionization is possible.     

Microstructure of vacuum-deposited tin thin films

Tin thin films of equal thickness were vacuum deposited on NaCl substrates at different deposition rates both in high vacuum (2×10^–5 Torr) and poor vacuum (1×10^–3 Torr). These films were examined by electron microscopy and the grain size and density in the films were determined. It was found that both in poor and high vacuum, as the deposition rate was increased the grain size decreased and grain density increased. However, the deposition rate must be increased by an order of magnitude in order to observe large changes in the grain size and density. It was also observed that the films prepared in poor vacuum, especially at low deposition rates, consist of islands with jagged edges. These observations have been interpreted on the basis of nucleation theory and the effect of adsorbed/chemisorbed gases on island growth in these films.     

Nano-particle thin films of tin oxides

Nano-particle thin films of tin oxides were deposited on SiO₂ substrates by using radio frequency (RF) magnetron sputtering with various substrate temperatures, sputtering powers and oxygen partial pressures. The tin oxides thin films were then investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS data suggested that the deposited tin oxides thin films are almost made up of half of SnO₂ and half of SnO. The oxygen partial pressure nearly does not affect the chemical stoichiometry of the thin films in our deposition conditions. SEM results showed that the tin oxides thin films were formed by nano-particles with size of about 60 nm. Sputtering power has a strong influence on the particle size of the thin films. Increase of sputtering power will enlarge the size of the particles.     

Phase transitions in cuprous sulphide evaporated thin films

The films of Cu_xS(1x2), prepared by evaporation in vacuum and condensation of stoichiometric sulphides of copper, change their phases by heat treatment in vacuum. Cu₂S chalcocite appears as the most stable phase in the range 270 to 450° C and the other sulphur rich phases transform into chalcocite presumably by a loss of sulphur. By electron diffraction we have confirmed the low temperature monoclinic chalcocite phase, the high temperature hexagonal chalcocite phase, the monoclinic djurleite phase, the cubic digenite low and high temperature forms and the hexagonal covellite phase. The low temperature digenite phase presents a superstructure which is similar to that observed by Kazinetset al. on digenite prepared by evaporation in vacuum on a single crystal substrate of NaCl at temperatures of 350 to 400° C. Electron diffraction data of chalcocite (Cu₂S), djurleite (Cu_1.93S), digenite (Cu_1,8S) are presented.     

Growth and characterisation of electrodeposited ZnO thin films

The electrochemical method has been used to deposit zinc oxide (ZnO) thin films from aqueous zinc nitrate solution at 80 °C onto fluorine doped tin oxide (FTO) coated glass substrates. ZnO thin films were grown between − 0.900 and − 1.025 V vs Ag/AgCl as established by voltammogram. Characterisation of ZnO films was carried out for both as-deposited and annealed films in order to study the effect of annealing. Structural analysis of the ZnO films was performed using X-ray diffraction, which showed polycrystalline films of hexagonal phase with (002) preferential orientation. Atomic force microscopy was used to study the surface morphology. Optical studies identified the bandgap to be ∼ 3.20 eV and refractive index to 2.35. The photoelectrochemical cell signal indicated that the films had n-type electrical conductivity and current-voltage measurements showed the glass/FTO/ZnO/Au devices exhibit rectifying properties. The thickness of the ZnO films was found to be 0.40 μm as measured using the Talysurf instrument, after deposition for 3 min. Environmental scanning electron microscopy was used to view the cross-section of glass/FTO/ZnO layers.     

Properties of indium tin oxide thin films prepared on the oxygen plasma-treated polycarbonate substrate

We prepared the indium tin oxide thin (ITO) film on the polymer substrate by using facing target sputtering method. To obtain a smooth surface of the ITO thin film for application of OLEDs, before deposition of the ITO thin film, the polymer substrate was given plasma surface treatment. The electrical and surface properties were measured by a Hall Effect measurement and a contact angle measurement. The structural and optical properties were evaluated by an X-ray diffractometer, an atomic force microscope and a UV/VIS spectrometer, respectively. All ITO thin films deposited on plasma-treated polymer substrate showed an average transmittance over 85% in visible range, and the lowest resistivity was 4.17 × 10^− 4 Ω cm.     

Spray pyrolysis deposition of indium sulphide thin films

In₂S₃ thin films were grown by the chemical spray pyrolysis (CSP) method using the pneumatic spray set-up and compressed air as a carrier gas. Aqueous solutions containing InCl₃ and SC(NH₂)₂ at a molar ratio of In/S = 1/3 and 1/6 were deposited onto preheated glass sheets at substrate temperatures T_s = 205-410 °C. The obtained films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM,) optical transmission spectra, X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). According to XRD, thin films deposited at T_s = 205-365 °C were composed of the (0 0 12) orientated tetragonal β-In₂S₃ phase independent of the In/S ratio in the spray solution. Depositions performed at T_s = 410 °C led to the formation of the In₂O₃ phase, preferably when the 1/3 solution was sprayed. Post-deposition annealing in air indicated that oxidation of the sulphide phase has a minor role in the formation of In₂O₃ at temperatures up to 450 °C. In₂S₃ films grown at T_s below 365 °C exhibited transparency over 70% in the visible spectral region and E_g of 2.90-2.96 eV for direct and 2.15-2.30 eV for indirect transitions, respectively. Film thickness and chlorine content decreased with increasing deposition temperatures. The XPS study revealed that the In/S ratio in the spray solution had a significant influence on the content of oxygen (Me-O, BE = 530.0 eV) in the In₂S₃ films deposited in the temperature range of 205-365 °C. Both XPS and EDS studies confirmed that oxygen content in the films deposited using the solution with the In/S ratio of 1/6 was substantially lower than in the films deposited with the In/S ratio of 1/3.     

Stripe domains in electrodeposited NiCo thin films

The presence of stripe domains (SD) in electrodeposited NiCo thin films was inferred from the specific form of the hysteresis loops. The critical field H_cr of this type of magnetization domain has been studied as a function of film composition, film thickness and annealing temperature. The range of the experimental parameters was: composition 0–50% Co in nickel, thickness 300–1000 nm and annealing temperature 300°–525°K.The experiments have shown that the magnetostriction-stress interaction (Saito et al.) and the columnar growth of crystallites separated by non-magnetic boundaries (Iwata et al.) are the two main causes for SD.