Doped Cadmium Sulfide Thin Films Research Articles

AC measurements of spray-deposited CdS:In thin films

Indium doped cadmium sulfide thin films (CdS:In) were produced by the spray pyrolysis technique on glass substrates. AC measurements were used to investigate the electrical properties of the films depending on Brick-layer model for polycrystalline materials. The measurements were performed at room temperature in the dark and room light in the frequency range from 20 Hz to 1 MHz using coplanar indium electrodes. The data were analyzed by using Bode plots for the impedance Z and dielectric loss tanδ with frequency f. It is found that the impedance has no dependence on frequency in the low frequency region but has 1/f dependence in the high frequency region. One dielectric loss peak is obtained, which means the presence of a single relaxation time, and hence the films are modeled by just one RC circuit which represents the grains. This means that there is just one conduction mechanism that is responsible for the conduction in the bulk, due to electronic transport through the grains. Real values of the impedance in the low frequency region and relaxation times for treated and as-deposited films were estimated.

The effect of annealing temperature on structural and optical properties of undoped and Cu doped CdS thin films

Cadmium sulphide (CdS) thin films were prepared chemical bath deposition technique. The films were doped with copper using the direct method consisting in the addition of a copper salt in the deposition bath of CdS. The doped films were annealed in air, at 250, 300 and 350°C, for 1h. The deposition films were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive analysis by X-rays (EDAX) and optical properties of CdS thin films before and after Cu doping. XRD analysis shows that the films are polycrystalline in nature with cubic crystalline structure. The various parameters such as crystallite size, micro strain and dislocation density were evaluated. SEM study shows that the total substrate surface is well covered by uniformly distributed spherical shaped grains. Optical transmittance study shows the presence of direct transition with band gap energy decrease 2.5–2.2eV.

Synthesis and characterisation of chlorine doped cadmium sulphide (CdS:Cl) nanoparticles on flexible substrates

Chlorine doped cadmium sulphide thin films have been prepared on flexible substrates using high vacuum evaporation (HVE) technique at room temperature. The structural properties have been determined through XRD and the effect of chlorine doping on the structural properties of these films has been investigated. The chemical analysis has been carried out through EDAX attached to the SEM system. The nanostructures have been identified in the SEM images and a significant effect of the chlorine doping has been noticed. The growth conditions and the characterisation results have been presented and discussed.

Fabrication of nanocrystalline manganese and tin doped and undoped CdS thin films by a novel RF-magnetron sputtering technique and its characterisations

Nanoparticles of cadmium sulphide (CdS) in thin film form have been synthesised by a higher pressure RF-magnetron sputtering technique on glass and Si substrates at different deposition conditions and with different metal doping like Mn and Sn in the films. X-ray diffraction and Selected Area Electron Diffraction (SAED) patterns confirmed the nanocrystalline cubic CdS phase formation. Transmission electron microscopic studies of the films revealed the manifestation of CdS nanoparticles with different sizes depending upon the deposition conditions. Compositions were determined through energy dispersive analysis of X-rays. UV-Vis-NIR spectrophotometric measurement showed that the films are highly transparent (∼85%) in the wavelength range 450-2600 nm and the band gaps of the films were calculated. Syntheses of highly Transparent Conducting Sulphide (TCS) films were achieved by Sn doping in the nano-CdS films. The conducting Sn doped CdS thin films also showed good field-emission properties with a turn-on field lying in the range 4.74-7.86 Vµm-1.

Characterizations of undoped and Cu doped CdS thin films using photothermal and other techniques

AbstractPhotothermal Deflection Spectroscopy (PDS) technique was used to study undoped and copper (Cu) doped cadmium sulphide (CdS) thin films. Variation in grain size and lattice strain due to Cu doping were analysed using X‐ray diffraction (XRD). Changes in mobility of carriers in CdS with Cu concentration was studied using PDS technique for the first time and results are compared with the earlier ones. Thickness of Cu diffused region in CdS was also calculated and compared with results from X‐Ray Photoelectron Spectroscopy (XPS) and Ellipsometry. Results from PDS technique are found to be agreeing with those from other experiments. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural evolution and optical characterization of indium doped cadmium sulfide thin films obtained by spray pyrolysis for different substrate temperatures

Indium doped cadmium sulfide thin films were prepared by spray pyrolysis on glass substrates at different temperatures ranging from 300°C to 450°C in 25°C steps, using aqueous solution of copper chloride and thiourea salts. We used In(COOH)3 as the dopant. Structural characterization was carried out by X-ray diffractometry and scanning electron microscopy and high resolution electron microscopy were used together with atomic force microscopy (AFM) to follow the evolution of structural and morphological parameters of the films with substrate temperature (Ts). At least two preferential growth, (1 1 2) for samples with Ts between 325°C and 400°C and (0 0 2) for Ts between 400°C and 450°C, respectively were detected. For the films obtained at higher substrate temperatures, HREM micrographs revealed the presence of a large number of structural defects together with nanostructured configurations. AFM revealed surface modifications of CdS:In grains at higher substrate temperature. The substrate temperature is directly related with the shift detected in the band gap values derived from optical of parameters.