Abstract
Cadmium selenide (CdSe) thin films were prepared by chemical bath deposition technique on glass substrates using cadmium acetate dihydrate as a source of Cd 2+ ions, and sodium selenosulphate as a source of Se 2- ions respectively. Triethanolamine and ammonia were used as complexing and pH controlling agent. Films were deposited at different bath temperatures ranging from room temperature to 80 o C while the pH value was kept constant around 10.50 ±0.10. We determined elemental composition of deposited film by X-ray photoelectron spectroscopy. Optical properties of films deposited at different bath temperatures are studied by absorption spectra and parameters like thickness, band gap and absorption coefficient were calculated from the optical transmission spectra. The optical spectra showed a small blue shift and the band gap was found to be greater than the bulk phase. Raman measurements performed at room temperature using Helium-neon laser and Argon laser confirmed the presence of longitudinal optical phonon modes. The selected area electron diffraction pattern for CdSe thin films indicated that they are having mixed nature i.e. both single crystalline and polycrystalline nature with planes of diffraction rings corresponding to cubic structure of CdSe respectively.
Highlights
During the past few decades, there has been increasing interest in the deposition and characterization of II–VI group semiconductor compound (ZnSe, CdS, CdTe, Cadmium selenide (CdSe) etc.) thin films because of their wide application in various fields of optoelectronic technology
The above mentioned advantages, much utility of this technique lies with the fact that in this technique, wastage of solution can be minimized since the obtained precipitate is usually stoichiometric and of high purity which can be further reused as starting material for other deposition techniques
Most of film deposition techniques reported the formation of CdSe thin films at high temperatures having hexagonal structure containing elemental or substrate impurities [31] whereas, our X-ray diffraction (Xrd) result confirmed that deposited films are of pure CdSe compound having cubic structure because no Xrd peak corresponding to elemental cadmium, selenium or substrate is observed [16] as reported in films deposited on stainless steel by electrodeposition technique [32] thereby suggesting chemical bath deposition (CBD) deposited films are well covered to the substrate
Summary
During the past few decades, there has been increasing interest in the deposition and characterization of II–VI group semiconductor compound (ZnSe, CdS, CdTe, CdSe etc.) thin films because of their wide application in various fields of optoelectronic technology. A variety of techniques have been used for the deposition of thin films and among all methods, chemical bath deposition (CBD) is being largely investigated as a convenient and low-cost technique for producing large-area thin films of semiconducting materials. Advantages of this technique includes requirement of very simple equipment, does not require high temperature or pressure, less incorporation of impurities, deposition of multicomponent chalcogenide thin films over a wide range of stoichiometry, high reproducibility, environment friendly, scope of converting intrinsic semiconductors to n-type or p-type and control of film thickness or stoichiometry by the optimization of various deposition conditions like temperature, time, concentration of reactants, complexing salt concentration etc. The above mentioned advantages, much utility of this technique lies with the fact that in this technique, wastage of solution can be minimized since the obtained precipitate is usually stoichiometric and of high purity which can be further reused as starting material for other deposition techniques
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