Thickness dependent variation in structural, optical and electrical properties of CdSe thin films

Cadmium selenide (CdSe) thin films of various thicknesses are deposited on ITO glass substrates by electrodeposition technique using a bath containing cadmium sulfate (3CdSO₄·8H₂O) and selenium dioxide (SeO₂) solution. The structural, optical and electrical characteristics of these thin films are analyzed by X-ray diffraction (XRD), UV–Vis spectrophotometer and four probes setup with current–voltage (I–V) source meter. The XRD study confirmed that the thin films possess polycrystalline nature with cubic structure. The decrease in full width at half maximum and increase in peaks intensity revealed that the crystalline properties of CdSe thin films were enhanced with film thickness. Optical analysis shown that the CdSe thin films possess direct band gap which decreases from 2.67 to 2.47 eV with the increase in thickness. Photoluminescence analysis further revealed an enhancement in optical quality of CdSe thin films with thickness. Electrical analysis (I–V characteristics) showed that the resistivity of CdSe thin film also decreased with increase in thickness. The decrease in the resistivity with increase in CdSe film thickness also accredited to the enhancement of crystallization in thin films.