Synthesis of CdS thin films at room temperature by RF-magnetron sputtering and study of its structural, electrical, optical and morphology properties

Thin films of cadmium sulfide (CdS) have been deposited at room temperature by using RF-magnetron sputtering at various deposition times. Films were systematically investigated using variety of techniques such as low angle XRD, UV-Visible spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), atomic force microscopy (AFM), transmission electron microscopy (TEM), four probe Van der Pauw method etc. Low angle XRD and TEM analysis revealed that films are polycrystalline having constant average crystalline size. EDAX revealed the formation of nearly stoichiometric CdS films. Surface morphology of CdS films examined using SEM shows the formation of smooth, continuous and dense films without defects such as cracks, pinholes, and protrusion. RMS roughness estimated using AFM increases with increase in deposition time. The optical studies showed decrease in band gap with increase in deposition time. The photodetector fabricated using RF sputtered CdS film show an excellent photo-response. Estimated value of growth exponent β was found ~ 0.53 which suggests uncorrelated growth of CdS films by RF sputtering. The uncorrelated growth of CdS was further confirmed by Monte-Carlo simulation.