Room-temperature preparation and properties of cadmium sulfide thin films by ion-beam sputtering deposition

Deposition of cadmium sulfide (CdS) thin film on BK7 glass substrates has been prepared by a dry and in situ fabrication process with ion-beam sputtering deposition at room temperature. The structural, optical and electrical properties of CdS thin film were investigated. X-ray diffraction (XRD) analysis indicates the formation of polycrystalline CdS film with the mixed structure of cubic and hexagonal wurtzite phase. The Raman peaks are observed at 304 cm−1 and 606 cm−1, and these peaks are identified as the first and second order LO optical phonons form of the CdS film. Energy dispersive X-ray Spectrometer (EDS) shows no other impurity elements, except Cd and S. The as-deposited film exhibits good transfer of the sintered target material with almost the same Cd/S ratio. Scan electron microscopy (SEM) and atomic force microscopy (AFM) reveal that the CdS thin film has a smooth surface and exhibited an obvious columnar growth indicating the c-axis preferred orientation. The detected room-mean-square (RMS) roughness by AFM is 0.76 nm. Optical transmission and absorption spectroscopy measurement reveal high absorption and energy band gap is of about 2.32 eV. The CdS thin film is of n-type conductivity and the resistivity is found to be in the order of 104 Ω cm. The CdS films annealed at 100 °C were demonstrated to be improvement in structural, electrical and optical properties.