Substrate temperature effects on structural and photoelectric properties of CdS thin films

Cadmium sulfide thin films were deposited on quartz substrates by magnetron sputtering method with varying substrate temperatures. X-ray diffraction patterns of prepared samples showed preferred orientation of (002) with pure hexagonal phase. Atomic force microscopy and scanning electron microscopy images exhibited a surface morphology with uniform and homogeneous grains. X-ray photoelectron spectroscopy (XPS) revealed peaks corresponding to cadmium, sulfur, carbon and oxygen atoms, and the high-resolution XPS surveys for cadmium 3d and sulfur 2p showed an obvious shift to lower binding energy as the substrate temperature raised. Meanwhile, the optical absorption coefficient gradually increased, and the transmittance was approximately 75%. The optical energy gap was as high as 2·40 eV at the substrate temperature of 200°C. Photoconductivity curves presented a rapid response, the lowest conductivity at steady state (only 1·6257 × 10⁻⁴ Ω⁻¹ cm⁻¹) and a high solar photoconductivity gain (G _p = 296·36) at substrate temperatures of up to 200°C.