Influence of Cd on structure, surface morphology, optical and electrical properties of nano crystalline ZnS films

Abstract

Transparent nano crystalline Zn1-xCdxS films were grown on glass substrates at 0.0125 M precursor concentration using chemical spray pyrolysis technique. The suitable optimized temperatures were adjusted from 673 K to 573 K for different compositions. The films with x< 0.40 have exhibited cubic phase with the crystalline plane of (1 1 1) orientation and for x> 0.30 have shown a hexagonal phase with (0 0 2) prominent plane. The lattice constants, crystallite size and dislocation density in the samples were estimated using X-ray diffraction data. The morphology of the films with higher Zn content exhibits fibrous structure and it changes to grain like structure on decreasing Cd concentration. XPS and EDAX analysis confirms the presence of elements in the deposits. The optical transmittance and energy band gap increased with increasing deposition temperature, whereas, decreased with increasing Cd dopant. The NLO behavior of the deposits indicates free carrier absorption induced two photon absorption processes. All deposits have shown n-type electrical conductivity. The film resistivity decreases with increase in deposition temperature and Cd content. The obtained Zn1-xCdxS films are suitable for device application of gas sensor and optical limiter.