Effect of number of cycles on SILAR deposited ZnSe thin films

Abstract

Nanocrystalline zinc selenide (ZnSe) thin films find important applications in the field of optoelectronics due to their peculiar physical properties. The deposition of ZnSe thin films through modified chemical deposition method namely SILAR technique is described here. The cationic precursor used was the aqueous solution of zinc acetate and anionic solution sodium selenosulphate. Ammonia served as pH adjuster in both precursors. The room temperature deposition resulted in well adhered thin films after 40, 50 and 60 deposition cycles. Samples showed polycrystalline hexagonal wurtzite structure and exhibited a well-defined nano structure. Film thickness was near 400 nm and grain size around 20 nm. Both thickness and grain size increased with number of deposition cycles. The crystal defect parameters like micro strain and dislocation density showed a reduction with increase in number of deposition cycles indicating a better crystal quality. The films exhibited very small absorbance and high transmission above 80% towards the visible and infra-red region. The optical band gap widened up to 2.90 eV with number of deposition cycles and is confirmed from the room temperature PL spectra.