Effect of ethanol concentration in photo enhanced chemically deposited ZnSe thin films

摘要

ZnSe nanostructured thin films are found to be potential candidates in various optoelectronic applications. They find applications in LEDs, buffer layer of photovoltaic cell etc. The samples were fabricated by a cost effective modified chemical route namely photo enhanced chemical deposition technique. The deposition of nanostructured ZnSe thin films took place from aqueous alkaline medium. The deposition bath at room temperature was illuminated by a UV lamp irradiating at 355 nm. Deposition solution contained zinc sulphate, sodium sulphite, sodium selenosulphate, hydrazine hydrate and triethanol ammine (TEA). The films were uniform and highly adherent. The films were deposited on soda lime glass substrate with various concentrations of ethanol in the deposition bath. The resulting samples were annealed at 373 K for 30 minutes. The deposited films were characterised by various techniques like XRD, UV-VIS-NIR spectrophotometer, SEM etc. The films were found to be polycrystalline in nature with hexagonal structures and addition of ethanol in the bath resulted in face centered cubic structure. The presence of ethanol in the bath introduced changes in structural, optical, and morphological properties of the thin films. The optical transmission of all the samples were above 70% in the visible region and almost uniform. The optical band gap found to decrease with increase in ethanol concentration from 2.74 eV to 2.52 eV whereas the grain size found to increase. The SEM images showed a porous structure which changed to nano flake like structure on the addition of ethanol in to the deposition bath.