PREPARATION AND CHARACTERIZATION OF NANO- STRUCTURED ZnS THIN FILMS GROWN ON GLASS AND N-TYPE Si SUBSTRATES USING A NEW CHEMICAL BATH DEPOSITION TECHNIQUE

Abstract

Nano-crystalline zinc sulfide thin films were prepared by a new chemical bath deposi- tion (CBD) technique onto glass and n-type (111)-oriented silicon substrates. Deposition took place at a temperature of 70 m C and a pH of 6.0, from an aqueous solution containing zinc acetate, thioacetamide, and ethylenediamine. Structural analysis using atomic force microscopy shows that the films deposited on silicon substrates contain 28-30 nm clusters, whereas much larger clusters (around 80-120 nm), comprise the films deposited on glass substrate. X-ray diffraction analysis indicates that both the film and powder formed in the reaction bath have cubic zincblende structure and the clusters in microstructure images are coalescences which they compose of nano-crystallites of about 4.5-13 nm in diameter. UV-Vis spectrophotometry mea- surements give an average transparency of around 70-80% in the visible range (400-700 nm) for the films with different thicknesses and deposition times. Direct band gap energy of these samples was measured to be in the range of 3.97-4.00 eV. Fourier transform infrared spectrum of the films reveals no peak due to any impurity.