STRUCTURE AND OPTICALLY PROPERTIES OF THE ZnSO LAYERS PREPARED BY THERMAL OXIDATION OF ZnS THIN FILMS

Abstract

. We have grown ZnS thin films by means of the radiofrequency (RF) magnetron sputtering technique onto c-Al 2 O 3 and Si substrates at a temperature of 300°С. An effect of thermal annealing on air in a temperature range from 450°С to 800°С on the properties of the deposited films was studied and discussed. It was found that the annealing of the ZnS films leads to a formation both ZnSО layers with different sulfur/oxygen content and pure ZnО layers. It is evidenced by XRD data and optical transmission measurements. An analysis of the optical transmission spectra allowed determining a dependence of the band-gap energy of the films on the conditions of the thermal oxidations on air. Summary The purpose of this paper is the growth of ZnS thin films using the radio-frequency (rf) magnetron sputtering; studying the effect of thermal annealing in air on the process of incorporation of oxygen anions into ZnS matrix; formation of ZnO 1-x Se x alloy films and investigation of their structural, electri-cal and optical properties. Methods of research. The crystalline structure and concentration of sulfur in grown films were investigated using DRON-4 technique within X-ray diffraction (XRD) and X-ray photo electronic spectroscopy (XPS), respectively. The optical transmission spectra were measured at 300 K using the advanced universal MDR-23 technique. The annealing was carried out in air at temperature Т а , varying from 350 °С to 800 °С, during three hours. Results of research. The XRD spectrum of newly grown ZnS films has the only one peak, which is characteristic for the cubic ZnS. At Т а varying from 450 °С to 700 °С, the mixed ZnS and ZnO phases are observed. Only at Т а ≥ 700 °C, ZnS completely transforms into ZnO with wurtsite structure. The grown ZnO 1-x S x films exhibit high transparency in the visible region of the spectrum (60 ÷ 90%). The value “bowing” of the parameter b = 3.5 eV, which characterizes the change in the width of the band gap E g (x), determined from the optical absorption spectra, was obtained. Conclusions. The presented results prove the possibility of guided control of the properties of ZnS films grown by rf-magnetron sputtering by choosing the optimal technological parameters, in particu-lar, temperature, annealing time, etc.