THE CHEMISTRY OF THE GROWTH OF ZNS DEPOSITED BY RF-SPUTTERING ONTO CADMIUM STANNATE .2. THE BULK

The composition of ZnS thin films prepared by r.f. sputtering onto cadmium stannate substrates was studied primarily as a function of sputtering atmosphere and film thickness. Pure argon, ArH2 and ArO2 sputter gases were investigated; oxygen was detected even in argon and ArH2 grown films and was attributed to the residual atmosphere in the sputtering chamber. Zn:S ratios were highest in films with the highest oxygen content. Both oxygen content and Zn:S ratio decreased with increasing film thickness; this is believed to be due to a decrease in oxygen in the residual atmosphere as deposition proceeds. It is concluded that a variable residual atmosphere can lead, via variation in the composition of the ZnS, to a gradation in fundamental electrical properties within a single sample and non-reproducibility from one sample to another. This is expected to be of importance in the use of ZnS thin films for direct coupled electroluminescence. © 1990.