Raman Study of Compositional Variations in ZnxCd1-xSe Films Prepared by Thermal Vacuum Evaporation

摘要

The effect of the sublayer thickness on the compositional variations in ternary ZnxCd1-xSe thin films (x = 0.4, 0.6 or 0.8) prepared by alloying of a large number of consecutively deposited ZnSe and CdSe sublayers has been investigated. The films were prepared on smooth glass substrates maintained at room temperature. Both ZnSe and CdSe sublayers have nominal thickness in the range 0.25-1.2 monolayers. Raman spectroscopy at resonance and non-resonance conditions has been used to get information about the compositional variations i.e., about the existence of Cd-rich phase. It has been found that for each composition the amount of Cd-rich phase is smaller in the films with the lower nominal thickness. Binary CdSe islands with size of 3-4 nm have been detected in the x = 0.4 films. A two-stage process has been suggested for the ZnxCd1-xSe film growth process-formation of ZnSe and CdSe grains with size of a few nm followed by Cd/Zn interdiffusion through the interfaces stimulated by the CdSe and ZnSe lattice mismatch.