Substrate temperature effect on crystallographic quality and surface morphology of zinc sulfide films on (100)-oriented silicon substrates by molecular-beam epitaxy

Abstract

The crystallographic quality and the surface morphology of ZnS films on (100) Si substrates by molecular-beam epitaxy are profoundly dependent on the substrate temperature Ts. When the Ts was below 300 °C, single crystalline films with twins grew along 〈100〉 directions in the initial stage of growth. However, when the film thickness was increased, the growth orientation changed from 〈100〉 to two 〈511〉 directions of the Si substrate. Namely, the relation of growth orientations between overgrowth and substrate is ZnS(111)∥Si(511). When the Ts was set between 340 and 370 °C, the grown films were single crystal with twins appearing initially and grew with a 〈100〉 orientation, but decreased with increasing film thickness. Especially in the case of Ts=340 °C, the ZnS film became best crystallized and exhibited the twin-free streaky pattern in the reflection high-energy electron diffraction pattern with a smooth surface morphology.