Zinc sulfide and terbium-doped zinc sulfide films grown by traveling wave reactor atomic layer epitaxy

Zinc sulfide (ZnS) and terbium-doped ZnS (ZnS:Tb) thin films were grown by traveling wave reactor atomic layer epitaxy (ALE). In the present work, ZnC l2, H2S, and tris (2,2,6,6-tetramethyl-3,5-heptandionato) terbium (Tb(tmhd) (3)) were used as the precursors. The dependence of crystallinity and Cl co ntent of ZnS films was investigated on the growth temperature. ZnS and ZnS: Tb films grown at temperatures ranging from 400 to 500 degrees C showed a h exagonal-2H crystalline structure. The crystallinity of ZnS film was greatl y enhanced as the temperature increased; At growth temperatures higher than 450 degrees C, the films showed preferred orientation with mainly (002) di ffraction peak. The Cl content decreased from approximately 9 to 1 at.% wit h the increase in growth temperature from 400 to 500 degrees C. The segrega tion of Cl near the surface region and the incorporation of O from Tb(tmhd) (3) during ALE process were also observed using Anger electron spectroscopy . The ALE-grown ZnS and ZnS:Tb films revealed very uniform thickness and sm ooth surface morphology in the observation using atomic force microscopy an d transmission electron microscopy.