MOCVD growth of non-epitaxial and epitaxial ZnS thin films

Thin films of ZnS have been deposited by MOCVD on both BaTa206/ITO/glass and Si substrates. Diethylzinc (DEZn) and H2S are used for deposition on substrates heated to the 250-400°C temperature range. The microstructure and properties of ZnS films were studied by X-ray diffractometry (XRD), ultraviolet/visible spectrophotometry (UVS) and scanning electron microscopy (SEM). Films prepared on BaTa206/ITO/glass were polycrystalline with mixed cubic and hexagonal phases. The hexagonal structure dominated for film thicknesses < 700 nm, while the cubic structure dominated for film thicknesses > 700 nm. The bandgap energy of ZnS films decreased and the surface morphology became worse with the increasing film thickness. Upon annealing 200-600 nm films at temperatures of 450-550°C in H2S for 1 h, the ZnS films developed an even stronger cubic (111) or hexagonal (002) preferred orientation. Polycrystalline ZnS films grown on Si(100) and (111) substrates tended to be cubic. Nucleation and growth rates on Si(100) substrates were initially faster than on Si(111) substrates. At 400°C, epitaxial growth of ZnS on Si(100) was achieved.