Interface structure of a-Si:H/ZnS multilayer films elucidated from electron-spin resonance and infrared-absorption measurements

Multilayer films consisting of hydrogenated amorphous silicon and zincsulfide (a-Si:H/ZnS) were prepared by glow-discharge decomposition of silane gas and diethylsulfur-diethylzinc gas mixture. Since a-Si:H/ZnS multilayer films do not have Si atoms in their barrier layer, they have an advantage of easy characterization of the a-Si:H well layer by using electron-spin resonance and infrared absorption. These measurements revealed that in an interface region within a distance of 10 nm from the interface, H atoms in a-Si:H are incorporated in the form of dihydride rather than in the form of monohydride. In accordance with the H bonding scheme, it was also found that the interface region in a-Si:H within a distance of several nanometers from the interface has a large Si dangling bond density of the order of 1018 cm-3. Transport properties in these films were also investigated.