PROPERTIES OF A-SI-H BASED INTERFACE TRANSIENT LAYERS MEASURED BY INSITU ELLIPSOMETRY

The transient layer for the initial stages of film growth of hydrogenated amorphous silicon (a-Si:H) on various substrates such as glass, indium tin oxide (ITO), tin oxide (SnO2) and silicon nitride (SiNx) were studied by in-situ ellipsometry. The glass substrate showed a decrease in refractive index of over the initial 80 Å and discontinuities in the refractive index exists in the range of 5 Å from the interface. Transparent electrodes such as ITO or SnO2 had a more pronounced influence on the refractive index, showing a decrease of over more than several hundred ångströms. Discontinuities in the refractive index at the interface did not exist. For the stacked layer of a-Si:H and a-SiNx:H, two nitrogen compositions were studied. The a-SiNx:H film with lower nitrogen content (N/Si = 0.55) influenced only the first 30 Å and the film with higher content (N/Si = 1.33) influenced over 50 Å. It is concluded that a-Si:H films have a compositional mixing layer over a range of 20-200 Å depending strongly on the substrate material. © 1989.