DENSITY-OF-STATES OF A-SI1-YNIY-H ALLOYS DETERMINED BY X-RAY AND OPTICAL SPECTROSCOPIES

The density of valence states of amorphous hydrogenated silicon-nickel a-Si1-yNiy:H alloys has been experimentally investigated by soft X-ra y emission (SXS) and optical spectroscopies. By SXS, partial Si 3p and Ni 3d valence states are obtained on a common energy scale referred t o the Fermi level. Our results show that, as the Ni content is increas ed, the uppermost valence band changes from Si 3p to hybridized Si 3p- Ni 3d states, leading to a finite density of states at the Fermi level . The results are discussed in relation to optical measurements perfor med on samples deposited at the same time.