THE THEORY OF DIELECTRIC FUNCTIONS AND ITS APPLICATION TO AMORPHOUS SI1-XNX

The similarity of shape between the dielectric function of a-Si and its amorphous alloys has led to the development of a scaling theory to describe these functions. The dielectric theory of Phillips is used to derive the scaling parameters for several models of the structure of amorphous silicon alloys, combining the contributions of the microscopic components using a self-consistent effective medium approximation. A homogeneous medium theory and two microscopic theories, one based on bonds and the other on tetrahedral units, are considered; the occurrence of voids is also considered. Comparison of predictions with experimental data for several thin film samples of amorphous Si1-xNx alloys, taken over the photon energy range 0-12 eV, is reported. The homogeneous medium theory clearly fails to describe the data. The two microscopic theories both describe them fairly well, the tetrahedron model being somewhat better.