Optical properties of non-crystalline Si, SiO, SiOx and SiO2

Optical data for non-crystalline Si, SiO, SiOx(x=1·5) and SiO2 are presented and analyzed for the energy region 1 to 26 eV. The results indicate that amorphous substances of all intermediate compositions between Si and SiO2 can be formed and that these materials are not simple mixtures of Si and SiO2 but rather the two atom species are blended on an atomic scale. More specifically, the Si bonding is tetrahedral (perhaps highly distorted) and of the type Si−(SivO4−v) where the distribution of atoms is essentially statistical. Further it is found that the optical properties of these layers are determined by the presence and grouping of Si−O and Si−Si bonds and that clusters of like bonds of the dimension of a Si−(Si4) or Si−(O4) tetrahedra have optical properties comparable to those exhibited by amorphous silicon or quartz, respectively, ‘in bulk’.