CHEMICAL-BOND AND RELATED PROPERTIES OF SIO2 .6. ELECTRONIC-STRUCTURE OF SIOX

Real‐space distributions of the pseudopotential and of the corresponding valence charge density are investigated in dependence on the chemical composition of SiOx with the help of three different crystal models, that means with a mixed‐crystal model, with a model in which five Si‐(SiyO4–y) crystals (y = 0 to 4) are compared, and a random‐bonding model for which a statistical distribution of the five possible bonding tetrahedra Si‐(SiyO4–y) within SiOx is considered. The superiority of the random‐bonding model to the mixture model, in which a simple mixture of Si and SiO2 is assumed, is demonstrated. Furthermore, it is shown that the composition rate of SiOx, at which the electronic properties of SiO2 begin to dominate, is x = 1.5 or even smaller, and that therefore the SiOx transition regions at the Si/SiO2 interfaces are somewhat thicker than commonly deduced from electronic SiOx properties. Selected problems concerning oxygen impurities in Si crystals and interactions between Si‐O and Si‐Si bonds in SiOx are discussed. The electronic dielectric function of SiOx is calculated. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA