Compositional and structural properties of sputter-deposited a-SiO x layers

Silicon oxide (SiO_x0<x<2) layers were prepared by magnetron sputtering from a polycrystalline silicon target in a well defined oxidation environment. The composition of the samples was measured using ion beam techniques. Infra-red spectroscopy (IR) was used to characterize the structure of the samples. A kink point at the compositional parameter x=1.2 was found in both the integrated absorption and the refractive index versus x. This is explained as a preferential cluster formation, especially tetrahedra of type Si-(Si, O ₃) and Si-(Si₃, O), when x>1.2. When the samples are close to SiO₂ stoichiometry, Si-(O₄) species are formed. For x<1.2, the silicon suboxide structure can be described by a random bonding distribution of Si-Si and Si-O bonds