(Invited) Strain Effects on Dielectric Properties of Thin, Crystalline Rare Earth Oxides on Silicon

Under certain conditions, thin rare earth oxide layers epitaxially grown on Si exhibit dielectric constants that are much larger than the known bulk values. We investigate the effect of lattice-mismatch induced strain on dielectric properties. First, we report on the dependence of that enhancement effect on layer thickness for epitaxial Gd2O3 on Si(111). Controlling the oxide composition in ternary (Gd1-xNdx)2O3 thin films enables us to tune the lattice mismatch to silicon, and thus the dielectric constants of the layer from 13 (close to the bulk value) up to 20. We show that simple tetragonal distortion of the cubic lattice is not sufficient to explain the observed enhancement effects. Therefore, we propose more severe strain induced structural phase deformations.