Lattice engineering of dielectric heterostructures on Si by isomorphic oxide-on-oxide epitaxy

Abstract

The isomorphic oxide-on-oxide epitaxy of Y2O3 on cubic Pr2O3(111)∕Si(111) support systems was studied to tailor the lattice constant of the dielectric heterostructure for future integration of functional semiconductors via heteroepitaxy on the Si material platform. Laboratory- and synchrotron-based x-ray diffraction was applied to study the structure as well as the epitaxy mechanism of Y2O3 on the cubic Pr2O3(111)∕Si(111) support. The oxide heterostructure is characterized by the formation of closed single crystalline cubic Y2O3(111) films which are in especial twin-free and exhibit an exclusive type B epitaxy orientation on the cubic Pr2O3(111)∕Si(111) system. Nondestructive depth profiling x-ray diffraction reveals that the epitaxy mechanism of Y2O3 films on cubic Pr2O3(111)∕Si(111) systems is determined by the formation of a transition layer with variable lattice parameters, changing with increasing depth from the Y2O3 values towards the parameters of the isomorphic Pr2O3 support. This transition layer thus effectively accomodates the relatively large lattice misfit of 4.8% between the isomorphic oxides. X-ray photoelectron depth profiling studies are applied to discriminate between strain and interface reaction effects in the formation of this transition region at the Y2O3∕Pr2O3 boundary. An interface reaction, forming a compositionally graded Pr2−xYxO3 (x=0–2) buffer layer at the oxide/oxide boundary, results as the most probable physical origin.