Atomically smooth and single crystalline Ge(111)/cubic-Pr2O3(111)/Si(111) heterostructures: Structural and chemical composition study

Engineered wafer systems are an important materials science approach to achieve the global integration of single crystalline Ge layers on the Si platform. Here, we report the formation of single crystalline, fully relaxed Ge(111) films by molecular beam epitaxial overgrowth of cubic Pr oxide buffers on Si(111) substrates. Reflection high-energy electron diffraction, scanning electron microscopy, and x-ray reflectivity show that the Ge epilayer is closed, flat, and has a sharp interface with the underlying oxide template. Synchrotron radiation grazing incidence x-ray diffraction and transmission electron microscopy reveal the type-A/B/A epitaxial relationship of the Ge(111)/cubic Pr2O3(111)/Si(111) heterostructure, a result also corroborated by theoretical ab initio structure calculations. Secondary ion mass spectroscopy confirms the absence of Pr and Si impurities in the Ge(111) epilayer, even after an annealing at 825 degrees C.