Growth of single-crystalline, atomically smooth MgO films on Ge(0 0 1) by molecular beam epitaxy

We investigate the growth of MgO thin films on Ge(0 0 1) via molecular beam epitaxy and find that the growth temperature plays a key role in the quality of MgO thin films. Reflection high-energy electron diffraction (RHEED) and atomic force microscopy show that the single-crystal quality and atomically smooth morphology are optimized for a growth temperature of 250 °C. RHEED and transmission electron microscopy indicate that the MgO is (0 0 1) oriented and the MgO unit cell has a 45° in-plane rotation with respect to that of Ge, providing a high-quality film and interface for potential spin-injection experiments.