Orientation-defined molecular layer epitaxy of α-Al 2O 3 thin films

Abstract

The intensity oscillation of reflection high-energy electron diffraction (RHEED) was observed for the first time during the growth of α-Al 2O 3 thin films. The observation was achieved in the laser MBE growth at temperatures between room temperature (20°C) and 420°C on the atomically regulated α-Al 2O 3 (1 0 1̄ 2), (1 1 2̄ 0) and (0 0 0 1) substrates. The RHEED oscillation had periodicities corresponding to the repeating molecular layer thicknesses. Atomic force microscopy on the film surfaces terminated at top and bottom stages of RHEED intensity verified that the oscillation accompanied the atomic-scale periodical change of the surface roughness by the two-dimensional epitaxy. Discussion is made on the charge and compositional structures of the molecular layers as the oscillation unit.