Surface structure of (1 1 (2)over-bar 0) Al2O3 single crystals after high temperature annealing

The surface Structure of a-plane (1 1 (2) over bar 0) Al2O3 single crystals with a <1 0 <(1)over bar> 0> inclined direction was studied as a function of annealing temperature using atomic force microscopy. The samples had a large increase in step height and terrace width with increasing annealing temperature. For the samples annealed at 1500 degrees C and 1600 degrees C the step edge structure became significantly faceted. The facets consisted of(0 0 0 1) and (1 0 (1) over bar 2) planes as a result of these two planes being the ones with the lowest surface energies in Al2O3. In addition, the Surface morphology displayed the formation of ridges 0.3 nm high and similar to 20 min wide at 1600 degrees C which originate from a tendency of the Surface to form a (4 x 1) reconstruction with the sharp step edges acting as reconstruction nucleation sites. (C) 2008 Elsevier B.V. All rights reserved.