Specific features of the formation of terrace-step nanostructures on the (0001) surface of sapphire crystals

The terrace-step structures on atomically smooth vicinal surfaces of sapphire crystals subjected to thermal annealing after mechanical and chemical treatments have been investigated by atomic-force microscopy. The influence of the vicinal angles and conditions of thermal treatment (including annealings in air and vacuum) of sapphire plates on the metric parameters of terrace-step structures has been analyzed. It is shown that steps with a height from monoatomic (0.22 nm) to 3 nm or more can be formed on the sapphire surface by changing the vicinal angle and thermal-treatment conditions. The results are interpreted in terms of the minimum surface energy and surface diffusion processes.