Surface morphology of c-plane sapphire (α-alumina) produced by high temperature anneal

A comparative study of the morphological surface evolution of c-plane (0001) α-Al2O3 upon annealing was investigated for non-miscut (i.e. substrates with 0° nominal miscut) and vicinal substrates. The samples were annealed in air at 1100 °C for different durations of time. Although non-miscut samples do not show any step bunching at this temperature, miscut substrates show a regular and ordered stepped morphology with clearly defined terraces as revealed by Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) image analysis. The surface morphology presents a number of coalescence points, i.e. locations where two steps merge and form a multiple step. Close to the coalescence points, parallel steps change direction to different low index direction.