Coarsening of two-dimensional Al2O3 islands on vicinal (1, −1, 0, 2) sapphire surfaces during annealing in air

The evolution of two-dimensional (2D) islands which result from a chemo-mechanical polishing of vicinal (1, −1, 0, 2) sapphire surfaces was explored by atomic force microscopy (AFM) after annealing in air. The evolution of the surface morphology is followed after isothermal annealing (1173 K) for duration varying from 1 h to 53 h and isochronal annealing at temperatures between 1023 K < T < 1253 K. Statistical analysis of the AFM images gives evidence that an anisotropic Ostwald ripening governs the evolution of the 2D island distribution. The activation energy for mass transport on the terrace is found to be 1.3 ± 0.1 eV.