Arrangement of rotational domains of the (√31×√31) R±9° reconstruction of Al2O3(0 0 0 1) revealed by non-contact AFM

Non-contact atomic force microscopy using a needle sensor with a phase shift feedback mechanism has been used to characterise Al2O3(0 0 0 1) surfaces prepared by annealing in 10−4 mbar partial pressures of oxygen. The preparation procedure leads to flat terraces with lengths in excess of 1000 nm and widths of order 40 nm separated by c/6 steps. The unit cell of the (√31×√31) R±9° reconstruction is resolved, with a single rotational domain on each of the terraces. The 18° rotation between the domains is observed exclusively at step edges. The mechanism of imaging the (√31×√31) R±9° reconstruction is discussed.