Atomic resolution and study of surface morphology of HgBaCuO single crystals by scanning probe methods

Superconducing HgBa2CuO4+x single crystals grown in an Al2O3 crucible using a high-pressure furnace (argon pressure = 10.1 kbar) show a clean and smoo th surface. Investigations by scanning tunnelling (STR I), scanning force ( SFM) and friction force (FFM) microscopies reveal an atomically flat surfac e with steps similar to 4 nm high in the [001] direction. At the surface, p articles are observed that may have been caused by ageing under ambient con ditions. These particles exhibit a contrast reversal in FFM images, implyin g that they consist of a different material than the underlying matrix, Occ asionally, free step-flow during crystal growth is hindered by atomic point defects, resulting in local step bending. Such processes may explain the m icrometre-sized indents found along the steps. On an atomic scale, STM meas urements reveal an approximately square atomic lattice (a 4.0-4.4 Angstrom) and an unexpected domain structure with edge dislocations and point defect s. Copyright (C) 1999 John Wiley & Sons, Ltd.