Surface engineering along the close-packed direction of SrTiO3

We have investigated the effects of wet etching with a 3:1 mixture of HCl:H NO3 and of annealing at 850 degreesC on the surface morphology of [1 1 1]-o riented SrTiO3 single crystals. Atomic force microscopy is used to demonstr ate that the surface morphology is a strong function of both etching and an nealing time. All surfaces have step heights equal to integral or half-inte gral multiples of the (1 1 1) interplanar spacing. However, step bunching, non-regular step heights, granularity, inhomogeneous surface morphology, an d etch pits are observed on many surfaces. A combination of etching and ann ealing leads to surfaces that are free of these irregularities and are char acterized by well-developed step-terrace structures: the terraces are appro ximate to 600 Angstrom wide, the step heights are either 1.2 Angstrom or 2. 3 Angstrom, which are a half or a whole (1 1 1) interplanar distance, respe ctively, and the step edges are parallel to a single <1 1 0 > -type directi on. The existence of these two step heights implies that the surfaces are t erminated by both SrO3 and Ti planes. (C) 2001 Elsevier Science B.V. All ri ghts reserved.