Surface engineering along the close-packed direction of SrTiO3

We have investigated the effects of wet etching with a 3:1 mixture of HCl:HNO3 and of annealing at 850 degreesC on the surface morphology of [1 1 1]-oriented SrTiO3 single crystals. Atomic force microscopy is used to demonstrate that the surface morphology is a strong function of both etching and annealing time. All surfaces have step heights equal to integral or half-integral multiples of the (1 1 1) interplanar spacing. However, step bunching, non-regular step heights, granularity, inhomogeneous surface morphology, and etch pits are observed on many surfaces. A combination of etching and annealing leads to surfaces that are free of these irregularities and are characterized by well-developed step-terrace structures: the terraces are approximate 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, respectively, and the step edges are parallel to a single <1 1 0 > -type direction. The existence of these two step heights implies that the surfaces are terminated by both SrO3 and Ti planes. (C) 2001 Elsevier Science B.V. All rights reserved.