Effect of surface orientation on intrinsic island formation on SrTiO3 surfaces

Intrinsic islands were formed on Nb-doped SrTiO3 (100) and (111) surfaces by high-temperature annealing (1200°C) under oxygen atmosphere. The influence of surface orientation on the chemical composition and structure of islands was investigated by using Auger electron spectroscopy, energy-dispersive X-ray spectroscopy as well as electron diffraction in a transmission electron microscope. For a given island size, the same compositional profiles were observed for both surface orientations. While the bigger islands (with a height of several 100 nm) contain almost only Sr as cations, the smaller islands (with a height of few 10 nm) also contain Ti. Identical lattice-plane distances in all islands point to a distinct crystal structure for islands growing on (001) and (111) surfaces.