Nanostructures on the SrTiO3(0 0 1) surface studied by STM

Atomic resolution scanning tunnelling microscopy of the SrTiO3(0 0 1) surface reveals that certain treatments give rise to two types of self-assembled nanostructures. Surfaces prepared through Ar ion sputtering and ultrahigh vacuum (UHV) annealing up to 900 °C form terraces with straight step edges that have a c(4×2) reconstruction. Following further UHV annealing above 900 °C nanolines of 1 nm width, 0.2 nm height, and variable length are created that run in 〈1 0 0〉 directions. On closest packing the nanolines are 2.4 nm apart and form a (6×2) overlayer. On further annealing the nanolines break up into nanodots of 0.2 nm height that form regular arrays. It is proposed that both structure types are created through non-stoichiometry of the surface region that results in nanocrystalline growth of either SrO or TiOx. SrTiO3 surfaces patterned in this way have the potential to serve as a template for the growth of metallic or semiconducting quantum structures.