Description:

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.   Some insulating oxide crystals are particularly attractive candidates because nanostructures grown on them will be electrically insulated from the substrate.  It is proposed that these structures could be used as arrays of nanowires and quantum dots. The patterned surfaces might also act as a suitable substrate for the growth of new metallic or semiconducting quantum structures.

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