SrTiO3(100) − √5 × √5 − R26.6 surface observed by high-resolution scanning tunneling microscopy

SrTiO3(100) - (√5 × √5) - R26.6 surfaces were studied by means of high-resolution scanning tunneling microscopy (STM) under ultrahigh vacuum conditions. By varying the bias voltage in the occupied state, it was possible to observe the arrangement of titanium and oxygen atoms in the unit cells of a (√5 × √5) surface superstructure, which revealed that the TiO2 layer is the terminating plane of the (√5 × √5) surface. In the STM images, peculiar protrusions were seen at the oxygen fourfold hollow site responsible for √5 × √5 periodicity. The protrusions are asymmetrical in contrast, which would be an important consideration in proposing accurate structural models for (√5 × √5) surface superstructures.

Research Highlights► We reported the surface structure of SrTiO3(100)-√5×√5-R26.6. ► High resolution scanning tunneling microscope observations were conducted at room temperatures in ultrahigh vacuum. ► Atomic orbitals of Ti and O atoms were observed and it is confirmed that √5×√5 surface is terminated by TiO2 plane. ► Asymmetrical structures appear at the O fourfold hollow site with √5×√5 periodicity. ► The asymmetrical structures are not simply consistent with the Sr-adatom model.