Direct visualization and control of SrO_x segregation on semiconducting Nb doped SrTiO₃ (100) surface

We investigated how SrO_x segregates on a Nb doped SrTiO₃ (100) surface by in air annealing. Using atomic force and photoemission electron microscopes, we can directly visualize the morphology and the electronic phase changes with SrO_x segregation. SrO_x islands less than 2 μm in size and 1–5 unit cells thick nucleate first and grow in a labyrinth domain pattern. After prolonged annealing, SrO_x forms a ~ 10 nm thick film. We show that the domain pattern can be controlled by introducing a surface miscut angle of SrTiO₃. Additionally, the segregated SrO_x has a lower work function, compared to that of SrTiO₃. These results suggest that the control and tunability of SrO_x segregation is applicable to the design of a new functional electronic devices in the semiconducting SrTiO₃ based heterostructure.