Figure 4

APB formation mechanism.
(a) Sketch for the atomic configuration of the surface rock-salt-type SrO double layer island surrounded by a SrO single layer, which is the prerequisite for the formation of APBs. (b) Sketch for the atomic configuration resulting in the formation of APB1 in (001) and APB2 in (010) during growth. (c) Surface morphology of the 20 nm Sr rich STO thin film determined by in-situ AFM shown in Fig. 3 prior to the LAO deposition.