Structural properties of ultrathin SrO film deposited on SrTiO(3)

The role of epitaxial strain and chemical termination in selected interfaces of perovskite oxide heterostructures is under intensive investigation because of emerging novel electronic properties. SrTiO[Image: see text] (STO) is one of the most used substrates for these compounds, and along its [Image: see text] direction allows for two nonpolar chemical terminations: TiO(2) and SrO. In this paper, we investigate the surface morphology and crystal structure of SrO epitaxial ultrathin films: from 1 to about 25 layers grown onto TiO[Image: see text] -terminated STO substrates. X-ray diffraction and transmission electron microscopy analysis reveal that SrO grows along its [Image: see text] direction with a 4% out-of-plane elongation. This large strain may underlay the mechanism of the formation of self-organized pattern of stripes that we observed in the initial growth. We found that the distance between the TiO[Image: see text] plane and the first deposited SrO layer is [Image: see text] nm, a value which is about 40% bigger than in the STO bulk. We demonstrate that a single SrO-deposited layer has a different morphology compared to an ideal atomically flat chemical termination.