Structural properties of ultrathin SrO film deposited on SrTiO3.

Gagnidze, T., Ma, H., Cancellieri, C., Bona, G.-L. & La Mattina, F.

Science and Technology of Advanced Materials 20, 456–463 (2019).

https://doi.org/10.1080/14686996.2019.1599693

Abstract
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  3  (STO) is one of the most used substrates for these compounds, and along its <001> direction allows for two nonpolar chemical terminations: TiO2 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  2-terminated STO substrates. X-ray diffraction and transmission electron microscopy analysis reveal that SrO grows along its [111] 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 2 plane and the first deposited SrO layer is 0.27(3) 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.