Anisotropic lattice strain relaxation of MgO/SrTiO3(001) in a textured island growth mode

The out-of-plane and in-plane lattice parameters were measured by in-situ reflection high-energy electron diffraction (RHEED) at the initial growth stage of MgO thin films on SrTiO3(001) substrates in the growth mode of islands. The in-plane lattice was found to relax immediately after initiating the film deposition, and the majority of the in-plane strain was relieved at the film thickness of 2 nm. Beyond the thickness, the in-plane lattice almost was kept unchanged, and the out-of-plane lattice continued to relax gradually. The anisotropic strain can be attributed to the change of strain energy due to film texture during the ripening process. The relationship between strain and texture, grain size was discussed from the viewpoint of energy competition.

► Simultaneous real-time measurement of the in-plane and out-of-plane lattice constants is very difficult during the film growth. However, in-situ RHEED observation can solve the problem for those films in an island growth mode, which has rarely been reported.
► We found the anisotropic strain during the growth of MgO/STO. The relationship between strain and texture, grain size was discussed from the viewpoint of energy competition.
► The results would be helpful to compute the in-plane and out-of-plane lattice constants through the analysis of RHEED pattern, and to understand the growth mechanism of initial growth behavior for the textured island growth mode.