Giant step bunching on SrTiO3 thin films grown epitaxially on vicinal MgO (100) surfaces

[Display omitted] •New process allows for the synthesis SrTiO3 thin film that displays extremely large step-terrace size.•Strong influence of annealing temperature on the evolution of the SrTiO3 surface morphology.•Monitoring the annealing temperature induces surface reorganisation of SrTiO3 surface nanostructures.•Detailed diffusion pathways in the SrTiO3 are identified. We report here the controlled formation of giant step bunching in the epitaxial growth of SrTiO3 thin film on vicinal MgO (100) substrates by on-axis radio-frequency (RF)-magnetron sputtering. We have studied the evolution of the surface morphology of such bunched steps by tuning the post-deposition annealing temperature. We demonstrate that the surface periodicity and reorganization of SrTiO3 nanostructures is widely enhanced under controlled post-annealing conditions in addition to Mg content diffusion in the SrTiO3 films. A morphology of facetted islands and bunched steps with extremely smooth terraces were obtained by post-annealing the SrTiO3 thin films at high temperatures. After a double post-annealing treatment at 900 °C and 700 °C, step bunching with a bunched step of fifteen-atomic unit cells and large terraced structures of about 1 µm width has been observed. The formation of these bunches of self-organized SrTiO3 nanostructures is of potential interest as templates for the growth of many functional materials.