Critical behaviour of the SrTiO3(001) surface at the structural phase transition

The morphology of the SrTiO3(001) surface through the cubic–tetragonal structural phase transition was investigated using X-ray reflectivity experiments. Below the bulk phase transition temperature, an X-ray reflectivity profile revealed marked variations with temperature, because of the occurrence and evolution of domain structures. Simultaneous measurements of Bragg reflection also indicated critical behaviour related to the domain structures in the bulk. Consequently, a significant difference between the temperature evolution of the spontaneous strain at the surface and that of the bulk was clearly exhibited. The simple, but powerful method adopted in the present study would provide a means of understanding structural properties completely, from self-organized domain patterns to microscopic structural modifications at the surface triggered by the structural phase transitions.