Laser Irradiation Induced Atomic Structure Modifications in Strontium Titanate

We studied the surface and subsurface structural modifications induced by pulsed laser irradiation on single-crystalline SrTiO3. Using atomic-resolution scanning transmission electron microscopy investigations, we showed that a laser-irradiated surface in single-crystalline SrTiO3 transforms into an amorphous phase with a subsurface oxygen-deficient disordered crystalline region which is attributed to laser-induced melting followed by unidirectional recrystallization. A computational approach to identify positions of individual atoms in atomic-resolution images was used to determine the bond lengths between Sr-Sr and Ti-Ti atoms, and thus the lattice distortions. We estimate similar to 4% lattice disorder in the disordered region compared with the pristine. This disorder increases up to similar to 16% towards the surface and transforms to an amorphous phase. Due to rapid recrystallization, these aforementioned structural transformations were accompanied by oxygen vacancies formation and change in the location coordination. With electron energy-loss spectroscopic analysis, we confirmed the transformation of Ti+4 to Ti+3 in the disordered region due to oxygen vacancy formation.

Automated summary

The study demonstrates that pulsed laser irradiation on single-crystalline SrTiO3 leads to surface transformation into an amorphous phase and the formation of an oxygen-deficient disordered crystalline region in the subsurface. These structural transformations are accompanied by lattice distortions, change in location coordination, and the formation of oxygen vacancies.