Conversion of the (001) Strontium Titanate Surface to Titanium Monoxide via Ultrafast High-Temperature Sintering

The reconstruction of crystal surfaces (the alteration of the surface structure from that of the bulk) is imperative for the development of catalysts and energy-related materials. In this study, ultrafast high-temperature sintering (UHS) was employed to rapidly heat and reconstruct a model surface, namely the (001) surface of a SrTiO3 single crystal. The structural changes were investigated by X-ray diffraction, scanning transmission electron microscopy, and electron energy-loss spectroscopy. Following treatment at 1650 °C for 180 s using UHS, a gold-colored transformation was observed on the surface; however, this was not the case after treatment at 1550 °C. Microscopic and spectroscopic analysis have revealed that the gold-colored surface layer possesses a thickness of approximately 100 nm, predominantly comprising rock salt-type cubic TiO. Furthermore, the electrical conductivity exhibited by the surface layer was very close to that reported for cubic TiO. The reconstruction mechanism of the (001) surface during UHS treatment was inferred to be similar to the incongruent sublimation of the SrTiO3 surface that has previously been observed under vacuum at extremely low oxygen partial pressures. In conclusion, UHS has been demonstrated to be a highly efficacious technique for expeditious reconstruction of crystal surfaces, encompassing other metal oxides.