Controlling Sr Volatilization for Atomically Flat Step-Terrace SrTiO3 Surface via H2O-Assisted Thermal Annealing

Authors:
Preprint
Publisher website
Google Scholar
Abstract
Atomically flat SrTiO3 (001) surfaces with well-defined step-terrace structures are essential for high-quality oxide heterostructures, but their high-temperature evolution is strongly affected by surface segregation and defect formation. Here, we investigated SrTiO3 (001) surfaces annealed at 1200 °C in dry-air, Ar, and humid-air using atomic force microscopy and thermodynamic analysis. Dry-air annealing initially promoted step formation, but prolonged annealing induced phase inhomogeneity, indicating the formation of a thermodynamically stable SrO-rich surface layer. Ar annealing did not suppress this problem and instead produced a disordered surface, likely due to oxygen-vacancy-related instability. In contrast, humid-air annealing delayed SrO segregation by increasing the volatility of excess Sr species through hydroxide formation, enabling a well-defined step-terrace structure within an intermediate annealing window. However, SrO segregation reappeared after extended humid annealing, showing that humidity provides kinetic suppression rather than thermodynamic elimination. These results suggest that precise control of atmosphere chemistry can serve as a general strategy for balancing surface segregation and volatility-driven cation removal in complex oxide substrate preparation.

This publication has 16 references indexed in Scilit: