Depth-resolved subsurface defects in chemically etched $SrTiO3$

Depth-resolved cathodoluminescence spectroscopy of atomically flat $TiO2$-terminated $SrTiO3$ single crystal surfaces reveals dramatic differences in native point defects produced by conventional etching with buffered HF (BHF) and an alternative procedure using $HCl–HNO3$ acidic solution (HCLNO), which produces three times fewer oxygen vacancies before and nearly an order of magnitude fewer after pure oxygen annealing. BHF-produced defect densities extend hundreds of nanometers below the surface, whereas the lower HCLNO-treated densities extend less than 50 nm. This “Arkansas” HCLNO etch and anneal method avoids HF handling and provides high-quality $SrTiO3$ surfaces with low native defect density for complex oxide heterostructure growth.