  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 nm 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
