Quest for a pristine unreconstructed SrTiO 3 ( 001 ) surface: An atomically resolved study via noncontact atomic force microscopy

The surfaces of perovskite oxides affect their functional properties, and while a bulk-truncated $(1\ifmmode\times\else\texttimes\fi{}1)$ termination is generally assumed, its existence and stability is controversial. Here, such a surface is created by cleaving the prototypical ${\mathrm{SrTiO}}_{3}$(001) in ultrahigh vacuum, and its response to thermal annealing is observed. Atomically resolved noncontact atomic force microscopy (nc-AFM) shows that intrinsic point defects on the as-cleaved surface migrate at temperatures above $200{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. At $400{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}\text{--}500{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, a disordered surface layer forms, albeit still with a $(1\ifmmode\times\else\texttimes\fi{}1)$ pattern in low-energy electron diffraction (LEED). Purely ${\mathrm{TiO}}_{2}$-terminated surfaces, prepared by wet-chemical treatment, are also disordered despite their $(1\ifmmode\times\else\texttimes\fi{}1)$ periodicity in LEED.