STRUCTURE AND ELECTRONIC STATES ON REDUCED SRTIO3(110) SURFACE OBSERVED BY SCANNING-TUNNELING-MICROSCOPY AND SPECTROSCOPY

The SrTiO3(110) surface, after annealing in ultrahigh vacuum (UHV) was observed by scanning tunneling microscopy/spectroscopy (STM/S). These observations were compared with the ultraviolet photoemission spectroscopy (UPS) and x-ray photoemission spectroscopy (XPS) data previously reported. The surface, after annealing at 800 °C, is dominated by flat regions where tunneling spectra are of metallic character, in agreement with the UPS data that showed a clear cutoff at the Fermi energy, EF. After annealing above 1000 °C, step edges along [11̄0] and rowlike structures along [001] with spacing approx.2.2 nm, close to 4√2a, are observed. The tunneling spectra showed an energy gap and an in-gap state approx.1 eV below EF, both of which are similar to those reported on the SrTiO3(100) surface after annealing in UHV. After 20 cycles of annealing above 1000 °C, a new ordering with c(2 × 6) periodicity is observed on the terraces. The STM/S results are explained by formation of (100) and (010) microfacets in the course of annealing in vacuum.