Ultraviolet photoemission and low-energy-electron diffraction studies of Ti O 2 (rutile) (001) and (110) surfaces

We have examined the (001) and (110) faces of Ti${\mathrm{O}}_{2}$ (rutile) using ultraviolet photoelectron spectroscopy (UPS), low-energy-electron diffraction (LEED), and Auger electron spectroscopy (AES). We found that the (001) surface is unstable and reconstructs or facets when annealed while the (110) surface is stable and does not reconstruct. Other indications of the relative instability of the (001) surface include the presence of a surface phase change for $Tg950\ifmmode^\circ\else\textdegree\fi{}$C, significant oxygen-adsorption effects, and thermal instability in the concentration of surface ${\mathrm{Ti}}^{3+}$-O-vacancy defects.