Angle-resolved photoemission studies of TiC(111) and TiC(100)

Abstract

Oriented single-crystal faces of TiC (100)-(1\ifmmode\times\else\texttimes\fi{}1) and TiC (111)-Ti (1\ifmmode\times\else\texttimes\fi{}1) have been studied with angle-resolved photoelectron spectroscopy using synchrotron radiation for $8\ensuremath{\le}h\ensuremath{\nu}\ensuremath{\le}70$ eV. From normal-emission spectra, criticalpoint energies have been determined for the occupied carbon $2s$ band (10-13 eV below ${E}_{F}$) and for the occupied Ti $3d$-C $2p$ band (${{L}_{3}}^{\ensuremath{'}}=\ensuremath{-}6$ eV, ${{L}_{3}}^{\ensuremath{'}}=\ensuremath{-}3$ eV, ${{X}_{4}}^{\ensuremath{'}}\ensuremath{-}{\ensuremath{\Delta}}_{1}=\ensuremath{-}4$ eV, ${{X}_{5}}^{\ensuremath{'}}=\ensuremath{-}0.5$ eV, and ${\ensuremath{\Delta}}_{5}=\ensuremath{-}0.8$ eV). Recent band calculations are shown to be qualitatively correct, although most calculations place the bands too close to the Fermi energy ${E}_{F}$. Critical points in the empty Ti $4s$-derived band (${{L}_{1}}^{\ensuremath{'}}=8.7$ eV and ${X}_{1}=11.5$ eV above ${E}_{F}$) have been identified through studies of final-state effects in normal emission. Three-dimensional density-of-states features were observed in normal-emission spectra, although such spectra should sample only the high-symmetry lines $\ensuremath{\Gamma}\ensuremath{-}\ensuremath{\Delta}\ensuremath{-}L$ and $\ensuremath{\Gamma}\ensuremath{-}\ensuremath{\Lambda}\ensuremath{-}L$; these could be due to the effects of bulk vacancies in the Ti${\mathrm{C}}_{0.93}$ crystal or to surface inhomogeneities incurred in the preparation process (ion etching and annealing).