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

Oriented single-crystal faces of TiC (100)-(1×1) and TiC (111)-Ti (1×1) have been studied with angle-resolved photoelectron spectroscopy using synchrotron radiation for $8\le h\nu \le 70$ 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 (${L_3}^{\prime }=-6\mathrm{}$ eV, ${L_3}^{\prime }=-3\mathrm{}$ eV, ${X_4}^{\prime }-{\Delta }_1=-4\mathrm{}$ eV, ${X_5}^{\prime }=-0.5\mathrm{}$ eV, and ${\Delta }_5=-0.8\mathrm{}$ 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 (${L_1}^{\prime }=8.7\mathrm{}$ eV and $X_1=11.5\mathrm{}$ 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 $\Gamma -\Delta -L$ and $\Gamma -\Lambda -L$; 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).