Angle-resolved photoemission from polar and nonpolar zinc oxide surfaces

We report the first angle-resolved photoemission spectra (ARPES) of polar and nonpolar surfaces of an ionic wurtzite-type compound semiconductor. We present experimental results obtained at photon energies between 20 and 80 eV on the polar zinc and oxygen and the nonpolar ($10\overline{1}0$) surfaces of ZnO and identify surface-induced features by comparison with recent theoretical calculations. Comparison between ARPES experiments and theory confirms the determination of the surface-atom geometry at $\mathrm{ZnO}\left(10\mathrm{}\overline{1}0\right)$ by low-energy electron diffraction studies.