Photoemission study of the bulk and surface electronic structure of single crystals of gold

Abstract

Angle-resolved energy distributions for photoelectrons emitted from the (111), (110), and (100) crystal faces of Au are presented for photon energies in the range 7.0-11.6 eV. The variation of peak-energy positions as a function of photon energy and electron emission angle has been studied. We have found very good qualitative agreement between the experimental results and the predictions of the three-step model applied to a relativistic-augmented-plane-wave band structure. To fit the theoretical peak-energy positions to the experimental data, it is necessary to lower bands Nos. 3, 4, and 5 (numbered from the bottom of the valence-band complex) by on the average 0.2 eV and to raise band No. 6 by 0.2 eV along the $\ensuremath{\Gamma}K$ symmetry line. Considerable emission must also be attributed to nondirect processes such as phonon-assisted nondirect transitions, scattering of electrons excited in direct transitions, and surface photoemission. A shoulder due to nondirect processes is always seen at -2.3 eV, whenever the emission due to direct transitions is low. The dispersion of the surface state in the $L$ gap has been measured. A parabolic fit to the data gives ${E}_{0}=0.45\ifmmode\pm\else\textpm\fi{}0.05$ eV and ${m}^{*}=(0.37\ifmmode\pm\else\textpm\fi{}0.05){m}_{0}$. We also report measurements on the local work function for the three low-index crystal faces.