Photoemission study of the Li/Ge(111)-3 x 1 reconstruction

In this article we report our findings on the electronic structure of the Li induced Ge(1 1 1)-3 x 1 reconstruction as determined by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and core-level spectroscopy using synchrotron radiation. The results are compared to the theoretical honeycomb-chainchannel (HCC) model for the 3 x 1 reconstruction as calculated using density functional theory (DFT). ARUPS measurements were performed in both the (Gamma) over bar - (M) over bar and (Gamma) over bar - (K) over bar directions of the 1 x 1 surface Brillouin zone at photon energies of 17 and 21.2 eV. Three surface related states were observed in the (Gamma) over bar - (K) over bar direction. In the (Gamma) over bar - (M) over bar direction, at least two surface states were seen. The calculated band structure using the single-domain HCC model for Li/Ge(1 1 1)-3 x 1 was in good agreement with experiment, allowing for the determination of the origin of the experimentally observed surface states. In the Ge 3d core-level spectra, two surface related components were identified, both at lower binding energy with respect to the Ge 3d bulk peak. Our DFT calculations of the surface core-level shifts were found to be in fair agreement with the experimental results. Finally, in contrast to the Li/Si(1 1 1)-3 x 1 case, no double bond between Ge atoms in the top layer was found. (C) 2009 Elsevier B.V. All rights reserved.