Lithium-induced dimer reconstructions on Si(001) studied by photoelectron spectroscopy and band-structure calculations

Abstract

The electronic and atomic structure of Si(001) with 0.5 and 1 ML of lithium have been studied experimentally using angle resolved ultraviolet photoelectron spectroscopy, Si $2p$ core level spectroscopy, and low energy electron diffraction. Experimental surface state dispersions are compared with recent theoretical results in the literature and with results from additional density functional theory calculations. Four adsorption configurations for the 0.5 ML $2\ifmmode\times\else\texttimes\fi{}2$ surface and three configurations for the 1 ML $2\ifmmode\times\else\texttimes\fi{}1$ surface are compared. Fittings of Si $2p$ core level data support the alternation of strongly and weakly buckled Si dimers of the $2\ifmmode\times\else\texttimes\fi{}2$ models and symmetric Si dimers of the $2\ifmmode\times\else\texttimes\fi{}1$ models based on the relative intensities of the surface components. As a tool to differentiate between the different $2\ifmmode\times\else\texttimes\fi{}2$ and $2\ifmmode\times\else\texttimes\fi{}1$ models surface state dispersions are used since they are sensitive to the positions of the Li adatoms.