Surface core-level shifts on clean Si(001) and Ge(001) studied with photoelectron spectroscopy and density functional theory calculations

Abstract

The $\text{Si}\text{ }2p$ and $\text{Ge}\text{ }3d$ core levels are investigated on the $c(4\ifmmode\times\else\texttimes\fi{}2)$ reconstructed surfaces of Si(001) and Ge(001), respectively. Calculated surface core-level shifts are obtained both with and without final state effects included. Significant core-level shifts are found within the four outermost atomic layers. A combination of the theoretical results and high-resolution photoemission data facilitates a detailed assignment of the atomic origins of the various components identified in the core-level spectra of both Si(001) and Ge(001).