Core-level spectroscopy study of the Li/Si(111)-3 x 1, Na/Si(111)-3 x 1, and K/Si(111)-3 x 1 surfaces

In this article we report Si 2p core-level spectroscopy results from the alkali (Li, Na, and K) induced Si(111)-3 x 1 reconstructions. The experimental results are compared to the theoretical honeycomb-chain channel (HCC) model for,the 3 x 1 reconstruction using density functional theory (DFT) to calculate core-level shifts using both initial and final-state calculation schemes. Si 2p core-level spectra for the Li, Na, and K reconstructions showed two surface related components lying on either side of the main bulk Si 2P(3/2) peak. An additional higher binding energy component was found for K. All core-level spectra showed strong similarities leading to the conclusion that the surfaces do indeed share a common structure. With increasing alkali metal size, the lower binding energy component was found to shift away from the main bulk peak. Our theoretical calculations also show a similar trend. It is concluded that the lower binding energy surface component originates from the alkali atom bonded Si atoms. The origin of the higher binding energy component was determined based on trends in the peak height and final-state DFT calculations. It was found that this component derives from several atoms in the first and second layers. Calculations which include final-state effects were found to be in good agreement with the experimentally determined surface core-level shifts