Study Of The Na-Si(111) 3x1 Interface Using Core-Level Photoemission Spectroscopy

The Na-Si(111) 3 x 1 and NaSi(111) interfaces with various coverages of Na have been investigated using low-energy electron diffraction Auger electron spectroscopy and photoemission spectroscopy (PES) with a synchrotron radiation source. In decomposing the PES peak from the Si 2p core level into the surface and bulk components, the relative shifts and intensities of the surface components as well as the band bending for the 3 x 1 interface are consistent with the structure model proposed by Monch. The evolution of the band bending from about 1 monolayer to thick Na coverage corresponds to the theory of the metal-induced gap states. The final Schottky barrier height is determined to be 0.38 +/- 0.05 eV and does not depend on whether a thicker Na layer is deposited on an ordered Na-Si(111) 3 x 1 surface or a disordered thin Na layer on Si(111).