MG-INDUCED SI(111)3X1 STRUCTURE STUDIED BY PHOTOELECTRON-SPECTROSCOPY

By means of angle resolved photoelectron spectroscopy using synchrotro n radiation, we have measured the valence band and surface sensitive S i2p core-level spectra for the Si(111)3 X 1-Mg surface. The dispersion of the valence band shows the fact that this surface has a semiconduc ting property and two surface states in the projected bulk band gap at the ($) over bar K point. From the fitting results of the Si2p core-l evel spectra, we find that the two surface shifted core-level componen ts, S'(1) and S'(2) stem from the Si atom with single dangling bond an d the Si atom bonding to the Mg atom, respectively. From experimental observations we suggest that the Si(111)3 X 1-Mg structure is formed b y ordering of Mg atoms on the ideal Si(111)1 X 1 surface, not by recon struction of Si atoms of the substrate.