Metastable de-excitation spectroscopy study on the local valence-electron states of the K/Si(100)2 × 1 surface

Abstract

The local electronic structure of a potassium adlayer on the Si(100)2 × 1 surface has been studied by metastable de-excitation spectroscopy (MDS), combined with surface characterization by Auger electron spectroscopy and work function variation. MDS spectra from K-adsorbed surfaces in the whole coverage region upto saturation exhibited a sharp peak just below E F originated mainly from the K 4s states. This finding strongly disagrees with the theoretical viewpoint of full ionization of adsorbed alkali-metal atoms by Ciraci and Batra. The MDS intensity for the K 4s-derived states increased rapidly with increasing K coverage θ K at around 0.4. It reached a maximum at θ K ≈ 0.7, which is followed by a small decrease towards θ K = 1.0. This tendency clearly demonstrates the large variation in the local density of the K 4s-derived states dependent upon coverage. Work function variation for the K/Si(100) system has been explained in terms of adsorption-induced redistribution of valence electrons.