Oxygen submonolayers on Mo(112): structure and work function

Abstract

Correlation between the work function change and the structure of oxygen submonolayers on the Mo(112) surface are studied using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and contact potential difference (CPD) methods. Oxygen was adsorbed at temperatures T = 78−300 K and thereafter the adlayers were annealed in a wide temperature range up to oxygen desorption. Temperature induced irreversible and reversible phase transitions are investigated. With coverage growth, formation of the monolayer proceeds through three first-order phase transitions, one of which is featured by a specific change in the course of the work function dependence on coverage. It is suggested that during this transition the oxygen adatoms may change their sites on the substrate from those of a short-bridge type to quasi-threefold ones, thus increasing their coordination number from two to three.