Adsorption of potassium on Cu(100) and coadsorption with oxygen: A study by AES, work function and secondary emission changes

Abstract

Evidence is found for a critical coverage of potassium, θ c, at which the mode of coadsorption of oxygen suddenly changes. This change occurs precisely at the coverage required for the work function minimum. In the high coverage region there are linear variations in work function; these point to the nucleation of a dense adsorbed potassium phase at θ c. The uptake of oxygen for high K coverages occurs effectively in two stages which can be related to the presence of adsorption sites which place negatively charged oxygen predominantly first below and then above the potassium layer.