Surface characterization of BaO on W. I: Deposited films

Abstract The characteristics of Auger transitions for BaO on W[100] have been investigated for various calibrated surface changes such as during the adsorption and desorption of different layers. Standard AES transitions involving W(170 V), O(510 V) and Ba(590 V) lines have provided information on the total Ba and O content on the surface. The interatomic and valence characteristics (i.e. Ba 4d-Ba 5p-O 2p at “68 V” and Ba 4d-Ba 5p-Ba 6s at “73 V”) being very sensitive to chemical interactions of the surface Ba and O, provided additional information so that one may choose a possible picture of the compositional manner in which the total O and Ba is distributed. In addition to this type of analysis, a method is presented whereby the surface is divided into regions of different composition whose AES characteristics are known from measurements of calibrated surfaces. A linear combination of these regions gives a total calculated value which is then compared to the experimental value. A close agreement can thus provide some assurance that proper choices have been made for the surface compositions. The results will show that generally the simplest, straight-forward choices usually give very good agreement with experiment. Other effects are discussed such as the effect of bond-breaking between Ba and O, the desorption of Ba and the persistence of excess O.