Simultaneous SIMS and EID investigation on the interaction of oxygen with a W (100) surface

Abstract

A UHV system, containing a beatable tungsten ribbon target (showing [100] planes), an ion source (Ar +, 2 keV) with mass separator, an electron source (300 eV), a quadrupole secondary ion mass filter, and a quadrupole gas analyzer is used for the study of the interaction of O 2 with W (100) by simultaneous, i.e. fast interchanging, “static” SIMS (secondary [ion-induced] ion mass spectrometry) and EID (electron-induced [ion] desorption). Two different adsorptive binding states can be distinguished: β 2 and β 1. The O + emission cross section under electron bombardment from the β 2 state is smaller by a factor of about 10 3 than from β 1 and is found to be temperature-dependent. After the state β 2 has been saturated and before the occupation of β 1 begins, an oxide formation process starts. This oxidation can be interpreted by a two-stage model.