XPS and ToF-SIMS characterization of a Finemet surface: effect of cooling

The surface composition of amorphous Finemet, Fe73Si15.8B7.2Cu1Nb3, was studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The as-received sample in the original state and after Ar+ sputter-cleaning was analyzed at room temperature as well as after cooling to -155 degrees C. In the cooled state, the surface oxide layer composed of oxides of the alloy constituents was found to become enriched with elemental iron and depleted of elemental silicon, boron, oxygen and carbon as compared to the state at room temperature. Interaction of residual water vapor and hydrogen with the complex oxide layer occurring at low temperatures is believed to be responsible for the enhanced formation of surface hydroxides of the alloy constituents. The processes resulting in the observed redistribution of the elements on the surface of Finemet at low temperatures are discussed. Copyright (C) 2006 John Wiley & Sons, Ltd.