Preferential sputtering and oxidation of Nb-Ta single crystals studied by low-energy ion scattering

To study preferential sputtering and oxidation, three monocrystalline NbxTa1-x(110) alloys (x = 0.25, 0.5, 0.75) as well as pure single crystals of Nb and Ta have been prepared by electron beam floating zone melting (EBFZM) and investigated by low-energy ion scattering (LEIS). After sputter cleaning, LEIS showed the enrichment of tantalum at the surface of all alloys. After exposure to oxygen, linear relationships between the oxygen and both the niobium and tantalum signals demonstrate that matrix effects do not influence the LEIS signals for these systems. The oxygen coverages of the different alloys have been determined by calibration against the Ni(100)-O c(2x2) surface. (Author)