Some aspects of a quantitative LEIS study of the potassium segregation at the V₆O₁₃(001) surface

Abstract

The influence on the low energy ion scattering (LEIS) signal intensities of a potassium segregation is studied at 800 K. It is possible to alter the potassium surface concentration by means of electron stimulated desorption. The higher this concentration, the lower the absolute count rate of the complete LEIS spectrum. This observation suggests that, in the case of helium scattering at the V6Ol3(0O1) surface, Auger neutralization processes and/or adiabatic resonant transitions are active. This fact allows the calculation of an upper and a lower limit for the ratio of the scattering cross sections for oxygen and vanadium. From a comparison with theoretical predictions based on the Moliere or Born-Mayer approximation of the Thomas-Fermi-Firsov potential, it follows that, under the given circumstances, low energy helium scattering is better described using the Moliere approximation. By using this potential model, it is also found that at 800K this potassium segregation is quite important giving rise to a steady state concentration of about one potassium atom per V6013(O01) surface unit cell.