Sputtering Analysis with PIXE

Abstract

The applicability of the particle induced x-ray emission (PIXE) in the determination of sputtering distributions and yields was studied. Sputtered particles were caught on foils for the 45 keV to 125 keV self sputtering of Fe, Ni, Cu, Ti, Mo and Au and for the 90 keV sputtering of both target and implanted particles of Ni+ + Cu, Cu+ + Ni, Ni+ + Fe, and As+ + Ag, and for the target particles of Ar+ + Au. Sputtered particles were collected in an ultra high vacuum (UHV) and in a poorer vacuum system with 99.99% pure Al catcher foils. PIXE data, the x-ray yields from 1 MeV proton and 2 MeV alpha particle beam bombardments, were used to determine the angular distribution of the sputtered products. The sputtering yield was calculated from the angular disbution data by integration over a hemisphere assuming azimuthal symmetry. The efficiency of the PIXE systems was calibrated with a standardized target such as 18 μg/cm2 Fe on the same 99.99% Al foil material. The Al x-ray yield of the catcher foils provided a normalization of all data from a given catcher foil. For a number of samples studied, we have been able to compare the distribution and yields obtained with PIXE to those measured by the Rutherford backscattering (RBS) technique. Also separate RBS analysis of Xe markers in the sputtering targets provided yield values. Comparision of the PIXE and RBS results indicate that the PIXE sputtering distribution and yield measurements are comparable.