Comparison of grazing-exit particle-induced X-ray emission with other related methods

Particle-induced X-ray emission (PIXE) is recognized as a trace analysis me thod; the Bremsstrahlung background, however, still limits the detection po wer in the low-energy region of spectrum. The grazing-incidence or grazing- exit arrangements are considered to be useful in order to reduce the backgr ound intensity. We measure grazing-incidence PIXE (GI-PIXE) and grazing-exi t PIXE (GE-PIXE) using an identical sample vacuum chamber to evaluate the p erformance of both methods. The sample used is a standard sample (Ca, Fe, N i and Zn) prepared on Si wafer by the spin-coating method. In GI-PIXE mode, a collimated 2.5 MeV proton beam irradiates the surface of the sample at g razing incident angles. However, it was difficult to reduce sufficiently th e background intensity in the GI-PIXE spectra because of the Bremsstrahlung background induced by secondary electrons. In the GE-PIXE mode, proton-ind uced X-rays are measured at grazing-exit angles. The background intensity i s reduced, because only the X-rays emitted from the near-surface layer can be detected in the grazing-exit arrangement. Furthermore, the result obtain ed for an Au-Cu thin film sample by GE-PIXE method was compared with the re sult obtained by other related methods: grazing-exit X-ray fluorescence and grazing-exit electron probe microanalysis. Similar results were obtained b y different methods, indicating that the same phenomena occur in all grazin g-exit X-rays measurements. One of the merits of the gazing-exit microprobe analysis method is in microanalysis using a small diameter electron probe, however, the damage by electron irradiation is more severe than that in GE -PIXE. (C) 2000 Elsevier Science B.V. All rights reserved.