Enhancement of electron-induced X-ray intensity for single particles under grazing-exit conditions

Ž . Grazing-exit electron probe microanalysis GE-EPMA was performed for single Al O and atmospheric particles, 2 3 Ž . deposited on a flat Si substrate coated by gold, by using an aperture 1 mm in diameter in front of an energy-dispersive X-ray detector. Silicon Ka X-rays from the Si substrate were strongly observed at an exit angle of ;458. However, they disappeared at grazing-exit angles about 08 and only the X-rays from particles were detected. Furthermore, Al Ka and O Ka intensities from single Al O particle were enhanced approximately threeand 2 3 Ž . Ž . sixfold at the grazing-exit angles ;18 , respectively, in comparison with those at large angle ;78 . The background intensities at the energy of Al Ka and O Ka almost monotonously decreased with decreasing exit angle. As a result, the intensity ratios of Al Ka and O Ka X-rays to the background intensities were enhanced fiveand sixfold, respectively. This enhancement is considered to be caused by the interference effect of both directly detected X-rays and reflected X-rays on the flat substrate. The similar results are also obtained for Al Ka , Si Ka , K Ka and Ca Ka emitted from single atmospheric particle. The significance of the matrix effect in the particle is also pointed out. Q 1999 Elsevier Science B.V. All rights reserved.