Grazing exit electron probe microanalysis for surface and particle analysis

We developed a new method of grazing exit electron probe microanalysis (GE- EPMA) and applied it to analyze both Si surfaces and Mg-salt particles. In conventional EPMA, X-rays are detected at an exit (takeoff) angle of approx imately 45 degrees. Therefore, when particles collected on a sample carrier are analyzed by EPMLA, the X-rays from both the particles and the carrier are detected, although we need only the X-rays emitted from the particle it self. In contrast to this, the X-rays are detected at grazing exit angles i n GE-EPMA. The X-rays emitted from deep inside of the sample are not detect ed under grazing exit conditions, and only X-rays emitted from the surface and the particle are measured. It was found that surface-sensitive analysis of a Si wafer was possible with low background at grazing exit angles. The intensity ratio of O K alpha to Si K alpha increased near zero degrees, in dicating that the Si wafer is covered with a native Si oxide, Moreover, Mg K alpha X-rays from a Mg-salt particle, which was deposited on the Si wafer , were detected with a small Si K alpha intensity at grazing exit angles of less than 0.5 degrees, By decreasing the exit angle to less than zero, onl y the top of the particle was observed; therefore, GE-EPMA measurement woul d make it possible to investigate the surface layer of one particle.