Coherent Bremsstrahlung--New Peaks in EDS (Energy Dispersive Spectroscopy): A New Unavoidable Artifact in Thin-Crystal X-Ray Microanalysis

摘要

The energy-dispersive x-ray emission spectrum shown in Fig.1 was obtained with a Philips EM400 transmission electron microscope operating at 100 kV and fitted with an EDAX Energy dispersive spectroscopy (EDS) system from a thin crystal of diamond. The numbered peaks shown are not due to characteristic x-ray emission from impurity atoms in the sample, They result from radiation from the beam electron itself, known as coherent bremsstrahlung, which is due to the juddering motion of the beam electron as it passes down a column of atoms in the crystal. This acceleration of the charged beam electron produces monochromatic, tunable, polarized x-ray emission within the region of the focussed electron probe. It has now been studied in many materials by EDS, and may have been mistaken for characteristic radiation in earlier microanalytical work.