Lowering the limit of detection in high spatial resolution electron beam microanalysis with the microcalorimeter energy dispersive X-ray spectrometer

Low-beam-energy X-ray microanalysis with the field-emission-gun scanning electron microscope suffers limitations due to physical factors of X-ray generation. Instrumental limitations are imposed by the poor resolution of the conventional semiconductor energy dispersive X-ray spectrometry. Wavelength dispersive X-ray spectrometry provides sufficient resolution to solve spectroscopic problems, but the poor geometric efficiency and the single channel nature of spectrum measurement restrict its practical use for low-beam-energy microanalysis. The microcalorimeter energy dispersive X-ray spectrometer combines high resolution (<10 eV) with energy dispersive operation. The utility of this new spectrometer is examined in four categories: (1) qualitative analysis; (2) quantitative analysis; (3) chemical speciation studies, and (4) measurement of trace constituents. For the low-beam-energy regime, the microcalorimeter energy dispersive X-ray spectrometer provides important new performance capabilities for qualitative analysis and chemical speciation studies. However, there are limitations for quantitative studies imposed by detector geometrical characteristics. In addition, trace element detection is impractical below 0.001 mass fraction with low-beam energy (<5 keV) because of count rate limitations.