Comparative Performance of SDD-EDS and WDS Detectors for Quantitative Analysis of Mineral Specimens: The Next Generation Electron Microprobe

With the development of silicon drift detectors (SDD), energy dispersive x-ray emission spectrometry is now capable of making compositional measurements of comparable precision as those that have been routinely obtained by wavelength dispersive spectrometers on electron microprobes [e.g., 1]. Large area silicon drift detectors, when placed near the specimen, subtend significantly larger solid angles than WDS detectors and so can make these measurements at considerably lower beam currents, making them particularly well-suited for use at the conditions ordinarily employed for scanning electron microscopes. The significantly lower resolution of SDDs compared to WDS spectrometers (although significantly improved over Si(Li) EDS detectors, particularly at low energies) limits their ability to make high precision measurements of minor element concentrations and precludes their determination of trace element concentrations. Additionally there are a number of severe x-ray peak overlaps that require a higher degree of energy/wavelength resolution than is possible with SDDs, despite the high quality of available EDS spectral deconvolution software. For these cases, WDS spectrometers are demonstrably superior in performance.