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Scanning transmission electron microscopy using a SEM: Applications to mineralogy and petrology

¹ Department of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, UK
² Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

^* E-mail: Martin.Lee{at}ges.gla.ac.uk

High-resolution imaging of electron-transparent samples using a scanning electron microscope, here termed low voltage (LV) STEM, is a new and valuable technique for studying Earth and planetary materials. The most effective method of LV-STEM imaging uses a pair of electron detectors positioned side-by-side beneath the thin sample. The detector directly underlying the sample forms bright-field images dominated by mass-thickness contrast. Activation of the detector offset from the sample yields dark-field images with a greater component of atomic number contrast. LV-STEM images with significant diffraction contrast can also be obtained, but require careful positioning of the sample relative to the electron detectors. In this study LV-STEM was used successfully to image sub-µm sized kaolinite crystals and tens of nm-sized etch pits on the gold-coated surfaces of weathered feldspar grains. Dark-field LV-STEM was also especially effective for characterizing very fine-scale intergrowths of Mg- and Fe-rich phyllosilicates within uniformly thin samples of the Murchison meteorite prepared using the focused ion beam (FIB) technique. LV-STEM is a quick and easy method for characterizing the morphology and internal structure of mineral and rock samples and may prove to be especially useful in geomicrobiology research.

KEYWORDS: SEM, STEM, feldspar, dark-field images, focused ion beam, kaolinite, meteorite

This article has been cited by other articles:

				M. R. Lee, D. J. Brown, M. E. Hodson, M. MacKenzie, and C. L. Smith Weathering microenvironments on feldspar surfaces: implications for understanding fluid-mineral reactions in soils Mineralogical Magazine, July 15, 2009; 72(6): 1319 - 1328. [Abstract] [Full Text] [PDF]