A scanning transmission electron microscope using a field emission gun is applied to elemental analysis of micro-areas, by means of electron energy loss spectrometry. The electron beam is focused to approximately 10Å diameter, and irradiates the specimen. Small particles are employed as specimens. A boron nitride particle, about 200Å in size, reveals sharp K-shell excitation edges of boron and nitrogen in its energy loss spectrum., These signals are estimated to be produced from the masses of 10
-21 grams order. The spectrum obtained from a chromium dioxide fine crystal is compared with the spectrum of X-ray microanalysis. Although the signal-to-background ratio of the energy loss spectrum is inferior to the X-ray spectrum, the former can detect the light element, oxygen.
Iron and oxygen are detected from a single ferritin particle, whose core is approximately 60A in size and composed of iron oxide hydrate molecules. The signal intensities are discussed, comparing with the ionization cross-sections.
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