The detection limits of electron beam microanalysis are determined for thin evaporated films of Ti, Fe, Cu, and Ge on fused quartz substrates. Both wavelength‐dispersive and energy‐dispersive spectrometers (WDS and EDS, respectively) are used. The optimum excitation voltage is calculated on the basis of the 3σ criterion. The experimental data (Uopt = 1.6 and 1.8 for EDS and WDS, respectively, U overvoltage ratio) agree well with theoretical ones if a modified Bethe ionization cross‐section Q ∼ ln U/Um with m = 0.7 is used in the calculation. The detection limits of the WDS are in the order of 10−2 μg/cm2. They are better than those of the EDS by a factor of about 30. Using absorption filters between sample and detector and working with inclined electron incidence the detection sensitivity of the EDS can be increased by a factor of about four. The resulting improvement of the reproducibility will be demonstrated for a 170 Å CrNi resistance film. A counting time of 400 s is sufficient to measure the intensity ratio of the Kα lines of Cr and Ni with a standard deviation of 1%.
Large synthetic crystals of alkaline earth metal fluorides, especially fluorite crystals, contain sometimes unknown small inclusions of hexagonal form. Samples of these crystals were investigated by microscope, X-ray, and microprobe analysis to identify the included small crystals. Optical behdviour of these inclusions, morphology, chemical composition, and the reaction with water allow their interpretation as high-temperature modifications of the anhydrous water soluble alkaline earth metal sulfates, partly transformed to the corresponding sulfides.Bei der Synthese groDer Kristalle der Erdalkalifluoride, insbesondere des Fluljspates entstehen unter besonderen Bedingungen in der Fluoridmatrix kleine, sechseckige Kristlllchen, die bisher nicht zweifelsfrei identifiziert werden konn ten.Die vorliegende Arbeit berichtet uber rnikroskopische, rontgenographische und MikrosondenUntersuchungen an diesen. Optisches Verhalten, Morphologie, Elementzusammensetzung und dic Reaktion mit Wasser konnen so gedeutet werden, daB es sich urspriinglich um wasserfreie. hexagonale Hochtemperatur-Modifikationen der wasserloslichen Erdalkalisulfate handelt, die teilweise in die entsprechenden Sulfide umgewandelt sind.
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