No abstract

A new atomic number correction is proposed for quantitative electron-probe microanalysis. Analytical expressions for the stopping power S and back-scatter R factors are derived which take into account atomic number of the target, incident electron energy and overvoltage; the latter expression is established using Monte Carlo calculations. The correct procedures for evaluating S and R for multi-element specimens are described. The new method, which overcomes some limitations inherent in either the Duncumb and Reed (1968) or the Philibert and Tixier (1968) atomic number corrections, may readily be used where specimens are inclined to the electron beam.

A Monte Carlo method based on Curgenven and Duncumb's treatment is described. It is shown that the predictions of the model agree well with experimental backscattered electron energy distributions and $ ( p z ) curves. The model is used to generate $ ( p z ) curves for a wide range of analytical conditions. Based on these data an examination is carried out of the way in which the mean depth of x-ray production varies with electron accelerating voltage, overvoltage and atomic number of the target. An expression for the mean depth is deduced ; the form of this expression is compared with that predicted by the Philibert model.

Electron probe microanalysis of oxygen in a range of binary and ternary oxides is described. Experimental data are presented for a range of electron accelerating voltages and for two different take-off angle instruments. The ratio of oxygen K emission from specimen and standard is found to reach a limiting value, the same for each instrument, as the applied voltage is increased. The observations are shown to support the thin-film model (Duncumb and Melford 1966) proposed for quantitative analysis of light elements and also to enable its range of applicability to be established in terms of specimen characteristics and experimental conditions. The model is used together with chemical composition data for the oxides, and a consistent set of mass absorption coefficients are calculated which are considered to be accurate within 10%. These new data are discussed and compared with previously published values.

An equation is developed for calculating the X-ray fluorescence produced in a coating by characteristic X-rays generated in the substrate material. The correction is applied to experimental microanalysis data obtained for thin coatings deposited on a range of substrate materials and is shown to give satisfactory results. An extension of the method to include multicomponent systems is then described.

No abstract

No abstract

No abstract