NEW METHOD FOR ABSORPTION CORRECTION IN HIGH-ACCURACY, QUANTITATIVE EDX MICROANALYSIS IN THE TEM INCLUDING LOW-ENERGY X-RAY-LINES

A new method for the absorption correction in quantitative EDX microan alysis in the TEM is outlined, which does not require the knowledge of specimen thickness and mass absorption coefficients for the correctio n procedure. Both quantities are frequently not available with the des ired accuracy for quantitative EDX analysis, in particular if low-ener gy X-ray lines are used. The absorption correction factor (ACF), a qua ntity well known from the usually applied Cliff-Lorimer k-factor metho d, is determined experimentally by taking advantage of special propert ies of the X-ray transmission coefficients. Two experimental procedure s for quantitative EDX are outlined. Which of the two procedures is to be applied depends on the amount of X-ray absorption present in the s ample and the take-off angle of the detector. Before starting experime ntal work, a criterion given in this paper allows one to determine whe ther method I or II should be used. In method I EDX spectra are acquir ed from one area of the sample at two different tilt angles of the spe cimen with respect to the detector. For method II both EDX and EELS sp ectra need to be recorded from three areas with different thicknesses but the same orientation. Both methods require standards from which sp ectra are to be acquired under the same vacuum conditions. The prepara tion of samples suited for this procedure will be outlined. With these new procedures not only quantitative EDX microanalysis including low- energy X-ray lines can be performed with improved accuracy, but one ca n also quantitatively determine the detector efficiency and compare de tector efficiencies of different detector systems on a quantitative ba sis.