Cliff-Lorimer method

Local thickness variations in a thin specimen complicate the quantitative analysis of a single element in the absence of precise knowledge of specimen thickness and without the ability to compare the measured x-ray intensities with those of thin standards. To avoid this difficulty, the x-ray intensity for the element of interest can be divided either by the intensity of a region of background between peaks as in the Hall method[8], or by the intensity from another element as in the Cliff-Lorimer method[9]. The former is largely used for biological analysis while the latter has become the standard thin specimen microanalysis method for materials science applications. The Cliff-Lorimer method is expressed in the following equation ... 

In TEM, EDS quantification is done using the standardless Cliff-Lorimer method (Cliff and Lorimer 1975 Lorimer G.W. 1987). This method stipulates that the above-background intensity ratio between two peaks is proportional to their weight fraction as... 

G. Cliff and G. W. Lorimer. J. Microscopy. 103, 203, 1975. This paper summarizes the Cliff-Lorimer analysis technique, but more complete reviews of the method may be found in References 1—4. 

Quantitative Analysis of Thin Specimens (Cliff-Lorimer and Methods)... 

For a given detector and a given pair of elements the last two factors give a single constant (Icab) that can be treated as a relative sensitivity factor. Both that factor and the method obtained their names after the two people who introduced them, Cliff and Lorimer (1975). The simplicity originates from the fact that the Uab factor does not depend either on the rest of elements also present in the sample or on the other parameters of the sample (thickness, density), as far as the thin film criterion is fulfilled. The Cliff-Lorimer factors can either be calculated using the known parameters of the detector or can be measured if a well-characterized thin film sample (standard) is available. In the first case the method is standardless. In the second case the known weight fractions and the measured intensity ratio provides the Cliff-Lorimer factor for the pair of elements. 

X-ray emission intensities were obtained from the spectra by using a digital filtering method which is available in the standard TN5500 software. For light elements up to, say, bromine, the only lines suitable for analysis are the Ka and K/9 emissions, and the Ka s were used as in the work of Cliff and Lorimer (16). Where overlap occurred between the Ka of one element and the K/9 of another, an experimentally determined correction was used our corrections were in good agreement with those measured by Heinrich et al. (32). 

Chemical composition analysis complementing the microstructural information obtained from EM is known as analytical EM (AEM). Important compositional variations or non-stoichiometry in a material which is seemingly phase pure or stoichiometric by the criterion of bulk diffraction techniques and compositions of surface layers can be revealed using AEM. For quantitative microanalysis a ratio method for thin crystals (Cliff and Lorimer 1975) is used, given by the equation ... 

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