Standardless quantitation of thin film specimens

This paper reviews the procedures available for the X-ray microanalysis of specimens in the form of thin self-supporting films without the use of standards. Standardless analysis refers to the procedure in which there is no requirement to prepare standards and then measure them during the course of the current analysis. The factors by which the measured X-ray intensities are converted to compositions are calculated for the elements of interest after the experimental measurements have been completed. These calculations are based on published tabulated data for the physical constants required, or evaluated from theoretical or empirical models. The physical parameters which are required to evaluate the characteristic X-ray production in the specimen are the fluorescence yield, the partition function and the X-ray production cross-section. Most analytical procedures ensure that other variables such as the specimen thickness and electron beam current are not required. Of the parameters mentioned, the first two have been examined and extensively tabulated in the literature. This paper focuses primarily on methods of evaluating the X-ray cross-sections for both the characteristic and bremsstrahlung production.The way in which the physical parameters are incorporated into the standardless quantitation methods for materials samples is described. A new standardless version of the continuum normalisation method for quantitative analysis for samples with organic matrices is introduced. Some techniques for making corrections for absorption to the observed intensities are discussed, and formulae are given for X-ray absorption and fluorescence which it may be necessary to use with thicker specimens.