SEM-XRF is an established technical term for adding a (typically micro-focus) X-ray generator (X-ray source) to a Scanning Electron Microscope (SEM). Technological progress in the fields of small-spot low-power X-ray tubes and of polycapillary X-ray optics has enabled the development of compact micro-focus X-ray sources that can be attached to a SEM equipped for energy-dispersive X-ray spectroscopy (EDS, EDX, EDXS or XEDS).[1]
As shown in the image at right, when micro-focus X-ray fluorescence (microXRF) is performed with a SEM, elemental analysis analytical figures of merit are extended to the point where trace level quantification and bulk analysis are possible.[2] By combining the analytical information obtained from the X-ray spectra excited with electrons and with photons respectively, the main elements as well as trace elements, of low and high atomic number, can be analyzed – albeit with different spatial resolutions.[3]
In 1986, Sandia and Lawrence Livermore National Labs coauthored a paper (with Kevex Corporation) regarding parameters affecting X-ray micro-fluorescence.[4] As a followup in 1988, Cross & Wherry described an X-ray micro-fluorescence analyzer which combines the nondestructive analytical method of X-ray fluorescence with relatively small spatial discrimination (less than 50 μm) such that composition (chemistry), thickness and micro-structural measurements can be made on a wide variety of heterogeneous materials in a few seconds. It was shown that, by scanning samples with an X-Y stage, quantitative or qualitative micro-structural information could be gathered.[5] Both these papers provided a preview into the coming integration of Micro-X-ray fluorescence with SEM.
By 1991, Pozsgai published a review article detailing the possibilities of carrying out x-ray micro-fluorescence analysis within the SEM context. The main approaches involved converting the electron optical column of an electron microscope into a transmission x-ray tube, using micro-focusing x-ray tubes, combining x-ray tubes with capillary techniques, as well as combining x-ray tubes with monochromators and applying synchrotron radiation.[6]
SEM-XRF was first commercialized by IXRF Systems (Austin, TX) in March 2005.[7] Bruker Corporation (Billerica, MA) followed in August 2013.[8]
^[Hodoroaba, V., Rackwitz, V., & Reuter, D. (2010). Micro-Focus X-Ray Fluorescence (µ-XRF) as an Extension of the Analytical SEM. Microscopy and Microanalysis, 16(S2), 904-905. doi:10.1017/S1431927610054115]