XEDS in the AEM: Has Everything Thing That Can be Invented, Been Invented?

There is a fairly old apocryphal quotation stating : “Everything that can be invented has been invented.” [1] attributed at one time to Charles H. Duell of the US Patent office in 1899. We all realize this is an absurd statement, and it is well documented that Duell actually said something quite different and urged the US Congress to encourage the advancement of science as well as to improve the patent system [2,3]. This does however bring to focus a salient point concerning x-ray spectroscopy, as it relates to analytical electron microscopy. For many years instrument developers have concentrated upon advances in electron-optics, with justifiable and demonstrated improvements in imaging and probe forming systems. Aberration correctors, high sensitivity imaging detectors and electron spectrometry systems abound [4] , however, there are only a few seminal events which mark evolutionary advances in x-ray spectrometry. Arguably we can list the foremost of these as: the invention of electron microprobe analysis (EMPA) by Castaing [5], the invention of the Lithium Drifted Silicon (Si(Li) solid state detector [6], the development of the first AEM (EMMA-4) [7] and the development of the Silicon Drift Detector (SDD)[8]. While these are all key events which mark the onset of major advances in our ability to perform microanalysis, by comparison they represent only a fraction of the investment in resources compared to the electron optical developments. A very large fraction of the instrumentation found in characterization facilities worldwide has ancilliary x-ray analysis subsystems. The majority of these ancilliary x-ray spectrometry systems have been interfaced to an electron optical column in the simplest possible configuration and although they are at times considered routine, this does not mean that we have achieved all that these resources can provide, nor does it mean that we have addressed fully all their methodological intricacies and/or potentials.