Channelling and atomic resolution STEM using X-ray emissions with absorption

Although quantitative analysis using soft characteristic X-rays is beset by relatively high absorption effects, the concomitant skewing (depending on detector-specimen geometry) of the detected X-ray signal towards ionizations which have occurred closer to the surface may have advantage in retaining coherent information compared with an incoherent contribution. It is envisaged that strong absorption of soft X-rays may enhance coherent contrast in both lattice images and channelling patterns compared to that derived from more energetic X-rays, particularly with specimen-detector geometry at a grazing angle of detection to enhance this effect. A Bloch wave approach provides a framework in which both ionization localization and absorption of generated X-rays may be accounted for, and enables explicit separation of coherent and incoherent contrast. An initially unexpected outcome is an ability to quantify the degree of cross-talk between projected columns of atoms in lattice resolution mode. It turns out that the incoherent component is responsible for most of the cross-talk.