Locating Atoms in Small Crystals by Combining Convergent Beam Electron Diffraction and Electron Channeling

Abstract

With the current focus on nanotechnology and nanomaterials, there is a growing interest for quantitative determination of composition and atomic arrangement within small volumes of materials. In chemical microanalysis the fast electrons within a subnanometer probe may excite inner shell electrons with accompanying element-characteristic energy losses and x-ray emission that originate in the electron-illuminated volume of a thin specimen. The change, under channeling conditions, of the yield of element characteristic x-ray emission was first observed by Duncumb [1], and the first observation in energy loss spectroscopy was done at Fritz-Haber-Institut [2]. These channeling effects, now often referred to as ALCHEMI, can be used to locate small concentrations of atoms within the unit cell of small crystals [3].