Electron Energy Loss Spectroscopy and Energy Dispersive X-ray Analysis

This chapter discusses the use of analytical transmission electron microscopy (TEM) to study the chemistry of materials at the nanoscale. Analytical TEM involves utilising the signals generated when a focused electron beam excites small volumes of material in a thin specimen. The most common analytical signals employed are emitted X-rays and direct energy losses induced in the transmitted primary electrons. These are measured using the spectroscopic techniques of energy dispersive X-ray analysis (EDX) and electron energy loss spectroscopy (EELS). Both EDX and EELS can be performed in a variety of modes, including the collection of individual spectra from a particular point of interest, or the mapping of the distribution of different elements over a specified area of the sample. Further to this, spectra from both techniques can be used to quantitatively assess concentration values for individual elements, and in the case of EELS, be used to determine additional information on bonding and the oxidation state of certain elements. The capabilities of both techniques are explained using material examples, so that the reader can identify and employ the best analysis procedure to extract the most appropriate information from their sample.