THE USE OF ELECTRON ENERGY-LOSS SPECTROSCOPY FOR MICROCHARACTERIZATION OF THIN SPECIMENS

Electron energy loss spectroscopy (EELS) studies the energy distribution of electrons that have been transmitted through a thin sample. The kinds of information which can be obtained from this study are presented. Basic instrumentation for EELS experiments is outlined, with emphasis on the avoidance of experimental artifacts.;The low-loss region in EELS can be used to measure the mean free path of fast electrons in a solid. Experimental results for the mean free paths of several materials are presented, together with theoretical calculations based on atomic and plasmon models.;The thickness of a thin film is often required in microcharacterization. A method based on a Kramers-Kronig sum rule is outlined; theory and experiments related with this method are presented in detail. The accuracy of this sum rule technique is estimated to be ;The inner-shell ionization edges in EELS are normally used to identify the presence of particular elements. Experiments were performed to investigate the effect on the signal/background ratio of the collection aperture and the thickness of the specimen. The results show that the core-edge signal/background ratio is increased by using dark-field illumination and thicker samples only in the case where the instrumental background is high. It appears more attractive to work under bright-field conditions and reduce the instrumental background to a low level by optimizing the design of the electron detector.