EELS characterisation of nanolayers and interfaces

摘要: It has been recognised for many years that electron energy-loss spectroscopy (EELS) carries a wealth of information concerning both the chemical composition and the electronic structure of the volume irradiated by the primary electron beam in an electron microscope. Within the scanning probe working mode, 'spectrum-imaging', which has emerged in the early nineties, is a most powerful method for data acquisition. It involves successively recording all energy-loss spectra corresponding to the different positions on the specimen surface explored by the incident probe. They can then be processed to extract relevant maps for the different sources of information: elemental composition from the intensity of the core-loss edges, band structure, local coordinance or valence states from the detailed monitoring of the fine structures (NES) on the edges. This approach has been highly efficient to investigate these properties across thin foils, generally prepared as cross-sections, so that the composition and electron states distributions can be monitored across the thickness of the films or at the interfaces with the substrate layer or with the next component in a multilayer stacking. The studied thin films cover many fields, from coatings prepared with different techniques (magnetron sputtering, preformed cluster deposition on surfaces, ion beam assisted deposition) for mechanical or optical applications to tunnel junctions in magneto-resistive devices. (Authors)