Energy-filtered high-resolution electron microscopy and composition-sensitive imaging

Energy-filtered electron imaging is one of the future directions of high-resolution electron microscopy (HREM). In this paper, characteristics and applications of energy-selected HREM are illustrated. Image contrast can be dramatically improved with the use of an energy filter. High-resolution chemical-sensitive imaging using ionization edge loss electrons is demonstrated in studies on Ni/Ti and A1/Ti multilayer thin films. It has been shown that the spatial resolution of energy-selected ionization edge electron images is dominated by the signal-to-noise ratio. Experimental parameters which may be selected to improve the signal-to-noise ratio are discussed. It is pointed out that since the width of the energy-selecting window is small, the energy-filtered ionization edge electron image is sensitive to the specimen composition, but the calculation of the specimen composition based on the energy-filtered images relies on the integrated ionization cross-sections which are largely determined by the solid state effects. Therefore, the energy-filtered ionization image should be referred as composition-sensitive image rather than compositional image.