Energy-filtered transmission electron microscopy of SimGen superlattices and SiGe heterostructures I. Experimental results

Energy-filtered transmission electron microscopy has been applied to SiGe superlattices and layered heterostructures in order to explore detection and resolution limits of elemental distribution images obtained by electron spectroscopic imaging (ESI). A Zeiss EM 912 Omega transmission electron microscope with an integrated imaging Omega energy filter at 120 keV and the JEOL ARM equipped with a GATAN imaging filter at 1250 keV have been used. The filters selected inelastically scattered electrons corresponding to the inner-shell losses of the Si L edge. The three-window technique was applied to obtain Si distribution images. ESI was performed on cross-section TEM samples of short-period SimGen superlattices (m,n: number of monolayers in the layer sequence), ultra-thin individual layers, and Si1 − yGey alloy buffer systems with composition gradient (0 < y < 0.4). Influences of different models for background subtraction and of correlation methods for specimen drift correction were investigated.