High-Resolution Transmission Electron Microscopy of Si/Ge Interfacial Structures

A <110> cross-sectional high-resolution transmission electron microscopy (HREM) method for atomic scale observation of Si/Ge interfacial structures has been developed. The HREM image intensities of Si and Ge are theoretically investigated under various imaging conditions. The results show that their images exhibit strong contrast for an EM specimen thickness near the Ge extinction distance (14.8 nm) under a focus-setting of -10 nm. This is due to the large difference in the {111} amplitudes between Ge and Si. An EM specimen preparation technique in which chemical etching was used to remove ion milling artifacts was employed to accomplish this observation. Using this HREM method, observations of the Si/Ge interfacial structure are achieved, giving information about interfacial ordering.