A new insight on crystalline strain and defect features by STEM–ADF imaging

Abstract

Scanning TEM with a High Angle Annular Dark Field (HAADF) detector is an outstanding tool for chemical analysis; it permits to image compositional variations at atomic scale as variation in the image intensity. However in the interpretation of HAADF images the role of elastic strain and crystallographic defects are often neglected. For low index specimen orientation crystal imperfections can become very important due to the interplay of strain and channeling effects. Thanks to a recently developed channeling model, the main strain effects on the image can be predicted. An adequate description of these phenomena makes HAADF an interesting technique to complement or substitute traditional TEM characterization in many relevant materials science contexts. Examples will be shown for the case of semiconductor quantum dot, core shell nanowires and dislocations.