QUANTIFICATION OF IRRADIATION DAMAGE GENERATED DURING HRTEM WITH 1250KEV ELECTRONS

We introduce a method to quantify the extend to which HRTEM imaging wi th high-energy electrons damages the specimen. The method rests on dig ital comparison of images recorded at increasing beam exposure times b ut otherwise constant conditions. Difference images we calculate from these original images reveal whether damaging preferentially occurs at extended defects like internal interfaces. Further image analysis all ows us to estimate how long one may image the specimen before irradiat ion damage interferes with solving the specimen structure at a given l evel of confidence. We demonstrate the usefulness of the method by app lying it to HRTEM images of two types of interfaces. the interface bet ween Cu and sapphire, and the Sigma 3 (111) twin boundary in NiAl, bot h imaged in a high voltage high resolution microscope operating with 1 250 keV electrons. From our results we conclude that under these condi tions HRTEM images of the two interfaces should be recorded during the first 10 min of observation in order to avoid irradiation-related art ifacts in structure analysis.