The consequences of the atomic size effect in quantitative high resolution electron microscopy

We investigate the effect upon HREM images of the static atomic displacements (SD) present in crystalline alloys with atomic size effect. Our method is to compare pairs of images of the same distributions of atoms (in III–V alloys) calculated with and without taking the SD into account. We show that large differences usually exist between these images, assess them quantitatively, and demonstrate that proper consideration of the SD is essential to achieve reliable composition analysis by HREM, in particular when the ‘chemical mapping’ technique is used. The effect of the SD depends on the specimen thickness and on the objective lens defocus.