High resolution electron microscopy of carbon structure

Abstract

SUMMARY An investigation is made of the inherent performance of a high‐resolution transmission electron microscope applied to the study of developing graphitic‐sheet structures in heat‐treated, coal‐tar pitch carbons. Image detail is shown to be highly dependant on instrumental defocus. It is not obvious which form will be assumed by artefacts in these images; consequently, anomalous features are illustrated by reference to a specific electron‐optical case and a corresponding light‐optical analogy. Despite the difficulties associated with locating an optimum level of focus, optical diffractometry confirms that adequate conditions of microscopy are attainable on a routine basis. In a quantitative analysis of morphology in coal‐tar pitch carbons, the technique reveals the cause of incipient, thermally‐induced, molecular distortions which evidently result in a regression in the improvement of order otherwise developing with progressive heat‐treatment.