Quantitative near‐edge structure analysis of diamond‐like carbon in the electron microscope using a two‐window method

Abstract

To extract quantitative electronic structure information from electron energy‐loss near‐edge structure typically necessitates the separation of spectra into linearly independent components. For this to be accomplished, certain conditions need to be met concerning the localization of chemical bonding and the linear scaling of fine structure with density of states. The dependence of the processing parameters, such as window widths and positions, of the commonly used ‘two‐window intensity‐ratio’ method to determine the distribution of π and σ bonding of diamond‐like carbon films is investigated. It is shown that, although the selection of the integration windows can lead to very large variations in the resultant bonding fractions, the placement of two small windows centred on the edge structures of interest does permit a robust and reliable estimate of bonding. It is demonstrated that the sp3 variations can be reproducibly monitored with a relative accuracy of about ± 5%, and an absolute concentration given with an accuracy of ± 13% for foils of thickness at least up to twice the inelastic mean free path. 1995 Blackwell Science Ltd