Optimization of ELNES processing using a four-parameter function: Application to SiC fibers

In the explanation of EELS spectra in terms of molecular orbitals, where th e local band structure is approximated as a linear combination of atomic or bitals of the excited atom and its immediate neighbours, It and L core-loss spectra are decomposed using a four-parameter function that models the ion ization continuum in a better way than 'classical' step functions. The peak s corresponding to particular chemical bondings are extracted and then fitt ed by Gaussian functions. The accuracy of such a technique is discussed in the case of Nicalon SIC fi bre compared to pure alpha-SiC. Because of this ionization continuum subtra ction we found, in agreement with previous XPS data, that the fibre contain s a particular SiCO bonding that is different from SIC and SiO and was not visible without this treatment. Moreover, the CK-edge analysis shows the pr esence of graphite-like carbon. The existence of CH bonding is also discuss ed. (C) 1999 John Wiley & Sons, Ltd.