PHASE IDENTIFICATION IN CARBON AND BN SYSTEMS BY EELS

Electron energy-loss spectroscopy measurements have been made on carbo n and BN polymorphs, as well as on a number of borides, carbides and n itrides present in sintered cBN based compacts. The similarity in crys tal symmetry between carbon and the isotructural BN system results in spectral similarities in both the low-loss features and electron energ y-loss near-edge structure associated with the particular core-loss io nization edges. ELNES features hold information on the nearest neighbo ur environment of the excited atom in a given phase. It is shown that the analysis of these features provides characteristic coordination fi ngerprints for the identification of carbon and BN allotropes. Similar ly, the comparison of ELNES features associated with B-K, C-K and N-K ionization edges provides fingerprints for the identification of B in TiB2 and B4C, C in TiC and B4C, and N in AlN, TiN and BN, respectively . An attempt is made to quantify the fraction of sp(3) bonding in diam ond-like carbon and cBN based cutting tool material from the relative intensity of the pi resonance in C-K and B-K ELNES, respectively.