CHARACTERIZATION OF NANOPHASE POWDERS PREPARED BY LASER SYNTHESIS

Si-based (Si-C-N and Si-C-Al) nanopowders prepared by laser synthesis process have been studied by XPS and XAES analyses. The changes of the silicon coordination as a function of the carbon fraction in Si-C-N powders have been investigated by a detailed analysis of Si 2p and Si KLL lines and the measurements of the Auger parameter E(k)(Si KLL) + E(b)(Si 2p). The non-linear dependence of the Auger parameter on the carbon fraction has been interpreted as due to the formation of a carbonitride nanophase, indicating that the ternary powders are not merely a mixture of silicon carbide and silicon nitride. In Si-C-Al powders it has been found that the incorporation of aluminium results in a modified structure of the silicon carbide, as shown by the variation of the different spectral features.