High-resolution electron energy-loss spectroscopy of undoped and nitrogen-doped tetrahedral amorphous carbon films

Undoped and nitrogen-doped amorphous carbon (ta-C) films deposited using a filtered cathodic vacuum are were investigated by high-resolution electron energy -loss spectroscopy in transmission. The carbon and nitrogen K-edge spectra show fine structure at the C ls to pi(*) excitations which gives information about the hybridization and coordination of the carbon and nitrogen atoms. The loss data were collected up to 50 eV and a Kramers-Kronig analysis was used to derive their complex dielectric functions. The is an element of(2), spectra show two features due to excitations of pi and sigma valence states. The pi feature is very small in ta-C deposited at 100 eV, consistent with its high sp(3) content. The development of the pi and sigma peaks with varying sp(2) content and their oscillator strengths allow us to resolve the degree of pi-sigma mixing which arises from disorder in more sp(3)-bonded carbons. (C) 2000 Elsevier Science S.A. All rights reserved.