sp3content of mass-selected ion-beam-deposited carbon films determined by inelastic and elastic electron scattering

Amorphous carbon films grown by low-energy mass-selected ion-beam deposition have been characterized by inelastic and elastic electron scattering. Films were grown using deposition energies from 10 up to 2000 eV. Most samples were deposited at room temperature with a few deposited at elevated substrate temperatures. Transmission electron-energy-loss spectra were recorded for all films both in the low-energy-loss region, where the bulk plasmon excitation is the primary feature of interest, and in the vicinity of the carbon $K$ edge where the data were used to estimate the fraction of $s{p}^3$ bonded atoms. Elastic-electron-scattering data were also recorded, and bond lengths and angles were extracted from these data. The carbon $K$-edge spectra indicate that the highest $s{p}^3$ content (about 80%) occurs for films grown with ion beam energies between about 50 and 600 eV and, furthermore, that the $s{p}^3$ content remains greater than 50% for deposition energies up to 2000 eV. Bond lengths and angles extracted from elastic-electron-scattering data support the conclusions drawn from the energy-loss data.