Preparation of carbon nanofibers by hot filament-assisted sputtering

Crystalline carbon thin films containing carbon nanofibers were obtained by using a hot filament-assisted sputtering system. Pure argon gas was employed as the sputtering gas. The crystal structure of the carbon thin films was investigated by XRD, XPS, TEM and TED. XPS profiles show the compositions of the films, which consisted of over 90% carbon atoms. From the results of observations using TEM and TED, it was revealed that the crystalline carbon films consisted of nanocrystal grains and nanofibers. To determine the valence state (sp3, sp2 and sp hybridization) of the carbon atoms in the films, laser raman spectra were examined and it was found that the films showed three Raman bands at 1581, 1368 and 1979 cm−1. The first two peaks belong to polycrystalline graphite and the last peak corresponds to carbyne, one of the allotropes of carbon.