In situ formation of onion-like carbon from the evaporation of ultra-dispersed nanodiamonds

We report the in situ formation of onion-like carbon (OLC) by evaporation from a nanodiamond source under ultra-high vacuum conditions. The OLC is characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) and is found to be highly defective but completely separated. The absence of any signature in XPS, Raman spectra and TEM associated with nanodiamond in the film suggests that the OLC is formed from carbon vapor or by the direct evaporation of only the smallest particles resulting from nanodiamond graphitization. The method thus provides a route to the formation of individually separated OLC nanoparticles.