Rie Ueno

Crystallite Size Dependence of Plasmon Energies in Polycrystalline Graphite Observed by Reflected Electron Energy Loss Spectroscopy

Both the energy losses of π electron plasmon and valence electron plasmon in polycrystalline graphite have been measured by reflected electron energy loss spectroscopy (REELS). It was found that when crystallites are smaller than 10 nm, the π plasmon energy is lower than the value estimated from the valence plasmon energy which directly reflects the density. Moreover, there is a correlation between the π plasmon energy and the relative intensity of the π plasmon peak to the elastic peak. Thus, the decrease of the π plasmon energy was explained by a crystallite size effect such as a decrease in π electron density. This REELS technique was applied to estimate the chemical state in carbon films obtained by thermal chemical vapor deposition (CVD). The two-dimensional distribution of the graphitic carbon was successfully measured at a spatial resolution of less than 1 µm.