Spectroscopic studies of nanocrystalline diamond materials

The structural and electronic properties of nanocrystalline diamond films synthesized by a modified hot-filament chemical vapour deposition process were investigated by both bulk- and surface-sensitive techniques. Diffraction and microscopy data show the films to consist of diamond grains with an average crystallite size of about 10–15 nm and a root-mean-square roughness of similar size. Carbon core-level excitations in transmission electron energy-loss spectroscopy reveal an sp2 content below 5%. The low energy loss spectra are quite similar to that of diamond crystal. The high sp3 content in the films was also confirmed by C 1s photoelectron plasmon energy loss features in X-ray photoemission experiments and by X-ray excited Auger-electron spectroscopy. We find that the hydrogen covered diamond surface gets contaminated after storage for several months under ambient conditions. Heating up to 500 °C in vacuo is required to desorb the adsorbate layer.