Electron-irradiation-induced ordering in tetrahedral-amorphous carbon films

We investigated in detail the structural ordering developed in films of tetrahedral amorphous carbon (ta-C) under 100 kV to 200 kV electron beams of transmission electron microscopes (TEM). From systematic measurements of electron diffraction and electron energy loss spectra (EELS), in selected areas the ordered structures were concluded to be multi-walled carbon nanotubes or warped graphitic platelets containing a high density of defects. The electron-irradiation-induced ordering can neither be accounted for by a sample heating nor be explained only by displacement damage caused by 200 kV electron irradiation. The essential process, that is enhanced, appears the atomic diffusion induced by electronic excitations due to the electron irradiation.