Crystalline structures of carbon complexes in amorphous carbon films

Amorphous carbon (a-C) films, 20 Mm thick, were deposited by sputtering on (001) Si substrates. A negative bias voltage was applied to the substrate d uring deposition to induce Ar+ ion bombardment with an energy of similar to 230 eV. The film microstructure was investigated by conventional transmiss ion electron microscopy as well as high-resolution electron microscopy. The films consist of an amorphous carbon matrix and crystallites with a platel et form. The crystallites are energetically metastable and easily degrade u nder electron beam irradiation. In addition. they are usually oriented alon g their sixfold or threefold axes, exhibiting lattice parameters larger tha n those of graphite and diamond. X-ray reflectivity density measurements an d high-resolution electron microscopy observations indicate that these crys tallites consist of packed complex carbon clusters. X-ray diffraction measu rements in rocking curve geometry support the existence of oriented crystal lites with interplanar spacings corresponding to those observed by transmis sion electron microscopy. (C) 2000 Elsevier Science S.A. All rights reserve d.