The microstructure of isotropic vapor-deposited carbon films

The structure of thin, vapor-deposited carbon films was characterized by transmission electron microscopy and electron diffraction. Selected area electron diffraction showed very weak and broad peaks, indicating that these carbons contain extremely small crystallites whose dimension in the crystallographic c-direction is about 8 to 10 a. The observed diffraction bands are (h, k, 1 = 0) type reflections, which suggests that individual crystallites consist of graphitic layer planes stacked in parallel groups but with no order between atoms in adjacent planes (turbostratic). The carbon films exhibit no preferred orientation, indicating that the small crystallites are randomly oriented in the film and that the films are therefore isotropic. The measured density (1.8 g/cm3) and the structure of the vapor-deposited carbons are accordingly similar to those of low-temperature isotropic (LTI) pyrolytic carbons.