Crystallization in Thin Films of Carbon and Silicon Monoxide

Abstract

Thin films of carbon or of silicon monoxide were observed while heated to 1000°C inside the electron microscope. Spherical graphite nuclei, approximately 200 Å in diameter, appear at 200°C in the carbon films. These nuclei maintain their spherical form to a temperature of 600°C while growing to 1800 Å in diameter. At this size the spheres become unstable and convert to crystals of hexagonal symmetry. At 700°C the crystals revert to spheres 3600 Å in diameter. The silicon monoxide films form 150-Å nuclei at 350°C; no further changes are noted until at 800°C the film recrystallizes. The recrystallized silicon monoxide film is identified as β crystobalite. For both materials, the nucleation temperatures and the sizes and shapes of the crystallites at a given temperature depended on the thicknesses of the films.