Effect of heat treatment on microstructures of magnetron sputtered amorphous carbon films

Abstract In this study, the effect of heat-treatment conditions at temperatures of 800–1200 °C on the structure of magnetron-sputtered amorphous carbon (a-C) films was characterized using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Results show that heat treatment leads to the formation of an ordered structure in a-C films, including an increased degree of graphitization, although the formed carbon crystal is not graphite. For heat-treatment temperatures above 900 °C, the crystalline structure of a-C films is enhanced, and the diffraction characteristic peaks of lonsdaleite (102) and C (109) appear near 2θ = 61.8° and 66.7°, respectively. At the same time, carbon microcrystalline aggregation and a lamellar crystal structure appear on the surface of the films. With increasing treatment temperature, carbon accumulation appears on the a-C film surfaces; the lamellar crystals disappear when the treatment temperature reaches 1200 °C, and flowing sand-like stacking is apparent on the film surfaces. With the deepening of the heat-treatment process, the columnar cross-sectional structure of the a-C films disappears. The surface roughness of the a-C films increases after heat treatment; except in the case of a treatment temperature of 1100 °C.