Thermal expansion dependence on the sp2 concentration of amorphous carbon and carbon nitride

Abstract The coefficients of thermal expansion of hydrogenated amorphous carbon (a-C:H) and carbon nitride (a-CNx:H) were determined using the thermally induced bending technique. Amorphous carbon films were prepared with different sp2 concentrations by varying the bias voltage in a glow discharge system in methane atmosphere. Carbon nitride films (a-CNx:H) were deposited by introducing nitrogen gas. It was observed that the thermal expansion of a-C:H depends on the concentration of sp2 bonded carbon, increasing to the value of graphite as the sp2 concentration approaches 100%. Similar effect was also observed in the carbon nitride films.