We determine the evolution of Si–H and C–H bonding during the growth of hydrogenated amorphous silicon carbide films by reactive magnetron sputtering of a Si target in (Ar+H2+CH4). Si–H and C–H modes are observed by infrared reflectance spectroscopy. An optical cavity substrate is used to enhance the sensitivity. We identify Si–H stretching modes at 2110 and 2145 cm−1due to Si–H clusters in microvoids and Si–H back‐bonded to carbon, respectively. C–H stretching modes are identified at 2870, 2900, and 2950 cm−1. These indicate dominantsp3bonding configuration for C. During initial growth, a transition layer rich in H and C is observed. Steady state growth is not achieved until ≳250 A˚ on SiO2substrates, and ∼70 A˚ ona‐Si:H substrates. ©1995 American Institute of Physics.