HYDROGEN DIFFUSION AND RELATED DEFECTS IN HYDROGENATED AMORPHOUS-SILICON CARBIDE

Films of a-SiC:H have been deposited by glow-discharge and annealed at differing temperatures in steps of 50-degrees-C in the range 200-450-degrees-C. Measurements of elemental composition by means of nuclear techniques, of infrared, photothermal deflection, optical and ESR spectroscopies, of dark and photoconductivity were performed for every annealing temperature. The hydrogen content (free and bonded to silicon and/or carbon), the spin density, the optical gap and the Urbach energy were deduced. By means of differential scanning calorimetry, the annealing behaviour has been interpreted. For annealing temperature lower than 250-degrees-C, an irreversible rearrangement of the network has been observed, while over 350-degrees-C hydrogen effusion occurs first and then crystallization.