Hydrogen in carbon foils made by DC glow discharge in ethylene

Thermal desorption has been studied from thin films of carbon prepared by dc glow discharge in ethylene. The only gases released in significant quantities are hydrogen and methane. Both releases can be characterised by a continuum of activation energies but the methane release peaks at a lower temperature than that from hydrogen. The estimated total hydrogen release is compared with the hydrogen content determined by nuclear scattering experiments. Infra red studies suggest that the majority of CH2 and CH3 bonds can be ruptured by annealing at 300°C, a temperature well below the hydrogen and methane release rate maxima. Possible hydrogen bonding modes and desorption mechanisms are discussed.