We therefore suggest that the film deposition in hydrogen ambient is affected by competitive adsorption of passivating species. Since no inhibiting effect was noted when using triethylboron (TEB) for CVD of B-C films, 9 we performed deposition runs with a mixture of TMB and TEB in hydrogen ambient to investigate if inhibiting species originates from the TMB molecule. We deposited a B-C film at 700 °C and 5000 Pa and equal partial pressure of TEB and TMB (𝑝 𝑇𝑀𝐵 = 𝑝 𝑇𝐸𝐵 = 3.25 Pa). No inhibition of the deposition was observed; Figure shows a cross section SEM micrograph of the resulting film with an average deposition rate of 21 nm/min which is of the same order of magnitude as when using only TEB 9 . This leads us to suggest that the inhibiting species are dihydrogen or atomic hydrogen.