The hypothesis that hydrogen ambient allows for decomposition of TMB into species not active for film deposition seems unlikely in the light of our previous study on CVD of B-C films from TMB where we noted a higher deposition rate and a higher B/C ratio for films deposited in hydrogen ambient, compared to films deposited in argon ambient. The hypothesis that the surface was rendered inactive was tested by depositing a film for 180 min in H2 with 𝑃 𝑇𝑀𝐵 = 3.25 Pa, then increasing 𝑃 𝑇𝑀𝐵 to 27.8 Pa and depositing 60 min more. The resulting film was 498 nm thick, which shows that the growth could resume at these conditions and therefore contradicts this hypothesis.