We recently showed that trimethylboron (B(CH3)3, TMB) can function as a single source precursor for CVD of boroncarbon thin films at 700-1100 °C and 5000 Pa in either a hydrogen or an argon ambient. We observed that the films deposited from TMB at 700 °C in a H2 ambient were thinner than those deposited in Ar ambient. This was unexpected as the hydrogen ambient opens more pathways for the decomposition of TMB. In addition, we noted that attempts to deposit thicker films by increasing the deposition time failed, where three times longer deposition resulted in similar film thickness.