Low Temperature CVD of Thin, Amorphous Boron-Carbon Films for Neutron Detectors

Thin, amorphous boron-carbon films were deposited at low temperature (400-600 °C) by thermally activated CVD using the organoborane triethylboron (TEB) as a single precursor. Two different carrier gases were tested. At 600 °C using argon as carrier gas the deposition rate was close to 1 μm/h. The film had a density of 2.14 g/cm with a B/C-ratio of 3.7. When hydrogen was used as carrier gas the film density was 2.42 g/cm, the B/C ratio 4.6 and the deposition rate 0.35 μm/h. The hydrogen content in the films was about 3-4 at%, regardless of deposition ambient and varied only with the deposition temperature. In addition, both the film composition and the film density were found to vary significantly with the deposition temperature and the deposition ambient. Based upon these results, a deposition mechanism for the growth of boroncarbon films from TEB, where the TEB molecule is decomposed to BH3 and hydrocarbons, is suggested.