Trimethylboron as Single-Source Precursor for Boron–Carbon Thin Film Synthesis by Plasma Chemical Vapor Deposition

Boron–carbon (BxC) thin films are potential neutron converting layers for 10B-based neutron detectors. However, as common material choices for such detectors do not tolerate temperatures above 500 °C, a low temperature deposition route is required. Here, we study trimethylboron B(CH3)3 (TMB) as a single-source precursor for the deposition of BxC thin films by plasma CVD using Ar plasma. The effect of plasma power, TMB/Ar flow ratio and total pressure, on the film composition, morphology, chemical bonding, and microstructures are investigated. Dense and boron-rich films (B/C = 1.9) are achieved at high TMB flow under a low total pressure and high plasma power, which rendered an approximate substrate temperature of ∼300 °C. Films mainly contain B–C bonds with the presence of B–O and C–C, which is attributed to be the origin of formed amorphous carbon in the films. The high H content (15 ± 5 at. %) is almost independent of deposition parameters and contributed to lower the film density (2.16 g/cm3). The plasma compositional analysis shows that the TMB molecule decomposes to mainly atomic H, C2, BH, and CH. A plasma chemical model for the decomposition of TMB with BH and CH as the plausible film depositing species in the plasma is proposed.