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 B-10-based neutron detectors. However, as common material choices for such detectors do not tolerate temperatures above 500 degrees 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 similar to 300 degrees 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/cm(3)). The plasma compositional analysis shows that the TMB molecule decomposes to mainly atomic H, C-2, 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.