Thermal CVD was performed in a horizontal hot-wall CVD reactor using TEB (semiconductor grade, from SAFC Hitech), as single source precursor for BxC and palladium membrane purified H2 as carrier gas and co-reactant and some depositions carried out with Ar (99.9997%) as carrier gas. The TEB was kept in a stainless-steel bubbler in a thermostat bath at 0 °C resulting in a vapor pressure of ~1.65 kPa. The films were deposited both on polished Si (100) and Si substrates with an 8:1 aspect ratio trench pattern, 8.5 μm wide and 70.4 μm deep. The substrates were diced into 10x10 mm pieces and degreased using ultrasonic bath, 3 min each in acetone and ethanol, followed by etching with RCA standard clean 1 (NH3:H2O2:H2O with relative concentrations 1:1:26) at 80 ⁰C and RCA standard clean 2 (HCl:H2O2:H2O with relative concentrations 1:1:22) at 80 ⁰C, and finally blow-dried with nitrogen gas. RCA clean is a procedure for removing particles absorbed on the Si surface using acidic and alkaline oxidizing solutions. The substrates were loaded into the SiC coated graphite susceptor, the reactor was pumped down, back-filled with H2 and heated to deposition temperatures with a 2000 sccm flow of H2 at 5 kPa regulated by a throttle valve on the process pump.