Surface modifications on as-grown boron doped CVD diamond films induced by the B2O3-ethanol-Ar system

Abstract

The surface termination of as-grown microcrystalline (MCD) and nanocrystalline (NCD) boron-doped diamond films was assessed by X-ray photoelectron spectroscopy (XPS) and water contact angle techniques. The diamond coatings were grown on mirror-polished silicon nitride ceramic substrates using the hot-filament chemical vapor deposition (HFCVD) technique. The boron doping source, boron oxide (B2O3) diluted in ethanol, was dragged by a constant Ar flow at different CH4/H-2 gas ratios and system pressures. The electrical resistivity of these semiconducting diamond films was obtained and their surfaces were further characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The results have shown that the increasing total pressure particularly affects the crystal size of the boron doped MCD samples by enhancing diamond renucleation due to the higher residence time of Ar. Also, both as-grown MCD and NCD surface types were found to be inherently hydrophobic, with contact angles similar to 90 degrees C, but retain significant amounts of oxygen bonded to carbon atoms mainly as C-O-C and C = O terminations. Such partial diamond surface oxidation is the result of a very unique stable gas mixture containing hydrogen, carbon and oxygen, when boron oxide and ethanol are added to methane during the CVD process. (C) 2016 Elsevier B.V. All rights reserved.