Elastic Properties, Sp3 Fraction, And Raman Scattering In Low And High Pressure Synthesized Diamond-Like Boron Rich Carbides

Dense BCx phases with high boron concentration are predicted to be metastable, superhard, and conductors or superconductors depending on boron concentration. However, up to this point, diamond-like boron rich carbides BCx (dl-BCx) phases have been thought obtainable only through high pressure and high temperature treatment, necessitating small specimen volume. Here, we use electron energy loss spectroscopy combined with transmission electron microscopy, Raman spectroscopy, surface Brillouin scattering, laser ultrasonics (LU) technique, and analysis of elastic properties to demonstrate that low pressure synthesis (chemical vapor deposition) of BCx phases may also lead to the creation of diamond-like boron rich carbides. The elastic properties of the dl-BCx phases depend on the carbon sp(2) versus sp(3) content, which decreases with increasing boron concentration, while the boron bonds determine the shape of the Raman spectra of the dl-BCx after high pressure-high temperature treatment. Using the estimation of the density value based on the sp(3) fraction, the shear modulus mu of dl-BC4, containing 10% carbon atoms with sp(3) bonds, and dl-B3C2, containing 38% carbon atoms with sp(3) bonds, were found to be mu = 19.3 GPa and mu = 170 GPa, respectively. The presented experimental data also imply that boron atoms lead to a creation of sp(3) bonds during the deposition processes. (C) 2014 AIP Publishing LLC.