Synthesis and characterization of boron-doped carbons

Two methods have been employed to prepare boron-doped carbon materials. One method utilized ion implantation to dope the surface region of vitreous carbon with up to 12 atomic % boron. The other method used CVD to prepare ~ 1-2 micron thick carbon coatings with various boron contents (0 to 15 atomic %). The quantitative compositional analysis of these materials was performed with the electron microprobe and ion microprobe. Graphitization and redistribution of the boron, due to heat treatment, was examined with SIMS depth profiling and X-ray diffraction. Primarily, X-ray photoelectron spectroscopy (XPS) was used to characterize the bonding state of boron before and after heat treatment and oxidation. It was found that boron could accommodate as many as five different chemical structures in the CVD carbon films. Some of these were identified as mixed BO and BC species (e.g.,{A figure is presented}, and one corresponded to the BC₃ type of bonding reported by Kaner. Most interestingly, oxidation caused boron segregation at the surface and shifted the bonding environment of these boron atoms to lower binding energy (less local electron density).