title: X-ray photoelectron spectroscopy and first principles calculation of BCN nanotubes.
abstract: Multiwalled boron carbonitride (BCN) nanotubes with two different structures were synthesized via thermal chemical vapor deposition; one has 10% C atoms homogeneously doped into BN nanotubes (B0.45C0.1N0.45 NTs), and the other has BN layers sheathed with 5-nm-thick C outerlayers (BN-C NTs). The electronic structures of the B, C, and N atoms were thoroughly probed by synchrotron X-ray photoelectron spectroscopy and the X-ray absorption near-edge structure method. The B0.45C0.1N0.45 NTs contain a significant amount of B-C and C-N bonding with a pyridine-like structure (hole structure), which reduces the pi bonding states of the B and N atoms. From the XPS valence band spectrum, the band gap was estimated to be about 2.8 eV. In the BN-C NTs, the C and BN domains are separated without forming the pyridine-like structure. Using the first principles method, we investigated the relative stabilities and electronic structures of the various isomers of the double-walled (12,0)@(20,0) BCN NTs. The C-outerlayer BN nanotube structure is the most stable isomer, when there exist no defects in the tubes with B/N = 1.0 (i.e., graphite-like structure). In addition, a reasonable model, which is characterized by the motives consisted of three pyridine-like rings around a hollow site, is presented for the local structure of C atoms in the B0.45N0.45C0.1 NTs. A considerable decrease of the band gap due to the 10% C doping was predicted, which was consistent with the experimental results.
authors.affiliation: Department of Chemistry, Korea University, Jochiwon 339-700, Korea.
authors.forename: Shin Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Jeunghee
authors.initials: J
authors.lastname: Park
authors.forename: Hyun Chul
authors.initials: HC
authors.lastname: Choi
authors.forename: Jae Pyung
authors.initials: JP
authors.lastname: Ahn
authors.forename: Jin Qiang
authors.initials: JQ
authors.lastname: Hou
authors.forename: Hong Seok
authors.initials: HS
authors.lastname: Kang