Electronic Structure of Si-Doped BN Nanotubes Using X-ray Photoelectron Spectroscopy and First-Principles Calculation

Silicon (Si)-doped multiwalled boron nitride nanotubes (BNNTs) were synthesized via thermal chemical vapor deposition. Electron energy-loss spectroscopy revealed that 5% of Si atoms were homogeneously doped into the BNNTs. X-ray absorption and photoelectron spectroscopy measurements demonstrated that the Si−B and Si−N bonding structures are produced, where both structures reduce the π bonding states of the BN sheets. The valence band analysis indicates that the Si doping decreases the band gap by about 1.7 eV. The first principles calculation of the Si-doped double-walled BNNTs suggests two distinctive doping structures; contiguous Si−Si bonding structures along the tube axis and a local hollow nitrogen-rich pyridine-like structure with a lone electron pair. It also predicts that the 4% Si-doped defective structures reduce the band gap of the BNNTs by 1.6 eV, which is in qualitative agreement with our experimental results.