title: Isotope effect on band gap and radiative transitions properties of boron nitride nanotubes.
abstract: We have carried out an isotope study on the band gap and radiative transition spectra of boron nitride nanotubes (BNNTs) using both experimental and theoretical approaches. The direct band gap of BNNTs was determined at 5.38 eV, independent of the nanotube size and isotope substitution, by cathodoluminescences (CL) spectra. At lower energies, several radiative transitions were observed, and an isotope effect was revealed. In particular, we confirmed that the rich CL spectra between 3.0 and 4.2 eV reflect a phonon-electron coupling mechanism, which is characterized by a radiative transition at 4.09 eV. The frequency red shift and peak broadening due to isotopic effect have been observed. Our Fourier transform infrared spectra and density functional theory calculations suggest that those radiative transitions in BNNTs could be generated by a replacement of some nitrogen atoms with oxygen.
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA. whan@bnl.gov
authors.forename: Wei-Qiang
authors.initials: WQ
authors.lastname: Han
authors.forename: Hua-Gen
authors.initials: HG
authors.lastname: Yu
authors.forename: Chunyi
authors.initials: C
authors.lastname: Zhi
authors.forename: Jianbin
authors.initials: J
authors.lastname: Wang
authors.forename: Zhenxian
authors.initials: Z
authors.lastname: Liu
authors.forename: Takashi
authors.initials: T
authors.lastname: Sekiguchi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Bando
mesh_terms: D001895:Boron / Q000737:chemistry; D001896:Boron Compounds / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D007554:Isotopes / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D001896:Boron Compounds; D007554:Isotopes; D046911:Macromolecular Substances; C017282:boron nitride; D001895:Boron