Efficient Gate-tunable light-emitting device made of defective boron nitride nanotubes: from ultraviolet to the visible

in Scientific Reports (2013), 3

Boron nitride is a promising material for nanotechnology applications due to its two-dimensional graphene-like, insulating, and highly-resistant structure. Recently it has received a lot of attention as a ... [more ▼]

Boron nitride is a promising material for nanotechnology applications due to its two-dimensional graphene-like, insulating, and highly-resistant structure. Recently it has received a lot of attention as a substrate to grow and isolate graphene as well as for its intrinsic UV lasing response. Similar to carbon, one-dimensional boron nitride nanotubes (BNNTs) have been theoretically predicted and later synthesised. Here we use first principles simulations to unambiguously demonstrate that i) BN nanotubes inherit the highly efficient UV luminescence of hexagonal BN; ii) the application of an external perpendicular field closes the electronic gap keeping the UV lasing with lower yield; iii) defects in BNNTS are responsible for tunable light emission from the UV to the visible controlled by a transverse electric field (TEF). Our present findings pave the road towards optoelectronic applications of BN-nanotube-based devices that are simple to implement because they do not require any special doping or complex growth. [less ▲]

Impact of the electron-electron correlation on phonon dispersion: Failure of LDA and GGA DFT functionals in graphene and graphite

in Physical Review. B (2008), 78(8),

We compute the electron-phonon coupling (EPC) of selected phonon modes in graphene and graphite using various ab initio methods. The inclusion of nonlocal exchange-correlation effects within the GW ... [more ▼]

We compute the electron-phonon coupling (EPC) of selected phonon modes in graphene and graphite using various ab initio methods. The inclusion of nonlocal exchange-correlation effects within the GW approach strongly renormalizes the square EPC of the A(1)' K mode by almost 80% with respect to density-functional theory in the LDA and GGA approximations. Within GW, the phonon slope of the A(1)' K mode is almost two times larger than in GGA and LDA, in agreement with phonon dispersions from inelastic x-ray scattering and Raman spectroscopy. The hybrid B3LYP functional overestimates the EPC at K by about 30%. Within the Hartree-Fock approximation, the graphene structure displays an instability under a distortion following the A(1)' 'phonon at K. [less ▲]

Absorption of BN nanotubes under the influence of a perpendicular electric field

in Physica Status Solidi B. Basic Research (2007), 244(11), 4288-4292

We calculate the optical absorption spectra of prototype (6,6) and (9,9) BN nanotubes in the presence of a perpendicular electric field. This model mimics a gated BN nanotube device. Even though the band ... [more ▼]

We calculate the optical absorption spectra of prototype (6,6) and (9,9) BN nanotubes in the presence of a perpendicular electric field. This model mimics a gated BN nanotube device. Even though the band-gap of the tubes decreases strongly as a function of the electric field strength, the absorption spectrum of the pure tubes remains remarkably constant up to high field-strength. We show that, in contrast, the levels which are responsible for defect-mediated photo-luminescence are shifted by the electric field. We address the use of BN nanotubes for optoelectronic applications. 0 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. [less ▲]