![]() ; Wirtz, Ludger ![]() 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 ▲] Detailed reference viewed: 175 (4 UL)![]() ; ; Wirtz, Ludger ![]() Patent (2012) The invention relates to a controllable frequency, broad spectrum light emitting source that includes boron nitride nanotubes with defects produced by the absence of a boron atom in the tubular structure ... [more ▼] The invention relates to a controllable frequency, broad spectrum light emitting source that includes boron nitride nanotubes with defects produced by the absence of a boron atom in the tubular structure and wherein the source is additionally provided with a means for generating an electrical field perpendicular to the tube. The invention may be used as a field effect transistor (adding electrodes) or as a source of conversion of energy of an incident bundle. [less ▲] Detailed reference viewed: 105 (4 UL)![]() ; Wirtz, Ludger ![]() in Nano Letters (2010), 10(4), 1172-1176 we present a new way to tune the electron phonon coupling (EPC) in graphene by changing the deformation potential with electron/hole doping. We show the EPC for highest optical branch at the high symmetry ... [more ▼] we present a new way to tune the electron phonon coupling (EPC) in graphene by changing the deformation potential with electron/hole doping. We show the EPC for highest optical branch at the high symmetry point K acquires a strong dependency on the doping level due to electron electron correlation not accounted in mean-field approaches. Such a dependency influences the dispersion (with respect to the laser energy) of the Raman D and 2D lines and the splitting of the 2D peak in multilayer graphene. Finally this doping dependence opens the possibility to construct tunable electronic devices through external control of the EPC. [less ▲] Detailed reference viewed: 94 (6 UL)![]() ; ; et al in Physical Review. B (2008), 77(12), We report the ultrafast dynamics of the 47.4 THz coherent phonons of graphite interacting with a photoinduced nonequilibrium electron-hole plasma. Unlike conventional materials, upon photoexcitation the ... [more ▼] We report the ultrafast dynamics of the 47.4 THz coherent phonons of graphite interacting with a photoinduced nonequilibrium electron-hole plasma. Unlike conventional materials, upon photoexcitation the phonon frequency of graphite upshifts, and within a few picoseconds relaxes to the stationary value. Our first-principles density functional calculations demonstrate that the phonon stiffening stems from the light-induced decoupling of the nonadiabatic electron-phonon interaction by creating a nonequilibrium electron-hole plasma. Time-resolved vibrational spectroscopy provides a window on the ultrafast nonquilibrium electron dynamics. [less ▲] Detailed reference viewed: 128 (2 UL)![]() Wirtz, Ludger ![]() in Physical Review Letters (2008), 100(18), Detailed reference viewed: 150 (3 UL)![]() ; Wirtz, Ludger ![]() 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 ▲] Detailed reference viewed: 315 (1 UL) |
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