Article

Defect-related photoluminescence of hexagonal boron nitride

Physical review. B, Condensed matter (Impact Factor: 3.66). 11/2008; DOI: 10.1103/PhysRevB.78.155204
Source: arXiv

ABSTRACT Photoluminescence of polycrystalline hexagonal boron nitride (hBN) was measured by means of time- and energy-resolved spectroscopy methods. The observed bands are related to DAP transitions, impurities and structural defects. The excitation of samples by high-energy photons above 5.4 eV enables a phenomenon of photostimulated luminescence (PSL), which is due to distantly trapped CB electrons and VB holes. These trapped charges are metastable and their reexcitation with low-energy photons results in anti-Stockes photoluminescence. The comparison of photoluminescence excitation spectra and PSL excitation spectra allows band analysis that supports the hypothesis of Frenkel-like exciton in hBN with a large binding energy.

0 Bookmarks
 · 
186 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: To convert wave energy into more suitable forms efficiently, a single-phase permanent magnet (PM) ac linear generator directly coupled to wave energy conversion is presented in this paper. Magnetic field performance of Halbach PM arrays is compared with that of radially magnetized structure. Then, the change of parameters in the geometry of slot and Halbach PM arrays' effect on the electromagnetic properties of the generator are investigated, and the optimization design guides are established for key design parameters. Finally, the simulation results are compared with test results of the prototype in wave energy conversion experimental system. Due to test and theory analysis results of prototype concordant with the finite-element analysis results, the proposed model and analysis method are correct and meet the requirements of direct-drive wave energy conversion system.
    IEEE Transactions on Applied Superconductivity 06/2014; 24(3):1-4. · 1.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hexagonal boron nitride (hBN) thin films were deposited on silicon and quartz substrates using sequential exposures of triethylboron and N2/H2 plasma in a hollow-cathode plasma-assisted atomic layer deposition reactor at low temperatures (≤450°C). A non-saturating film deposition rate was observed for substrate temperatures above 250°C. BN films were characterized for their chemical composition, crystallinity, surface morphology, and optical properties. X-ray photoelectron spectroscopy (XPS) depicted the peaks of boron, nitrogen, carbon, and oxygen at the film surface. B 1s and N 1s high-resolution XPS spectra confirmed the presence of BN with peaks located at 190.8 and 398.3 eV, respectively. As deposited films were polycrystalline, single-phase hBN irrespective of the deposition temperature. Absorption spectra exhibited an optical band edge at ~5.25 eV and an optical transmittance greater than 90% in the visible region of the spectrum. Refractive index of the hBN film deposited at 450°C was 1.60 at 550 nm, which increased to 1.64 after postdeposition annealing at 800°C for 30 min. These results represent the first demonstration of hBN deposition using low-temperature hollow-cathode plasma-assisted sequential deposition technique.
    Journal of the American Ceramic Society 09/2014; · 2.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The emission of BCNO phosphors has been easily tuned from the violet to the near red regions by varying the carbon content. Here we report the optimal conversion of graphene oxide (GO) into BCNO hybrid nanostructures by one-step air oxidation with boric acid and urea. White lighting phosphor was obtained in which the doped porous graphene acts as an interconnecting framework generating and transferring electrons under excitation light. Various carbon-related levels in the BN band structures play an essential role in emitting full colour white light. The quantum confinement in the various kinds of GQDs and GO are also beneficial to widen the emission spectrum.
    RSC Advances 06/2014; 2014(4):26855-26860. · 3.71 Impact Factor

Full-text (3 Sources)

Download
75 Downloads
Available from
Jun 6, 2014