Search query: h-BN PL

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abstract: A quantitative analysis of the excitonic luminescence efficiency in hexagonal boron nitride (h BN) is carried out by cathodoluminescence in the ultraviolet range and compared with zinc oxide and diamond single crystals. A high quantum yield value of ~50% is found for h BN at 10 K comparable to that of direct band gap semiconductors. This bright luminescence at 215 nm remains stable up to room temperature, evidencing the strongly bound character of excitons in bulk h BN. Ab initio calculations of the exciton dispersion confirm the indirect nature of the lowest energy exciton whose binding energy is found equal to 300+ 50 meV, in agreement with the thermal stability observed in luminescence. The direct exciton is found at a higher energy but very close to the indirect one, which solves the long debated Stokes shift in bulk h BN.
author_names: Leonard Schue

Lorenzo Sponza

Alexandre Plaud

Hakima Bensalah

Kenji Watanabe

Takashi Taniguchi

Francois Ducastelle

Annick Loiseau

J Barjon
title: Bright Luminescence from Indirect and Strongly Bound Excitons in h BN.
venue: Physical review letters
year: 2019

abstract: Abstract Brittleness, relative high friction coefficient and wear rate limit the applications of ceramic coatings as wear resistant layers. However, because embedding additives with ceramic matrix has demonstrated to be an effective way to improve coating performances, different contents and size of h BN were added into an YSZ suspension. Afterwards, the YSZ/h BN composite coatings were manufactured by suspension plasma spray and their tribological analysis indicated that: i) the reduction of the friction coefficient and wear rate can be achieved by incorporating h BN into YSZ coating. ii) finer h BN particle is more helpful to enhance the tribological properties of the coating. iii) the optimum content is dependent on h BN particle sizes. iv) when the contents and the size of the h BN inclusion increase, the probability distribution of the micro hardness can become bi modal. Three worn surface conditions were summarized and their wear mechanisms were discussed as well.
author_names: Yongli Zhao

Yan Wang

Zexin Yu

Marie-Pierre Planche

Francois Peyraut

Hanlin Liao

Audrey Lasalle

Alain Allimant

Ghislain Montavon
title: Microstructural, mechanical and tribological properties of suspension plasma sprayed YSZ/h BN composite coating
year: 2018

abstract: Abstract The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h BN) flakes is demonstrated. Formation of single layer graphene is clearly apparent in Raman spectra which display sharp optical phonon bands. Atomic force microscope images and Raman maps reveal that the graphene grown depends on the surface morphology of the h BN substrates. The growth is governed by the high mobility of the carbon atoms on the h BN surface, in a manner that is consistent with van der Waals epitaxy. The successful growth of graphene layers depends on the substrate temperature, but is independent of the incident flux of carbon atoms.
author_names: Jorge M Garcia

Ulrich Wurstbauer

Antonio Levy

Loren N Pfeiffer

Aron Pinczuk

Annette S Plaut

Lei Wang

Cory R Dean

Roberto Buizza

Arend van der Zande

James C Hone

Kenji Watanabe

Takashi Taniguchi
title: Graphene growth on h BN by molecular beam epitaxy
year: 2012

abstract: Hexagonal boron nitride (h BN) and graphite are structurally similar but with very different properties. Their combination in graphene based devices is now of intense research focus, and it becomes particularly important to evaluate the role played by crystalline defects on their properties. In this paper, the cathodoluminescence (CL) properties of hexagonal boron nitride crystallites are reported and compared to those of nanosheets mechanically exfoliated from them. First, the link between the presence of structural defects and the recombination intensity of trapped excitons, the so called D series, is confirmed. Low defective h BN regions are further evidenced by CL spectral mapping (hyperspectral imaging) allowing us to observe new features in the near band edge region, tentatively attributed to phonon replicas of exciton recombinations. Second, the h BN thickness was reduced down to six atomic layers, using mechanical exfoliation, as evidenced by atomic force microscopy. Even at these low thicknesses, the luminescence remains intense and exciton recombination energies are not strongly modified with respect to the bulk, as expected from theoretical calculations, indicating extremely compact excitons in h BN.
author_names: Aur'elie Pierret

Jorge Loayza

Bruno Berini

Andreas C Betz

Bernard Placcais

Franccois Ducastelle

J Barjon

Annick Loiseau
title: Excitonic recombinations in h BN: From bulk to exfoliated layers
year: 2014

abstract: Abstract BN/metal sulfide composite (BN/In 2 S 3 was prepared by a facile in situ one pot hydrothermal method. The as synthesized photocatalyst was characterized by X ray powder diffraction (XRD) UV vis diffuse reflection spectroscopy (DRS) scanning electron microscopy (SEM) transmission electron microscopy (TEM) N 2 sorption analysis, electron spin resonance (ESR) photoluminescence emission spectra (PL) and X ray photoelectron spectroscopy (XPS) The results show that compared with single In 2 S 3 the BN/In 2 S 3 photocatalyst exhibits excellent photocatalytic performance for selective oxidation of aromatic alcohols to aromatic aldehydes under visible light irradiation. The enhanced photocatalytic activity of BN/In 2 S 3 composite is mainly attributed to the unique physicochemical properties of BN nanosheet, which acts as a promoter for photoexcited holes transfer, thereby improving the charge separation efficiency and prolonging photoexcited electrons lifetime. Effects of the type of aromatic alcohol and the added scavenger on the photocatalytic efficiency were also investigated. O 2 radicals and photogenerated holes play decisive roles for photocatalytic oxidation of aromatic alcohols to aromatic aldehydes. This approach is versatile for constructing other high efficiency photocatalysts such as BN/CdS, BN/Cd x Zn 1 x S and BN/ZnIn 2 S 4 It is hoped that this work could provide new insights to construct the BN based composites for extensive photocatalytic applications.
author_names: Sugang Meng

Xiangju Ye

Xiaofeng Ning

Mengli Xie

Xianliang Fu

Shifu Chen
title: Selective oxidation of aromatic alcohols to aromatic aldehydes by BN/metal sulfide with enhanced photocatalytic activity
year: 2016

abstract: Abstract Novel graphene like BN modified BiOBr materials have been synthesized via an ionic liquid assisted solvothermal process. The structure, morphology, optical and electronic properties were explored by the XRD, XPS, FT IR, SEM, TEM, DRS, PL, EIS and photocurrent. The photocatalytic performance of the graphene like BN/BiOBr materials was evaluated by the degradation of colorless antibiotic agent ciprofloxacin (CIP) tetracycline hydrochloride (TC) and rhodamine B (RhB) under visible light irradiation. When the mass fraction of graphene like BN is 1% the graphene like BN/BiOBr materials exhibited the highest activity. The enhanced light harvesting ability and higher separation efficiency of photogenerated electron hole pairs by the modification of graphene like BN contributed to the higher photocatalytic activity. The photo degradation is dominant by the O2 and hole oxidation process. This exploration of graphene like BN modified BiOBr open a window for the use of other graphene like BN based composites in photocatalysis field.
author_names: Jun Di

Jiexiang Xia

Mengxia Ji

Bin Wang

Sheng Yin

Qi Zhang

Zhigang Chen

Huaming Li
title: Advanced photocatalytic performance of graphene like BN modified BiOBr flower like materials for the removal of pollutants and mechanism insight
year: 2016

abstract: Abstract High active BN/CdS composite photocatalysts were prepared by the ball milling method. The prepared BN/CdS composites were characterized by the X ray powder diffraction (XRD) transmission electron microscopy (TEM) UV vis absorption spectra (UV vis) and fluorescence emission spectra (PL) The effects of the loading amounts of BN and the ball milling time on the H2 evolution rate were investigated. The results indicated that the tight contact of CdS with h BN can be achieved, and the photocatalytic activity of CdS could be improved substantially by coupling with a proper amount of milled h BN. The optimal loading amount of h BN was found to be 5 wt% and the milling time was 1 h. In the Pt/CdS/BN photocatalytic system, both the Pt as the electron acceptor and the BN as the hole transfer may cause the improvement of the CdS activity. The highest H2 evolution rate over the Pt/BN/CdS photocatalyst can reach as high as ~17.563 mmol g 1 h 1.
author_names: Ruizhen Zhang

Jian Wang

Peide Han
title: Highly efficient photocatalysts of Pt/BN/CdS constructed by using the Pt as the electron acceptor and the BN as the holes transfer for H2 production
year: 2015

abstract: Abstract Graphene like BN/AgBr hybrid materials were synthesized using the facile water bath method and characterized using X ray diffraction (XRD) energy dispersive X ray spectrometry (EDS) transmission electron microscopy (TEM) X ray photoelectron spectroscopy (XPS) UV vis diffuse reflectance spectroscopy (DRS) photoluminescence (PL) Fourier transform infrared spectra (FT IR) inductively coupled plasma optical emission spectrometry (ICP OES) and Brunner Emmet Teller (BET) analysis. The photocatalytic activity of the graphene like BN/AgBr hybrid materials was evaluated using methyl orange (MO) as a target organic pollutant. The results indicated that the photocatalytic activity of AgBr could be significantly improved by coupling with a proper amount of graphene like BN. In addition, the optical loading amount of graphene like BN was observed to be 1 wt% The MO molecules can be decomposed completely within 15 min under visible light irradiation, and the photocatalyst can be reused 5 times without losing activity. The XRD pattern of the cycling sample revealed that no diffraction peaks of metallic Ag were present, which indicated that introducing a small amount of graphene like BN can effectively suppress the reduction of silver ions. The results of the photocurrent and impedance analysis indicated that a small amount of graphene like BN was beneficial for the separation of photogenerated electrons and holes, which could enhance the photoactivity of graphene like BN/AgBr. Based on the experimental results, a possible visible light photocatalytic degradation mechanism is also discussed.
author_names: Jiajia Chen

Jiaxiang Zhu

Zulin Da

Hui Xu

Jia Yan

Haiyan Ji

Huoming Shu

Huaming Li
title: Improving the photocatalytic activity and stability of graphene like BN/AgBr composites
year: 2014

abstract: Herein, novel graphene like BN/BiOBr composite was prepared through a facile solvothermal method in the presence of reactable ionic liquid [C16mim]Br. The structure and morphology of the as prepared samples were investigated by X ray diffraction (XRD) Transmission electron microscopy, field emission scanning electron microscope, energy dispersive X ray spectrometry, UV vis diffuse reflectance spectroscopy, Fourier transform infrared spectra and photoluminescence (PL) The photocatalytic activity was evaluated by the degradation of Rhodamine B (RhB) aqueous solution under visible light irradiation. Results showed that the 0.05 wt% BN/BiOBr composite catalysts exhibit higher photoactivity than pure BiOBr. The enhanced photocatalytic activity was attributed to the efficient separation of the photogenerated electron hole pairs of the composites which was confirmed by the electrochemical impedance spectroscopy, photocurrent and PL analysis. Meanwhile, the main active species of BN/BiOBr during the photocatalysis process were determined to be holes (h+
author_names: Bin Wang

Jun Di

Jiexiang Xia

Li Xu

Hui Xu

Qi Zhang

Zhigang Chen

Huaming Li
title: Graphene like BN/BiOBr composite: synthesis via a reactable ionic liquid and enhanced visible light photocatalytic performance
year: 2016

abstract: Photoluminescence (PL) from femtosecond laser modified regions inside cubic boron nitride (c BN) was measured under UV and visible light excitation. Bright PL at the red spectral range was observed, with a typical excited state lifetime of ~4 ns. Sharp emission lines are consistent with PL of intrinsic vibronic defects linked to the nitrogen vacancy formation (via Frenkel pair) observed earlier in high energy electron irradiated and ion implanted c BN. These, formerly known as the radiation centers, RC1, RC2, and RC3, have been identified at the locus of the voids formed by a single femtosecond laser pulse. The method is promising to engineer color centers in c BN for photonic applications.
author_names: Ricardas Buividas

Igal Aharonovich

Gediminas Seniutinas

Xue Wang

Ludovic Rapp

Andrei V Rode

Takashi Taniguchi

Saulius Juodkazis
title: Photoluminescence from voids created by femtosecond laser pulses inside cubic BN.
venue: Optics letters
year: 2015