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Interplay Between Cr Dopants and Vacancy Clustering in the Structural and Optical Properties of WSe2

Submitted by ltizei on Wed, 2017-11-01 04:41
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Here, we analyze the effect of Cr doping on WSe2 crystals. The topology and the chemistry of the doped samples have been investigated by atom-resolved STEM microscopy combined with EEL spectroscopy. Cr (measured to have formal valence 3+) occupies W sites (formal valence 4+), indicating a possible hole doping. However, single or double Se-vacancies cluster near Cr atoms, leading to an effective electron doping. These defects organization can be explained by the strong binding energy of the CrW—Vse complex obtained by in DFT calculations. In highly Cr-doped samples, a local phase transition from the 2H to the to 1T phase is observed, which has been previously reported for other electron-doped transition metal dichalcogenides. Cr-doped crystals suffers a compressive strain, resulting in an isotropic lattice contraction and in an anisotropic optical bandgap energy shift (25 meV in-plane and 80 meV out-of-plane).


C-H. Ho, W-H. Chen, K.K. Tiong, K-Y. Lee, A. Gloter, A. Zobelli, O. Stephan, and L. H. G. Tizei, ACS nano (2017)

Point Defects in h-BN as efficient UV quantum emitters

Submitted by eels on Thu, 2017-01-05 15:18
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Single photons sources (SPS) play a central role in the experimental foundation of quantum computing. Currently, there is a large scientific effort in identifying new bright and stable single-photon emission sources, with the aim of extending the spectral range achievable by quantum emitters. In the last years low dimensional layered semiconductors appeared as new promising optical materials and low energy SPS have been identified in transition metal dichalcogenides. In this work, thanks to a newly developed optical set-up integrated in a scanning transmission electron microscope, we have identified a new very bright UV single photon emitter in hexagonal boron nitride. Read more »

Publications

Ho, C.-H., et al. Interplay Between Cr Dopants and Vacancy Clustering in the Structural and Optical Properties of WSe2. ACS Nano 11, 11162 (2017).
N. Nair, M., et al. Band Gap Opening Induced by the Structural Periodicity in Epitaxial Graphene Buffer Layer. Nano Letters 17, 2681-2689 (2017).
Vuong, T.Q.P., et al. Phonon symmetries in hexagonal boron nitride probed by incoherent light emission. 2D Materials 4, 011004 (2017).
Amato, M., Kaewmaraya, T., Zobelli, A., Palummo, M. & Rurali, R. Crystal Phase Effects in Si Nanowire Polytypes and Their Homojunctions. Nano Letters 16, 5694–5700 (2016).
Bourrellier, R., et al. Bright UV Single Photon Emission at Point Defects in h -BN. Nano Letters 16, 4317 (2016).
Tararan, A., Zobelli, A., Benito, A.M., Maser, W.K. & Stéphan, O. Revisiting Graphene Oxide Chemistry via Spatially-Resolved Electron Energy Loss Spectroscopy. Chemistry of Materials 28, 3741 (2016).
Palacio, I., et al. Atomic Structure of Epitaxial Graphene Sidewall Nanoribbons: Flat Graphene, Miniribbons, and the Confinement Gap. Nano Letters 15, 182 - 189 (2015).
Arenal, R., et al. Atomic Configuration of Nitrogen-Doped Single-Walled Carbon Nanotubes. Nano Letters 14, 5509 - 5516 (2014).
Bourrellier, R., et al. Nanometric Resolved Luminescence in h-BN Flakes: Excitons and Stacking Order. ACS Photonics 1, (2014). Download: bourrellier-acs-photonics.pdf (7.37 MB)
Walls, M., et al. Identification of Ferrous-Ferric Fe3O4 Nanoparticles in Recombinant Human Ferritin Cages. Microscopy and Microanalysis 19, 835 - 841 (2013).
Yang, Z., Lisiecki, I., Walls, M. & Pileni, M.-P. Nanocrystallinity and the Ordering of Nanoparticles in Two-Dimensional Superlattices: Controlled Formation of Either Core/Shell (Co/CoO) or Hollow CoO Nanocrystals. ACS Nano 7, 1342 - 1350 (2013).
Yang, Z., Walls, M., Lisiecki, I. & Pileni, M.-P. Unusual Effect of an Electron Beam on the Formation of Core/Shell (Co/CoO) Nanoparticles Differing by Their Crystalline Structures. Chemistry of Materials 25, 2372 - 2377 (2013).
Mignot, A., et al. A Top-Down Synthesis Route to Ultrasmall Multifunctional Gd-Based Silica Nanoparticles for Theranostic Applications. Chemistry - A European Journal n/a - n/a (2013).doi:10.1002/chem.201203003 Download: Mignot_Chemistry13_NPs-SiGd.pdf (2.51 MB)
Santana, A., Zobelli, A., Kotakoski, J., Chuvilin, A. & Bichoutskaia, E. Inclusion of radiation damage dynamics in high-resolution transmission electron microscopy image simulations: The example of graphene. Physical Review B 87, (2013).
Yang, Z., et al. A Phase-Solution Annealing Strategy to Control the Cobalt Nanocrystal Anisotropy: Structural and Magnetic Investigations. The Journal of Physical Chemistry C 116, 15723 - 15730 (2012).
Eswara Moorthy, S.K., Rousseau, O., Viret, M. & Kociak, M. Nanoscale Chemical and Structural Characterization of Transient Metallic Nanowires using Aberration-Corrected STEM-EELS. Nano Letters 12, 2732 - 2739 (2012). Download: nl204374v.pdf (1.74 MB)
Hu, M.-H., et al. Investigation of the thermal stability of Mg/Co periodic multilayers for EUV applications. Applied Physics A 106, 737 - 745 (2012).
Zobelli, A., et al. A comparative study of density functional and density functional tight binding calculations of defects in graphene. physica status solidi (b) 249, 276 - 282 (2012). Download: zobelli_pssb_2012.pdf (2.01 MB)
Cavalier, M., Walls, M., Lisiecki, I. & Pileni, M.P. How Can the Nanocrystallinity of 7 nm Spherical Co Nanoparticles Dispersed in Solution Be Improved?. Langmuir 27, 5014–5020 (2011).
Susi, T., et al. Nitrogen-Doped Single-Walled Carbon Nanotube Thin Films Exhibiting Anomalous Sheet Resistances. Chemistry Of Materials 23, 2201–2208 (2011).
Trasobares, S., et al. Chemical Imaging at Atomic Resolution as a Technique To Refine the Local Structure of Nanocrystals. Angewandte Chemie-International Edition 50, 868–872 (2011). Download: Angew. Chem. Int. Ed. 2011 Trasobares.pdf (649.98 KB)
Zagonel, L.F., et al. Nanometer Scale Spectral Imaging of Quantum Emitters in Nanowires and Its Correlation to Their Atomically Resolved Structure. Nano Letters 11, 568–573 (2011). Download: Nano Lett. 2011 Zagonel.pdf (4.51 MB)
Ivanovskaya, V.V., et al. Low-Energy Termination of Graphene Edges via the Formation of Narrow Nanotubes. Physical Review Letters 107, 065502 (2011). Download: PhysRevLett.107.065502.pdf (506.32 KB)
Ivanovskaya, V.V., et al. Enhanced H_{2} catalytic formation on specific topological defects in interstellar graphenic dust grain models. Physical Review B 82, (2010). Download: H2catalysis.pdf (233.91 KB)
Ivanovskaya, V.V., et al. Hydrogen adsorption on graphene: a first principles study. The European Physical Journal B 76, 481 - 486 (2010). Download: H-at-Graphene.pdf (254.61 KB)
Rodriguez-Lorenzo, L., et al. Zeptomol Detection Through Controlled Ultrasensitive Surface-Enhanced Raman Scattering. Journal Of The American Chemical Society 131, 4616–+ (2009). Download: J. Am. Chem. Soc. 2009 Rodríguez-Lorenzo.pdf (927.32 KB)
Arenal, R., et al. Optical gap measurements on individual boron nitride nanotubes by electron energy loss spectroscopy. Microscopy And Microanalysis 14, 274–282 (2008).
Zobelli, A., Gloter, A., Ewels, C.P. & Colliex, C. Shaping single walled nanotubes with an electron beam. Physical Review B 77, 045410 (2008). Download: PhysRevB.77.045410.pdf (1.13 MB)
Nelayah, J., et al. Mapping surface plasmons on a single metallic nanoparticle. Nature Physics 3, 348–353 (2007). Download: Nat Phys 2007 Nelayah.pdf (676.34 KB)
Zobelli, A., Gloter, A., Ewels, C.P., Seifert, G. & Colliex, C. Electron knock-on cross section of carbon and boron nitride nanotubes. Physical Review B 75, (2007). Download: crosssec.pdf (399.11 KB)
Zobelli, A., et al. Defective Structure of BN Nanotubes:  From Single Vacancies to Dislocation Lines. Nano Letters 6, 1955 - 1960 (2006).
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