Supporting Information: Boron-Doped Graphene

Transcription

1 Supporting Information: Boron-Doped Graphene Nanoribbons: Electronic Structure and Raman Fingerprint Boris V. Senkovskiy,, Dmitry Yu. Usachov, Alexander V. Fedorov,,, Tomas Marangoni, Danny Haberer, Cesare Tresca,, Gianni Profeta, Vasile Caciuc, # Shigeru Tsukamoto, # Nicolae Atodiresei, # Niels Ehlen, Chaoyu José Maria C. Andrei Yu. Varykhalov, Alexei Nefedov, Christof Wöll, Timur K. Kim, Moritz Hoesch,, Felix R. Fischer,,, and Alexander Grüneis, II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, Köln, Germany St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, , Russia IFW Dresden, P.O. Box , Dresden D-01171, Germany Department of Chemistry, University of California at Berkeley, Tan Hall 680, Berkeley, CA 94720, USA Department of Physical and Chemical Sciences and SPIN-CNR, University of L Aquila, Via Vetoio 10, I Coppito, Italy Institut des Nanosciences de Paris, Sorbonne Universités-UPMC univ Paris 6 and CNRS-UMR 7588, 4 place Jussieu, F Paris, France #Peter Grünberg Institut (PGI-1) and Institute for Advanced Simulation (IAS-1), Forschungszentrum Jülich and JARA, D Jülich, Beamline, Synchrotron SOLEIL & Universite Paris-Saclay, L Orme des Merisiers, Saint Aubin-BP 48, Gif sur Yvette Cedex, France Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany Institut für Funktionelle Grenzflächen (IFG), Karlsruher Institut für Technologie (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, Germany Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, United Kingdom DESY Photon Science, Deutsches Elektronen-Synchrotron, Notkestrasse 85, Hamburg, Germany Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States Kavli Energy Nanosciences Institute at the University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States senkovskiy@ph2.uni-koeln.de; grueneis@ph2.uni-koeln.de 1

2 The effect of air on the B-7AGNRs Figure S1: (a) XPS spectra of the B 1s core level of B-7AGNRs/Au(788) after transfer into the UHV system using a glove bag under a flow of nitrogen gas. This transfer method does not guarantee complete protection from the moisture and oxygen, and as a result, new peak due to the Lewis acid-base reaction (B sites in B-7AGNRs act as a Lewis acid 1 ) appears at higher binding energy (188.8 ev). (b) Raman spectra of B-7AGNRs/Au(111) recorded at the same conditions as the spectrum in Fig. 4 in the main text, but after 10 minutes exposure to air. We observe reduction of the intensity and disappearance of characteristic Raman peaks (particularly RBLM). Because of the low signal, one can also observe the oxygen peak at 1555 cm 1, which appears due to the passage of the laser through the air before reaching the UHV system. Theoretical details Figure S2 shows our starting configurations for the B-7AGNR on (4 9) Au(111). In addition to the band structure depicted in Fig. 3 of the main manuscript in Figure S3 we present the projected density of states (PDOS) for the B-7AGNR on Au(111). Finally, it is important to analyze the bonding nature of the B-doped nanoribbon on Au(111). From a geometrical point of view, a key feature of this hybrid system is that the adsorbed nanoribbon is characterized by a geometrical corrugation of 0.5 Å arising from the difference in height between the regions around the B atoms at 2.6 Å and those between them at 3.1 Å. This geometrical corrugation of the B-doped 7AGNR on Au(111) is then directly reflected by the charge density difference 1 depicted in Figure S4. 1 The charge density difference ρ diff is defined as ρ diff = ρ tot (ρ nanoribbon ρ Au(111) ), where ρ tot is the charge density of the hybrid B-7AGNR/Au(111) system while ρ nanoribbon and ρ Au(111) represent the charge density of the freestanding B-7AGNR and the Au(111) surface, respectively, in their relaxed geometries taken from the interacting B-7AGNR/Au(111) system. 2

3 (a) (b) (c) Figure S2: (Color online) The starting configurations for B-7AGNR on (4 9) Au(111) with 2 boron atoms in (a) top, (b) hcp and (c) fcc adsorption positions. Note that the ground-state adsorption geometry corresponds to the (b) hcp configuration that is by 0.42 ev more stable than the (a) top one but almost degenerate with respect to the (c) fcc configuration. More specifically, one can observe a charge density accumulation in the pz atomic-like orbitals of the B atoms that occurs with a charge density depletion in the dz2 atomic-like orbitals of the Au atoms around the B ones. Furthermore, the charge density accumulation between these B and Au atoms clearly indicates the presence of a local chemical bond. This charge rearrangement at the nanoribbon-surface interface is also accompanied by a depletion in π system of B-doped 7AGNR and by a accumulation in the σ states of the nanoribbon due to a change from the sp2 -hybridization in the pristine 7AGNR to a sp3 -like one when adsorbed on Au(111). Overall, this behavior is similar to that observed for graphene 3 and hexagonal BN 4 on Ir(111) that revealed that on this surface graphene is physisorbed with a local chemical modulation. ARPES To detect the conduction band (CB) states of B-7AGNRs on Au(788) below the Fermi 1 level we performed ARPES measurements around kk = 0 at k = 1.6 A, which according to the calculations for freestanding system corresponds to the maximum photoemission intensity of the CB (Fig. S5). 3

4 PDOS (states/ev) 5.0 B-7AGNR σ B-7AGNR π Bσ Bπ E-EF (ev) 2.0 Figure S3: (Color online) The projected density of states (PDOS) for the σ (i.e., the sum of the in-plane px + py atomic orbitals) and π (i.e., out-of-plane pz ) contributions of the B-7AGNR on the (4 9) Au(111) substrate. As a key feature, at the Fermi energy EF the electronic states of the nanoribbon are dominated by the π-states originating from its C and H atoms. Note that PDOS was obtained for 4 k-points in the irreducible part of the Brillouin zone. Figure S4: (Color online) Lateral view of the charge density difference obtained for B-7AGNR on (4 9) Au(111) corresponding to a cut through a plane containing all 4 B atoms. The isosurface visualized in these plots corresponds to 0.01 e /A 3 with the charge accumulation plotted in yellow and the charge depletion in cyan. As a general feature, note (1) a charge density accumulation in the pz atomic-like orbitals of the B atoms and (2) charge depletion in the dz2 atomic-like orbitals of the Au atoms around the B ones. This figure has been generated using VESTA. 2 4

5 Figure S5: ARPES scans of (a) clean Au(788) and (b) B-7AGNRs on Au(788) along k at k = 1.6 Å 1. For B-7AGNRs/Au(788) system an additional intensity appears near the Fermi level. This intensity may be related to the partially occupied CB. Raman calculations Figure S6: Non-resonant Raman intensities of in-plane phonon modes for B-7AGNRs for all laser polarizations calculated using the Placzek approximation. 5 Here the dependence on the laser energy is neglected. Since the Raman scattering for GNRs actually depends upon the laser energy, 6 the calculated intensities are not reproduced in our experimental spectra. However, it is a good approximation to reveal Raman active modes, which may be observed by varying the laser energy and polarization. 5

6 Figure S7: The eigenvectors and the frequencies (cm 1 ) of the in-plane phonon modes of B-7AGNRs according to the calculations of non-resonant Raman spectra for all polarizations of the incident and scattered light. References 1. Kawai, S.; Saito, S.; Osumi, S.; Yamaguchi, S.; Foster, A. S.; Spijker, P.; Meyer, E. Atomically Controlled Substitutional Boron-Doping of Graphene Nanoribbons. Nat. Commun. 2015, 6, Momma, K.; Izumi, F. VESTA 3 for Three-Dimensional Visualization of Crystal, Volumetric and Morphology Data. J. Appl. Cryst. 2011, 44, Busse, C.; Lazic, P.; Djemour, R.; Coraux, J.; Gerber, T.; Atodiresei, N.; Caciuc, V.; 6

7 Brako, R.; N Diaye, A. T.; Blügel, S.; Zegenhagen, J.; Michely, T. Graphene on Ir(111): Physisorption with Chemical Modulation. Phys. Rev. Lett. 2011, 107, zum Hagen, F. H. F.; Zimmermann, D. M.; Silva, C. C.; Schlueter, C.; Atodiresei, N.; Jolie, W.; Martínez-Galera, A. J.; Dombrowski, D.; Schröder, U. A.; Will, M.; Lazić, P.; Caciuc, V.; Blügel, S.; Lee, T.-L.; Michely, T.; Busse, C. Structure and Growth of Hexagonal Boron Nitride on Ir(111). ACS Nano 2016, 10, Lazzeri, M.; Mauri, F. First-Principles Calculation of Vibrational Raman Spectra in Large Systems: Signature of Small Rings in Crystalline SiO 2. Phys. Rev. Lett. 2003, 90, Talirz, L.; Sde, H.; Dumslaff, T.; Wang, S.; Sanchez-Valencia, J. R.; Liu, J.; Shinde, P.; Pignedoli, C. A.; Liang, L.; Meunier, V.; Plumb, N. C.; Shi, M.; Feng, X.; Narita, A.; Mllen, K.; Fasel, R.; Ruffieux, P. On-Surface Synthesis and Characterization of 9-Atom Wide Armchair Graphene Nanoribbons. ACS Nano 2017, 11,