Universität zu Köln

Senkovskiy, Boris V., Usachov, Dmitry Yu., Fedorov, Alexander V., Haberer, Danny, Ehlen, Niels, Fischer, Felix R. and Gruneis, Alexander (2018). Finding the hidden valence band of N=7 armchair graphene nanoribbons with angle-resolved photoemission spectroscopy. 2D Materials. IOP Publishing. ISSN 2053-1583

Preview

PDF HiddenBand_2DMaterials_revised2.pdf Download (4MB)

Abstract

To understand the optical and transport properties of graphene nanoribbons, an unambiguous determination of their electronic band structure is needed. In this work we demonstrate that the photoemission intensity of each valence sub-band, formed due to the quantum confinement in quasi-one-dimensional (1D) graphene nanoribbons, is a peaked function of the two-dimensional (2D) momentum. We resolve the long-standing discrepancy regarding the valence band effective mass (m*VB) of armchair graphene nanoribbons with a width of N=7 carbon atoms (7-AGNRs). In particular, angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy report m*VB ~ 0.2 and ~ 0.4 of the free electron mass (me), respectively. ARPES mapping in the full 2D momentum space identifies the experimental conditions for obtaining a large intensity for each of the three highest valence 1D sub-bands. Our detail map reveals that previous ARPES experiments have incorrectly assigned the second sub-band as the frontier one. The correct frontier valence sub-band for 7-AGNRs is only visible in a narrow range of emission angles. For this band we obtain an ARPES derived effective mass of 0.4 me, a charge carrier velocity in the linear part of the band of 0.63 X 10^6 m/s and an energy separation of only ~ 60 meV to the second sub-band. Our results are of importance not only for the growing research field of graphene nanoribbons but also for the community, which studies quantum confined systems.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Senkovskiy, Boris V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Usachov, Dmitry Yu. UNSPECIFIED UNSPECIFIED UNSPECIFIED Fedorov, Alexander V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Haberer, Danny UNSPECIFIED UNSPECIFIED UNSPECIFIED Ehlen, Niels UNSPECIFIED UNSPECIFIED UNSPECIFIED Fischer, Felix R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gruneis, Alexander UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-81664
DOI:	doi.org/10.1088/2053-1583/aabb70
Journal or Publication Title:	2D Materials
Date:	4 April 2018
Publisher:	IOP Publishing
ISSN:	2053-1583
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics II
Subjects:	Natural sciences and mathematics Physics
Funders:	ERC grant no. 648589 ’SUPER-2D’, GR 3708/2-1, Saint Petersburg State University research Grant No. 11.65.42.2017, U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award no. DE-SC0010409, Center for Energy Efficient Electronics Science NSF Award 0939514, European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement n.312284 (CALIPSO)
Projects:	DFG project CRC 1238 (project A1)
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/8166