Universität zu Köln

Zhu, Jingyi, German, Raphael, Senkovskiy, Boris V. ORCID: 0000-0003-1443-6780, Haberer, Danny, Fischer, Felix R., Grueneis, Alexander and van Loosdrecht, Paul H. M. (2018). Exciton and phonon dynamics in highly aligned 7-atom wide armchair graphene nanoribbons as seen by time-resolved spontaneous Raman scattering. Nanoscale, 10 (37). S. 17975 - 17983. CAMBRIDGE: ROYAL SOC CHEMISTRY. ISSN 2040-3372

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Abstract

The opening of a band gap in graphene nanoribbons induces novel optical and electronic properties, strongly enhancing their application potential in nanoscale devices. Knowledge of the optical excitations and associated relaxation dynamics are essential for developing and optimizing device designs and functionality. Here we report on the optical excitations and associated relaxation dynamics in surface aligned 7-atom wide armchair graphene nanoribbons as seen by time-resolved spontaneous Stokes and anti-Stokes Raman scattering spectroscopy. On the anti-Stokes side we observe an optically induced increase of the scattering intensity of the Raman active optical phonons which we assign to changes in the optical phonon populations. The optical phonon population decays with a lifetime of similar to 2 ps, indicating an efficient optical-acoustic phonon cooling mechanism. On the Stokes side we observe a substantial decrease of the phonon peak intensities which we relate to the dynamics of the optically induced exciton population. The exciton population shows a multi-exponential relaxation on the hundreds of ps time scale and is independent of the excitation intensity, indicating that exciton-exciton annihilation processes are not important and the exsistence of dark and trapped exciton states. Our results shed light on the optically induced phonon and exciton dynamics in surface aligned armchair graphene nanoribbons and demonstrate that time-resolved spontaneous Raman scattering spectroscopy is a powerful method for exploring quasi-particle dynamics in low dimensional materials.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Zhu, Jingyi UNSPECIFIED UNSPECIFIED UNSPECIFIED German, Raphael UNSPECIFIED UNSPECIFIED UNSPECIFIED Senkovskiy, Boris V. UNSPECIFIED orcid.org/0000-0003-1443-6780 UNSPECIFIED Haberer, Danny UNSPECIFIED UNSPECIFIED UNSPECIFIED Fischer, Felix R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Grueneis, Alexander UNSPECIFIED UNSPECIFIED UNSPECIFIED van Loosdrecht, Paul H. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-169520
DOI:	10.1039/c8nr05950k
Journal or Publication Title:	Nanoscale
Volume:	10
Number:	37
Page Range:	S. 17975 - 17983
Date:	2018
Publisher:	ROYAL SOC CHEMISTRY
Place of Publication:	CAMBRIDGE
ISSN:	2040-3372
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics II
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language WALLED CARBON NANOTUBES; ELECTRONIC-STRUCTURE; LO PHONONS; SPECTROSCOPY; PROBE; PHOTOCONDUCTIVITY; ANNIHILATION; SPECTRA; DIAMOND; FILMS Multiple languages Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/16952