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Morphological imperfections of epitaxial graphene: from a hindrance to the generation of new photo-responses in the visible domain

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posted on 20.01.2020 by Amira Ben Gouider Trabelsi, Feodor Kusmartsev, Marat Gaifullin, Derek Michael Forrester, Anna Kusmartseva, M. Oueslati
We report the discovery of remarkable photo-physical phenomena with characteristics unique to epitaxial graphene grown on 6H-SiC (000-1). Surprisingly, the graphene electrical resistance increases under light illumination in contrast to conventional materials where it normally decreases. The resistance shows logarithmic temperature dependences which may be attributed to an Altshuler-Aronov effect. We show that the photoresistance depends on the frequency of the irradiating light, with three lasers (red, green, and violet) used to demonstrate the phenomenon. The counterintuitive rise of the positive photoresistance may be attributed to a creation of trapped charges upon irradiation. We argue that the origin of the photoresistance is related to the texture formed by graphene flakes. The photovoltage also exists and increases with light intensity. However, its value saturates quickly with irradiation and does not change in time. The saturation of the photovoltage may be associated with the formation of a quasi-equilibrium state of the excited electrons and holes associated with a charge redistribution between the graphene and SiC substrate. The obtained physical picture is in agreement with the photoresistance measurements: X-Ray photoelectron spectrometry "XPS", atomic force microscopy "AFM", Raman spectroscopy and the magnetic dependence of photo resistance decay measurements. We also observed non-decaying photoresistance and linear magnetoresistance in magnetic fields up to 1 T. We argue that this is due to topological phases, spontaneously induced by persistent current formation within graphene flake edges by magnetic fields.

Funding

The authors thank the EPSRC for funding under KTA grant – “Developing prototypes and a commercial strategy for nanoblade technology”.

History

School

  • Science

Department

  • Physics

Published in

Nanoscale

Citation

BEN GOUIDER TRABELSI, A. ... et al, 2017. Morphological imperfections of epitaxial graphene: from a hindrance to the generation of new photo-responses in the visible domain. Nanoscale, 9 (32), pp. 11463-11474.

Publisher

Royal Society of Chemistry

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution 3.0 Unported (CC BY 3.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/by/3.0/

Acceptance date

07/05/2017

Publication date

2017-05-11

Notes

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Supplementary data for this article is available in the Loughborough Data Repository at doi:10.17028/rd.lboro.4986233.

ISSN

2040-3364

eISSN

2040-3372

Language

en

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