MRS Meetings and Events

 

EL05.04.14 2024 MRS Spring Meeting

Design of Electronic Structure and Transport in S-Doped Few-Layer Graphene

When and Where

Apr 23, 2024
5:00pm - 7:00pm

Flex Hall C, Level 2, Summit

Presenter

Co-Author(s)

Armin Sahinovic1,Paolo Fortugno1,Nicholas Wilson2,Hartmut Wiggers1,Rossitza Pentcheva1

Universität Duisburg-Essen1,University of Waterloo2

Abstract

Armin Sahinovic1,Paolo Fortugno1,Nicholas Wilson2,Hartmut Wiggers1,Rossitza Pentcheva1

Universität Duisburg-Essen1,University of Waterloo2
Compared to a single sheet of graphene, few-layer graphene (FLG) shows additional degrees of freedom dependent on the number of layers and interlayer interactions, leading to a unique combination of surface and bulk-like states [1]. While the properties N- and S-doped monolayer graphene have been addressed previously [2,3], the interplay between defects, doping and the layered structure of FLG are largely unknown.<br/><br/>Based on density functional theory calculations we explore the effect of sulfur doping and vacancies on FLG. The formation energies and electronic structure of different defect types are assessed as a function of concentration and distribution. Direct incorporation of S into the lattice is associated with a high formation energy, which can be reduced by the creation of additional vacancies to bond the sulfur dopands. The most energetically favorable defect configuration is a hypervalent S bonding state in the single vacancy system. While this defect opens a small gap of 0.151 eV in the monolayer system, the multilayer system maintains a Dirac point with linear dispersion. Intriguingly, doped monolayer double vacancies promote weak ferromagnetism not present in the multilayer counterpart. We find a strong layer dependence of the doping allowing for a design of the electronic structure. The surface layers are most prone to doping, giving rise to complex buckling, resulting in a modified band structure and a band gap opening at certain doping concentrations not found for doping in the inner layers. Moreover, doping just below the surface layer allows to preserve the linear dispersion of the Dirac cone in the surface layer.<br/><br/>Initial experimental work on the synthesis of S-doped few-layer graphene (FLG) in a microwave plasma reactor confirms the incorporation of sulfur into the graphene structure and shows that electronic conductivity can be increased by up to 50% compared to undoped FLG. This is consistent with the transport properties, obtained via the BoltZtrap2 code [4], revealing that S doping systematically enhances the conductivity in single-layer and few-layer graphene. Charge-transfer from the doped to the surrounding pristine layers leads to indirect doping, additionally enhancing the transport in FLG compared to the monolayer case. In contrast, when FLG is doped in the surface layers the charge transfer is impeded by the buckling and local charge accommodation, thus a smaller increase of conductivity is found. In this work we show that tailoring the incorporation of S into FLG enables one to modify selectively the electronic structure in view of energy conversion and storage applications e.g. as a battery material, or in catalysis (oxygen reduction).<br/><br/>We acknowledge gratefully funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - IRTG 2803 - 461605777 and support of the Natural Sciences and Engineering Council of Canada (NSERC), [CREATE 565360]. Computing time was granted by the Center for Computational Sciences and Simulation of the University of Duisburg-Essen (DFG Grants No.~INST 20876/209-1 FUGG and No.~INST 20876/243-1 FUGG).<br/><br/>[1] F. Mak <i>et al.</i>, Proc. Natl. Acad. Sci. 107, 14999 (2010)<br/>[2] S. Fiori <i>et al.</i>, Carbon 171, 704 (2021)<br/>[3] J.H Lee <i>et al.,</i> Nanomaterials, 9, 268 (2019)<br/>[4] G. K.H. Madsen <i>et al.</i>, Comput. Phys. Commun., 231, 140 (2018)

Keywords

defects | graphene

Symposium Organizers

Silvija Gradecak, National University of Singapore
Lain-Jong Li, The University of Hong Kong
Iuliana Radu, TSMC Taiwan
John Sudijono, Applied Materials, Inc.

Symposium Support

Gold
Applied Materials

Session Chairs

Lain-Jong Li
John Sudijono

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