Change search
ReferencesLink to record
Permanent link

Direct link
Electronic transport through zigzag/armchair graphene nanoribbon heterojunctions
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.ORCID iD: 0000-0003-0007-0394
2012 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 24, no 9, 095801- p.Article in journal (Refereed) Published
Abstract [en]

The electronic transport properties of a graphene nanoribbon (GNR) are known to be sensitive to its width, edges and defects. We investigate the electronic transport properties of a graphene nanoribbon heterojunction constructed by fusing a zigzag and an armchair graphene nanoribbon (zGNR/aGNR) side by side. First principles results reveal that the heterojunction can be either metallic or semiconducting, depending on the width of the nanoribbons. Intrinsic rectification behaviors have been observed, which are largely sensitive to the connection length between the zGNR and aGNR. The microscopic origins of the rectification behavior have been revealed. We find that the carrier type can alter from electrons to holes with the bias voltage changing from negative to positive; the asymmetrical transmission spectra of electrons and holes induced by the interface defects directly results in the rectification behavior. The results suggest that any methods which can enhance the asymmetry of the transmission spectra between holes and electrons could be used to improve the rectification behavior in the zGNR/aGNR heterojunction. Our findings could be useful for designing graphene based electronic devices.

Place, publisher, year, edition, pages
2012. Vol. 24, no 9, 095801- p.
Keyword [en]
National Category
Condensed Matter Physics
URN: urn:nbn:se:kth:diva-91600DOI: 10.1088/0953-8984/24/9/095801ISI: 000300641000022ScopusID: 2-s2.0-84857241091OAI: diva2:513422
QC 20120402Available from: 2012-04-02 Created: 2012-03-19 Last updated: 2013-01-23Bibliographically approved
In thesis
1. Electron and Spin Transport in Graphene-Based Nanodevices
Open this publication in new window or tab >>Electron and Spin Transport in Graphene-Based Nanodevices
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is devoted to the multi-scale modeling of electron and spin transport in graphene-based nanodevices. Several devices with fascinating structures and attractive properties have been designed by means of state-of-the-art computational methods, which include ab-initio molecular dynamics (MD) simulations for the geometry, density functional theory (DFT) for the electronic structure, and non-equilibrium Green’s functions (NEGF) for carriers transport properties.

Poly-crystalline graphenes offer ample opportunities to make devices with desirable properties. We have systematically studied a type of poly-crystalline graphene constructed by zigzag and armchair graphene nanoribbons (ZGNR and AGNR). It is found that the choice of the supercells in modeling with periodic boundary conditions (PBC) has strong implications on the electronic and magnetic properties of such hybrid systems. A model with minimal lattice mismatch is obtained, which could be regarded as the most appropriate model for hybrid GNRs. With this model, it is revealed that the hybrid GNR is of ferromagnetism with a high Curie temperature. We have then designed armchair/zigzag graphene nanoribbon heterojunctions (AGNR|ZGNR) with a well-defined conductance oscillation and rectification behavior. It is shown that the resonance or nonresonance of the frontier orbitals between AGNR and ZGNR is the source of the oscillation and the asymmetric structure is the root of the rectification. A high rectification ratio can be achieved by tuning the width of ZGNR to enhance the asymmetric character of transmission function and to minimize the backward current.

The electron transport properties of graphene can be modified by hydrogenation strips (HSs) formed from the absorbed hydrogen atoms. We have designed a new graphene nanoribbon that has zigzag-edged HSs placed at its middle region. It is found that the HS can electrically separate the GNR into sub-GNRs and each HS introduces two spin-polarized conducting edge-like states around the Fermi level. This leads to a significant enhancement of the conductance and the spinpolarization. We have also found that by introducing embedding a short sp3-edged section into the sp2-edged ZGNRs or a short sp2-edged section into the sp3-edged ZGNRs, the orbital symmetry mismatch between these two sections can induce the opening of the conductance energy gap in ZGNRs over a wide energy region. This simple strategy explains many unexplained experimental results and offers a simple strategy to design GNRs with a proper energy gap.

We have also carefully examined the spin-polarization of chiral GNRs with reconstructed (2,1)-edges. It is found that the unsaturated (2,1)-edged chiral GNRs can possess strong current polarizations (nearly 100%) and a striking negative differential resistance (NDR) behavior.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xii, 85 p.
Trita-BIO-Report, ISSN 1654-2312 ; 2013:3
National Category
Theoretical Chemistry
Research subject
SRA - Transport
urn:nbn:se:kth:diva-116568 (URN)978-91-7501-622-1 (ISBN)
Public defence
2013-02-18, FA32, AlbaNova Universitetscentrum, Roslagstullsbacken, Stockholm, 15:02 (English)
TrenOp, Transport Research Environment with Novel Perspectives

QC 20130123

Available from: 2013-01-23 Created: 2013-01-21 Last updated: 2013-01-23Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Li, Xiao-FeiLuo, Yi
By organisation
Theoretical Chemistry and Biology
In the same journal
Journal of Physics: Condensed Matter
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 61 hits
ReferencesLink to record
Permanent link

Direct link