Electronic properties of graphene from tight-binding simulations

Thumbnail Image
Files
isbn9789526058153.pdf (2.97 MB)
Journal Title
Journal ISSN
Volume Title
School of Science | Doctoral thesis (article-based) | Defence date: 2014-09-12
Checking the digitized thesis and permission for publishing
Instructions for the author
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Author
Date
2014
Department
Teknillisen fysiikan laitos
Department of Applied Physics
Major/Subject
Mcode
Degree programme
Language
en
Pages
60 + app. 110
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 122/2014
Abstract
Graphene is an effectively two-dimensional semimetallic material consisting of a sheet of carbon atoms arranged in a hexagonal lattice. Due to its high electron mobility and special electronic properties, it is considered to be a promising candidate for various future electronic applications. Freestanding graphene was discovered as late as in 2004, but since then it has become the focus of numerous studies, sparking not only scientific but also significant commercial interest. Realizing the potential of the material requires both theoretical, numerical, and experimental studies. An important computational model for studying the electronic properties of graphene is the so-called tight-binding (TB) model. In the TB model, the charge carriers of a material are described using effective parameters, which can be either derived from more complex models or fitted to experimental or computational results. In this Thesis, the TB model was used to study both the local density of states (LDOS) of graphene as well as electronic transport in graphene. Simulating the LDOS of graphene is important, since it may be more or less directly measured using scanning tunneling microscopy (STM), and is thus extremely helpful for characterizing the properties of nanometer-sized graphene samples. The results presented in this Thesis, which show good agreement between simulations and STM measurements, help to determine the electronic structure of graphene quantum dots on various substrates. Simulations of electronic transport aid in making graphene useful for semiconductor applications. Graphene may be turned semiconducting by various means, such as by cutting it into ribbons or by adding disorder. In this Thesis, it was showed how scaling theory can be utilized to obtain the conductance of a mesoscopically sized disordered graphene device using first-principles-based results and how the localization length of the charge carriers can be obtained effectively using the so-called Kubo-Greenwood method. The results aid in interpreting experimental conductance measurements and in estimating how strong disorder is required to turn graphene into an effective semiconductor. 

Grafen är ett effektivt tvådimensionellt material som består av kolatomer arrangerade i ett hexagonalt gitter. Tack vare speciella elektroniska egenskaper, som laddningsbärarnas höga mobilitet, anses grafen vara en lovande kandidat för framtida elektroniska tillämpningar. Fristående grafen upptäktes så sent som 2004, men sedan dess har materialet blivit fokus för otaliga studier. Förutom ett vetenskapligt intresse, har grafen under den senaste tiden också skapat ett betydande kommersiellt intresse. För att förverkliga materialets potential krävs både teoretiska, numeriska och experimentella studier. Den så kallade starkbindningsmodellen är en viktig numerisk modell för simulering av grafen. I starkbindningsmodellen beskrivs laddningsbärarna med hjälp av effektiva parametrar, som kan härledas med hjälp av mera komplexa numeriska metoder eller genom att anpassa dem till experimentella resultat. I denna avhandling används starkbindningsmodellen till att simulera både lokal tillståndstäthet samt elektronisk transport i grafen. Att simulera lokal tillståndstäthet är viktigt, eftersom den kan mer eller mindre direkt mätas genom sveptunnelmikroskopi. Därmed är metoden extremt användbar för att karakterisera nanometerstora grafenflagor. Resultaten som presenteras i denna avhandling visar att simuleringarna stämmer bra överens med experimentella resultat. Simuleringar av elektronisk transport kan hjälpa med att få grafen användbart för halvledarapplikationer. Grafen kan fås till att bli en halvledare med olika metoder, till exempel genom att skära den i strimlor eller lägga till oordning i det annars perfekta gittret. I denna avhandling visas hur man kan använda ab initio -baserade metoder för att beräkna grafens konduktans och hur den så kallade Kubo-Greenwood-metoden kan användas till att beräkna laddningsbärarnas lokaliseringslängd. Dessa resultat hjälper att tolka experimentella mätresultat och att estimera hur stark oordning krävs för att ändra grafen till en effektiv halvledare.
Description
Supervising professor
Nieminen, Risto, Aalto Distinguished Prof., Aalto University, Department of Applied Physics, Finland
Thesis advisor
Harju, Ari, Adjunct Prof., Aalto University, Department of Applied Physics, Finland
Keywords
graphene, tight-binding, electronic transport, scanning tunneling microscopy, grafen, starkbindning, elektronisk transport, sveptunnelmikroskopi
Other note
Parts
  • [Publication 1]: Y. Hancock, A. Uppstu, K. Saloriutta, A. Harju and M. J. Puska. Generalized tight-binding transport model for graphene nanoribbon-based systems. Physical Review B, 81, 245402, 2010.
    DOI: 10.1103/PhysRevB.81.245402. View at publisher
  • [Publication 2]: J. van der Lit, M. P. Boneschanscher, D. Vanmaekelbergh, M. Ijäs, A. Uppstu, M. Ervasti, A. Harju, P. Liljeroth and I. Swart. Suppression of electron-vibron coupling in graphene nanoribbons contacted via a single atom. Nature Communications, 4, 2023, 2013.
    DOI: 10.1038/ncomms3023. View at publisher
  • [Publication 3]: M. Ijäs, M. Ervasti, A. Uppstu, P. Liljeroth, J. van der Lit, I. Swart, and A. Harju. Electronic states in finite graphene nanoribbons: Effect of charging and defects. Physical Review B, 88, 075429, 2013.
    DOI: 10.1103/PhysRevB.88.075429. View at publisher
  • [Publication 4]: S. K. Hämäläinen, Z. Sun, M. P. Boneschanscher, A. Uppstu, M. Ijäs, A. Harju, D. Vanmaekelbergh, and Peter Liljeroth. Quantum-Confined Electronic States in Atomically Well-Defined Graphene Nanostructures. Physical Review Letters, 107, 236803, 2011.
    DOI: 10.1103/PhysRevLett.107.236803. View at publisher
  • [Publication 5]: R. Drost, A. Uppstu, F. Schulz, S. K. Hämäläinen, M. Ervasti, A. Harju, and P. Liljeroth. Electronic States at the Graphene - Hexagonal Boron Nitride Zigzag Interface. Accepted for publication in Nano Letters, July 2014.
    DOI: 10.1021/nl501895h. View at publisher
  • [Publication 6]: Z. Fan, A. Uppstu, T. Siro and A. Harju. Efficient linear-scaling quantum transport calculations on graphics processing units and applications on electron transport in graphene. Computer Physics Communications, 185, 28, 2014.
    DOI: 10.1016/j.cpc.2013.08.009. View at publisher
  • [Publication 7]: M. Oksanen, A. Uppstu, A. Laaksonen, D. J. Cox, M. F. Craciun, S. Russo, A. Harju and P. Hakonen. Single-mode and multimode Fabry-Perot interference in suspended graphene. Physical Review B, 89, 121414(R), 2013.
    DOI: 10.1103/PhysRevB.89.121414. View at publisher
  • [Publication 8]: A. Uppstu, Z. Fan and A. Harju. Obtaining localization properties efficiently using the Kubo-Greenwood formalism. Physical Review B, 89, 075420, 2014.
    DOI: 10.1103/PhysRevB.89.075420. View at publisher
  • [Publication 9]: A. Uppstu, K. Saloriutta, A. Harju, M. Puska and A.-P. Jauho. Electronic transport in graphene-based structures: An effective cross-section approach. Physical Review B, 85, 041401(R), 2012.
    DOI: 10.1103/PhysRevB.85.041401. View at publisher
  • [Publication 10]: K. Saloriutta, A. Uppstu, A. Harju and M. J. Puska. Ab initio transport fingerprints for resonant scattering in graphene. Physical Review B, 86, 235417, 2012.
    DOI: 10.1103/PhysRevB.86.235417. View at publisher
  • [Publication 11]: A. Uppstu and A. Harju. High-field magnetoresistance revealing scattering mechanisms in graphene. Physical Review B, 86, 201409(R), 2012.
    DOI: 10.1103/PhysRevB.86.201409. View at publisher
  • [Publication 12]: Y. Hancock, K. Saloriutta, A. Uppstu, A. Harju and M. J. Puska. Spin-Dependence in Asymmetric, V-Shaped-Notched Graphene Nanoribbons. Journal of Low Temperature Physics, 153, 393, 2008.
    DOI: 10.1007/s10909-008-9838-y. View at publisher
Citation
Permanent link to this item
https://urn.fi/URN:ISBN:978-952-60-5815-3
Collections
[diss] Perustieteiden korkeakoulu / SCI