ArchivIA Università degli Studi di Catania
 

ArchivIA - Archivio istituzionale dell'Universita' di Catania >
Tesi >
Tesi di dottorato >
Area 01 - Scienze matematiche e informatiche >

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10761/3683

Data: 27-mar-2017
Autori: Coco, Marco
Titolo: Monte Carlo study of charge and phonon transport in graphene
Abstract: In this thesis, we investigate charge transport in graphene. Graphene is one of the most important new materials with a wide range of properties, rarely together in the same material, and it is the ideal candidate for future electronic devices. The dynamics of electrons in the conduction band is analyzed, by considering values of Fermi levels high enough to neglect the dynamics in the valence band. This is equivalent to a n-type doping for traditional semiconductors. Degeneracy effects are very important in graphene and then it becomes mandatory to consistently include the Pauli exclusion principle. We develop a new Direct Simulation Monte Carlo (DSMC) procedure to solve the Boltzmann transport equation, that properly takes into account the Pauli principle. For a cross-validation of the results, we also solve the Boltzmann equation in a deterministic way by using the Discontinuous Galerkin method. The agreement of the results is excellent. A comparison of the new DSMC results with those obtained by means of well established hydrodynamical models are presented as well, and again the agreement is very good. This new approach is applied to study the transport properties in suspended monolayer graphene and then in a layer of graphene on different substrates, obtaining the expected results as the degradation of mobilities. Regarding phonon transport, we investigate the thermal effects in a suspended monolayer graphene due to the charge flow under an applied electric field. A complete model is considered, with all the phonon branches, both in-plane and out of plane ones. Moreover, we describe the phonon populations without any approximation of the distribution with an equivalent Bose-Einstein one. The distribution is built by means of the intermediate results arising from the new DSMC, by counting the number of the emission and absorption processes due to the interaction between electrons and phonons. The phonon-phonon interaction is treated in a standard way with a BGK approximation. We are able to determine the increase of the temperature due to the charge flow and to predict its raise for any values of electric fields and Fermi energies. Moreover, it is shown that the inclusion of a complete phonon model leads to a lower heating effect with respect to other simplified models.
InArea 01 - Scienze matematiche e informatiche

Full text:

File Descrizione DimensioniFormatoConsultabilità
CCOMRC85E08C351C-Marco_Coco_PhD_Thesis.pdfPhD Thesis Marco Coco25,29 MBAdobe PDFVisualizza/apri


Tutti i documenti archiviati in ArchivIA sono protetti da copyright. Tutti i diritti riservati.


Segnala questo record su
Del.icio.us

Citeulike

Connotea

Facebook

Stumble it!

reddit


 

  Browser supportati Firefox 3+, Internet Explorer 7+, Google Chrome, Safari

ICT Support, development & maintenance are provided by the AePIC team @ CILEA. Powered on DSpace Software.