Brasil

Dados do Trabalhos de Conclusão

UNIVERSIDADE FEDERAL DO ABC
NANOCIÊNCIAS E MATERIAIS AVANÇADOS (33144010006P9)
Electronic and Transport Properties of Graphene Nanoribbons with Adsorbed Transition Metal Impurities: Spin-Orbit Interaction
WUDMIR YUDY ROJAS VERASTEGUI
DISSERTAÇÃO
07/11/2013

Graphene is a truly two dimensional material - a single carbon atom thick system. Its exceptional electronic properties combined with its weak spin-orbit (SO) interaction - which lead to large spin relaxation length - make it a very interesting material for studying spin transport. Therefore, graphene is considered as a promising candidate for spintronics applications - use of the electron spin degree of freedom instead of its charge - where one can exploit graphene unique electronic properties. However, graphene lacks of energy gap which is essential for the design of digital transistors. This problem can be solved by cutting graphene into strips known as graphene nanoribbons (GNRs) since the band gap depends on its width. Unfortunately, experimental techniques employed to synthesize these GNRs typically include undesired metal atom as impurities which can lead to the introduction of SO and consequently to signi cant spin- ip processes in conduction electrons. Our work concerns a rst principles study of electronic structure and spin-dependent electron transport of Ni and Ir adatoms on armchair graphene nanoribbon taking into account the SO interaction. We have used a combination of density functional theory (DFT) and non-equilibrium Green's function (NEGFs) methods to carry out those calculations. Moreover, using a recursive NEGFs we also consider a large number of Ni impurities randomly distributed along the AGNR to study transport properties of realistic devices. Finally, we performed the spin relaxation length calculations at speci c energy regions of the disordered system. We found Ni and Ir adatoms prefer hollow sites close to the edges of the AGNR and also we observed SO has induced splitting of the bands close to the Fermi energy, the intensity of those splitting, clearly depend on the adsorption position of the adatoms. We found that single defect and disordered structures exhibit the highest transmission coecients - both spin conserving (SC) and spin-ip (SF) - when the most stable adsorption system is considered. Moreover, we observed the SC current of the Ni single defect systems is rather higher than the Ir single defect system and conversely the SF current is smaller. Furthermore, from our Polarization (P) results of the disordered systems at speci c energy regions, we found that some energy regions are well behaved - P tends to zero when the device length increase - whereas the others exhibit unusual trends where further calculations is needed to get a better understanding. Finally, we found small spin relaxation lengths - for those well behaved energy regions - compared with Graphene's spin relaxation length.

.
-
-
1
138
INGLES
UNIVERSIDADE FEDERAL DO ABC

Contexto

NANOCIÊNCIAS E MATERIAIS AVANÇADOS
SIMULAÇÃO E MODELAGEM
-

Banca Examinadora

ALEXANDRE REILY ROCHA
Sim
Nome Categoria
CEDRIC ROCHA LEAO Docente
ROBERTO HIROKI MIWA Participante Externo

Financiadores

Financiador - Programa Fomento Número de Meses
UNIVERSIDADE FEDERAL DO ABC - Pró reitoria de Pós Graduação 5
CONS NAC DE DESENVOLVIMENTO CIENTIFICO E TECNOLOGICO - Bolsa de Mestrado no País GM 4
FUND COORD DE APERFEICOAMENTO DE PESSOAL DE NIVEL SUP - Programa de Demanda Social 15

Vínculo

-
-
-
Não