Theoretical study of heterostructures based on two-dimensional materials.

Name: Everson dos Santos Souza
Type: PhD thesis
Publication date: 26/10/2018
Advisor:

Namesort descending Role
Wanderlã Luis Scopel Advisor *

Examining board:

Namesort descending Role
Antônio Canal Neto Internal Examiner *
Edson Passamani Caetano Internal Examiner *
Fabio Arthur Leão de Souza External Examiner *
Jorge Luis Gonzalez Alfonso Internal Examiner *
Rodrigo Garcia Amorim External Examiner *
Wanderlã Luis Scopel Advisor *

Summary: This thesis presents a theoretical investigation of two heterostructures based on 2Dmaterials: (i) substitutionally cobalt-doped graphene bilayer (Co/GBL) on the Cu(111) surface [Co/GBL/Cu(111)] and (ii) a graphene-MoSe2 in-plane lateral heterostructure. The properties of these systems were studied through simulations of X-ray Absorption Near-Edge Structure (XANES) spectroscopy and/or electronic structure methods based on Density Functional Theory (DFT). Our results indicate a magnetic switching phenomenon in the Co/GBL/Cu(111) system, that is, the capability of switch on and off the magnetization of the Co-doped graphene bilayer on Cu(111). This phenomenon is based on control of Co/GBL ↔ Cu(111) electronic charge transfer by an external electric field; which adjust the electronic occupation of the Co-3dz2 and C-2pz orbitals near the Fermi level and, as a consequence, the magnetic properties of Co-doped graphene bilayer. In the graphene-MoSe2 system, based on energetic stability criteria for different structural models, we found that zigzag and Klein edges of graphene can serve as a nucleation site for the formation of energetically stable graphene-MoSe2 interfaces, WHERE different structural morphologies are possible. For the energetically more likely interface geometries, were carried out additional characterizations of electronic and structural properties through simulations of XANES spectroscopy at the C K-edge. The analysis of the absorption spectra indicated the feasibility of identifying
different interface geometries in the graphene-MoSe2 hybrid system from XANES spectroscopy measurements. The results also revealed that the local electronic and magnetic properties depend on the interface atomic structure. In particular, we found half-metallicity characteristic (conduction in only one of the two spin channels) at certain interface geometries, which has great potential for spintronics applications.

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