Defesa de Tese de Doutorado #397 – Gilberto Rodrigues da Silva Junior – 29/04/2022
Interplay of crystalline strain and electronic properties in topological insulators and semiconductor thin films grown by Molecular Beam Epitaxy
Autor: Gilberto Rodrigues da Silva Junior
Banca Examinadora
Prof. Ângelo Malachias de Souza (Orientador)
DF/UFMG
Prof. Ricardo Wagner Nunes
DF/UFMG
Myriano Henriques de Oliveira Junior
DF/UFMG
Profa. Beatriz Diaz Moreno
Canadian Light Source
Prof. Matheus Josué de Souza Matos
DF/UFOP
Orientação
Prof. Ângelo Malachias de Souza (Orientador)
DF/UFMG
Resumo do Trabalho
In this thesis, we studied three different types of samples, all obtained by the molecular beam epitaxy technique (MBE). In the first set of samples, epitaxial layers of Silicon-Germanium (SiGe) after the Germanium condensation process were studied. Our results show that, starting from a low concentration Si0.92Ge0.08 layer grown on top of a crystalline Si (001) on SOI substrates, we can reach desirable Ge concentration with a non-monotonic interplay on in-plane and out-of-plane strain. The Ge concentration and SiGe layer thickness was evaluated by a combination of secondary ion mass spectroscopy (SIMS) and synchotron X-ray measurements (diffraction and reflectivity).
In the second set of samples, we have studied the first stages of the heteroepitaxial growth of layered bismuth telluride (Bi2Te3) topological insulator on top of highly oriented pyrolitic graphite (HOPG). Samples were investigated by atomic force microscopy (AFM), synchrotron
x-ray diffraction (XRD), and micro-Raman spectroscopy. AFM images show hexagonal/triangular flat islands with exposed HOPG areas for the low coverage regime. The existence of pseudomorphic strain at the initial Bi2Te3 layers was retrieved by both XRD and Raman spectroscopy. Finally, in the third set of samples, we studied the morphological and electronic properties of Bi2Te3 layers doped with Europium (Eu) atoms. Bi2Te3 layers were deposited on a Barium fluoride (BaF2) substrate and characterized by atomic force microscopy (AFM) and scanning tunneling microscopy/spectroscopy (STM/STS) techniques. Our results indicate regions along the sample surface in which the signature of the topological surface states disappears as well as the existence of a second crystalline phase.
Tópico: Defesa de Tese – Gilberto Rodrigues da Silva Junior
Hora: 29 abr. 2022 02:00 da tarde São Paulo
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