Banca de DEFESA: ALEXANDRE OLIVIERI KRAUS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : ALEXANDRE OLIVIERI KRAUS
DATA : 25/06/2021
HORA: 14:00
LOCAL: Online
TÍTULO:

NaNbO₃ Vacancy Defects and Thin-film Biaxial Strain Effects: a First-Principles Approach

PÁGINAS: 62
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física da Matéria Condensada
ESPECIALIDADE: Estruturas Eletrônicas e Propriedades Elétricas de Superfícies; Interf. e Partículas
RESUMO:

The conversion of solar energy into chemical energy through water-splitting photocatalysis offers a clean route for hydrogen gas production. Albeit NaNbO₃ has water-splitting activity, its less abundant UV light absorption severely limits hydrogen production. We investigate, with first-principles simulations, the point defect’s and surface states’ impact on the orthorhombic NaNbO 3 crystalline and electronic structure for light absorption closer to a more abundant visible spectrum. Both Na and O charged vacancy formations inserts empty states on the band gap, with defects being selectively favored by oxidating and reducing chemical environments, respectively. Empty states presence next to the band gap edges could reduce it, promoting light absorption closer to the visible spectrum. On another approach, the bulk cleavage at [100] direction formed a NaNbO terminated nanometric thin-film with metallic surface states. We have shown that biaxial strain can modulate the surface’s charge excess but could not recover the bulk’s semiconductor character. This electronic structure contrasts with the similar NaTaO₃ , which remained semiconductor at relaxed and strained states on equivalent thin-film orientation. Transition metal electronegativity played an essential role at this, as Ta cation required major atomic rearranges for charge redistribution while on Nb cation charge remained hybridized with conduction bands.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1760410 - JEVERSON TEODORO ARANTES JUNIOR
Membro Titular - Examinador(a) Interno ao Programa - 1957564 - CEDRIC ROCHA LEAO
Membro Titular - Examinador(a) Externo ao Programa - 1544394 - PAULA HOMEM DE MELLO
Membro Suplente - Examinador(a) Interno ao Programa - 1309493 - PEDRO ALVES DA SILVA AUTRETO
Membro Suplente - Examinador(a) Externo ao Programa - 1765425 - MARCIO GUSTAVO DI VERNIERI CUPPARI