Electronic Properties of Single-layer In2 Se3 : from Photocatalysis to Non-trivial Band Topology.

Name: Erik Fissicaro Procopio
Type: PhD thesis
Publication date: 02/09/2022
Advisor:

Namesort descending Role
Wanderlã Luis Scopel Advisor *
Wendel Silva Paz Co-advisor *

Examining board:

Namesort descending Role
Ângelo Malachias de Souza External Examiner *
Edson Passamani Caetano Internal Examiner *
Rodrigo Garcia Amorim External Examiner *
Wanderlã Luis Scopel Advisor *
Wendel Silva Paz Co advisor *

Summary: In this thesis, the potential applicability of single layers of ferroelectric
α-In2Se3 in photocatalytic hydrogen gas generation, via band gap engineering, and a topological phase transition induced by oxygen incorporation are explored via ab initio calculations, based on Density Functional Theory (DFT). For pristine In2Se3, our results indicate that via band gap engineering, under certain pH levels, the band alignment favors the use of this material in photocatalytic activity in water-splitting processes. Furthermore, motivated by recent research related to topological phase transitions in 2D materials by strain engineering and surface oxygen incorporation, a systematic study of the latter was employed to evaluate the possibility of such transition in this system. A handful of oxygen sources were used to determine if such reaction would occur: O2 molecules (triplet and singlet spin states), H2O molecules and atomic oxygen. Our ndings suggest that adsorption only occurs for singlet O2 and atomic oxygen. Moreover, total energy analysis for these sources indicate that there is no apparent active Se surface site selectivity, i.e., the adsorption might happen uniformly. The newly formed α-In2Se3O layer was shown
to present non-trivial band topology which was then modulated by an external applied electric eld, highlighting a field-effect switching of the topological order.

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