Vibrational Properties of the Bi2Se3 Orthorhombic Metastable Phase

TL;DR

This study investigates the vibrational and structural properties of the metastable orthorhombic phase of Bi2Se3 using Raman spectroscopy and ab-initio calculations, revealing specific vibrational modes and phase transformation behavior.

Contribution

It provides new experimental and computational data on the vibrational properties of the metastable orthorhombic Bi2Se3 phase, which was previously lacking.

Findings

Identification of specific Raman-active vibrational modes in orthorhombic Bi2Se3

Observation of phase recrystallization from orthorhombic to rhombohedral with temperature

Support of experimental results by density functional theory calculations

Abstract

Chalcogenides materials are being considered as some of the most promising systems for energy harvesting and energy conversion. Among them, the orthorhombic family of compounds X2Y3 (with X= Bi, Sb and Y= S, Se) has attracted special attention due to its interesting atomic structure, thermoelectric and optical properties. While Bi2S3 and Sb2Se3 have being already applied to solar cells, the new metastable Bi2Se3 is still a challenge due to the lack of data and knowledge on its properties. Here, the vibrational and structural properties of the orthorhombic metastable phase of Bi2Se3 were investigated by using Raman spectroscopy and ab-initio calculations. We perform Raman spectrum measurements along in-situ thermal treatment on samples grown by electrochemical deposition. We show that by increasing the temperature occurs an improved crystallization in the orthorhombic structure, followed by a recrystallization to the usual rhombohedral phase. Our results point out for specific Raman modes of the orthorhombic phase. First principle computational results based on density functional theory support the experimental data and describe three singlet Raman active vibrational modes, Ag1, B2g and Ag2.