Effects of strain and electric field on electronic and optical properties of monolayer γ-GeX (X = S, Se and Te)
Journal
Applied Surface Science
Journal Volume
582
Start Page
152321
ISSN
01694332
Date Issued
2022
Author(s)
Abstract
We investigate the mechanical, electronic, and optical properties of monolayer GeX (X= S, Se, and Te) with γ structure based on density-functional theory calculations. We find that the mechanical anisotropy of γ-GeS is higher than those of γ-GeSe and γ-GeTe, because of its strongest ionic bond. In the unstrained case, γ-GeX is an indirect-gap semiconductor with the Mexican-hat (MH) dispersion in the valence band. By applying tensile and biaxial strains, both energy band gap and valley positions are controlled. On the other hand, by applying an external electric field, the energy band gap is decreased to zero because of the downward interlayer band. We also find that the in-plane optical absorptions of monolayer γ-GeX in the visible-light region are comparable to that of the monolayer transition metal dichalcogenides such as MoS2. Due to the unique structure in the z direction, the monolayer γ-GeX also shows a high value of the out-of-plane optical absorptions. The strain engineering significantly modifies the optical absorption in the visible light, while the effect of the external electric field on the optical properties is weak. Our results will be helpful to design the electro-optical devices based on monolayer materials with MH band.
Subjects
Energy Band Gap
External Electric Field
Mexican-hat Band
Optical Absorption
Strain Engineering
Γ-gex
Density Functional Theory
Electric Fields
Energy Gap
Germanium Compounds
Layered Semiconductors
Light
Light Absorption
Molybdenum Compounds
Optical Properties
Strain
Transition Metals
Density-functional Theory Calculations
Effects Of Strains
Electronic And Optical Properties
Energy Bandgaps
External Electric Field
Mechanical Anisotropy
Mexican-hat Band
Strain Engineering
Structure-based
Γ-gex
Monolayers
Publisher
Elsevier B.V.
Type
journal article