Structural and electronic properties of atomically thin germanium selenide polymorphs

Abstract

tronic counterpart to the layered group V semiconductors [25]. Similarly, GeSe is an isoelectronic counterpart to the group V semiconductors and has the same layered structures. α-GeSe nanosheets have been synthesized by several methods and applied in photodetector devices [11,12]. The semiconducting electronic properties of α-GeSe have been confirmed by a recent theoretical investigation [26]. However, the stability and electronic properties of the GeSe monolayers in the other polymorphs have not been investigated. A systematic theoretical investigation of their structures and properties will not only enrich our understanding of the property variations of the polymorphs, but it will also facilitate potential applications. Despite some theoretical and experimental studies of α-GeSe being reported, many important questions still remain unknown: what are the stabilities of the GeSe monolayers in the different phases? How do the electronic properties vary with the different phase structures? In this work, we aim to answer these questions.In this work, by comprehensive density functional theory (DFT) calculations, we report the discovery of the four previously unknown phases of the GeSe monolayer in addition to layered α-GeSe: β-GeSe, γ-GeSe, δ-GeSe, and ε-GeSe. The five polymorphs of GeSe exhibit versatile energy band gaps, which are very significant for broadband optoelectronic and photonic applications. In particular, β-GeSe is an indirect band-gap semiconductor with a band gap of 3.01 eV calculated using the HSE06 exchange-correlation functional. From the band edge alignment, the conduction band minimum (CBM) and valence band maximum (VBM) energies of β-GeSe are −2.54 and −5.55 eV, respectively, which indicates that it is a promising material Using comprehensive density functional theory calculations, we systematically investigate the structure, stability, and electronic properties of five polymorphs of GeSe monolayer, and highlight the differences in their structural and electronic properties. Our calculations show that the five free-standing polymorphs of GeSe are stable semiconductors. β-GeSe, γ-GeSe, δ-GeSe, and ε-GeSe are indirect gap semiconductors, whereas α-GeSe is a direct gap semiconductor. We calculated Raman spectra and scanning tunneling microscopy images for the five polymorphs. Our results show that the β-GeSe monolaye r is a candidate for water splitting.

Design of graphene-like gallium nitride and WS2/WSe2 nanocomposites for photocatalyst applications

“…In this work, all the calculations were performed using Cambridge Serial Total Energy Package (CASTEP) [13,34] based on the density functional theory (DFT). The ultrasoft pseudopotentials were employed to describe the electron-ion interaction.…”

“…Despite of the gapless drawback that hinders its practical applications in the field effective transistors (FETs) [2], graphene still exhibits great potentials in various applications such as electrodes in supercapacitance and lithium-ion batteries [3][4][5] , thermal conductive layers [6] in the electronic devices due to its ultra-high thermal conductivity, non-metal catalyst [7] owning to its chemical stability, etc. Foremost, graphene has triggered and boosted the prosperity and the progress of diverse 2D materials [8][9][10][11][12][13], which display distinctive and excellent properties in comparison to their bulk counterparts.…”

A promising two-dimensional solar cell donor: Black arsenic–phosphorus monolayer with 1.54 eV direct bandgap and mobility exceeding 14,000 cm2V−1s−1

“…Therefore, the selective of electron-donor and electron-acceptor semiconducting materials for the XSCs are extremely important. [7] Typical two-dimensional (2D) semiconductors, [8][9][10][11][12][13][14][15][16][17][18][19] especially phosphorene and arsenene, have been recognized as promising materials in device applications recent years.…”

Stable single-layer structure of group-V elements

“…Ram et al [24] predicted a sp 2 hybridized 2D allotrope of carbon, named pentahexoctite, * ethem.akturk@adu.edu.tr † ciraci@fen.bilkent.edu.tr with mechanical strength comparable to that of graphene. In addition, Zhang et al [25] predicted five atomically thin, free-standing germanium selenide (GeSe) polymorphs, which have high kinetic stability and energy band gaps in the visible region. It has been shown that MoS 2 , which is normally a semiconductor in the SL honeycomb structure, possesses both massless Dirac and heavy fermions when it is formed in a planar, SL square/octagon (s/o) structure with a 2D square lattice [26].…”