InSe

/Tag: InSe

Gate-Defined Quantum Confinement in InSe-based van der Waals Heterostructures. (arXiv:1805.05896v1 [cond-mat.mes-hall])

2018-05-16T19:58:54+00:00 May 16th, 2018|Categories: Publications|Tags: , , |

Indium selenide, a post-transition metal chalcogenide, is a novel two-dimensional (2D) semiconductor with interesting electronic properties. Its tunable band gap and high electron mobility have already attracted considerable research interest. Here we demonstrate strong quantum confinement and manipulation of single electrons in devices made from few-layer crystals of InSe using electrostatic gating. We report on gate-controlled quantum dots in the Coulomb blockade regime as well as one-dimensional quantization in point contacts, revealing multiple plateaus. The work represents an important milestone in the development of quality devices based on 2D materials and makes InSe a prime candidate for relevant electronic and optoelectronic applications.

Published : "arXiv Mesoscale and Nanoscale Physics".

Monolayer group-III monochalcogenides by oxygen functionalization: a promising class of two-dimensional topological insulators. (arXiv:1805.03821v1 [cond-mat.mtrl-sci])

2018-05-11T19:59:03+00:00 May 11th, 2018|Categories: Publications|Tags: , |

Monolayer group-III monochalcogenides (MX, M = Ga, In; X = S, Se, Te), an emerging category of two-dimensional (2D) semiconductors, hold great promise for electronics, optoelectronics and catalysts. By first-principles calculations, we show that the phonon dispersion and Raman spectra as well as the electronic and topological properties of monolayer MX can be tuned by oxygen functionalization. Chemisorption of oxygen atoms on one side or both sides of the MX sheet narrows or even closes the band gap, enlarges work function, and significantly reduces the carrier effective mass. More excitingly, InS, InSe and InTe monolayers with double-side oxygen functionalization are 2D topological insulators with sizeable bulk gap up to 0.21 eV. Their low-energy bands near the Fermi level are dominated by the px and py orbitals of atoms, allowing band engineering via in-plane strains. Our studies provide viable strategy for realizing quantum spin Hall effect in monolayer group-III monochalcogenides at room temperature, and utilizing these novel 2D materials for high-speed and dissipationless transport devices.

Published in: "arXiv Material Science".

The role of surface chemical reactivity in the stability of electronic nanodevices based on two-dimensional materials “beyond graphene” and topological insulators. (arXiv:1805.00729v1 [cond-mat.mtrl-sci])

2018-05-03T19:58:49+00:00 May 3rd, 2018|Categories: Publications|Tags: , , , , |

Here, we examine the influence of surface chemical reactivity toward ambient gases on the performance of nanodevices based on two-dimensional materials “beyond graphene” and novel topological phases of matter. While surface oxidation in ambient conditions was observed for silicene and phosphorene with subsequent reduction of the mobility of charge carriers, nanodevices with active channels of indium selenide, bismuth chalcogenides and transition-metal dichalcogenides are stable in air. However, air-exposed indium selenide suffers of p-type doping due to water decomposition on Se vacancies, whereas the low mobility of charge carriers in transition-metal dichalcogenides increases the response time of nanodevices. Conversely, bismuth chalcogenides require a control of crystalline quality, which could represent a serious hurdle for up scaling.

Published : "arXiv Mesoscale and Nanoscale Physics".

Effects of Graphene/BN Encapsulation, Surface Functionalization and Molecular Adsorption on the Electronic Properties of Layered InSe: A First-Principles Study. (arXiv:1804.05180v1 [cond-mat.mtrl-sci])

2018-04-17T19:59:37+00:00 April 17th, 2018|Categories: Publications|Tags: , , , , , |

By using first-principles calculations, we investigated the effects of graphene/boron nitride (BN) encapsulation, surface functionalization by metallic elements (K, Al, Mg and typical transition metals) and molecules (tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE)) on the electronic properties of layered indium selenide (InSe). It was found that an opposite trend of charge transfer is possible for graphene (donor) and BN (acceptor), which is dramatically different from phosphorene where both graphene and BN play the same role (donor). For InSe/BN heterostructure, a change of the interlayer distance due to an out-of-plane compression can effectively modulate the band gap. Strong acceptor abilities to InSe were found for the TCNE and TCNQ molecules. For K, Al and Mg-doped monolayer InSe, the charge transfer from K and Al atoms to the InSe surface was observed, causing an n-type conduction of InSe, while p-type conduction of InSe observed in case of the Mg-doping. The atomically thin structure of InSe enables the possible observation and utilization of the dopant-induced vertical electric field across the interface. A proper adoption of the n- or p-type dopants allows for the modulation of the work function, the Fermi level pinning, the band bending, and the photo-adsorbing efficiency near the InSe surface/interface. Investigation on the adsorption of transition metal atoms on InSe showed that Ti-, V-, Cr-, Mn-, Co-adsorbed InSe are spin-polarized, while Ni-, Cu-, Pd-, Ag- and Au-adsorbed InSe are non-spin-polarized. Our results shed lights on the possible ways to protect InSe structure and modulate its electronic properties for nanoelectronics and electrochemical

Published in: "arXiv Material Science".

Hybrid $mathbf{k}·mathbf{p}$ tight-binding model for intersubband optics in atomically thin InSe films

2018-04-12T14:31:13+00:00 April 12th, 2018|Categories: Publications|Tags: |

Author(s): S. J. Magorrian, A. Ceferino, V. Zólyomi, and V. I. Fal’koWe propose atomic films of n-doped γ-InSe as a platform for intersubband optics in the infrared and far-infrared range, coupled to out-of-plane polarized light. Depending on the film thickness (number of layers) and the amount of n-doping of the InSe film, these transitions span from ∼0.7 eV for bil…[Phys. Rev. B 97, 165304] Published Thu Apr 12, 2018

Published in: "Physical Review B".

InSe: a two-dimensional material with strong interlayer coupling. (arXiv:1803.09919v1 [cond-mat.mtrl-sci])

2018-03-28T19:58:56+00:00 March 28th, 2018|Categories: Publications|Tags: , |

Atomically thin, two-dimensional (2D) indium selenide (InSe) has attracted considerable attention due to large tunability in the band gap (from 1.4 to 2.6 eV) and high carrier mobility. The intriguingly high dependence of band gap on layer thickness may lead to novel device applications, although its origin remains poorly understood, and generally attributed to quantum confinement effect. In this work, we demonstrate via first-principles calculations that strong interlayer coupling may be mainly responsible for this phenomenon, especially in the fewer-layer region, and it could also be an essential factor influencing other material properties of {beta}-InSe and {gamma}-InSe. Existence of strong interlayer coupling manifests itself in three aspects: (i) indirect-to-direct band gap transitions with increasing layer thickness; (ii) fan-like frequency diagrams of the shear and breathing modes of few-layer flakes; (iii) strong layer-dependent carrier mobilities. Our results indicate that multiple-layer InSe may be deserving of attention from FET-based technologies and also an ideal system to study interlayer coupling, possibly inherent in other 2D materials.

Published : "arXiv Mesoscale and Nanoscale Physics".

InSe monolayer: synthesis, structure and ultra-high second-harmonic generation

2018-03-20T16:31:38+00:00 March 20th, 2018|Categories: Publications|Tags: , |

III–IV layered materials such as indium selenide have excellent photoelectronic properties. However, synthesis of materials in such group, especially with a controlled thickness down to monolayer, still remains challenging. Herein, we demonstrate the successful synthesis of monolayer InSe by physical vapor deposition (PVD) method. The high quality of the sample was confirmed by complementary characterization techniques such as Raman spectroscopy, atomic force microscopy (AFM) and high resolution annular dark field scanning transmission electron microscopy (ADF-STEM). We found the co-existence of different stacking sequence ( β – and γ -InSe) in the same flake with a sharp grain boundary in few-layered InSe. Edge reconstruction is also observed in monolayer InSe, which has a distinct atomic structure from the bulk lattice. Moreover, we discovered that the second-harmonic generation (SHG) signal from monolayer InSe shows large optical second-order susceptibility that is…

Published in: "2DMaterials".

InSe: a two-dimensional material with strong interlayer coupling

2018-03-07T02:24:17+00:00 March 7th, 2018|Categories: Publications|Tags: , |

Nanoscale, 2018, Accepted ManuscriptDOI: 10.1039/C7NR09486H, PaperYuanhui Sun, shulin Luo, Xin-Gang Zhao, Koushik Biswas, Songlin Li, Lijun ZhangAtomically thin, two-dimensional (2D) indium selenide (InSe) has attracted considerable attention due to large tunability in the band gap (from 1.4 to 2.6 eV) and high carrier

Published in: "RSC Nanoscale".

Characterization, optical properties and electron(exciton)-phonon interaction in bulk In2Se3 crystals and InSe nanocrystals in In2nSe3 confinement. (arXiv:1802.02781v1 [cond-mat.mtrl-sci])

2018-02-09T19:59:20+00:00 February 9th, 2018|Categories: Publications|Tags: , , |

Complex electron-microscopic, energy-dispersed and wide-temperature optical absorption and photoluminescence (PL) investigations are carried out into Bridgeman-grown layered In2Se3 crystals. It is shown that In2Se3 crystals as a whole have a homogeneous concentration of In and Se atoms, corresponding with In2Se3 stoichiometry. Nevertheless, In2Se3 crystals contain a significant amount of dislocations, on which nano-sized interspersions of crystal phases of pure InSe, In6Se7 and monoclinic red Se settle down. Optical wide-temperature investigations of In2Se3 allow us to do the following: establish the width of the band-gap, the exciton binding energy; determine the frequency of a half-layer A-phonon, which takes part in electron (exciton)-phonon interaction; and to evaluate the effective masses of carriers and the dielectric permeability. Finally, blue shift of the band-gap and character of the electron (exciton)-phonon interaction of nano-sized 3D InSe crystals confined in an In2Se3 crystal matrix; influence of an InSe nanocrystal radius and of an ensemble of 3D InSe nanocrystals with different radii for an increase of the exciton emission/absorption half-width line with temperature and radii of InSe nanocrystals are discussed.

Published in: "arXiv Material Science".

Ultrasensitive tunability of the direct bandgap of 2D InSe flakes via strain engineering

2018-01-29T16:30:58+00:00 January 29th, 2018|Categories: Publications|Tags: |

InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ~239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ~154 meV/% for uniaxial tensile strain and ~140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimen…

Published in: "2DMaterials".

Ultrasensitive Tunability of the Direct Bandgap of Two-dimensional InSe Flakes via Strain Engineering. (arXiv:1801.07538v1 [cond-mat.mes-hall])

2018-01-24T19:58:54+00:00 January 24th, 2018|Categories: Publications|Tags: |

InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ~ 239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ~ 154 meV/% for uniaxial tensile strain and ~ 140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimentally reported in two-dimensional materials.We developed a theoretical understanding of the strain-induced bandgap change through first-principles DFT and GW calculations. We also confirmed the bandgap change by photoconductivity measurements using excitation light with different photon energies. The highly tunable bandgap of InSe in the infrared regime should enable a wide range of applications, including electro-mechanical, piezoelectric and optoelectronic devices.

Published : "arXiv Mesoscale and Nanoscale Physics".

Hybrid $mathbf{kcdot p}$-tight-binding model for intersubband optics in atomically thin InSe films. (arXiv:1801.07052v1 [cond-mat.mes-hall])

2018-01-23T19:58:54+00:00 January 23rd, 2018|Categories: Publications|Tags: |

We propose atomic films of n-doped $gamma$-InSe as a platform for intersubband optics in the infrared (IR) and far infrared (FIR) range, coupled to out-of-plane polarized light. Depending on the film thickness (number of layers) of the InSe film these transitions span from $sim 0.7$ eV for bilayer to $sim 0.05$ eV for 15-layer InSe. We use a hybrid $mathbf{k} cdot mathbf{p}$ theory and tight-binding model, fully parametrized using density functional theory, to predict their oscillator strengths and thermal linewidths at room temperature.

Published : "arXiv Mesoscale and Nanoscale Physics".

High-Performance Photo-Electrochemical Photodetector Based on Liquid-Exfoliated Few-Layered InSe Nanosheets with Enhanced Stability

2017-12-19T18:30:00+00:00 December 19th, 2017|Categories: Publications|Tags: , |

Abstract The band gap of few-layered 2D material is one of the significant issues for the application of practical devices. Due to the outstanding electrical transport property and excellent photoresponse, 2D InSe has recently attracted rising attention. Herein, few-layered InSe nanosheets with direct band gap are delivered by a facile liquid-phase exfoliation approach. We have synthesized a photoelectrochemical (PEC)-type few-layered InSe photodetector that exhibits high photocurrent density, responsivity, and stable cycling ability in KOH solution under the irradiation of sunlight. The detective ability of such PEC InSe photodetector can be conveniently tuned by varying the concentration of KOH and applied potential suggesting that the present device can be a fitting candidate as an excellent photodetector. Moreover, extendable optimization of the photodetection performance on InSe nanosheets would further enhance the potential of the prepared InSe in other PEC-type devices such as dye-sensitized solar cells, water splitting systems, and solar tracking equipment. A photoelectrochemical photodetector fabricated from indium selenide nanosheets with preferable adjustable response performances to sunlight is presented. Specifically, the detection ability of such a detector can be conveniently regulated by tuning the concentration of electrolyte and the applied potential. The as-fabricated InSe detector responds to sunlight and its photocurrent density can reach 300 nA cm−2 with no degeneration.

Published in: "Advanced Functional Materials".

Atomic-scale mechanisms of defect- and light-induced oxidation and degradation of InSe. (arXiv:1712.04662v1 [cond-mat.mtrl-sci])

2017-12-14T19:59:24+00:00 December 14th, 2017|Categories: Publications|Tags: , , , , |

Layered indium selenide (InSe), a new two-dimensional (2D) material with a hexagonal structure and semiconducting characteristic, is gaining increasing attention owing to its intriguing electronic properties. Here, by using first-principles calculations, we reveal that perfect InSe possesses a high chemical stability against oxidation, superior to MoS2. However, the presence of intrinsic Se vacancy (VSe) and light illumination can markedly affect the surface activity. In particular, the excess electrons associated with the exposed In atoms at the VSe site under illumination are able to remarkably reduce the dissociation barrier of O2 to ~0.2 eV. Moreover, at ambient conditions, the splitting of O2 enables the formation of substitutional (apical) oxygen atomic species, which further cause the trapping and subsequent rapid splitting of H2O molecules and ultimately the formation of hydroxyl groups. Our findings uncover the causes and underlying mechanisms of InSe surface degradation via the defect-photo promoted oxidations. Such results will be beneficial in developing strategies for the storage of InSe material and its applications for surface passivation with boron nitride, graphene or In-based oxide layers.

Published in: "arXiv Material Science".

Unusual phonon behavior and ultra-low thermal conductance of monolayer InSe

2017-11-29T14:26:19+00:00 November 29th, 2017|Categories: Publications|Tags: , |

Nanoscale, 2017, Accepted ManuscriptDOI: 10.1039/C7NR07779C, PaperHangbo Zhou, Yongqing Cai, Gang Zhang, Yong-Wei ZhangMonolayer indium selenide (InSe) has shown many fascinating properties, such as high electron mobility, quantum Hall effect and anomalous optical response. However, its phonon properties, thermal transport properties and its…The content

Published in: "RSC Nanoscale".

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