InSe

/Tag: InSe

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+00:00April 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+00:00April 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+00:00March 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+00:00March 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+00:00March 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+00:00February 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+00:00January 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+00:00January 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+00:00January 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+00:00December 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+00:00December 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+00:00November 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".

Largely tunable band structures of few-layer InSe by uniaxial strain. (arXiv:1711.01715v1 [cond-mat.mes-hall])

2017-11-07T19:59:02+00:00November 7th, 2017|Categories: Publications|Tags: , |

Due to the strong quantum confinement effect, few-layer {gamma}-InSe exhibits a layer-dependent bandgap, spanning the visible and near infrared regions, and thus recently draws tremendous attention. As a two-dimensional material, the mechanical flexibility provides an additional tuning knob for the electronic structure. Here, for the first time, we engineer the band structures of few-layer and bulk-like InSe by uniaxial tensile strain, and observe salient shift of photoluminescence (PL) peaks. The shift rate of the optical gap is approximately 90-100 meV per 1% strain for 4- to 8-layer samples, which is much larger than that for the widely studied MoS2 monolayer. Density functional calculations well reproduce the observed layer-dependent bandgaps and the strain effect, and reveal that the shift rate decreases with increasing layer number for few-layer InSe. Our study demonstrates that InSe is a very versatile 2D electronic and optoelectronic material, which is suitable for tunable light emitters, photo-detectors and other optoelectronic devices.

Published : "arXiv Mesoscale and Nanoscale Physics".

Ab initio phonon thermal transport in monolayer InSe, GaSe, GaS, and alloys

2017-10-17T10:29:39+00:00October 17th, 2017|Categories: Publications|Tags: , |

We compare vibrational properties and phonon thermal conductivities ( κ ) of monolayer InSe, GaSe, and GaS systems using density functional theory and Peierls–Boltzmann transport methods. In going from InSe to GaSe to GaS, system mass decreases giving both increasing acoustic phonon velocities and decreasing scattering of these heat-carrying modes with optic phonons, ultimately giving ##IMG## [http://ej.iop.org/images/0957-4484/28/45/455706/nanoaa8b39ieqn1.gif] {${kappa }_{mathrm{InSe}}lt {kappa }_{mathrm{GaSe}}lt {kappa }_{mathrm{GaS}}$} . This behavior is demonstrated by correlating the scattering phase space limited by fundamental conservation conditions with mode scattering rates and phonon dispersions for each material. We also show that, unlike flat monolayer systems such as graphene, in InSe, GaSe and GaS thermal transport is governed by in-plane vibrations. Alloying of InSe, GaSe, and GaS systems provides an effective method for modulati…

Published in: "Nanotechnology".

Multiband $mathbf{k}·mathbf{p}$ theory of monolayer $Xmathrm{Se}$ ($X=mathrm{In},phantom{rule{0.28em}{0ex}}mathrm{Ga}$)

2017-10-11T20:30:27+00:00October 11th, 2017|Categories: Publications|Tags: |

Author(s): Ma Zhou, Rui Zhang, Jiangpeng Sun, Wen-Kai Lou, Dong Zhang, Wen Yang, and Kai ChangMultiband k⋅p Hamiltonians near the high symmetric points in the Brillouin zones of two-dimensional (2D) materials are widely used to predict and understand the unique transport and optical properties of 2D materials. Based on the crystal symmetry of 2D materials, the authors develop a multiband k⋅p Hamiltonian for monolayer GaSe and InSe using the theory of invariants. The authors establish the relationship between the crystal lattice symmetry and the Hamiltonian matrix elements, accounting for spin-orbit interaction and strain. The work provides a systematic way to construct the relevant multiband k⋅p Hamiltonian for various monolayer and few-layer materials.[Phys. Rev. B 96, 155430] Published Wed Oct 11, 2017

Published in: "Physical Review B".

Giant Quantum Hall Plateau in Graphene Coupled to an InSe van der Waals Crystal

2017-10-10T20:30:27+00:00October 10th, 2017|Categories: Publications|Tags: , |

Author(s): Z. R. Kudrynskyi, M. A. Bhuiyan, O. Makarovsky, J. D. G. Greener, E. E. Vdovin, Z. D. Kovalyuk, Y. Cao, A. Mishchenko, K. S. Novoselov, P. H. Beton, L. Eaves, and A. PatanèInduced transfer of charge carriers is demonstrated in a graphene-based field-effect transistor, leading to a quantum Hall plateau.[Phys. Rev. Lett. 119, 157701] Published Tue Oct 10, 2017

Published in: "Physical Review Letters".

Fast photoresponse and high detectivity in copper indium selenide (CuIn 7 Se 11 ) phototransistors

2017-10-03T14:31:20+00:00October 3rd, 2017|Categories: Publications|Tags: , |

The fast and sensitive detection of light can lead to a variety of optoelectronics and/or photonic-based applications in fields ranging from fast optical switching devices to health and environmental monitoring systems. Although several systems based on organic and inorganic materials show high sensitivity to visible light, in general they suffer from slow response times. Here we show that phototransistors fabricated using multilayers of CuIn 7 Se 11 exhibit response times of ~ tens of µ s with responsivity ( R ) values  >  10 AW −1 and with external quantum efficiencies reaching beyond 10 3 % when excited with a 658 nm wavelength laser. These devices also show high specific detectivity ( D * ) values of ~10 12 Jones. The responsivity and detectivity exhibited by these phototransistors are at least an order of magnitude better than commercially available conventional Si-based photodetectors, coupled w…

Published in: "2DMaterials".

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