InSe: a two-dimensional material with strong interlayer coupling

Morbec

et al. 2018

Phys. Rev. Materials

First-principles calculations based on density-functional theory were performed to investigate heterostructures of group-III monochalcogenides (GaS, GaSe, InS and InSe) and the effects of the incommensurability on their electronic structures. We considered two heterostructures, GaS/GaSe, which has a lattice mismatch of 4.7%, and GaSe/InS, with a smaller mismatch of 2.1%, and we computed the cost of having commensurate structures; we also examined the potential energy landscape of both heterostructures, in order to simulate the realistic situation of incommensurate systems. We found that a commensurate heterostructure may be realized in GaSe/InS as the interaction energy of this system with the monolayers assuming the average lattice constant is smaller than the interaction energy of an incommensurate system in which each layer keeps its own lattice constant. For GaS/GaSe, on the other hand, we found that the incommensurate heterostructure is energetically more favorable than the commensurate one, even when taking into account the energetic cost due to the lack of proper registry between the layers. Since the commensurate condition requires that one (or both) layer(s) is (are) strained, we systematically investigated the effect of strain on the band gaps and band edge positions of the monolayer systems. We found that, in all monolayers, the conduction band minimum is more than 2 times more sensitive to applied strain than the valence band maximum; this was observed to strongly affect the band alignment of GaS/GaSe, as it can change from type-I to type-II with a small variation in the lattice constant of GaS. GaSe/InS heterostructure was found to have a type-II alignment, which is robust with respect to strain in the range of −2 to +2%.

Section: A Monolayer Gas Gase Ins and Insesupporting

confidence: 88%

Section: A Monolayer Gas Gase Ins and Insesupporting

confidence: 78%

Commensurate versus incommensurate heterostructures of group-III monochalcogenides

Morbec

et al. 2018

Phys. Rev. Materials

Advanced Optical Materials

“…In particular, the band edge recombination is very sensitive to the layer thickness due to quantum confinement and strong interlayer coupling in the InSe nanosheets. [ 3,32 ]…”

Section: Resultsmentioning

confidence: 99%

Enhanced Optical Emission from 2D InSe Bent onto Si‐Pillars

Mazumder

Xie

Kudrynskyi

et al. 2020

Self Cite

Controlling the propagation and intensity of an optical signal is central to several technologies ranging from quantum communication to signal processing. These require a versatile class of functional materials with tailored electronic and optical properties, and compatibility with different platforms for electronics and optoelectronics. Here, the inherent optical anisotropy and mechanical flexibility of atomically thin semiconducting layers are investigated and exploited to induce a controlled enhancement of optical signals. This enhancement is achieved by straining and bending layers of the van der Waals crystal indium selenide (InSe) onto a periodic array of Si‐pillars. This enhancement has strong dependence on the layer thickness and is modelled by first‐principles electronic band structure theory, revealing the role of the symmetry of the atomic orbitals and light polarization dipole selection rules on the optical properties of the bent layers. The effects described in this paper are qualitatively different from those reported in other materials, such as transition metal dichalcogenides, and do not arise from a photonic cavity effect, as demonstrated before for other semiconductors. The findings on InSe offer a route to flexible nano‐photonics compatible with silicon electronics by exploiting the flexibility and anisotropic and wide spectral optical response of a 2D layered material.

Advanced Optical Materials

“…The bulk InSe is a direct bandgap, and the bandgap value is suitably 1.25 eV, which is suitable for making a light‐emitting device. [ 26 ] In addition, experiments and theories have proved that due to the quantum confinement effect, as the number of InSe layers is reduced to few layers, it will undergo a transition from the direct bandgap to the indirect bandgap, and the bandgap value increases to 2.6 eV, [ 27–29 ] which makes it have a broad prospect in the application of optoelectronics. Hybridization of the In and Se atomic orbitals results in a relatively light electron effective electron mass (0.143 m 0 ) [ 30 ] in the plane of the layer, which results in a field effect transistor fabricated using multiple layers of InSe with high electron mobility rate (10 3 cm 2 V −1 s −1) ) [ 20 ] and on/off current ratio (10 8 ) [ 31 ] over the transition metal disulfide at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Liquid‐Exfoliated Few‐Layer InSe Nanosheets for Broadband Nonlinear All‐Optical Applications

Liao

Shan

et al. 2020

of the triangle formed by the three lower selenium atoms. [18,19] Since the atomicscale thin InSe has been successfully stripped by mechanical methods, [20,21] it has been prepared by chemical vapor transport (CVT), [22,23] colloidal ligand template, [24] and pulsed laser deposition (PLD). [25] The bulk InSe is a direct bandgap, and the bandgap value is suitably 1.25 eV, which is suitable for making a lightemitting device. [26] In addition, experiments and theories have proved that due to the quantum confinement effect, as the number of InSe layers is reduced to few layers, it will undergo a transition from the direct bandgap to the indirect bandgap, and the bandgap value increases to 2.6 eV, [27][28][29] which makes it have a broad prospect in the application of optoelectronics. Hybridization of the In and Se atomic orbitals results in a relatively light electron effective electron mass (0.143 m 0 ) [30] in the plane of the layer, which results in a field effect transistor fabricated using multiple layers of InSe with high electron mobility rate (10 3 cm 2 V −1 s −1) ) [20] and on/off current ratio (10 8 ) [31] over the transition metal disulfide at room temperature. In addition, 2D layered semiconductor InSe is used to fabricate, photodetectors, image sensors, heterojunction devices, and the like. [32][33][34] Although InSe-based devices and theories are developing rapidly, experimental investigations of the interaction between light and InSe have rarely been reported.Spatial self-phase modulation (SSPM) is a third-order nonlinear phenomenon in which the phase of incident light is modulated by its own intensity, [35] which has become an effective method for characterizing the nonlinear characteristics of 2D materials. The nonlinear refractive index coefficients of a large number of materials have been measured by this method, including graphene, [36] MoS 2 , [37] black phosphorus (BP), [38] Mxene, [39] etc. Cross-phase modulation (XPM) occurs because the signal light undergoes additional phase accumulation or variation caused by another co-propagating switched beam. [40] In this contribution, XPM refers to the change in optical phase of the beam caused by the interaction of two beams in a nonlinear medium (InSe). Nonreciprocal light propagation is of great significance for the field of optical communication and integrated photonics. Currently implemented methods include photons with specially designed waveguides, optomechanical systems, interband transitions, etc. [41][42][43][44] Some selenides also have NLO properties, such as GeSe, SnSe, and NbSe 2 , [45][46][47] where the SSPM effect of GeSe and NbSe 2 has been reported. [47,48] The nonlinear optical response of 2D materials has attracted wide attention in the recent year due to their strong nonlinearity and broadband characteristics. A new optical scheme is presented enabling the implementation of the broadband nonlinear optical response and their all-optical applications of few-layered InSe nanosheets. First, few-layer InSe nanosheets are synthesized by u...