Search query: Asymmetric electric field screening in van der Waals heterostructures

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abstract: A long standing challenge facing the combination of two dimensional crystals into heterojunction is the unknown effect of mixing layer of different electronic properties (semiconductors, metals, insulators) on the screening features of the fabricated device platforms including their functionality. Here we use a compelling set of theoretical and experimental techniques to elucidate the intrinsic dielectric screening properties of heterostructures formed by MoS2 and graphene layers. We experimentally observed an asymmetric field screening effect relative to the polarization of the applied gate bias into the surface. Surprisingly, such behavior allows selection of the electronic states that screen external fields, and it can be enhanced with increasing of the number of layers of the semiconducting MoS2 rather than the semi metal. This work not only provides unique insights on the screening properties of a vast amount of heterojunction fabricated so far, but also uncovers the great potential of controlling a fundamental property for device applications.Charge density reorganization at the interface between 2D materials may lead to electric field screening. Here, the authors investigate the dielectric screening properties of MoS2/graphene van der Waals heterostructures and identify an asymmetric electric response under different directions of the applied electric field.
author_names: Luhua Li

Tian Tian

Qiran Cai

Chih-Jen Shih

Elton J G Santos
title: Asymmetric electric field screening in van der Waals heterostructures
venue: Nature Communications
year: 2018

abstract: We investigated the electronic properties of bilayer van der Waals heterostructures consisting of MoS2 and WS2 under an external electric field using the density functional theory with the effective screening medium method. Our calculation shows that carrier accumulation in the heterostructures strongly depends on the mutual arrangement of MoS2 and WS2 with respect to the counter electrode. We further demonstrate that carrier accumulation also depends on the carrier species, biaxial strain, and interlayer stacking arrangement because of the band alignment near the band gap attributed to interlayer orbital hybridization.
author_names: Mina Maruyama

Susumu Okada
title: Asymmetric carrier accumulation in van der Waals heterostructures of MoS2/WS2 under an external electric field
venue: Applied Physics Express
year: 2019

abstract: Since the discovery of graphene, a broad range of two dimensional (2D) materials has captured the attention of the scientific communities. Materials, such as hexagonal boron nitride (hBN) and the transition metal dichalcogenides (TMDs) family, have shown promising semiconducting and insulating properties that are very appealing for the semiconductor industry. Recently, the possibility of taking advantage of the properties of 2D based heterostructures has been investigated for low power nanoelectronic applications. In this work, we aim at evaluating the relation between the nature of the materials used in such heterostructures and the amplitude of the layer to layer charge transfer induced by an external electric field, as is typically present in nanoelectronic gated devices. A broad range of combinations of TMDs, graphene, and hBN has been investigated using density functional theory. Our results show that the electric field induced charge transfer strongly depends on the nature of the 2D materials used in the van der Waals heterostructures and to a lesser extent on the relative orientation of the materials in the structure. Our findings contribute to the building of the fundamental understanding required to engineer electrostatically the doping of 2D materials and to establish the factors that drive the charge transfer mechanisms in electron tunneling based devices. These are key ingredients for the development of 2D based nanoelectronic devices.
author_names: A H Lu

Michel Houssa

Iuliana P Radu

Geoffrey Pourtois
title: Toward an Understanding of the Electric Field Induced Electrostatic Doping in van der Waals Heterostructures: A First Principles Study.
venue: ACS applied materials interfaces
year: 2017

abstract: The discovery of two dimensional (2D) ferroic materials has stimulated substantial efforts in developing emergent functionalities by synthesizing van der Waals (vdW) heterostructures, and one promising effect is the nonvolatile electrical control of magnetism in magnetoelectric (ME) heterostructures consisting of coupled 2D vdW ferromagnetic and ferroelectric layers. In this paper, it is proposed that the asymmetric interfacial coupling in such heterostructures may seriously distort the ferroelectric double well potential, thus destabilizing the ferroelectricity. We investigate this consequence in \mathrm{F}\mathrm{e}}_{3}\mathrm{GeT}\mathrm{e}}_{2}\ensuremath{\alpha}\ensuremath{ \mathrm{I}\mathrm{n}}_{2}\mathrm{S}\mathrm{e}}_{3} vdW heterostructure using the first principles calculations. It is revealed that one of the two potential wells for ferroelectric monolayer \ensuremath{\alpha}\ensuremath{ \mathrm{I}\mathrm{n}}_{2}\mathrm{S}\mathrm{e}}_{3} is suppressed by the asymmetric interfacial coupling between electric polarization and the built in electric field induced by intrinsic charge transfer, while the ferroelectric bistability can be recovered when the \ensuremath{\alpha}\ensuremath{ \mathrm{I}\mathrm{n}}_{2}\mathrm{S}\mathrm{e}}_{3} layer is thicker than three unit cells. Therefore, this work presents an alternative mechanism of critical thickness for the 2D ferroelectricity in ME vdW heterostructures.
author_names: Xiaokun Huang

Guannan Li

Changfeng Chen

Xin Nie

Xiang-ping Jiang

Jun-ming Liu
title: Interfacial coupling induced critical thickness for the ferroelectric bistability of two dimensional ferromagnet/ferroelectric van der Waals heterostructures
year: 2019

abstract: Controlling the half metallicity of 2D magnets is of great significance for both fundamental research and potential applications in quantum information storage, transmission and processing. Among the possible 2D magnetic heterostructures, those with intrinsic magneto electric coupling have a great potential in this field. Herein we theoretically investigate the experimentally feasible CrI3 CrGeTe3heterobilayers (Cr H) and show electric field dependent half metallicity. Besides the stacking dependent magnetization in Cr H, robust half metallicity can be induced in ferromagnetic and ferrimagnetic heterobilayers by an electric field over 0.6 V A 1. This is due to the electric controlled band alignment in such asymmetric band structure. Furthermore, a spin polarized band crossing is introduced in its type II spin channel for a continuously increased electric field. Thus, the magnetic heterobilayer (e.g.Cr H) with spin polarized band alignment represents a promising materials platform for the design of 2D controllable magnetoelectronic and spintronic devices.
author_names: Cheng Tang

Lei Zhang

Stefano Sanvito

Aijun Du
title: Electric controlled half metallicity in magnetic van der Waals heterobilayer
year: 2020

abstract: The dielectric screening is one of the most fundamental properties of 2D materials which is used to characterize electronic properties such as storage capacity of charge or energy. We numerically investigate three potential heterostructures of MoS2 Graphene and their corresponding interlayer interactions. Applying a density functional approach to the lowest energy structure of the interlayer, we find that, within a lower field regime 10 MV/cm) the dielectric constant is independent of the vertical electric field and dependent of the interlayer distance and stacking pattern of heterostructures composed of MoS2 and Graphene. From the calculation results of the induced charge throughout the heterostructure, we find how the van der Waals interaction influences the dielectric constant.
author_names: Ashutosh Kumar Singh

Seunghan Lee

Hoonkyung Lee

Hiroshi Watanabe
title: Dielectric Constant and van der Waals Interlayer Interaction of MoS2 Graphene Heterostructures
venue: 2020 IEEE 15th International Conference on Nano/Micro Engineered and Molecular System (NEMS)
year: 2020

abstract: We systematically explore the electronic and transport properties of Graphene CrBr$_{3} heterolayer based on \emph{ab initio} density functional theory simulations. Our result shows the modulation in electronic band gap with applied electric field variation from 0.5 to +0.5 V/\AA} The electric field variation marked linear and non linear trend for band gap modulation due to polarization effects between the two layers. It is found that the transmission at the interface is spin polarized upto 71.2\ and the magnetic moment is found to be invariant. Moreover, complex band structure and transmission spectrum reveals the possibilities of spin transmission in Graphene CrBr$_{3} heterostructure via magnetic proximity effect. The merits of electric field tunability and magnetic proximity effect in this 2D layered ferromagnetic semiconductor heterostructure will be beneficial to extend its suitability in spintronics device applications.
author_names: Sushant Kumar Behera

Mayuri Bora

Sapta Sindhu Paul Chowdhury

Pritam Deb
title: Magnetic proximity effect and electric field modulation in Graphene CrBr$_{3} van der Waals heterostructure
year: 2019

abstract: Monolayer MoS2 is a direct band gap semiconductor with large exciton binding energy, which is a promising candidate for the application of ultrathin optoelectronic devices. However, the optoelectronic performance of monolayer MoS2 is seriously limited to its growth quality and carrier mobility. In this work, we report the direct vapor growth and the optoelectronic device of vertically stacked MoS2/MoSe2 heterostructure, and further discuss the mechanism of improved device performance. The optical and high resolution atomic characterizations demonstrate that the heterostructure interface is of high quality without atomic alloying. Electrical transport measurements indicate that the heterostructure transistor exhibits a high mobility of 28.5 cm2/(V*s) and a high on/off ratio of 107. The optoelectronic characterizations prove that the heterostructure device presents an enhanced photoresponsivity of 36 A/W and a remarkable detectivity of 4.8 x 1011 Jones, which benefited from the interface induced built in electric field and carrier dependent Coulomb screening effect. This work demonstrates that the construction of two dimensional (2D) semiconductor heterostructures plays a significant role in modifying the optoelectronic device properties of 2D materials.
author_names: Fang Li

Boyi Xu

Wen Yang

Zhaoyang Qi

Chao Ma

Yajuan Wang

Xuehong Zhang

Zhuoran Luo

Delang Liang

Dong Li

Ziwei Li

Anlian Pan
title: High performance optoelectronic devices based on van der Waals vertical MoS2/MoSe2 heterostructures
venue: Nano Research
year: 2020

abstract: Combining van der Waals heterostructures by stacking different two dimensional materials on top of each other layer by layer can enhance their desired properties and greatly extend the applications of the parent materials. In this work, by means of first principles calculations, we investigate systematically the structural and electronic properties of six different stacking configurations of a Si/GaSe heterostructure. The effect of biaxial strain and electric field on the electronic properties of the most energetically stable configuration of the Si/GaSe heterostructure has also been discussed. At the equilibrium state, the electronic properties of the Si/GaSe heterostructure in all its stacking configurations are well kept as compared with that of single layers owing to their weak van der Waals interactions. Interestingly, we find that a sizable band gap is opened at the Dirac K point of silicene in the Si/GaSe heterostructure, which could be further controlled by biaxial strain or electric field. These findings open up a possibility for designing silicene based electronic devices, which exhibit a controllable band gap. Furthermore, the Si/GaSe heterostructure forms an n type Schottky contact with a small Schottky barrier height of 0.23 eV. A transformation from the n type Schottky contact to a p type one, or from the Schottky contact to an ohmic contact may occur in the Si/GaSe heterostructure when strain or an electric field is applied.
author_names: P T T Le

Nguyen Ngoc Hieu

Le Minh Bui

Huynh V Phuc

Bui D Hoi

Bin Amin

Chuong Van Nguyen
title: Structural and electronic properties of a van der Waals heterostructure based on silicene and gallium selenide: effect of strain and electric field.
venue: Physical chemistry chemical physics PCCP
year: 2018

abstract: Indium Selenide (In2Se3) is a newly emerged van der Waals (vdW) ferroelectric material, which unlike traditional insulating ferroelectric materials, is a semiconductor with a bandgap of about 1.36 eV. Ferroelectric diodes and transistors based on In2Se3 have been demonstrated. However, the interplay between light and electric polarization in In2Se3 has not been explored. In this paper, we found that the polarization in In2Se3 can be programmed by optical stimuli, due to its semiconducting nature, where the photo generated carriers in In2Se3 can alter the screening field and lead to polarization reversal. Utilizing these unique properties of In2Se3, we demonstrated a new type of multifunctional device based on 2D heterostructures, which can concurrently serve as a logic gate, photodetector, electronic memory and photonic memory. This dual electrical and optical operation of the memories can simplify the device architecture and offer additional functionalities, such as ultrafast optical erase of large memory arrays. In addition, we show that dual gate structure can address the partial switching problem commonly observed in In2Se3 ferroelectric transistors, as the two gates can enhance the vertical electric field and facilitate the polarization switching in the semiconducting In2Se3. These discovered effects are of general nature and should be observable in any ferroelectric semiconductor. These findings deepen the understanding of polarization switching and light polarization interaction in semiconducting ferroelectric materials and open up their applications in multifunctional electronic and photonic devices.
author_names: Kai Xu

Weiman Jiang

Xueshi Gao

Zijing Zhao

Tony Low

Wenjuan Zhu
title: Optical control of ferroelectric switching and multifunctional devices based on van der Waals ferroelectric semiconductors.
venue: Nanoscale
year: 2020