With the use of density functional theory calculations and addition of van der Waals correction, the graphene/HfS$_2$ heterojunction is constructed, and its electronic properties are examined thoroughly. This interface is determined as $n$-type Ohmic and the impacts of different amounts of interlayer distance and strain on the contact are shown using Schottky barrier height and electron injection efficiency. Dipole moment and workfunction of the interface are also altered when subjected to change in these two categories. The transition between Ohmic to Schottky contact is also depicted to be possible by applying a perpendicular electric field, proving this to be yet another useful method for tuning different properties of this structure. The conclusions given in this paper can exert an immense amount of influence on the development of two-dimensional HfS$_2$ based devices in the future.
Poor electrical conductivity and large volume expansion during repeated charge and discharge is what has characterized many battery electrode materials in current use. This has led to 2D materials, specifically multi-layered 2D systems, being considered as alternatives. Among these 2D multi-layered systems are the graphene-based van der Waals heterostructures with transition metal di-chalcogenides (TMDCs) as one of the layers. Thus in this study, graphene-Hafnium disulphide (Gr-HfS$_2$) system, has been investigated as a prototype Gr-TMDC system for application as battery electrode. Density fu…
In a first-principles study based on density-functional theory and many-body perturbation theory we investigate the electronic properties and the optical excitations of ZrS$_2$ and HfS$_2$ monolayers and their van der Waals heterostructure. Both materials have an indirect quasi-particle band gap, which amounts to about 2.8 eV in ZrS$_2$ and to 2.6 eV in HfS$_2$. In both systems the valence-band maximum is at $Γ$ and the conduction-band minimum at M. Spin-orbit coupling induces a splitting of about 100 meV at the $Γ$ point in the valence band, while it does not affect the conduction band. The o…
The van der Waals heterostructures of allotropes of phosphorene ($α$- and $β-P$) with MoSe2 (H-, T-, ZT- and SO-MoSe2) are investigated in the framework of state-of-the-art density functional theory. The semiconducting heterostructures, $β$-P /H-MoSe2 and $α$-P / H-MoSe2, forms anti-type structures with type I and type II band alignments, respectively, whose bands are tunable with external electric field. $α$-P / ZT-MoSe2 and $α$-P / SO-MoSe2 form ohmic semiconductor-metal contacts while Schottky barrier in $β$-P / T-MoSe2 can be reduced to zero by external electric field to form ohmic contact…
Two-dimensional (2D) materials viz. transition metal dichalcogenides (TMD) and transition metal oxides (TMO) offer a platform that allows creation of heterostructures with a variety of properties. The optoelectronic industry has observed an upheaval in the research arena of MoS$_2$ based van der Waals (vdW) heterostructures (HTSs) and Janus structures. Therefore, interest towards these structures are backed by the selectivity in terms of electronic and optical properties. The present study investigates the photocatalytic ability of bilayer, MoS$_2$ and Janus (MoSSe) based vdW HTSs viz. MoS$_2$…
Owing to its outstanding electronic properties, black phosphorus (BP) is considered as a promising material for next-generation optoelectronic devices. In this work, devices based on BP/MXene (Zrn+1CnT2, T = O, F, OH, n = 1, 2) van der Waals (vdW) heterostructures are designed via first-principles calculations. Zrn+1CnT2 compositions with appropriate work functions lead to the formation of Ohmic contact with BP in the vertical direction. Low Schottky barriers are found along the lateral direction in BP/Zr2CF2, BP/Zr2CO2H2, BP/Zr3C2F2, and BP/Zr3C2O2H2 bilayers, and BP/Zr3C2O2 even exhibits Ohm…
Using first-principles calculations, we study the structural and electronic properties of the bilayer SnS/graphene, bilayer SnS/bilayer graphene (AA-stacked), bilayer SnS/bilayer graphene (AB-stacked) and monolayer SnS/graphene/monolayer SnS van der Waals (vdW) heterostructures. Electronic properties of all components of the vdW heterostructures are well preserved, which reflects the weakness of the vdW interaction. In the cases of bilayer SnS/graphene and bilayer SnS/bilayer graphene (AA-stacked), an Ohmic contact is formed which can be turned first into p-type and then into n-type Schottky c…
Achieving good quality Ohmic contacts to van der Waals materials is a challenge, since at the interface between metal and van der Waals material, different conditions can occur, ranging from the presence of a large energy barrier between the two materials to the metallization of the layered material below the contacts. In black phosphorus (bP), a further challenge is its high reactivity to oxygen and moisture, since the presence of uncontrolled oxidation can substantially change the behavior of the contacts. In this study, we investigate the influence of the metal used for the contacts to bP a…
Cold source field-effect transistor with type-III band-aligned HfS$_2$/WTe$_2$ heterostructure
College of Physics and Electronic Engineering and Center for Computational Sciences, Sichuan Normal University（四川师范大学物理与电子工程学院及计算科学中心）；Centre for the Physics of Materials and Department of Physics, McGill University（麦吉尔大学材料物理中心及物理系）；School of Integrated Circuit, Peking University（北京大学集成电路学院）；Beijing Advanced Innovation Center for Integrated Circuits（北京集成电路先进创新中心）；College of Physics and Optoelectronic Engineering, Shenzhen University（深圳大学物理与光电工程学院）
We report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe2 field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ~ 0.3 k ohm.um, high on/off ratios up to > 109, and high drive currents exceeding 320 uA um-1. These favorable characteristics are combined with a two-terminal field-effect hole mobility ~ 2x102 cm2 V-…
Two-dimensional (2D) materials exhibit a number of improved mechanical, optical, electronic properties compared to their bulk counterparts. The absence of dangling bonds in the cleaved surfaces of these materials allows combining different 2D materials into van der Waals heterostructures to fabricate p-n junctions, photodetectors, 2D-2D ohmic contacts that show unexpected performances. These intriguing results are regularly summarized in comprehensive reviews. A strategy to tailor their properties even further and to observe novel quantum phenomena consists in the fabrication of superlattices …
Université Grenoble Alpes, CEA, CNRS, IRIG-SPINTEC（格勒诺布尔阿尔卑斯大学）；Laboratoire de Physique de l’Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris（巴黎高等师范学院物理实验室）；PSI Center for Scientific Computing, Theory and Data, Paul Scherrer Institute（保罗谢勒研究所）；Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay（巴黎萨克雷大学）；Université Paris-Saclay, UVSQ, CNRS, GEMaC（巴黎萨克雷大学）
The electronic and the structural properties of two dimensional van der Waals metal/semiconductor heterostructures have been investigated through first-principles calculations. We have considered the recently synthesized borophene [Science {\bf 350}, 1513 (2015)], and the planar boron sheets (S1 and S2) [Nature Chemistry {\bf 8}, 563 (2016)] as the 2D metal layer, and the transition metal dichalcogenides (TMDCs) \mose, and \wse\ as the semiconductor monolayer. We find that the energetic stability of those 2D metal/semiconductor heterojunctions is mostly ruled by the vdW interactions; however, …
Scalable, universal and conformal direct electrodes microprinting for high-performance van der Waals-integrated two-dimensional electronics and flexible applications
The Schottky barrier height ($E_{SBH}$) is a crucial factor in determining the transport properties of semiconductor materials as it directly regulates the carrier mobility in opto-electronics devices. In principle, van der Waals (vdW) Janus heterostructures offer an appealing avenue to controlling the ESBH. However, the underlying atomistic mechanisms are far from understood conclusively, which prompts for further research in the topic. To this end, here, we carry out an extensive first principles study of the electronic properties and $E_{SBH}$ of several vdW Janus MXY/Graphene (M=Mo, W; X, …
Strain and spin orbit coupling effects on electronic and optical properties of 2D CX/graphene (X = S, Se, Te) vdW heterostructure for solar energy harvesting
