Tunable electronic and optical properties of BAs/WTe2heterostructure for theoretical photoelectric device design

The geometric structure of the BAs/WTe2heterojunction was scrutinized by employingab initiocalculations grounded on density functional theory. Multiple configurations are constructed to determine the equilibrium state of the heterojunction with optimal stability. The results show that the H1-type heterojunction with interlayer distance of 3.92 Å exhibits exceptional stability and showcases a conventional Type-II band alignment, accompanied by a direct band gap measuring 0.33 eV. By applying external electric field and introducing strain, one can efficaciously modulate both the band gap and the quantity of charge transfer in the heterojunction, accompanied by the transition of band alignment from Type-II to Type-I, which makes it expected to achieve broader applications in light-emitting diodes, laser detectors and other fields. Ultimately, the heterojunction undergoes a transformation from a semiconducting to a metallic state. Furthermore, the outstanding optical characteristics inherent to each of the two monolayers are preserved, the BAs/WTe2heterojunction also serves to enhance the absorption coefficient and spectral range of the material, particularly within the ultraviolet spectrum. It merits emphasis that the optical properties of the BAs/WTe2heterojunction are capable of modification through the imposition of external electric fields and mechanical strains, which will expand its applicability and potential for future progression within the domains of nanodevices and optoelectronic apparatus.

High-performance and self-powered photodetectors from an S-scheme Cs2SnI2Cl2/Cs2TiI6 heterojunction: a DFT+NAMD study

The recently reported two-dimensional (2D) Ruddlesden-Popper perovskite materials exhibit a plethora of advantages, making them an ideal candidate for constructing high-performance photodetectors. The mixed 2D/3D Cs2SnI2Cl2/Cs2TiI6 heterojunction is an S-scheme heterojunction and has excellent light trapping ability. Due to the spontaneous transfer of carriers caused by different work functions, a built-in electric field is formed in the heterojunction and the self-powered capability is provided. Through the nonadiabatic molecular dynamics (NAMD) method, it is found that the heterojunction exhibits fast photoresponse, low losses and efficient carrier separation. In addition, biaxial compressive strain can not only broaden the photoresponse of the Cs2SnI2Cl2/Cs2TiI6 heterojunction in the near-infrared region and enhance the optical absorption coefficient of the heterojunction, but also enhance the self-powered ability of the heterojunction. Our discoveries present a highly effective avenue for the future development of high-performance, self-powered hybrid optoelectronic devices.

Electrical field and biaxial strain tunable electronic properties of the PtSe2/Hf2CO2 heterostructure

The structure and electronic properties of two-dimensional vertical van der Waals PtSe2/Hf2CO2 heterostructure have been investigated based on first-principles calculations. The results show that the PtSe2 and Hf2CO2 monolayers form a type-I heterostructure with both the conduction band minimum (CBM) and valence band maximum (VBM) located at the Hf2CO2 layer. The electronic properties of PtSe2/Hf2CO2 heterostructure can be effectively adjusted by applying external electric field or biaxial strain. The transition in band alignment from type-I to type-II can be manipulated by controlling the strength and direction of the electric field. Additionally, the transition from type-I to type-II have also taken place under the strains, and the band gap of the PtSe2/Hf2CO2 heterostructure decreases with increasing the compressive or tensible strain. Under a strong strain of -8%, the PtSe2/Hf2CO2 heterostructure can transform from semiconductor to metal. These findings provide a promising method to tune the electronic properties of PtSe2/Hf2CO2 heterostructure and design a new vdW heterostructure in the applications for electronic and optoelectronic devices.

Enhanced photocatalytic performance of a stable type-II PtSe2/GaSe van der Waals heterostructure

In this investigation, the structural, electronic, and optical properties of two-dimensional van der Waals heterostructure (vdwHS) PtSe2/GaSe with three different configurations have been studied using density functional theory with the generalized gradient approximation. All three optimized vdwHSs PtSe2/GaSe have positive phonon frequencies and hexagonal unit cells. The hybrid exchange-correlation functional has been employed to study the electronic properties of vdwHSs PtSe2/GaSe. The vdwHSs PtSe2/GaSe shows semiconducting behavior with indirect Type-II bandgaps, which have been confirmed by the charge density difference, electrostatic potential, work function, and band edge calculations. Additionally, from the band edge positions, the vdwHSs PtSe2/GaSe are analyzed for photocatalytic activities. The optical properties such as extinction coefficient, refractive index, reflectivity, energy loss spectrum, and absorption coefficient have been studied using norm-conserving pseudo-potentials. The vdwHSs PtSe2/GaSe exhibit consistent absorption from the visible to the ultraviolet region of the electromagnetic spectrum. From the obtained results, we conclude that vdwHSs PtSe2/GaSe could be utilized for H2 production through photocatalytic activity as well as for optoelectronic devices and their application.

Insights into selected 2D piezo Rashba semiconductors for self-powered flexible piezo spintronics: material to contact properties

The new paradigm in electronics consists in realizing the seamless integration of many properties latent in nanomaterials, such as mechanical flexibility, strong spin-orbit coupling (Rashba spin splitting-RSS), and piezoelectricity. Taking cues from the pointers given on 1D ZnO nanowires (ACS Nano2018121811-20), the concept can be extended to multifunctional two-dimensional (2D) materials, which can serve as an ideal platform in next-generation electronics such as self-powered flexible piezo-spintronic device. However, a microscopically clear understanding reachable from the state-of-the-art density functional theory-based approaches is a prerequisite to advancing this research domain. Atomic-scale insights gained from meticulously performed scientific computations can firmly anchor the growth of this important research field, and that is of undeniable relevance from scientific and technological outlooks. This article reviews the scientific advance in understanding 2D materials hosting all the essential properties, i.e. flexibility, piezoelectricity, and RSS. Important 2D semiconducting monolayers that deserve a special mention, include monolayers of buckled MgX (X = S, Se, Te), CdTe, ZnTe, Janus structures of transition metal trichalcogenides, Janus tellurene and 2D perovskites. van Der Waals multilayers are also built to design multifunctional materials via modulation of the stacking sequence and interlayer coupling between the constituent layers. External electric field, strain engineering and charge doping are perturbations mainly used to tune the spintronic properties. Finally, the contact properties of these monolayers are also crucial for their actual implementation in electronic devices. The nature of the contacts, Schottky/Ohmic, needs to be carefully examined first as it controls the device's performance. In this regard, the rare occurrence of Ohmic contact in graphene/MgS van der Waals hetero bilayer has been presented in this review article.

Interface contact and modulated electronic properties by in-plain strains in a graphene-MoS2 heterostructure

Designing a specific heterojunction by assembling suitable two-dimensional (2D) semiconductors has shown significant potential in next-generation micro-nano electronic devices. In this paper, we study the structural and electronic properties of graphene-MoS₂ (Gr-MoS₂) heterostructures with in-plain biaxial strain using density functional theory. It is found that the interaction between graphene and monolayer MoS₂ is characterized by a weak van der Waals interlayer coupling with the stable layer spacing of 3.39 Å and binding energy of 0.35 J m^-2. In the presence of MoS₂, the linear bands on the Dirac cone of graphene are slightly split. A tiny band gap about 1.2 meV opens in the Gr-MoS₂ heterojunction due to the breaking of sublattice symmetry, and it could be effectively modulated by strain. Furthermore, an n-type Schottky contact is formed at the Gr-MoS₂ interface with a Schottky barrier height of 0.33 eV, which can be effectively modulated by in-plane strain. Especially, an n-type ohmic contact is obtained when 6% tensile strain is imposed. The appearance of the non-zero band gap in graphene has opened up new possibilities for its application and the ohmic contact predicts the Gr-MoS₂ van der Waals heterojunction nanocomposite as a competitive candidate in next-generation optoelectronics and Schottky devices.

Tunable Schottky barrier in Janus-XGa2Y/Graphene (X/Y = S, Se, Te;X≠Y) van der Waals heterostructures

Two-dimensional (2D) Janus materials have attracted significant attention due to their asymmetrical structures and unique electronic properties. In this work, by using the first-principles calculation based on density functional theory, we systematically investigate the electronic properties of 6 types of Janus-XGa₂Y/Graphene van der Waals heterostructures (vdWHs). The results show that the Janus-XGa₂Y/Graphene vdWHs are connected by weak interlayer vdW forces and can form n-type Schottky contact, p-type Schottky contact or Ohmic contact when the spin-orbit coupling (SOC) is not considered. However, when considering SOC, only the SeGa2S/G and G/SeGa2S vdWHs show n-type Schottky contact, and other vdWHs show Ohmic contacts. In addition, the Schottky barriers and contact types of SeGa₂S/Graphene and Graphene/SeGa₂S vdWHs can be effectively modulated by interlayer distance and biaxial strain. They can be transformed from intrinsic n-type Schottky contact to p-type Schottky contact when the interlayer distances are smaller than 2.65 Å and 2.90 Å, respectively. They can also be transformed to Ohmic contact by applying external biaxial strain. Our work can provide useful guidelines for designing Schottky nanodiodes, field effect transistors or other low-resistance nanodevices based on the 2D vdWHs.

Electronic properties and interface contact of graphene/CrSiTe3 van der Waals heterostructures

Electronic properties and interface contact of Graphene-based heterostructure Graphene/CrSiTe3 (Gr/CrSiTe3) is modulated by tuning the interfacial distance, along with appling an external electric field. Our first-principles calculations show that the...

Coherent control of interlayer vibrations in Bi2Se3 van der Waals thin-films

Interlayer vibrations with discrete quantized modes in two-dimensional (2D) materials can be excited by ultrafast light due to the inherent low dimensionality and van der Waals force as a restoring force. Controlling such interlayer vibrations in layered materials, which are closely related to fundamental nanomechanical interactions and thermal transport, in spatial- and time-domain provides an in-depth understanding of condensed matters and potential applications for advanced phononic and photonics devices. The manipulation of interlayer vibrational modes has been implemented in a spatial domain through material design to develop novel optoelectronic and phononic devices with various 2D materials, but such control in a time domain is still lacking. We present an all-optical method for controlling the interlayer vibrations in a highly precise manner with Bi₂Se₃ as a promising optoelectronic and thermoelasticity material in layered structures using a coherently controlled pump and probe scheme. The observed thickness-dependent fast interlayer breathing modes and substrate-induced slow interfacial modes can be exactly explained by a modified linear chain model including coupling effect with substrate. In addition, the results of coherent control experiments also agree with the simulation results based on the interference of interlayer vibrations. This investigation is universally applicable for diverse 2D materials and provides insight into the interlayer vibration-related dynamics and novel device implementation based on an ultrafast timescale interlayer-spacing modulation scheme.

Tunable Schottky barrier in InTe/graphene van der Waals heterostructure

The structures and electronic properties of InTe/graphene van der Waals heterostructures are systematically investigated using the first-principles calculations. The electronic properties of InTe monolayer and graphene are well preserved respectively and the bandgap energy of graphene is opened to 36.5 meV in the InTe/graphene heterostructure. An n-type Schottky contact is formed in InTe/graphene heterostructure at the equilibrium state. There is a transformation between n-type and p-type Schottky contact when the interlayer distance is smaller than 3.56 Å or the applied electric field is larger than -0.06 V Å^-1. In addition, the Schottky contact converts to Ohmic contact when the applied vertical electric field is larger than 0.11 V Å^-1 or smaller than -0.13 V Å^-1.

Tuning the Schottky barrier height in graphene/monolayer-GeI2van der Waals heterostructure

We use first-principles simulations to investigate the structural and electronic properties of a heterostructure formed by graphene and monolayer GeI2(m-GeI2). While graphene has been extensively studied in the last 15 years, m-GeI2has been recently proposed to be a stable 2D semiconductor with a wide-band gap, Liuet al(2018J. Phys. Chem.C12222137). By staking both structures we obtain a metal-semiconductor junction, with great potential for applications in the designing of new (opto)electronic devices. The results show that the graphene Dirac cone is preserved in the graphene/m-GeI2heterostructure. We find that there are no chemical bonds at the graphene and m-GeI2interface, thus the heterostructure interactions are ruled by van der Waals (vdW) forces. The interface between graphene and m-GeI2results in a n-type Schottky contact. Furthermore, we show that a transition from n-type to p-type Schottky contact can be obtained by decreasing the interlayer distance. We also modulated the Schottky barrier heights by applying a perpendicular external electric field through the vdW heterostructure. In particular, positive values resulted in an increase of the n-type Schottky barrier height, while negative electric field values induced a transition from n-type to p-type Schottky contact. From our results, we show that m-GeI2is an interesting material to design new electronic Schottky devices based on graphene vdW heterostructures.

The effects of strain and electric field on the half-metallicity of pristine and O-H/C-N-decorated zigzag graphene nanoribbons

In zigzag graphene nanoribbons (ZGNRs), the spin polarized edge states play a significant role in the electronic structure. The two ferromagnetically ordered edges anti-ferromagnetically coupled with each other, which would result in the half-metallicity under electric field. Given that the strain, external electric field, and edge decorations are the main means of tuning the magnetism and electronic property of one-dimentional materials. It motivates us to study the combine effects on ZGNRs of these methods. So, in present work, the corporate influences of the tensile strain, transverse electric field, and asymmetric edge decoration by  -OH and  -CN groups on the magnetism and electronic property of 8-ZGNR have been studied using the density functional theory. The calculational results indicate that the arising strain can modulate the response of electronic and magnetic properties to external electric field, improving the magnetism and extending the electric field range in which the ZGNR presents half-metallicity. In addition, the O-H/C-N groups decorated ZGNR possesses a lower critic electric field and a larger electric field range for realizing half-metallicity comparing with the unstrained pristine ZGNR.

MoB2: a new multifunctional transition metal diboride monolayer

Several layered transition metal borides can now be realized by a simple and general fabrication method (Fokwa et al 2018 Adv. Mater. 30 1704181), inspiring our interest to transition metal borides monolayer. Herein, we predict a new two-dimensional (2D) transition metal diboride MoB₂ monolayer (ML) and study its intrinsic mechanical, thermal, electronic, and transport properties. The MoB₂ ML has isotropic mechanic properties along the zigzag and armchair directions with a large Young's stiffness, and has an ultralow room-temperature thermal conductivity. The Mo atoms dominate the metallic nature of MoB₂ ML. It shows an obvious electrical anisotropy and a current-limiting behavior. Our findings suggest that MoB₂ ML is a promising multifunctional material used in ultrathin high-strength mechanical materials, heat insulating materials, electrical-anisotropy-based materials, and current limiters. It is helpful for the experimentalists to further prepare and utilize the transition metal diboride 2D materials.

Effects of different surface functionalization on the electronic properties and contact types of graphene/functionalized-GeC van der Waals heterostructures

Constructing vertical heterostructures by placing graphene (Gr) on two-dimensional materials has recently emerged as an effective way to enhance the performance of nanoelectronic and optoelectronic devices.

Electronic and optical properties of a Janus SnSSe monolayer: effects of strain and electric field

In this paper, detailed investigations of the electronic and optical properties of a Janus SnSSe monolayer under a biaxial strain and electric field using ab initio methods are presented.

C2N/BlueP van der Waals hetero-structure: an efficient photocatalytic water splitting 2D material

Constructing van der Waals (vdW) hetero-structures is an effective and feasible method to enhance two-dimensional (2D) materials with desired properties and to extend the application of the original materials. In this work, we establish a C₂N/BlueP vdW hetero-structure and explore its photocatalytic water splitting performance by investigating the electronic structure, band edge alignment, charge transfer, optical absorption and strain response based on the density functional theory (DFT) method. Numerical results indicate that the C₂N/BlueP hetero-structure possesses a proper direct bandgap and intrinsic type-II band alignment, which are beneficial to the space separation of photo-generated electron-hole pairs. The optical absorption of the hetero-structures is enhanced from the visible to ultraviolet light region compared with those of both individual monolayers. More importantly, the valence band maximum (VBM) is lower than the oxidation potential of water, and the conduction band minimum (CBM) is higher than the reduction potential of water, which indicates the proper photocatalytic potential for water splitting of the C₂N/BlueP hetero-structure. By applying a small vertical pressure perpendicular to the hetero-structure with roughly 6% interlayer compression, both the band alignment and the optical absorption can be improved, which gives better performance of photocatalytic water splitting for the C₂N/BlueP hetero-structure.

First-principles investigation on electronic properties and band alignment of group III monochalcogenides

Using first-principles calculations, we investigated the electronic properties and band alignment of monolayered group III monochalcogenides. First, we calculated the structural and electronic properties of six group III monochalcogenides (GaS, GaSe, GaTe, InS, InSe, and InTe). We then investigated their band alignment and analysed the possibilities of forming type-I and type-II heterostructures by combining these compounds with recently developed two-dimensional (2D) semiconducting materials, as well as forming Schottky contacts by combining the compounds with 2D Dirac materials. We aim to provide solid theoretical support for the future application of group III monochalcogenides in nanoelectronics, photocatalysis, and photovoltaics.

Strain engineering on the electronic states of two-dimensional GaN/graphene heterostructure

Combining two different layered structures to form a van der Waals (vdW) heterostructure has recently emerged as an intriguing way of designing electronic and optoelectronic devices. Effects of the strain on the electronic properties of GaN/graphene heterostructure are investigated by using first-principles calculation. In the GaN/graphene heterostructure, the strain can control not only the Schottky barrier, but also contact types at the interface. Moreover, when the uniaxial strain is above -1% or the biaxial strain is above 0%, the contact type transforms to ohmic contact. These results provide a detailed understanding of the interfacial properties of GaN/graphene and help to predict the performance of the GaN/graphene heterostructure on nanoelectronics and nanocomposites.

Effects of out-of-plane strains and electric fields on the electronic structures of graphene/MTe (M = Al, B) heterostructures

Contacts between graphene and two-dimensional (2D) semiconductors have been widely investigated because of their tunable Schottky barrier height (SBH) by means of applied out-of-plane strains, electric fields, etc. Here, based on first-principles calculations, we study the effects of out-of-plane strains (a tensile or compressive strain) and electric fields on the electronic structures of graphene/MTe (M = Al, B) heterostructures. The calculated results indicate that p-type Schottky barriers are formed at the graphene/AlTe and graphene/BTe interfaces with 0.72 and 0.49 eV, respectively. The increase in the interlayer distances (tensile strains) between graphene and MTe can induce a transition from a p-type to n-type Schottky contact. On the other hand, the decrease in the interlayer distances (compressive strains) can transform graphene/MTe into semiconductors, which originates from graphene/MTe with a large compressive strain that makes the two carbon sublattices inequivalent, inducing a band gap. In addition, the applied electric fields can modulate effectively the contact formation (a Schottky or Ohmic contact) and the doping of graphene in graphene/MTe heterostructures. Our study suggests two facile methods to tune the electronic properties of graphene/MTe heterostructures and offer a possibility for graphene/MTe heterostructure-based electronic devices.

Tuning the Electronic and Magnetic Properties of Graphene Flake Embedded in Boron Nitride Nanoribbons with Transverse Electric Fields: First-Principles Calculations

The electronic and magnetic properties of h-BN nanoribbions embedded with graphene nanoflakes (CBNNRs) are systematically studied by ab initio calculations. The CBNNRs with zigzag or armchair edges are all bipolar magnetic semiconductors (BMSs). The band gaps of zigzag CBNNRs (zCBNNRs) change linearly with the transverse electric field (E-field) for the first-order Stark effect, whereas for the armchair CBNNRs (aCBNNRs), the band gaps vary quadratically with the E-field for the second-order Stark effect. For zCBNNRs and aCBNNRs, they could transform from BMS to spin gapless semiconductor (SGS), metal, and half-metal (HM) under different transverse E-fields. The CBNNRs may transform into a semiconductor or HM, under the same E-fields, depending on the position of graphene flakes. The CBNNRs introduce local magnetic moment at carbon atoms, and the magnetic moment is determined by the size of the graphene flakes. These observations open the door to applications of CBNNRs in spintronic devices.

Electronic and magnetic properties of a black phosphorene/Tl2S heterostructure with transition metal atom intercalation: a first-principles study

Using density functional theory calculations, the structural, electronic and magnetic properties of a black phosphorene/Tl2S heterostructure (BP/Tl2S) and the BP/Tl2S intercalated with transition metal atoms (TMs) have been detailed investigated. It is demonstrated that the BP/Tl2S is a type-I van der Waals (vdW) heterostructure with an indirect band gap of approximately 0.79 eV. The BP/Tl2S experiences a transition from type-I to type-II when various strains are applied. In addition, the BP/Tl2S intercalated with TMs (TM-BP/Tl2S) exhibits various kinds of meaningful electronic and magnetic properties. Several TM-BP/Tl2S systems are still non-magnetic ground states and six TM-BP/Tl2S (Ti-, V-, Cr-, Mn-, Fe-, Tc-) systems are ferromagnetic. Interestingly, three TM-BP/Tl2S (V-, Cr-, Mn-) systems display half-metallic character. The Fe-BP/Tl2S and Tc-BP/Tl2S are dilute magnetic semiconductors (DMSs), while TM-BP/Tl2S (Mo-, Pd-, Ni-) systems are semiconductors. The other TM-BP/Tl2S systems become metals. These results may open a new avenue for application of the BP/Tl2S in future spintronic and electronic devices.

Recent Advances in 2D Lateral Heterostructures

Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from two-dimensional (2D) materials. A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials. These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences. Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures; the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties. In this review, we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction, where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials. Afterward, we discuss the applications and experimental synthesis of lateral 2D heterostructures. Moreover, a perspective on lateral 2D heterostructures is given at the end.

Dipole controlled Schottky barrier in the blue-phosphorene-phase of GeSe based van der Waals heterostructures

Controlling the interface structure is of utmost importance to regulating the nanoscale Schottky barrier height (SBH). Herein, by using first-principles calculations, the electronic properties of the graphene (G) based blue-phosphorene-phase of GeSe van der Waals (vdW) heterostructures, including M/G and X/G interfaces (M = Ge; X = Se), are systematically investigated. When the layer spacing exceeds the vdW gap, n-type Schottky contacts are formed for both MX/G and XM/G heterojunctions. With the layer spacing decreasing to equilibrium distances, due to different charge transfer across the interface, MX/G and XM/G heterojunctions display n- and p-type Schottky contacts, respectively. Further decreasing the layer distance makes both heterojunctions transit into p-type ones. The layer-spacing-dependent SBHs can be rationalized by the increased charge transfer across the interface and the resulting interfacial dipole enhancement. Enlightened by the finding of dipole-controlled SBHs, using MX as building blocks, two different stacking patterns, i.e., nMX-MX-G and nXM-XM-G (n = 1 and 2), are designed to further modulate the SBH. Interestingly, due to the presence of the intrinsic dipole of MX, it is found that the magnitude and orientation of the interfacial dipole can be artificially engineered. With n increasing from 0 to 2, nMX-MX-G with an X/G interface changes from the n-type Schottky contact to Ohmic contact. The Fermi level meets the conduction band and G shows a p-type doping feature finally. Likewise, transition from p-type Schottky contact to Ohmic contact is observed for the nXM-XM-G with M/G interface, accompanied by the Fermi level touching the valence band and the feature of n-type doping for G. The role of nMX stacking seems like the role of applying an external electric field (E-field): applying positive E-field is equivalent to the increase of dipole moment while negative E-field corresponds to the offset of dipole moment. In brief, the SBHs of GeSe/G contact are found to be tunable which originates from the intrinsic dipole of MX. The predictable SBHs for these kinds of charming built-in dipole systems are expected to be highly desirable in electronic devices.

Elastic Anisotropy and Optic Isotropy in Black Phosphorene/Transition-Metal Trisulfide van der Waals Heterostructures

Anisotropic two-dimensional materials with direction-dependent mechanical and optical properties have attracted significant attention in recent years. In this work, based on density functional theory calculations, unexpected elastic anisotropy and optical isotropy in van der Waals (vdW) heterostructures have been theoretically proposed by assembling the well-known anisotropic black phosphorene (BP) and transition-metal trisulfides MS₃ (M = Ti, Hf) together. It is interesting to see that the BP/MS₃ vdW heterostructures show anisotropic flexibility in different directions according to the elastic constants, Young's modulus, and Poisson's ratio. We have further unraveled their physical origin of the type-II band structure nature with their conduction band minimum and valence band maximum separated in different layers. In particular, our results on the optical response functions including the excitonic effects of the BP/MS₃ vdW heterostructures suggest their unexpected optical isotropies together with the enhancements of the solar energy conversion efficiency.

Tailoring the structural and electronic properties of an SnSe2/MoS2 van der Waals heterostructure with an electric field and the insertion of a graphene sheet

van der Waals heterostructures by stacking different two-dimensional materials are being considered as potential materials for nanoelectronic and optoelectronic devices because they can show the most potential advantages of individual 2D materials.

Proximity effects in graphene and ferromagnetic CrBr3 van der Waals heterostructures

Schematic of the magnetic proximity effect in a van der Waals heterostructure formed by a graphene monolayer, induced by its interaction with a two-dimensional ferromagnet (CrBr₃) for designing a single-gate field effect transistor.

Band alignment and optical features in Janus-MoSeTe/X(OH)2 (X = Ca, Mg) van der Waals heterostructures

van der Waals heterostructures can be effectively used to enhance the electronic and optical properties and extend the application range of two-dimensional materials.

Structural and electronic properties of a van der Waals heterostructure based on silicene and gallium selenide: effect of strain and electric field

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.