Tiny Band Gap Research Articles

Emerging topological states in EuMn2Bi2: A first principles prediction

New materials with magnetic order driven topological phases are hugely sought after for their immense application potential. In this work, we propose a new compound EuMn2Bi2 from our first principles density functional theory calculations to host novel topological phases such as Dirac/Weyl semimetal and topological insulator in its different magnetic states which are energetically close to one another. The new compound EuMn2Bi2 is found to be dynamically stable from our phonon calculations supporting its experimental preparation in future. By comparing the total energies of various possible magnetic structures of EuMn2Bi2, we identified the ground state. The magnetic ground state is found to be a normal insulator with tiny band gap which is an order of magnitude less than the same in another well studied sister compound EuMn2As2. However, there exist other magnetic states energetically very close to the ground state in EuMn2Bi2 which display remarkable non-trivial band topology such as Dirac/Weyl points close to the Fermi level and topological insulator state driven by magnetic order which is not observed in EuMn2As2. The energetic proximity of these magnetic order driven topological phases makes them tunable via external handle such as magnetic field indicating that the proposed new material EuMn2Bi2 would be a very versatile magnetic topological material if prepared experimentally in future.

Natural honey (Mellifera) assisted combustion synthesis of ZnO, Ag-ZnO and Fe-ZnO nanoparticles for ethanol gas sensor applications

Biogenic combustion with Mellifera (Honey) capping produced ZnO, Ag-doped ZnO, and Fe-doped ZnO nanoparticles. The phase and crystal structure of metal oxide nanoparticles (MONPs) have been recorded through XRD spectrum. It confirms that the prepared metal oxides are within the nanoscale range. The average crystallite size of Fe-doped ZnO is 8.8 nm, smaller than ZnO and Ag-doped nanoparticles. The vibrational spectra of ZnO, Ag-doped ZnO, and Fe-doped ZnO nanoparticles confirm functional group stretching vibrational modes. The exterior surface morphology of all metal oxide nanoparticles was captured by FESEM. Metal oxide nanoparticle compositional analysis shows elemental presence, atomic, and weight %. The optical properties of metal oxide nanoparticles have been examined using UV–vis spectroscopy. The band gap energy of ZnO nanoparticles reduced from 2.68 eV to 1.74 eV under Fe doing and increased to 2.9 eV under Ag doing. Metal oxide thermal stability is also being investigated to determine how it affects ZnO nanoparticles. Fe-doped ZnO nanoparticles have greater sensor properties than other metal oxides due to their tiny size, band gap, and stability. Gas sensor behaviour of three metal oxide nanoparticles was examined in various accepts. It proves Fe-doped ZnO is a promising gas sensor material.

Spin–orbit coupling tunable electronic properties of [formula omitted]-MoS[formula omitted] and ternary Janus [formula omitted]-MoSSe monolayers: Theoretical prediction

MoS2 can exist in many different polytypes, such as trigonal prismatic, distorted octahedral, or octahedral. The 2H-phase of MoS2 has been extensively studied in recent times, but there are very few studies focusing on the remaining phases, especially the distorted octahedral T′)-phase. Here, we design the MoS2 monolayer and Janus MoSSe structure in the 1T′ phase and study their electronic properties within the framework of first-principles calculations. Both 1T′-MoS2 and 1T′-MoSSe monolayers are confirmed to have structural stability and anisotropic mechanical characteristics. Interestingly, while the 1T′-MoS2 monolayer exhibits metallic characteristics, Janus MoSSe in the 1T′ phase is a semiconductor with a small band gap of 0.04 eV. More interestingly, a tiny bandgap of 0.05 eV has opened up in the 1T′-MoS2 monolayer due to the spin–orbit coupling effect. We also study the mobility of carriers in the semiconductor Janus 1T′-MoSSe monolayer. 1T′-MoSSe monolayer exhibits a high anisotropic carrier mobility due to its high anisotropic crystal structure. Surprisingly, 1T′-MoSSe monolayer possesses extremely high electron mobility, up to 4.58×103 cm2 V−1 s−1. Our findings give a deeper insight into the 1T′-phase of transition metal dichalcogenide and its Janus structure.

Visible-light-driven 2D carbonaceous-based SnSe nanohybrid soft materials: A photocatalyst for efficient photo reduction of malachite green dye

Preserving a healthy environment of air, land, and water requires the treatment of dangerous organic effluents. Efficiently degrading hazardous pollutants requires low-cost, high-absorption visible-light-driven photocatalysts. Furthermore, the tin selenide exhibited a tiny band gap that promotes the faster recombination of electrons and holes, and rGO shows restacking morphology that reduces the surface area of the materials. Both issues have been resolved by adding the rGO into SnSe to make an rGO/SnSe resolving the restacking issue and narrowing the band gap. In this research work, we report a hydrothermally synthesize tin selenide (SnSe) sustained on reduced graphene oxide (rGO) nanosheets as photocatalysts. Our research focuses on the degradation of hazardous industrial malachite green dye. Our analysis suggests that the rGO/SnSe nanocomposite effectively degrades malachite green (MG) dyes by 95.52% compared to pure SnSe (83.52%). The rGO sheets facilitate electron (e-) excitation from the valence band (V.B) to the conduction band (C.B), which significantly enhances the photocatalytic performance. We also investigated the reusability of the photocatalyst and the mineralization activity of a malachite green (MG) pollutant to check the photocatalytic mechanism and stability. The reusability test indicates that rGO/SnSe exhibited excellent 86.45% stability. The scavenger’s analysis suggests that electrons (e-) and holes (h+) play a significant part in the photocatalytic mineralization of MG dye. Our research explores that the rGO/SnSe nanohybrid is a significant material for wastewater treatment, solar energy conversion as well as environmental restoration.

Crucial role of interfacial interaction in 2D polar SiGe/GeC heterostructures

The planar charge transfer is a distinctive characteristic of the two-dimensional (2D) polar materials. When such 2D polar materials are involved in vertical heterostructures (VHs), in addition to the van der Waals (vdW) interlayer interaction, the interfacial interaction triggered by the in-plane charge transfer will play a crucial role. To deeply understand such mechanism, we conducted a comprehensive theoretical study focusing on the structural stability and electronic properties of 2D polar VHs built by commensurate SiGe/GeC bilayers with four species ordering patterns (classified as a C-group with patterns I and II and a Ge-group with patterns III and IV, respectively). It was found that the commensurate SiGe/GeC VHs are mainly stabilized by interfacial interactions (including the electrostatic interlayer bonding, the vdW force, as well as the sp 2/sp 3 orbital hybridization), with the Ge-group being the most energetically favorable than the C-group. A net charge redistribution occurs between adjacent layers, which is significant (∼0.23–0.25 e cell−1) in patterns II and IV, but slightly small (∼0.05–0.09 e cell−1) in patterns I and III, respectively, forming spontaneous p–n heterojunctions. Such interlayer charge transfer could also lead to a polarization in the interfacial region, with the electron depletion (accumulation) close to the GeC layer and the electron accumulation (depletion) close to the SiGe layer in the C-group (the Ge-group). This type of interface dipoles could induce a built-in electric field and help to promote photogenerated electrons (holes) migration. Furthermore, a semi-metal nature with a tiny direct band gap at the SiGe layer and a semiconducting nature at the GeC layer indicate that the commensurate SiG/GeC VHs possess a type-I band alignment of heterojunction and have a wide spectrum of light absorption capabilities, indicating its promising applications for enhancing light-matter interaction and interfacial engineering.

The effects of MS2 (M = Mo or W) substrates on electronic properties under electric fields in germanene-based field-effect transistors

Germanene has attracted significant attention due to its novel electronic properties and strong spin-coupling effect. However, the tiny band gap of the germanene dramatically limits its application in field-effect transistors (FETs). Inspired by the utilization of the substrates and electric fields to adjust the band gaps of two-dimensional materials, we investigated the fundamental mechanism of electric fields on the atomic structures and electronic properties of germanene supported by MS2 (M = Mo or W) substrates through first-principles calculation. The results show that the substrates can induce a symmetry breaking in the germanene sublattice via van der Waals interaction, leading to a sizable band gap at the Dirac point. In addition, the band gaps of the germanene/MS2 heterostructures can be effectively modulated by applying an external electric field. Under suitable electric fields, the considerable band gap values of CMo germanene/MoS2 and TGeL-W germanene/WS2 configurations can open the maximum band gaps with 263 and 247 meV, which satisfy the requirements of FETs at room temperature. Meanwhile, the evolutions of charge transfers under electric fields were explored to illustrate how electric fields and substrates promote the electronic properties of germanene. More interestingly, a Schottky–Ohmic transition can occur when a specific electric field is imposed on the germanene/MS2 heterostructures. Note that the hole and electron carrier mobilities of germanene/MS2 heterostructures are still significantly preserved, showing some superior electronic performances than some heterostructures. The results provide a critical theoretical guide for improving the electronic properties of germanene, and demonstrate the designed germanene/MS2 heterostructures with the tunable band gaps and higher carrier mobilities as germanene-based FETs.

Precise Design of Molecular Ferroelectrics with High TC and Tunable Band Gap by Molecular Modification.

Molecular ferroelectric materials are widely applied in piezoelectric converters, non-volatile memorizers, and photovoltaic devices due to their advantages of adjustable structure, lightweight, easy processing, and environmental friendliness. However, designing multifunctional molecular ferroelectrics with excellent properties has always been a great challenge. Herein, a multiaxial molecular ferroelectric is successfully designed by modifying the quasi-spherical cation dabco with CuBr2 to obtain halogenated [Bretdabco]CuBr4 (Bretdabco = N-bromoethyl-N'-diazabicyclo [2.2.2]octane), which crystallizes in polar point groups (C6). Typical ferroelectric behaviors featured by the P-E hysteresis loop and switched ferroelectric domain are exhibited. Notably, the molecular ferroelectric shows a high TC of 460 K, which is rare in the field and could greatly expand the application range of this material. In addition, the band gap is adjustable through the regulation of halogen. Both the UV absorption spectra and theoretical calculations indicate that the molecular ferroelectrics belong to a direct band gap (2.14 eV) semiconductor. This tunable and narrow band gap semiconductor molecular ferroelectric material with high TC can be utilized more effectively in the study of optoelectronics and sensors, including piezoelectric energy harvesters. This research may provide a promising approach for the development of multiaxial molecular ferroelectrics with a tiny band gap and high TC.

Hydrogenation-induced ultrahigh stabilization and tunable electronic structures of two-dimensional orthorhombic diboron diphosphide

Using density-functional theory calculations, we have studied hydrogenated two-dimensional (2D) orthorhombic diboron diphosphorus (O-B2P2). It is found that hydrogenation can transit the pristine O-B2P2 from a tiny bandgap semiconductor to a wide- and indirect-bandgap semiconductor, and the bandgaps are dependent on hydrogenation configurations. Moreover, our calculations have revealed that the three hydrogenated O-B2P2 nanostructures are both dynamically and thermally stable, and their bandgaps are estimated to be 2.8–4.2 eV according to hybrid potential calculations. They are predicted to possess strongly anisotropic mechanical and carrier transport properties, allowing potential applications for in-plane anisotropic and high-performance electronic devices. Hydrogenated O-B2P2 nanostructures exhibit strong absorbance of ultraviolet light and their bandgaps can be linearly modulated by tensile strain. Our findings demonstrate novel mechanical and electronic properties of hydrogenated O-B2P2 nanostructures, combined with excellent stability in ambient conditions, suggesting that they could be promising candidates for strongly anisotropic electronic and sensor devices.

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.

Rational design of a C3N/C3B p-n heterostructure as a promising anode material in Li-ion batteries.

It is urgent to develop high-performance anode materials for lithium-ion batteries. In this work, a C3N/C3B p-n heterostructure was systematically investigated by first-principles calculations. The bonding strength of Li in C3N is relatively low (-0.53 eV), whereas the C3N/C3B heterostructure (-1.64 eV to -2.84 eV) can greatly improve the bonding strength without compromising the Li migration capability. The good bonding strength and Li mobility in the C3N/C3B heterostructure are mainly caused by the synergy effect and internal electric field of the p-n heterostructure. Moreover, the electronic structures indicate that the C3N/C3B heterostructure has good conductivity with a tiny bandgap of 0.09 eV. Compared to pristine C3N, the stiffness of the C3N/C3B heterostructure improved significantly (549.35 N m-1). Besides, the C3N/C3B heterostructure presents a high lithium-ion storage capacity (986.61 mA h g-1). The ultrahigh stiffness, good conductivities of electrons and ions, high bonding strength of Li, and high capacity show that the C3N/C3B heterostructure is a prospective anode material for lithium-ion batteries.

Symmetry breaking induced bandgap opening in epitaxial germanene on WSe2

Germanene has attracted much attention because the material was predicted to host Dirac fermions. However, the synthesis of germanene is still in its infancy; moreover, the predicted tiny bandgap induced by the spin–orbit coupling is far from practical applications for nanoelectronic devices. Herein, quasi-freestanding germanene with linear dispersion relation of the band structure is well grown on a WSe2/Au(100) substrate. Band structure calculations reveal that the interaction of germanene with the substrate destroys the sublattice symmetry. The energy-dependent contribution of σ orbitals responsible for band crossing at the Fermi level around the Γ point induces asymmetric density of states at the Dirac point. Upon annealing in ultra-high vacuum, we observe a bandgap opening in germanene of about ∼0.17 eV, which is attributed to a sublattice symmetry breaking in germanene and the emergence of a net electric field. This work provides an effective method to tune or tailor the electronic properties of germanene, paving the way to germanene-based field-effect applications.

The controllable electronic characteristics and Schottky barrier of graphene/GaP heterostructure via interlayer coupling and in-plane strain

Establishing the desired heterostructures by assembling suitable semiconductor materials has shown significant potential for applications in next-generation micro-nano electronic devices. In this present contribution, we demonstrate the geometric structure and electronic properties of graphene/GaP heterostructure by first-principles calculations. It is found that the heterostructure is characterized by weak interlayer coupling accompanying the stable layer spacing of 3.40 Å and binding energy of −39.35 meV, meaning that the interlayer is dominated by van der Waals (vdW) force. The electronic band structure of free-standing graphene and GaP monolayers are preserved well. Meanwhile, a tiny bandgap of approximatively 20 meV at the Dirac point of graphene is opened, which is attributed to the breakdown of sublattice symmetry. In the ground state, the Schottky contact of p-type is present with the n-type and p-type SBH of 1.71 eV and 0.10 eV, respectively, which can be effectively induced by imposing interlayer coupling as well as in-plane strains. Especially, the transition of p-Schottky contact to p-Ohmic contact occurs when the layer spacing decreases to 3.20 Å or the strain increases to +2 %. These theoretical results may offer potential guiding principle in future electronic devices.

Ferromagnetic Weyl metal in EuAgP

The combination of band topology with magnetic ordering provides an excellent platform to realize various magnetic topological phases. Based on first-principle calculations and symmetry analysis, we predict that two distinct topological phases can be switched in the ferromagnetic material EuAgP by tuning the direction of magnetic moment. In the absence of spin-orbit coupling (SOC), the material is half-metallic with only one spin-up channel around the Fermi level, giving rise to a pair of triple points (TPs) along C6 axis, protected by the point group symmetry. As the magnetic moment is oriented along the z direction (with SOC included), the emergent TP in the absence of SOC splits into two Weyl points (WPs), featuring the nontrivial Fermi arcs on the side surface; however, when the magnetic moment is rotated to the x direction, a tiny band gap (<3.0 meV) appears around the TP due to the breaking of rotation symmetry, which can be regarded as the nearly TP. The intrinsic anomalous Hall conductivity of EuAgP is calculated for the different ferromagnetic states, which is sensitive to the magnetic ordering. Furthermore, we propose to realize the ideal Weyl semimetal with a single pair of WPs close to the Fermi level via partially substituting Eu by Ba.

New stable two dimensional silicon carbide nanosheets

Abstract We predict the existence of new two dimensional (2D) silicon carbide nanostructures employing ab initio density-functional theory calculations. These structures are composed of tetragonal and hexagonal rings with C─C and Si─C bonds arranged in a buckling plane. They are proven to be thermodynamically and mechanically stable with relatively low formation energy, implying potential fabrication in labs. They exhibit strong ductility and anisotropicity from their strain-stress relations and directional dependence of mechanical moduli. The materials maintain phonon stability upon the application of mechanical strain up to 27% with fantastic ductile property. The proposed 2D SiC2 structure possesses a tiny direct band gap of 0.02 eV predicted using HSE06 functional and the band gap can be opened up through multiple approaches such as hydrogenation and strain application. The gap values can be strategically tuned in the range of 0.02–1.72 eV and the direct/indirect gap nature can be further manipulated. In contrast, a closely related isostructural 2D SiC shows an indirect HSE band gap of 1.80 eV and strain engineering its value between 0.0–1.95 eV. The unique properties in these newly proposed structures might have potential applications in future nanomechanics and electronics.

Strain effect on the electronic and optical properties of Germanene/MoS2 heterobilayer

The strain effect on the electronic and optical properties of Germanene/MoS2 heterobilayer have been investigated by using first principles calculations with vdW corrections. Different stacking patterns of Germanene/MoS2 heterobilayer have been designed, which all show similar electronic and optical properties. Germanene is found to interact with MoS2 monolayer via weak vdW interactions, only leading to a tiny band gap opened with its Dirac cone well preserved. This implies MoS2 monolayer can be a suitable semiconducting substrate for germanene adhension. Through various in-plane external strains, the opened Dirac gap of heterobilayer can be further modulated and a semiconductor-metal transition even occurs. In addition, the Germanene/MoS2 heterobilayer can exhibit much wider optical adsorption range together with a red-shift in adsorption edge compared to individual layers. The position and intensity of optical adsorption peaks in ultraviolet and visible light regions also can be effectively tuned by applying external strains. With the strain controllable electronic and optical properties, Gemanene/MoS2 heterobilayer is expected to be a candidate for applications in new functional nanoelectronic and optoelectronic devices.

Systematic Enumeration of Low‐Energy Graphyne Allotropes Based on a Coordination‐Constrained Searching Strategy

Based on a coordination‐constrained searching strategy, 48 new graphyne allotropes are discovered and systematically optimized by first‐principles calculations. Among these newly discovered 2D carbons, 127‐E20Y16‐0, 191‐E24Y24‐0, 191‐E18Y18‐0, and 191‐E24Y36‐0 with energies lower than those of the experimentally synthesized γ‐graphdiyne, β‐graphdiyne, and carbon ene‐yne are further confirmed to be dynamically, mechanically, and also thermally stable phases. Their fundamental electronic and mechanical properties are systematically studied and compared with those of γ‐graphdiyne and γ‐graphyne. The Heyd−Scuseria−Ernzerhof (HSE06)‐based electronic band structures reveal that 127‐E20Y16‐0, 191‐E24Y24‐0, 191‐E18Y18‐0, and 191‐E24Y36‐0 are semiconductors with bandgaps of 0.489, 0.994, 0.012, and 0.167 eV, respectively. Their narrow or tiny bandgap features suggest that they are potential materials for photodetecting in the ultra‐infrared region. The calculated mechanical properties of the hexagonal 191‐E24Y24‐0, 191‐E18Y18‐0, and 191‐E24Y36‐0 are just slightly dependent on the crystalline direction, and are similar to those of γ‐graphdiyne and γ‐graphyne. However, the tetragonal 127‐E20Y16‐0 shows obvious anisotropic features in both Young's modulus and Poisson's ratio. The results presented herein further enrich the structures of the family of graphyne allotropes. In view of their remarkable stability and potential applications in photoelectronics and nanomechanics, the newly discovered 127‐E20Y16‐0, 191‐E24Y24‐0, 191‐E18Y18‐0, and 191‐E24Y36‐0 are expectable targets for future experiments.

Vertical van der Waals Heterostructure of Single Layer InSe and SiGe

We present a first-principles investigation on the stability, electronic structure and mechanical response of ultra-thin heterostructure composed of single layers of InSe and SiGe. First, by per- forming total energy optimization and phonon calculations, we show that single layers of InSe and SiGe can form dynamically stable heterostructures in 12 different stacking types. Valence and conduction band edges of the heterobilayers form a type-I heterojunction having a tiny bandgap ranging between 0.09-0.48 eV. Calculations on elastic-stiffness tensor reveal that two mechanically soft single layers form a heterostructure which is stiffer than constituent layers due to relatively strong interlayer interaction. Moreover, phonon analysis show that the bilayer heterostructure has highly Raman active modes at 205.3 and 43.7 cm −1 , stemming from out-of-plane interlayer mode and layer breathing mode, respectively. Our results show that, as a stable type-I heterojunction, ultra-thin heterobilayer of InSe/SiGe holds ...

First principles study of the adsorption of hydrated heavy metals on graphene quantum dots

The adsorption of hydrated heavy metals on graphene quantum dots is investigated using the density functional theory. The considered heavy metals are Cd and Pb that are hexa-, penta-, and tetrahydrated with water molecules. Various adsorption schemes are considered such as surface and edge adsorption, and the interaction with functional groups attached to the flake's edges. The calculated positive adsorption energy implies that the considered graphene flakes are able to adsorb the hydrated heavy metals through all the proposed positions and interactions. Both physical and chemical adsorption have been observed, the physical adsorption is characterized by longer adsorption distance and lower adsorption energy with respect to the chemical adsorption. The adsorbed heavy metals have a significant effect on the electronic properties of the graphene flakes. The wide energy gap (∼3.7 eV) of the hexagonal flake decreases to ∼0.6 eV by surface-adsorption of hexahydrated Cd. This decrease occurs due to the inclusion of new energy states to the band structure which in turn leads to shifting of the highest occupied molecular orbital toward the Fermi level. The effect on the tiny band gap of the triangular flake is very small, the highest occupied and lowest unoccupied molecular orbitals are unaffected by the adsorption process. The calculated total charge on the hydrated metals implies that the charge transfer strongly depends on the interaction scheme. The lowest charge transfer from tetrahydrated Pb to the triangular flakes is observed in case of surface adsorption, Q = −0.05 (e), and the largest charge transfer, Q = 1.1 (e), is observed in the adsorption of tetrahydrated Cd on 2NH-functionalized triangular flake.

Bidirectional heterostructures consisting of graphene and lateral MoS2/WS2 composites: a first-principles study.

First-principles calculations have been performed to explore the structural and electronic properties of bidirectional heterostructures composed of graphene and (MoS2)X/(WS2)4−X (X = 1, 2, 3) lateral composites and compare them with those of heterobilayers formed by graphene and pristine MS2 (M = Mo, W). The band gaps of the lateral heterostructures lie between those of pristine MoS2 and WS2. The weak coupling between the two layers can induce a tiny band-gap opening of graphene and formation of an n-type Schottky contact at the G-(MoS2)X/(WS2)4−X interface. Moreover, the combination ratio of MoS2/WS2 can control the electronic properties of G-(MoS2)X/(WS2)4−X. By applying external electric fields, the band gaps of (MoS2)X/(WS2)4−X (X = 0, 1, 2, 3, 4) monolayers undergo a direct–indirect transition, and semiconductor–metal transitions can be found in WS2. External electric fields can also be used effectively to tune the binding energies, charge transfers, and band structures (the types of Schottky and Ohmic contacts) of G-(MoS2)X/(WS2)4−X heterostructures. These findings suggest that G-(MoS2)X/(WS2)4−X heterostructures can serve as high-performance nano-electronic devices.

First principles study of the electronic properties and Schottky barrier in vertically stacked graphene on the Janus MoSeS under electric field

In this paper, we design novel ultra-thin graphene/MoSeS and graphene/MoSSe heterostructures and investigate systematically their structural and electronic properties as well as the effect due to perpendicularly applied electric field on the heterostructure. Our results show that the electronic properties of both the graphene (Gr) and Janus MoSeS monolayer are well kept in the Gr/MoSeS and Gr/MoSSe heterostructures due to weak interaction between them. The interlayer distance between the Gr and Janus MoSeS monolayer is derived to be 3.34 Å, whereas the binding energy in the heterostructure is found to be -3 meV per carbon atom, indicating the weak interactions between the Gr and Janus MoSeS layers. We find that in both Gr/MoSeS and Gr/MoSSe heterostructures, the Gr becomes a semiconductor with a tiny band gap of about 3 meV, forming between the π and π∗ bands at the high symmetry K point. The appearance of the fundamental band gap in the Gr makes it suitable for application in electronics and optoelectronics like as field effect transistors. Furthermore, the Gr/MoSeS heterostructure forms an n-type Schottky contact with the Schottky barrier height of 0.53 eV at the equilibrium state. Our results also indicate that the electric field applied perpendicularly to the heterostructure could control not only the Schottky barrier height, but also the Schottky contact type from the n-type to p-type. Based on these extraordinary electronic properties of ultra-thin Gr/MoSeS heterostructures, which are expected to be with applications in nanoelectronic and optoelectronic devices in the future experiments.