Electronic structure and optical properties of nitrogen-doped antimonene under biaxial strain: first-principles study

CONTENT

In this thesis, the role of N atom doping and biaxial strain in modulating the electronic structure and optical properties of antimonene has been deeply investigated using a first-principles approach based on density-functional theory. The results show that N doping significantly reduces the band gap of antimonene and introduces new electronic states, thus affecting its electronic structure. In terms of optical properties, N doping reduces the static permittivity of antimonene and alters its absorption, reflection, and energy loss properties. In addition, biaxial strain further enhanced the modulation effect of these properties. This study not only provides theoretical support for the application of antimonene in the field of high-performance two-dimensional electronic and optoelectronic devices, but also reveals strain and doping as an effective means to modulate the physical properties of two-dimensional materials.

METHODS

For the calculations, we used the DFT-based CASTEP software package for the simulation of the electronic structure. In order to more accurately characterize the weak interactions between two-dimensional materials, we specifically introduced the Van der Waals dispersion correction. We have chosen the Perdew-Burke-Ernzerhof (PBE) exchange-correlation generalization under the generalized gradient approximation (GGA) and combined it with the Van der Waals correction term in order to fully consider the electronic structure of antimonene. For the calculation parameter settings, we set the truncation energy to 400 eV to ensure the accuracy of the calculation. Meanwhile, we adopt a 6 × 6 × 1 k-point grid for Brillouin zone sampling to obtain more accurate energy band structure and density of states information. For the convergence settings, the convergence criteria for both the system energy and the interaction force between atoms were set to 1 × 10-5 eV and 0.01 eV/Å, respectively. We selected a 3 × 3 × 1 supercell model with 18 Sb atoms. A vacuum thickness of 18 Å was established in the Z direction, which is sufficient to avoid interactions between the two atomic layers above and below the periodic structure.

Properties of Layered TMDC Superlattices for Electrodes in Li-Ion and Mg-Ion Batteries

In this work, we present a first-principles investigation of the properties of superlattices made from transition metal dichalcogenides for use as electrodes in lithium-ion and magnesium-ion batteries. From a study of 50 pairings, we show that, in general, the volumetric expansion, intercalation voltages, and thermodynamic stability of vdW superlattice structures can be well approximated with the average value of the equivalent property for the component layers. We also found that the band gap can be reduced, improving the conductivity. Thus, we conclude that superlattice construction can be used to improve material properties through the tuning of intercalation voltages toward specific values and by increasing the stability of conversion-susceptible materials. For example, we demonstrate how pairing SnS2 with systems such as MoS2 can change it from a conversion to an intercalation material, thus opening it up for use in intercalation electrodes.

Comprehensive Insights into the Family of Atomically Thin 2D-Materials for Diverse Photocatalytic Applications

2D materials with their fascinating physiochemical, structural, and electronic properties have attracted researchers and have been used for a variety of applications such as electrocatalysis, photocatalysis, energy storage, magnetoresistance, and sensing. In recent times, 2D materials have gained great momentum in the spectrum of photocatalytic applications such as pollutant degradation, water splitting, CO2 reduction, NH3 production, microbial disinfection, and heavy metal reduction, thanks to their superior properties including visible light responsive band gap, improved charge separation and electron mobility, suppressed charge recombination and high surface reactive sites, and thus enhance the photocatalytic properties rationally as compared to 3D and other low-dimensional materials. In this context, this review spot-lights the family of various 2D materials, their properties and their 2D structure-induced photocatalytic mechanisms while giving an overview on their synthesis methods along with a detailed discussion on their diverse photocatalytic applications. Furthermore, the challenges and the future opportunities are also presented related to the future developments and advancements of 2D materials for the large-scale real-time photocatalytic applications.

Tunable electronic structures, Rashba splitting, and optical and photocatalytic responses of MSSe-PtO2 (M = Mo, W) van der Waals heterostructures

Binding energies, AIMD simulation and phonon spectra confirm both the thermal and dynamical stabilities of model-I and model-II of MSSe-PtO2 (M = Mo, W) vdWHs. An indirect type-II band alignment in both the models of MSSe-PtO2 vdWHs and a larger Rashba spin splitting in model-II than in model-I provide a platform for experimental design of MSSe-PtO2 vdWHs for optoelectronics and spintronic device applications. Transfer of electrons from the MSSe layer to the PtO2 layer at the interface of MSSe-PtO2 vdWHs makes MSSe (PtO2) p(n)-type. Large absorption in the visible region of MoSSe-PtO2 vdWHs, while blue shifts in WSSe-PtO2 vdWHs are observed. In the case of model-II of MSSe-PtO2 vdWHs, a further blue shift is observed. Furthermore, the photocatalytic response shows that MSSe-PtO2 vdWHs cross the standard water redox potentials confirming their capability to split water into H+/H2 and O2/H2O.

Effect of strain on the electronic structure and optical properties of Cr-doped monolayer MoS2

CONTEXT

In this paper, the electronic and optical properties of Cr-doped monolayer MoS2 under uniaxial tensile strain are investigated by first-principle calculations. It is shown that uniaxial tensile strain can significantly change the electronic and optical properties of Cr-doped monolayer MoS2, and the bandgap value of the intrinsic MoS2 system gradually decreases with the increase of tensile strain, while the bandgap value of the Cr-doped MoS2 system is relatively stable. However, when the stretching reaches a certain degree, both the intrinsic and doped systems become metallic. From the analysis of the density of states, it is found that new electronic states and energy levels appear in the intrinsic MoS2 system and all Cr-doped monolayer MoS2 systems with the increase of the tensile strain, but the changes in the density of states diagrams of the Cr-doped monolayer MoS2 system are relatively small, which is mainly attributed to the effect of the Cr-doped atoms. The analysis of optical properties displays that the stretched doped system differs from the intrinsic MoS2 system in terms of dielectric function, absorption and reflection, energy loss function, and refractive index. Our results suggest that uniaxial tensile strain can be used as an effective means to modulate the electronic structure and optical properties of Cr-doped monolayer MoS2. These findings provide a theoretical basis for understanding the optoelectronic properties of MoS2 and its doped systems as well as their applications in optoelectronic devices.

METHODS

Based on the first principle of density functional theory framework and the CASTEP module in Materials Studio software (Perdew et al. in Phys Rev Lett 77(18):3865-3868, 1996). The structure of Cr atom-doped MoS2 systems and MoS2 systems were optimized using the generalized gradient approximation plane-wave pseudopotential method (GGA) and Perdew-Burke-Ernzerhof (PBE) generalized functions under 3%, 6%, and 9% tensile deformation, and the corresponding formation energy, bond length, electronic structure, and optical properties of the models were analyzed. The Grimme (J Comput Chem 27(15):1787-1799, 2006) vdW correction with 400 eV cutoff was used in Perdew-Burke-Ernzerhof (PBE) functional to optimize the geometry until the forces and energy converged to 0.02 eV/Å and 1.0e-5eV/atom, respectively. For each model structure optimization, the K-point grid was assumed to be 4×4×1, using the Monkhorst-Pack special K-point sampling method. After the MoS2 supercell convergence test, the plane-wave truncation energy was chosen to be 400 eV. Following geometric optimization, the iterative accuracy converged to no less than 1.0×10-5 eV/atom for total atomic energy and less than 0.02 eV/Å for all atomic forces. We created a vacuum layer of 18 Å along the Z-axis to prevent the impact of periodic boundary conditions and weak van der Waals forces between layers on the monolayer MoS2. In this paper, a total of 27 atoms were used for the 3×3×1 supercell MoS2 system, which consists of 18 S atoms and 9 Mo atoms.

First-principles study of BX-SiS (X = As, P) van der Waals heterostructures for enhanced photocatalytic performance

The vertical integration of two-dimensional (2D) materials through weak van der Waals (vdW) interactions is gaining tremendous attention for application in nanotechnology and photovoltaics. Here, we performed first-principles study of the electronic band structure, optical and photocatalytic properties of vertically stacked heterostructures based on boron pnictides BX (X = As, P) and SiS monolayers. Both heterobilayers possess a stable geometry and reveal type I band alignment with a direct band gap, indicating substantial transfer of charge across the junction of the same layer. Interestingly, a redshift is found in the visible light region of the optical absorption spectra of BX-SiS heterobilayers. The comparatively larger hole mobility (14 000 cm2 V-1 s-1) of BP-SiS preferably allows hole conduction in the zigzag-direction. More importantly, the excellent band edge values of the standard redox potential and smaller Gibbs free energy for the adsorption of hydrogen (ΔGH*) make them ideal for performing the hydrogen evolution reaction (HER) mechanism under solar irradiation. These findings offer exciting opportunities for developing next-generation devices based on BX-SiS heterobilayers for promising applications in nanoelectronics, optoelectronic devices and photocatalysts for water dissociation into hydrogen to produce renewable clean energy.

A first principles study of a van der Waals heterostructure based on MS2 (M = Mo, W) and Janus CrSSe monolayers

The strategy of stacking two-dimensional materials for designing van der Waals heterostructures has gained tremendous attention in realizing innovative device applications in optoelectronics and renewable energy sources. Here, we performed the first principles calculations of the geometry, optoelectronic and photocatalytic performance of MS₂-CrSSe (M = Mo, W) vdW heterostructures. The mirror asymmetry in the Janus CrSSe system allows the designing of two models of the MS₂-CrSSe system by replacing S/Se atoms at opposite surfaces in CrSSe. The feasible configurations of both models of the MS₂-CrSSe system are found energetically, dynamically and thermally stable. The studied heterobilayers possess an indirect type-I band alignment, indicating that the recombination of photogenerated electrons and holes in the CrSSe monolayer is hence crucial for photodetectors and laser applications. Remarkably, a red-shift in the optical absorption spectra of MS₂-CrSSe makes them potential candidates for light harvesting applications. More interestingly, all heterobilayers (except W(Mo)S₂-CrSSe of model-I(II)) reveal appropriate band edge positions of the oxidation and reduction potentials of the photocatalysis of water dissociation into H⁺/H₂ and O₂/H₂O at pH = 0. These results shed light on the practical design of the MS₂-CrSSe system for efficient optoelectronic and photocatalytic water splitting applications.

Two-dimensional ferroelectric MoS2/Ga2O3 heterogeneous bilayers with highly tunable photocatalytic and electrical properties

Two-dimensional van der Waals heterostructures with strong intrinsic ferroelectrics are highly promising for novel devices with designed electronic properties. The polarization reversal transition of the 2D ferroelectric Ga₂O₃ monolayer offers a new approach to tune the photocatalytic and electrical properties of MoS₂/Ga₂O₃ heterogeneous bilayers. In this work, we study MoS₂/Ga₂O₃ heterogeneous bilayers with different intrinsic polarization using hybrid-functional calculations. We closely investigate the structural, electronic and optical properties of two stable stacking configurations with opposite polarization. The results reveal a distinct switch from type-I to type-II heterostructures owing to polarization reversal transition of the 2D ferroelectric Ga₂O₃ monolayer. Biaxial strain engineering leads to type-I-to-II and type-II-to-III transitions in the two polarized models, respectively. Intriguingly, one of the MoS₂/Ga₂O₃ heterolayers has a larger spatial separation of the valence and conduction band edges and excellent optical absorption ranging from infrared to ultraviolet region under biaxial strain, thus ensuring promising novel applications such as flexible electrical and optical devices. Based on the highly tunable physical properties of the bilayer heterostructures, we further explore their potential applications, such as photocatalytic water splitting and field-controlled switch channel in MOSFET devices.

Intriguing interfacial characteristics of the CS contact with MX2 (M = Mo, W; X = S, Se, Te) and MXY ((X ≠ Y) = S, Se, Te) monolayers

Using (hybrid) first principles calculations, the electronic band structure, type of Schottky contact and Schottky barrier height established at the interface of the most stable stacking patterns of the CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) MS vdWH are investigated. The electronic band structures of CS–MX₂ and CS–MXY MS vdWH seem to be simple sum of CS, MX₂ and MXY monolayers. The projected electronic properties of the CS, MX₂ and MXY layers are well preserved in CS–MX₂ and CS–MXY MS vdWH. Their smaller effective mass (higher carrier mobility) render promising prospects of CS–WS₂ and CS–MoSeTe as compared to other MS vdWH in nanoelectronic and optoelectronic devices, such as a high efficiency solar cell. In addition, we found that the effective mass of holes is higher than that of electrons, suggesting that these heterostructures can be utilized for hole/electron separation. Interestingly, the MS contact led to the formation of a Schottky contact or ohmic contact, therefore we have used the Schottky Mott rule to calculate the Schottky barrier height (SBH) of CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) MS vdWH. It was found that CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) (in both model-I and -II) MS vdWH form p-type Schottky contacts. These p-type Schottky contacts can be considered a promising building block for high-performance photoresponsive optoelectronic devices, p-type electronics, CS-based contacts, and for high-performance electronic devices.

Electronic band structure, type of Schottky contact and Schottky barrier height established at the interface of the CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) MS vdWH.

First principles study of electronic and optical properties and photocatalytic performance of GaN-SiS van der Waals heterostructure

The vertical stacking of two-dimensional materials via van der Waals (vdW) interaction is a promising technique for tailoring the physical properties and fabricating potential devices to be applied in the emerging fields of materials science and nanotechnology. The structural, electronic and optical properties and photocatalytic performance of a GaN-SiS vdW heterostructure were explored using first principles calculations. The most stable stacking configuration found energetically stable, possesses a direct staggered band gap, which is crucial for separating photogenerated charged carriers in different constituents and is efficacious for solar cells. Further, the charge transfer occurred from the SiS to GaN layer, indicating that SiS exhibits p-type doping in the GaN-SiS heterobilayer. Interestingly, a systematic red-shift was observed in the optical absorption spectra of the understudy heterobilayer system. Moreover, the conduction band edge and valence band edge of the monolayers and corresponding heterostructure were located above and below the standard redox potentials for photocatalytic water splitting, making these systems promising for water dissociation for hydrogen fuel production. The results provide a route to design the GaN-SiS vdW heterostructure for the practical realization of next-generation light detection and energy harvesting devices.

Electronic and Optical Properties of Atomic-Scale Heterostructure Based on MXene and MN (M = Al, Ga): A DFT Investigation

After the discovery of graphene, a lot of research has been conducted on two-dimensional (2D) materials. In order to increase the performance of 2D materials and expand their applications, two different layered materials are usually combined by van der Waals (vdW) interactions to form a heterostructure. In this work, based on first-principles calculation, some charming properties of the heterostructure constructed by Hf2CO2, AlN and GaN are addressed. The results show that Hf2CO2/AlN and Hf2CO2/GaN vdW heterostructures can keep their original band structure shape and have strong thermal stability at 300 K. In addition, the Hf2CO2/MN heterostructure has I-type band alignment structure, which can be used as a promising light-emitting device material. The charge transfer between the Hf2CO2 and AlN (or GaN) monolayers is 0.1513 (or 0.0414) |e|. The potential of Hf2CO2/AlN and Hf2CO2/GaN vdW heterostructures decreases by 6.445 eV and 3.752 eV, respectively, across the interface. Furthermore, both Hf2CO2/AlN and Hf2CO2/GaN heterostructures have remarkable optical absorption capacity, which further shows the application prospect of the Hf2CO2/MN heterostructure. The study of this work provides theoretical guidance for the design of heterostructures for use as photocatalytic and photovoltaic devices.

Recent Progress in LDH@Graphene and Analogous Heterostructures for Highly Active and Stable Photocatalytic and Photoelectrochemical Water Splitting

Photocatalytic (PC) and photoelectrochemical (PEC) water splitting is a plethora of green technological process, which transforms copiously available photon energy into valuable chemical energy. With the augmentation of modern civilization, developmental process of novel semiconductor photocatalysts proceeded at a sweltering rate, but the overall energy conversion efficiency of semiconductor photocatalysts in PC/PEC is moderately poor owing to the instability ariseing from the photocorrosion and messy charge configuration. Particularly, layered double hydroxides (LDHs) as reassuring multifunctional photocatalysts, turned out to be intensively investigated owing to the lamellar structure and exceptional physico-chemical properties. However, major drawbacks of LDHs material are its low conductivity, sluggish mass transfer and structural instability in acidic media, which hinder their applicability and stability. To surmount these obstacles, the formation of LDH@graphene and analogus heterostructures could proficiently amalgamate multi-functionalities, compensate distinct shortcomings, and endow novel properties, which ensure effective charge separation to result in stability and superior catalytic activities. Herein, we aim to summarize the currently updated synthetic strategies used to design heterostructures of 2D LDHs with 2D/3D graphene and graphene analogus material as graphitic carbon nitride (g-C₃ N₄ ), and MoS₂ as mediator, or interlayer support, or co-catalyst or vice versa for superior PC/PEC water splitting activities along with long-term stabilities. Furthermore, latest characterization technique measuring the stability along with variant interface mode for imparting charge separation in LDH@graphene and graphene analogus heterostructure has been identified in this field of research with understanding the intrinsic structural features and activities.

Stacking effects in van der Waals heterostructures of blueP and Janus XYO (X = Ti, Zr, Hf: Y = S, Se) monolayers

Using first-principles calculations, the geometry, electronic structure, optical and photocatalytic performance of blueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers and their corresponding van der Waal heterostructures in three possible stacking patterns, are investigated. BlueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers are indirect bandgap semiconductors. A tensile strain of 8(10)% leads to TiSeO(ZrSeO) monolayers transitioning to a direct bandgap of 1.30(1.61) eV. The calculated binding energy and AIMD simulation show that unstrained(strained) blueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers and their heterostructures are thermodynamically stable. Similar to the corresponding monolayers, blueP-XYO (X = Ti, Zr, Hf: Y = S, Se) vdW heterostructures in three possible stacking patterns are indirect bandgap semiconductors with staggered band alignment, except blueP-TiSeO vdW heterostructure, which signifies straddling band alignment. Absorption spectra show that optical transitions are dominated by excitons for blueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers and the corresponding vdW heterostructures. Both E VB and E CB in TiSO, ZrSO, ZrSeO and HfSO monolayers achieve energetically favorable positions, and therefore, are suitable for water splitting at pH = 0, while TiSeO and HfSeO monolayers showed good response for reduction and fail to oxidise water. All studied vdW heterostructures also show good response to any produced O2, while specific stacking reduces H+ to H2.

Strain-tunable electronic structure and anisotropic transport properties in Janus MoSSe and g-SiC van der Waals heterostructure

The van der Waals heterostructures (vdWHs) create a multi-purpose platform to design unique structures for efficient photovoltaic and optoelectronic applications. In this study, on the basis of the first-principles calculations, we present a type-II semiconducting MoSSe/g-SiC vdWH with a moderate bandgap value of 1.31 eV. In particular, the large conduction band offset of 1.18 eV and valence band offset of 0.90 eV are distinguished, which can act as powerful driving forces to promote interlayer charge transfer. Moreover, MoSSe/g-SiC vdWH possesses high carrier mobilities and anisotropic transport properties with a larger transport current along the zigzag direction. More importantly, tensile strain can transform indirect into direct band gap and enhance the visible-light absorption while sustaining type-II band alignment. These results reveal the new physical nature of MoSSe/g-SiC vdWH and demonstrate its practical application potential in photovoltaics and optoelectronic nanodevices.

Electronic properties of Janus MXY/graphene (M = Mo, W; X ≠ Y = S, Se) van der Waals structures: a first-principles study

Based on the first-principles calculations, we studied the intrinsic dipole moment and electronic properties of Janus MXY (M = Mo, W; X ≠ Y = S, Se) monolayers, bilayers and heterostructures with graphene, and the possibility of MXY encapsulating graphene. The results show that Janus MXY monolayer has an intrinsic dipole moment and a direct band gap. However, for MXY bilayers strong interlayer coupling will cause direct to indirect band gap transition, and the existence of the dipole moment leads to a significantly large interlayer band offset, being the driving force for the formation of interlayer excitons. In MXY/graphene heterostructures, changes in the direction of intrinsic dipole moment will cause a change in Schottky barrier height and even the transition between p- and n-type Schottky contacts. Independent of the interface atomic layer of Janus MXY, on one hand, the Dirac cone still exists in graphene, proving that MXY is an ideal coating material. On the other hand, the type-II band alignment will disappear as the intrinsic dipole moment disappears, confirming that the intrinsic dipole moment plays a vital role in the formation of a large band offset. Our results provide guidance for the study of interlayer excitonic states, the experimental construction of atomically thin p-n junctions and the encapsulation of graphene.

Optoelectronic and photocatalytic applications of hBP-XMY (M = Mo, W; (X ≠ Y) = S, Se, Te) van der Waals heterostructures

Stacking of layers via weak van der Waals interactions is an important technique for tuning the physical properties and designing viable electronic products. Using first-principles calculations, the geometry, electronic structure, and optical and photocatalytic performance of novel vdW heterostructures based on hexagonal boron phosphide (hBP) and Janus (XMY (M = Mo, W; (X ≠ Y) = S, Se, Te)) monolayers are investigated. Favorable (dynamically and energetically) stacking patterns of two different models of hBP-XMY heterostructures are presented with an alternative order of chalcogen atoms at opposite surfaces in SMSe. A direct type-II band alignment is obtained in both models of hBP-SMoSe, hBP-SWSe and hBP-SeWTe, while the rest are type-II indirect bandgap semiconductors. The Bader charge, and planer-averaged and plane-averaged charge density differences are investigated, which show that hBP donates electrons to the SMoSe and SWSe layer in the hBP-SMoSe and hBP-SWSe vdW heterostructure, while in the case of the hBP-SMoTe (hBP-SWTe) and hBP-SeMoTe (hBP-SeWTe) vdW heterostructures, the transfer of electrons is observed from SMoTe (SWTe) and SeMoTe (SeWTe) to hBP. The imaginary part of the dielectric function shows that the lowest energy transitions are dominated by excitons with a systematic red shift for heavier chalcogen atoms. Furthermore, the photocatalytic performance indicates that the hBP-XMY (M = Mo, W; (X ≠ Y) = S, Se, Te) vdW heterostructures in model-I are suitable for water splitting at pH = 0.

Intriguing electronic structure and photocatalytic performance of blueP-SMSe and blueP-SeMS (M = Mo, W) van der Waals heterostructures

Van der Waals (vdW) combination of two dimensional (2D) materials in the form of a heterostructure is a widely accepted tool for tailoring properties and designing novel nanoelectronic and energy harvesting applications. The stacking geometry and electronic and photocatalytic properties of vdW heterostructures based on blueP and Janus SMSe and SeMS (M = Mo, W) monolayers are investigated by using first principles calculations. Two alternate stacking configurations of both heterostructures with an alternative order of chalcogen atoms in SMSe and SeMS (M = Mo, W) are constructed and found to be energetically and thermally stable. The feasible stackings of both heterostructures exhibit type-II band alignment (except blueP–SeMoS), hence are promising for light detection devices. In particular, the suitable positions of the valence and conduction band edges of all the heterostructures (except blueP–SMoSe) are appropriate for standard redox potentials and are capable of splitting water into O₂/H₂O and H⁺/H₂. The findings pave the way for potential applications of these heterobilayer systems in future nanoelectronics, optoelectronics and photocatalytic water dissociation.

The stacking geometry and electronic and photocatalytic properties of vdW heterostructures based on blueP and Janus SMSe and SeMS (M = Mo, W) monolayers are investigated using first principles calculations.

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.

Electronic structures, and optical and photocatalytic properties of the BP–BSe van der Waals heterostructures

The combination of two-dimensional materials in the form of van der Waals (vdW) heterostructures has been shown to be an effective method for designing electronic and optoelectronic equipment.

Van der Waals heterostructures of SiC and Janus MSSe (M = Mo, W) monolayers: a first principles study

Favorable stacking patterns of two models with alternative orders of chalcogen atoms in SiC-MSSe (M = Mo, W) vdW heterostructures are investigated using density functional theory calculations. Both model-I and model-II of the SiC-MSSe (M = Mo, W) vdW heterostructures show type-II band alignment, while the spin orbit coupling effect causes considerable Rashba spin splitting. Furthermore, the plane-average electrostatic potential is also calculated to investigate the potential drops across the heterostructure and work function. The imaginary part of the dielectric function reveals that the first optical transition is dominated by excitons with high absorption in the visible region for both heterostructures. Appropriate band alignments with standard water redox potentials enable the capability of these heterostructures to dissociate water into H⁺/H₂ and O₂/H₂O.

Using DFT calculations, we have investigated the electronic structure, Rashba effect, optical and photocatalytic performance of SiC-MSSe (M = Mo, W) van der Waals heterostructures with different stacking patterns of chalcogen atoms.

Electronic structure, optoelectronic properties and enhanced photocatalytic response of GaN–GeC van der Waals heterostructures: a first principles study

In this work, we systematically studied the electronic structure and optical characteristics of van der Waals (vdW) heterostructure composed of a single layer of GaN and GeC using first principles calculations. The GaN–GeC vdW heterostructure exhibits indirect band gap semiconductor properties and possesses type-II energy band arrangement, which will help the separation of photogenerated carriers and extend their lifetime. In addition, the band edge positions of the GaN–GeC heterostructure meet both the requirements of water oxidation and reduction energy, indicating that the photocatalysts have the potential for water decomposition. The GaN–GeC heterostructure shows obvious absorption peaks in the visible region, leading to the efficient use of solar energy. Tensile and compressive strains of up to 10% are also proposed. Tensile strain leads to an increase in the blue shift of optical absorption, whereas a red shift is observed in the case of the compressive strain. These fascinating characteristics make the GaN–GeC vdW heterostructure a highly effective photocatalyst for water splitting.

In this work, we systematically studied the electronic structure and optical characteristics of van der Waals (vdW) heterostructure composed of a single layer of GaN and GeC using first principles calculations.

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.

Investigation on photocatalytic mechanism of graphitic SiC (g-SiC)/MoS2 van der Waals heterostructured photocatalysts for overall water splitting

Two-dimensional MoS₂-based heterostructures have been given great attention due to their excellent properties.

Using van der Waals heterostructures based on two-dimensional blue phosphorus and XC (X = Ge, Si) for water-splitting photocatalysis: a first-principles study

BlueP/SiC and BlueP/GeC vdW heterostructures are high-efficiency photocatalysts for water-splitting at pH 0 and 7, respectively.

Rationally designed 2D/2D SiC/g-C3N4 photocatalysts for hydrogen production

Visible-light driven photocatalytic hydrogen production from water is a hotspot in renewable energy.

Optoelectronic and solar cell applications of Janus monolayers and their van der Waals heterostructures

Janus monolayers and their van der Waals heterostuctures are investigated by hybrid density functional theory calculations.