Based on first-principles density functional theory calculation,we discover a novel form of spin-orbit(SO)splitting in two-dimensional(2D)heterostructures composed of a single Bi(111)bilayer stacking with a 2D semicon...Based on first-principles density functional theory calculation,we discover a novel form of spin-orbit(SO)splitting in two-dimensional(2D)heterostructures composed of a single Bi(111)bilayer stacking with a 2D semiconducting In_(2)Se_(2) or a 2D ferroelectricα-In_(2)Se_(3) layer.Such SO splitting has a Rashba-like but distinct spin texture in the valence band around the maximum,where the chirality of the spin texture reverses within the upper spin-split branch,in contrast to the conventional Rashba systems where the upper branch and lower branch have opposite chirality solely in the region below the band crossing point.The ferroelectric nature ofα-In_(2)Se_(3) further enables the tuning of the spin texture upon the reversal of the electric polarization with the application of an external electric field.Detailed analysis based on a tight-binding model reveals that such SO splitting texture results from the interplay of complex orbital characters and substrate interaction.This finding enriches the diversity of SO splitting systems and is also expected to promise for spintronic applications.展开更多
Polarization-induced two-dimensional hole gases(2DHG)in GaN/AlGaN/GaN heterostructures offer a promising pathway for advancing p-channel transistors.This work investigates the impact of p-GaN thickness on hole distrib...Polarization-induced two-dimensional hole gases(2DHG)in GaN/AlGaN/GaN heterostructures offer a promising pathway for advancing p-channel transistors.This work investigates the impact of p-GaN thickness on hole distribution and transport through temperature-dependent Hall measurements and TCAD simulations.It is demonstrated that the p-channel is composed of holes both in the p-GaN layer and in the 2DHG at the GaN/AlGaN heterointerface at 300 K,whereas at 77 K,the p-channel conduction is dominated solely by the 2DHG at the GaN/AlGaN heterointerface.The results also reveal the formation of a polarization-induced 2DHG at the GaN/AlGaN interface,exhibiting a high sheet density of 2.2×10^(13)cm^(-2)and a mobility of 16.2 cm^(2)·V^(-1)·s^(-1)at 300 K.The 2DHG sheet density remains nearly independent of p-GaN thickness when the p-GaN layer exceeds 30 nm.However,for p-GaN layers thinner than 30 nm,the 2DHG sheet density strongly depends on the p-GaN thickness,which is attributed to the gradual extension of the depletion region toward the GaN/AlGaN interface under the influence of surface trap states.展开更多
Step heterostructures are predicted to hold a profound catalytic performance because of the rearranged electronic structure at their interface.However,limitations in the morphology of heterostructures prepared by hydr...Step heterostructures are predicted to hold a profound catalytic performance because of the rearranged electronic structure at their interface.However,limitations in the morphology of heterostructures prepared by hydrothermal reactions or molten salt-assisted strategies make it challenging to directly assess charge distribution and evaluate a single interface's hydrogen evolution reaction(HER)performance.Here,we prepared two-dimensional MoO_(2)/MoS_(2) step heterostructures with a large specific surface area by the chemical vapor deposition method.Surface Kelvin probe force microscopy and electrical transport measurement verified the asymmetric charge distribution at a single interface.By fabricating a series of micro on-chip electrocatalytic devices,we investigate the HER performance for a single interface and confirm that the interface is essential for superior catalytic performance.We experimentally confirmed that the enhancement of the HER performance of step heterostructure is attributed to the asymmetric charge distribution at the interface.This work lays a foundation for designing highly efficient catalytic systems based on step heterostructures.展开更多
Research on p-channel field-effect transistors(p-FETs)remains limited,primarily due to the significantly lower conductivity of the two-dimensional hole gas(2DHG)compared to the two-dimensional electron gas(2DEG)in n-c...Research on p-channel field-effect transistors(p-FETs)remains limited,primarily due to the significantly lower conductivity of the two-dimensional hole gas(2DHG)compared to the two-dimensional electron gas(2DEG)in n-channel field-effect transistors(n-FETs),which poses a significant challenge for monolithic integration.In this study,we investigate the impact of epitaxial structure parameters on 2DHG properties in p-Ga N/Al Ga N/Ga N heterostructures through semiconductor technology computer-aided design(TCAD)simulations and theoretical calculations,identifying the conditions necessary to achieve high-density 2DHG.Our simulations demonstrate that increasing the p-Ga N thickness leads to two critical thicknesses determined by surface states and acceptor ionization concentration:one corresponds to the onset of 2DHG formation,and the other to its saturation.Lowering the donor surface state energy level and increasing the acceptor ionization concentration promote 2DHG formation and saturation,although the saturated density remains independent of surface states.Additionally,a higher Al composition enhances intrinsic ionization due to stronger polarization effects,thereby increasing the 2DHG sheet density.Consequently,to achieve high-density 2DHG in p-Ga N/Al Ga N/Ga N heterostructures,it is essential to increase the Al composition,ensure that the p-Ga N thickness exceeds the critical thickness for 2DHG saturation,and maximize the acceptor ionization concentration.This study elucidates the impact of epitaxial structure parameters on 2DHG properties in p-Ga N/Al Ga N/Ga N heterostructures and provides valuable guidance for the optimization of p-FET designs.展开更多
Two-dimensional(2D)materials,due to its excellent mechanical,unique electrical and optical properties,have become hot materials in the field of photocatalysis.Especially,2D heterostructures can well inhibit the recomb...Two-dimensional(2D)materials,due to its excellent mechanical,unique electrical and optical properties,have become hot materials in the field of photocatalysis.Especially,2D heterostructures can well inhibit the recombination of photogenerated electrons and holes in photocatalysis because of its special energy band structures and carrier transport characteristics,which are conducive to enhancing photoenergy conversion capacity and improving oxidation and reduction ability,so as to purify pollutants and store energy.In this minireview,we summarize recent theoretical progress in direct Z-scheme photocatalysis of 2D heterostructures,focusing on physical mechanism and improving catalytic efficiency.Current challenges and prospects for 2D direct Z-scheme photocatalysts are discussed as well.展开更多
Magnetotransport properties of two-dimensional electron gases （2DEG） in AlxGa1-x N/GaN heterostructures with different Al compositions are investigated by magnetotransport measurements at low temperatures and in hig...Magnetotransport properties of two-dimensional electron gases （2DEG） in AlxGa1-x N/GaN heterostructures with different Al compositions are investigated by magnetotransport measurements at low temperatures and in high magnetic fields. It is found that heterostructures with a lower Al composition in the barrier have lower 2DEG concentration and higher 2DEG mobility.展开更多
Interfacial superconductivity(IS)has been a topic of intense interest in condensed matter physics,due to its unique properties and exotic photoelectrical performance.However,there are few reports about IS systems cons...Interfacial superconductivity(IS)has been a topic of intense interest in condensed matter physics,due to its unique properties and exotic photoelectrical performance.However,there are few reports about IS systems consisting of two insulators.Here,motivated by the emergence of an insulator-metal transition in type-Ⅲ heterostructures and the superconductivity in some“special”two-dimensional(2D)semiconductors via electron doping,we predict that the 2D heterostructure SnSe_(2)/PtTe_(2) is a model system for realizing IS by using firstprinciples calculations.Our results show that due to slight but crucial interlayer charge transfer,SnSe_(2)/PtTe_(2) turns to be a type-Ⅲ heterostructure with metallic properties and shows a superconducting transition with the critical temperature(T_(c))of 3.73 K.Similar to the enhanced electron–phonon coupling(EPC)in the electrondoped SnSe_(2) monolayer,the IS in the SnSe_(2)/PtTe_(2) heterostructure mainly originates from the metallized SnSe_(2) layer.Furthermore,we find that its superconductivity is sensitive to tensile lattice strain,forming a domeshaped superconducting phase diagram.Remarkably,at 7%biaxial tensile strain,the superconducting T_(c) can increase more than twofold(8.80 K),resulting from softened acoustic phonons at the𝑀point and enhanced EPC strength.Our study provides a concrete example for realizing IS in type-Ⅲ heterostructures,which waits for future experimental verification.展开更多
As emerging two-dimensional(2D)materials,carbides and nitrides(MXenes)could be solid solutions or organized structures made up of multi-atomic layers.With remarkable and adjustable electrical,optical,mechanical,and el...As emerging two-dimensional(2D)materials,carbides and nitrides(MXenes)could be solid solutions or organized structures made up of multi-atomic layers.With remarkable and adjustable electrical,optical,mechanical,and electrochemical characteristics,MXenes have shown great potential in brain-inspired neuromorphic computing electronics,including neuromorphic gas sensors,pressure sensors and photodetectors.This paper provides a forward-looking review of the research progress regarding MXenes in the neuromorphic sensing domain and discussed the critical challenges that need to be resolved.Key bottlenecks such as insufficient long-term stability under environmental exposure,high costs,scalability limitations in large-scale production,and mechanical mismatch in wearable integration hinder their practical deployment.Furthermore,unresolved issues like interfacial compatibility in heterostructures and energy inefficiency in neu-romorphic signal conversion demand urgent attention.The review offers insights into future research directions enhance the fundamental understanding of MXene properties and promote further integration into neuromorphic computing applications through the convergence with various emerging technologies.展开更多
The development of optoelectronic technologies demands photodetectors with miniaturization,broadband operation,high sensitivity,and low power consumption.Although 2D van der Waals(vd W)heterostructures are promising c...The development of optoelectronic technologies demands photodetectors with miniaturization,broadband operation,high sensitivity,and low power consumption.Although 2D van der Waals(vd W)heterostructures are promising candidates due to their built-in electric fields,ultrafast photocarrier separation,and tunable bandgaps,defect states limit their performance.Therefore,the modulation of the optoelectronic properties in such heterostructures is imperative.Surface charge transfer doping(SCTD)has emerged as a promising strategy for non-destructive modulation of electronic and optoelectronic characteristics in two-dimensional materials.In this work,we demonstrate the construction of high-performance p-i-n vertical heterojunction photodetectors through SCTD of MoTe_(2)/ReS_(2)heterostructure using p-type F_(4)-TCNQ.Systematic characterization reveals that the interfacial doping process effectively amplifies the built-in electric field,enhancing photogenerated carrier separation efficiency.Compared to the pristine heterojunction device,the doped photodetector exhibits remarkable visible to nearinfrared(635-1064 nm)performance.Particularly under 1064 nm illumination at zero bias,the device achieves a responsivity of 2.86 A/W and specific detectivity of 1.41×10^(12)Jones.Notably,the external quantum efficiency reaches an exceptional value of 334%compared to the initial 11.5%,while maintaining ultrafast response characteristics with rise/fall times of 11.6/15.6μs.This work provides new insights into interface engineering through molecular doping for developing high-performance vd W optoelectronic devices.展开更多
Hydrogen production by photoelectrochemical(PEC) water splitting converts the inexhaustible supply of solar radiation to storable H2 as clean energy and thus has received widespread attention.The efficiency of PEC wat...Hydrogen production by photoelectrochemical(PEC) water splitting converts the inexhaustible supply of solar radiation to storable H2 as clean energy and thus has received widespread attention.The efficiency of PEC water splitting is largely determined by the properties of the photoelectrodes.Two-dimensional(2 D) layered transition metal dichalcogenides(TMDs) are promising candidates for photoelectrodes due to their atomic layer thickness,tunable bandgap,large specific surface area,and high carrier mobility.Moreover,the construction of 2 D TMDs heterostructures provides freedom in material design,which facilitates the further improvement of PEC water splitting.This review begins by describing the mechanism of PEC water splitting and the advantages of 2 D TMDbased heterostructures for photo electrodes.Then,the design considerations of the heterostructures for enhanced PEC efficiency are comprehensively reviewed with a focus on material selection,band engineering,surface modification,and long-term durability.Finally,current challenges and future perspectives for the development of photoelectrodes based on 2 D TMDs heterostructures are addressed.展开更多
Regarding the reverse process of materials growth,etching has been widely concerned to indirectly probe the growth kinetics,offering an avenue in governing the growth of two-dimensional(2D)materials.In this work,inter...Regarding the reverse process of materials growth,etching has been widely concerned to indirectly probe the growth kinetics,offering an avenue in governing the growth of two-dimensional(2D)materials.In this work,interface-driven anisotropic etching mode is demonstrated for the first time to be generally applied to 2D heterostructures.It is shown that the typical in-plane graphene and hexagonal boron nitride(h-BN)heterostructures follow a multi-stage etching behavior initiated first along the interfacial region between the two materials and then along edges of neighboring h-BN flakes and finally along central edges of hBN.By accurately tuning etching conditions in the chemical vapor deposition process,series of etched 2D heterostructure patterns are controllably produced.Furthermore,scaled formation of graphene and h-BN heterostructures arrays has been realized with full assist of as-proposed etching mechanism,offering a direct top-down method to make 2D orientated heterostructures with order and complexity.Detection of interface-driven multi-staged anisotropic etching mode will shed light on understanding growth mechanism and further expanding wide applications of 2D heterostructures.展开更多
Research on two-dimensional(2D) materials and related van der Waals heterostructures(vdWHs) is intense and remains one of the leading topics in condensed matter physics.Lattice vibrations or phonons of a vdWH provide ...Research on two-dimensional(2D) materials and related van der Waals heterostructures(vdWHs) is intense and remains one of the leading topics in condensed matter physics.Lattice vibrations or phonons of a vdWH provide rich information,such as lattice structure,phonon dispersion,electronic band structure and electron–phonon coupling.Here,we provide a mini review on the lattice vibrations in vdWHs probed by Raman spectroscopy.First,we introduced different kinds of vdWHs,including their structures,properties and potential applications.Second,we discussed interlayer and intralayer phonon in twist multilayer graphene and MoS2.The frequencies of interlayer and intralayer modes can be reproduced by linear chain model(LCM)and phonon folding induced by periodical moiré potentials,respectively.Then,we extended LCM to vdWHs formed by distinct 2D materials,such as MoS2/graphene and hBN/WS2 heterostructures.We further demonstrated how to calculate Raman intensity of interlayer modes in vdWHs by interlayer polarizability model.展开更多
Two-dimensional （2D） Van der Waals heterostructures have aroused extensive concerns in recent years. Their fabrica- tion calls for facile and efficient transfer techniques for achieving well-defined structures. In t...Two-dimensional （2D） Van der Waals heterostructures have aroused extensive concerns in recent years. Their fabrica- tion calls for facile and efficient transfer techniques for achieving well-defined structures. In this work, we report a simple and effective dry transfer method to fabricate 2D heterostructures with a clean interface. Using Propylene Carbonate （PC） films as stamps, we are able to pick up various 2D materials flakes from the substrates and unload them to the receiving substrates at an elevated temperature. Various multilayer heterostructures with ultra-clean interfaces were fabricated by this technique. Furthermore, the 2D materials can be pre-pattemed before transfer so as to fabricate desired device structures, demonstrating a facile way to promote the development of 2D heterostructures.展开更多
To reveal the internal physics of the low-temperature mobility of two-dimensional electron gas （2DEG） in Al- GaN/GaN heterostructures, we present a theoretical study of the strong dependence of 2DEG mobility on Al c...To reveal the internal physics of the low-temperature mobility of two-dimensional electron gas （2DEG） in Al- GaN/GaN heterostructures, we present a theoretical study of the strong dependence of 2DEG mobility on Al content and thickness of AlGaN barrier layer. The theoretical results are compared with one of the highest measured of 2DEG mobility reported for AlGaN/GaN heterostructures. The 2DEG mobility is modelled as a combined effect of the scat- tering mechanisms including acoustic deformation-potential, piezoelectric, ionized background donor, surface donor, dislocation, alloy disorder and interface roughness scattering. The analyses of the individual scattering processes show that the dominant scattering mechanisms are the alloy disorder scattering and the interface roughness scattering at low temperatures. The variation of 2DEG mobility with the barrier layer parameters results mainly from the change of 2DEG density and distribution. It is suggested that in AlGaN/GaN samples with a high Al content or a thick AlGaN layer, the interface roughness scattering may restrict the 2DEG mobility significantly, for the AlGaN/GaN interface roughness increases due to the stress accumulation in AlGaN layer.展开更多
Thermoelectric properties of bulk and bilayer two-dimensional （2D） MoS2/MoSe2 het- erostructures are investigated using density functional theory in conjunction with semi- classical Boltzmann transport theory. It is...Thermoelectric properties of bulk and bilayer two-dimensional （2D） MoS2/MoSe2 het- erostructures are investigated using density functional theory in conjunction with semi- classical Boltzmann transport theory. It is predicted that the bulk 2D heterostructures could considerably enhance the thermoelectric properties as compared with the bulk MoSe2. The enhancement originates from the reduction in the band gap and the presence of interlayer van der Waals interactions. We therefore propose the 2D MoS2/MoSe2 heterostructures as a possible candidate material for thermoelectric applications.展开更多
The inherent catalytic anisotropy of two-dimensional(2D) materials has limited the enhancement of LiO_(2) batteries(LOBs) performance due to the significantly different adsorption energies on 2D and edge surfaces.Tuni...The inherent catalytic anisotropy of two-dimensional(2D) materials has limited the enhancement of LiO_(2) batteries(LOBs) performance due to the significantly different adsorption energies on 2D and edge surfaces.Tuning the adsorption strength in 2D materials to the reaction intermediates is essential for achieving high-performance LOBs.Herein,a MnS/MoS_(2) heterostructure is designed as a cathode catalyst by adjusting the adsorption behavior at the surface.Different from the toroidal-like discharge products on the MoS_(2) cathode,the MnS/MoS_(2) surface displays an improved adsorption energy to reaction species,thereby promoting the growth of the film-like discharge products.MnS can disturb the layer growth of MoS_(2),in which the stack edge plane features a strong interaction with the intermediates and limits the growth of the discharge products.Experimental and theoretical results confirm that the MnS/MoS_(2) heterostructure possesses improved electron transfer kinetics at the interface and plays an important role in the adsorption process for reaction species,which finally affects the morphology of Li_2O_(2),In consequence,the MnS/MoS_(2) heterostructure exhibits a high specific capacity of 11696.0 mA h g^(-1) and good cycle stability over 1800 h with a fixed specific capacity of 600 mA h g^(-1) at current density of100 mA g^(-1) This work provides a novel interfacial engineering strategy to enhance the performance of LOBs by tuning the adsorption properties of 2D materials.展开更多
Since the successful fabrication of two-dimensional (2D) ferromagnetic (FM) monolayer CrI3 and Cr2Ge2Te6, 2D FM materials are becoming an exciting research topic in condensed matter physics and materials fields, as th...Since the successful fabrication of two-dimensional (2D) ferromagnetic (FM) monolayer CrI3 and Cr2Ge2Te6, 2D FM materials are becoming an exciting research topic in condensed matter physics and materials fields, as they provide a good platform to explore the fundamental physical properties of magnetic materials under 2D limit. In this review, we summarize the theoretical research progress of intrinsic 2D FM materials and related van der Waals heterostructures (vdWHs) including their electronic structures, magnetism, Curie temperature, valley polarization, and band alignment. Moreover, we also summarize recent researches on the methods that used to regulate the above properties of 2D FM materials and vdWHs, such as defects, doping, strain, electric field and interlayer coupling. These studies show that 2D FM materials have broad application prospects in spintronics and valleytronics. However, there are still many problems waiting to be solved on the way to practical application.展开更多
Two-dimensional(2D)/quasi-2D organic-inorganic halide perovskites are regarded as naturally formed multiple quantum wells with inorganic layers isolated by long organic chains,which exhibit layered structure,large exc...Two-dimensional(2D)/quasi-2D organic-inorganic halide perovskites are regarded as naturally formed multiple quantum wells with inorganic layers isolated by long organic chains,which exhibit layered structure,large exciton binding energy,strong nonlinear optical effect,tunable bandgap via changing the layer number or chemical composition,improved environmental stability,and excellent optoelectronic properties.The extensive choice of long organic chains endows 2D/quasi-2D perovskites with tunable electron-phonon coupling strength,chirality,or ferroelectricity properties.In particular,the layered nature of 2D/quasi-2D perovskites allows us to exfoliate them to thin plates to integrate with other materials to form heterostructures,the fundamental structural units for optoelectronic devices,which would greatly extend the functionalities in view of the diversity of 2D/quasi-2D perovskites.In this paper,the recent achievements of 2D/quasi-2D perovskite-based heterostructures are reviewed.First,the structure and physical properties of 2D/quasi-2D perovskites are introduced.We then discuss the construction and characterizations of 2D/quasi-2D perovskite-based heterostructures and highlight the prominent optical properties of the constructed heterostructures.Further,the potential applications of 2D/quasi-2D perovskite-based heterostructures in photovoltaic devices,light emitting devices,photodetectors/phototransistors,and valleytronic devices are demonstrated.Finally,we summarize the current challenges and propose further research directions in the field of 2D/quasi-2D perovskite-based heterostructures.展开更多
It is a rapidly developed subject in expanding the fundamental properties and application of two-dimensional(2D)materials.The weak van der Waals interaction in 2D materials inspired researchers to explore 2D heterostr...It is a rapidly developed subject in expanding the fundamental properties and application of two-dimensional(2D)materials.The weak van der Waals interaction in 2D materials inspired researchers to explore 2D heterostructures(2DHs)based broadband photodetectors in the far-infrared(IR)and middle-IR regions with high response and high detectivity.This review focuses on the strategy and motivation of designing 2DHs based high-performance IR photodetectors,which provides a wide view of this field and new expectation for advanced photodetectors.First,the photocarriers'generation mechanism and frequently employed device structures are presented.Then,the 2DHs are divided into semimetal/semiconductor 2DHs,semiconductor/semiconductor 2DHs,and multidimensional semi-2DHs;the advantages,motivation,mechanism,recent progress,and outlook are discussed.Finally,the challenges for next-generation photodetectors are described for this rapidly developing field.展开更多
CONSPECTUS:Two-dimensional(2D)heterostructures have created many novel properties and triggered a variety of promising applications,thus setting off a boom in the modern semiconductor industry.As the first road to ste...CONSPECTUS:Two-dimensional(2D)heterostructures have created many novel properties and triggered a variety of promising applications,thus setting off a boom in the modern semiconductor industry.As the first road to step into adequately exploring the properties and real applications,the material preparation process matters a lot.Adhering to the concept of epitaxial growth,chemical vapor deposition(CVD)shows great potential for the preparation of heterostructures for commercialization.展开更多
基金Project supported by the Science Fund from the Ministry of Science and Technology of China(Grant Nos.2017YFA0204904 and 2019YFA0210004)the National Natural Science Foundation of China(Grant Nos.11674299 and 11634011)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)the Fund of Anhui Initiative Program in Quantum Information Technologies(Grant No.AHY170000)the Fundamental Research Funds for the Central Universities,China(Grant No.WK3510000013).
文摘Based on first-principles density functional theory calculation,we discover a novel form of spin-orbit(SO)splitting in two-dimensional(2D)heterostructures composed of a single Bi(111)bilayer stacking with a 2D semiconducting In_(2)Se_(2) or a 2D ferroelectricα-In_(2)Se_(3) layer.Such SO splitting has a Rashba-like but distinct spin texture in the valence band around the maximum,where the chirality of the spin texture reverses within the upper spin-split branch,in contrast to the conventional Rashba systems where the upper branch and lower branch have opposite chirality solely in the region below the band crossing point.The ferroelectric nature ofα-In_(2)Se_(3) further enables the tuning of the spin texture upon the reversal of the electric polarization with the application of an external electric field.Detailed analysis based on a tight-binding model reveals that such SO splitting texture results from the interplay of complex orbital characters and substrate interaction.This finding enriches the diversity of SO splitting systems and is also expected to promise for spintronic applications.
基金supported by the National Key Research and Development Program of China(Grant No.2024YFE0205000)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20243037)+2 种基金the National Natural Science Foundation of China(Grant Nos.62074077 and 61921005)the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20231098)the Collab-orative Innovation Center of Solid State Lighting and Energy-Saving Electronics.
文摘Polarization-induced two-dimensional hole gases(2DHG)in GaN/AlGaN/GaN heterostructures offer a promising pathway for advancing p-channel transistors.This work investigates the impact of p-GaN thickness on hole distribution and transport through temperature-dependent Hall measurements and TCAD simulations.It is demonstrated that the p-channel is composed of holes both in the p-GaN layer and in the 2DHG at the GaN/AlGaN heterointerface at 300 K,whereas at 77 K,the p-channel conduction is dominated solely by the 2DHG at the GaN/AlGaN heterointerface.The results also reveal the formation of a polarization-induced 2DHG at the GaN/AlGaN interface,exhibiting a high sheet density of 2.2×10^(13)cm^(-2)and a mobility of 16.2 cm^(2)·V^(-1)·s^(-1)at 300 K.The 2DHG sheet density remains nearly independent of p-GaN thickness when the p-GaN layer exceeds 30 nm.However,for p-GaN layers thinner than 30 nm,the 2DHG sheet density strongly depends on the p-GaN thickness,which is attributed to the gradual extension of the depletion region toward the GaN/AlGaN interface under the influence of surface trap states.
基金National Natural Science Foundation of China,Grant/Award Numbers:52288102,52090022,62274087,52472306Science Research Project of Hebei Education Department,Grant/Award Number:BJ2021040Natural Science Foundation of Hebei Province of China,Grant/Award Numbers:E2024203054,E2022203109。
文摘Step heterostructures are predicted to hold a profound catalytic performance because of the rearranged electronic structure at their interface.However,limitations in the morphology of heterostructures prepared by hydrothermal reactions or molten salt-assisted strategies make it challenging to directly assess charge distribution and evaluate a single interface's hydrogen evolution reaction(HER)performance.Here,we prepared two-dimensional MoO_(2)/MoS_(2) step heterostructures with a large specific surface area by the chemical vapor deposition method.Surface Kelvin probe force microscopy and electrical transport measurement verified the asymmetric charge distribution at a single interface.By fabricating a series of micro on-chip electrocatalytic devices,we investigate the HER performance for a single interface and confirm that the interface is essential for superior catalytic performance.We experimentally confirmed that the enhancement of the HER performance of step heterostructure is attributed to the asymmetric charge distribution at the interface.This work lays a foundation for designing highly efficient catalytic systems based on step heterostructures.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFB3604203)the Key Research and Development Program of Guangdong Province,China(Grant No.2024B0101060002)the Key Research and Development Program of Shenzhen City,China(Grant No.JCYJ20241202130036043)。
文摘Research on p-channel field-effect transistors(p-FETs)remains limited,primarily due to the significantly lower conductivity of the two-dimensional hole gas(2DHG)compared to the two-dimensional electron gas(2DEG)in n-channel field-effect transistors(n-FETs),which poses a significant challenge for monolithic integration.In this study,we investigate the impact of epitaxial structure parameters on 2DHG properties in p-Ga N/Al Ga N/Ga N heterostructures through semiconductor technology computer-aided design(TCAD)simulations and theoretical calculations,identifying the conditions necessary to achieve high-density 2DHG.Our simulations demonstrate that increasing the p-Ga N thickness leads to two critical thicknesses determined by surface states and acceptor ionization concentration:one corresponds to the onset of 2DHG formation,and the other to its saturation.Lowering the donor surface state energy level and increasing the acceptor ionization concentration promote 2DHG formation and saturation,although the saturated density remains independent of surface states.Additionally,a higher Al composition enhances intrinsic ionization due to stronger polarization effects,thereby increasing the 2DHG sheet density.Consequently,to achieve high-density 2DHG in p-Ga N/Al Ga N/Ga N heterostructures,it is essential to increase the Al composition,ensure that the p-Ga N thickness exceeds the critical thickness for 2DHG saturation,and maximize the acceptor ionization concentration.This study elucidates the impact of epitaxial structure parameters on 2DHG properties in p-Ga N/Al Ga N/Ga N heterostructures and provides valuable guidance for the optimization of p-FET designs.
基金the National Key R&D Program of China(No.2017YFA0204800)the National Natural Science Foundation of China(Nos.22033002,21525311,and 21973011)the Scientific Research Foundation of Graduate School of Southeast University(No.YBPY1968).
文摘Two-dimensional(2D)materials,due to its excellent mechanical,unique electrical and optical properties,have become hot materials in the field of photocatalysis.Especially,2D heterostructures can well inhibit the recombination of photogenerated electrons and holes in photocatalysis because of its special energy band structures and carrier transport characteristics,which are conducive to enhancing photoenergy conversion capacity and improving oxidation and reduction ability,so as to purify pollutants and store energy.In this minireview,we summarize recent theoretical progress in direct Z-scheme photocatalysis of 2D heterostructures,focusing on physical mechanism and improving catalytic efficiency.Current challenges and prospects for 2D direct Z-scheme photocatalysts are discussed as well.
文摘Magnetotransport properties of two-dimensional electron gases （2DEG） in AlxGa1-x N/GaN heterostructures with different Al compositions are investigated by magnetotransport measurements at low temperatures and in high magnetic fields. It is found that heterostructures with a lower Al composition in the barrier have lower 2DEG concentration and higher 2DEG mobility.
基金supported by the National Key R&D Program of China (Grant Nos.2022YFA1403103 and 2019YFA0308603)the National Natural Science Foundation of China (Grant No.12304167)the Shandong Provincial Natural Science Foundation of China (Grant No.ZR2023QA020)。
文摘Interfacial superconductivity(IS)has been a topic of intense interest in condensed matter physics,due to its unique properties and exotic photoelectrical performance.However,there are few reports about IS systems consisting of two insulators.Here,motivated by the emergence of an insulator-metal transition in type-Ⅲ heterostructures and the superconductivity in some“special”two-dimensional(2D)semiconductors via electron doping,we predict that the 2D heterostructure SnSe_(2)/PtTe_(2) is a model system for realizing IS by using firstprinciples calculations.Our results show that due to slight but crucial interlayer charge transfer,SnSe_(2)/PtTe_(2) turns to be a type-Ⅲ heterostructure with metallic properties and shows a superconducting transition with the critical temperature(T_(c))of 3.73 K.Similar to the enhanced electron–phonon coupling(EPC)in the electrondoped SnSe_(2) monolayer,the IS in the SnSe_(2)/PtTe_(2) heterostructure mainly originates from the metallized SnSe_(2) layer.Furthermore,we find that its superconductivity is sensitive to tensile lattice strain,forming a domeshaped superconducting phase diagram.Remarkably,at 7%biaxial tensile strain,the superconducting T_(c) can increase more than twofold(8.80 K),resulting from softened acoustic phonons at the𝑀point and enhanced EPC strength.Our study provides a concrete example for realizing IS in type-Ⅲ heterostructures,which waits for future experimental verification.
基金supported by the NSFC(12474071)Natural Science Foundation of Shandong Province(ZR2024YQ051,ZR2025QB50)+6 种基金Guangdong Basic and Applied Basic Research Foundation(2025A1515011191)the Shanghai Sailing Program(23YF1402200,23YF1402400)funded by Basic Research Program of Jiangsu(BK20240424)Open Research Fund of State Key Laboratory of Crystal Materials(KF2406)Taishan Scholar Foundation of Shandong Province(tsqn202408006,tsqn202507058)Young Talent of Lifting engineering for Science and Technology in Shandong,China(SDAST2024QTB002)the Qilu Young Scholar Program of Shandong University。
文摘As emerging two-dimensional(2D)materials,carbides and nitrides(MXenes)could be solid solutions or organized structures made up of multi-atomic layers.With remarkable and adjustable electrical,optical,mechanical,and electrochemical characteristics,MXenes have shown great potential in brain-inspired neuromorphic computing electronics,including neuromorphic gas sensors,pressure sensors and photodetectors.This paper provides a forward-looking review of the research progress regarding MXenes in the neuromorphic sensing domain and discussed the critical challenges that need to be resolved.Key bottlenecks such as insufficient long-term stability under environmental exposure,high costs,scalability limitations in large-scale production,and mechanical mismatch in wearable integration hinder their practical deployment.Furthermore,unresolved issues like interfacial compatibility in heterostructures and energy inefficiency in neu-romorphic signal conversion demand urgent attention.The review offers insights into future research directions enhance the fundamental understanding of MXene properties and promote further integration into neuromorphic computing applications through the convergence with various emerging technologies.
基金financial support from 2024 Domestic Visiting Scholar Program for Teachers'Professional Development in Universities(Grant No.FX2024022)National Natural Science Foundation of China(Grant No.61904043)。
文摘The development of optoelectronic technologies demands photodetectors with miniaturization,broadband operation,high sensitivity,and low power consumption.Although 2D van der Waals(vd W)heterostructures are promising candidates due to their built-in electric fields,ultrafast photocarrier separation,and tunable bandgaps,defect states limit their performance.Therefore,the modulation of the optoelectronic properties in such heterostructures is imperative.Surface charge transfer doping(SCTD)has emerged as a promising strategy for non-destructive modulation of electronic and optoelectronic characteristics in two-dimensional materials.In this work,we demonstrate the construction of high-performance p-i-n vertical heterojunction photodetectors through SCTD of MoTe_(2)/ReS_(2)heterostructure using p-type F_(4)-TCNQ.Systematic characterization reveals that the interfacial doping process effectively amplifies the built-in electric field,enhancing photogenerated carrier separation efficiency.Compared to the pristine heterojunction device,the doped photodetector exhibits remarkable visible to nearinfrared(635-1064 nm)performance.Particularly under 1064 nm illumination at zero bias,the device achieves a responsivity of 2.86 A/W and specific detectivity of 1.41×10^(12)Jones.Notably,the external quantum efficiency reaches an exceptional value of 334%compared to the initial 11.5%,while maintaining ultrafast response characteristics with rise/fall times of 11.6/15.6μs.This work provides new insights into interface engineering through molecular doping for developing high-performance vd W optoelectronic devices.
基金the National Key R&D Program of China(Nos.2018YFA0306900 and 2018YFA0209500)the National Natural Science Foundation of China(No.21872114)the Fundamental Research Funds for the Central Universities(No.20720210009)。
文摘Hydrogen production by photoelectrochemical(PEC) water splitting converts the inexhaustible supply of solar radiation to storable H2 as clean energy and thus has received widespread attention.The efficiency of PEC water splitting is largely determined by the properties of the photoelectrodes.Two-dimensional(2 D) layered transition metal dichalcogenides(TMDs) are promising candidates for photoelectrodes due to their atomic layer thickness,tunable bandgap,large specific surface area,and high carrier mobility.Moreover,the construction of 2 D TMDs heterostructures provides freedom in material design,which facilitates the further improvement of PEC water splitting.This review begins by describing the mechanism of PEC water splitting and the advantages of 2 D TMDbased heterostructures for photo electrodes.Then,the design considerations of the heterostructures for enhanced PEC efficiency are comprehensively reviewed with a focus on material selection,band engineering,surface modification,and long-term durability.Finally,current challenges and future perspectives for the development of photoelectrodes based on 2 D TMDs heterostructures are addressed.
基金funding from the National Natural Science Foundation of China(No.52002267).
文摘Regarding the reverse process of materials growth,etching has been widely concerned to indirectly probe the growth kinetics,offering an avenue in governing the growth of two-dimensional(2D)materials.In this work,interface-driven anisotropic etching mode is demonstrated for the first time to be generally applied to 2D heterostructures.It is shown that the typical in-plane graphene and hexagonal boron nitride(h-BN)heterostructures follow a multi-stage etching behavior initiated first along the interfacial region between the two materials and then along edges of neighboring h-BN flakes and finally along central edges of hBN.By accurately tuning etching conditions in the chemical vapor deposition process,series of etched 2D heterostructure patterns are controllably produced.Furthermore,scaled formation of graphene and h-BN heterostructures arrays has been realized with full assist of as-proposed etching mechanism,offering a direct top-down method to make 2D orientated heterostructures with order and complexity.Detection of interface-driven multi-staged anisotropic etching mode will shed light on understanding growth mechanism and further expanding wide applications of 2D heterostructures.
基金the National Key Research and Development Program of China (Grant No.2016YFA0301204)the National Natural Science Foundation of China (Grant Nos.11874350 and 11434010)
文摘Research on two-dimensional(2D) materials and related van der Waals heterostructures(vdWHs) is intense and remains one of the leading topics in condensed matter physics.Lattice vibrations or phonons of a vdWH provide rich information,such as lattice structure,phonon dispersion,electronic band structure and electron–phonon coupling.Here,we provide a mini review on the lattice vibrations in vdWHs probed by Raman spectroscopy.First,we introduced different kinds of vdWHs,including their structures,properties and potential applications.Second,we discussed interlayer and intralayer phonon in twist multilayer graphene and MoS2.The frequencies of interlayer and intralayer modes can be reproduced by linear chain model(LCM)and phonon folding induced by periodical moiré potentials,respectively.Then,we extended LCM to vdWHs formed by distinct 2D materials,such as MoS2/graphene and hBN/WS2 heterostructures.We further demonstrated how to calculate Raman intensity of interlayer modes in vdWHs by interlayer polarizability model.
基金supported by the National Basic Research Program of China(Grant Nos.2013CB934500 and 2013CBA01602)the National Natural Science Foundation of China(Grant Nos.61325021,11574361,and 51572289)+1 种基金the Key Research Program of Frontier Sciences,CAS,(Grant No.QYZDB-SSW-SLH004)the Strategic Priority Research Program(B),CAS(Grant No.XDB07010100)
文摘Two-dimensional （2D） Van der Waals heterostructures have aroused extensive concerns in recent years. Their fabrica- tion calls for facile and efficient transfer techniques for achieving well-defined structures. In this work, we report a simple and effective dry transfer method to fabricate 2D heterostructures with a clean interface. Using Propylene Carbonate （PC） films as stamps, we are able to pick up various 2D materials flakes from the substrates and unload them to the receiving substrates at an elevated temperature. Various multilayer heterostructures with ultra-clean interfaces were fabricated by this technique. Furthermore, the 2D materials can be pre-pattemed before transfer so as to fabricate desired device structures, demonstrating a facile way to promote the development of 2D heterostructures.
基金supported by the Key Program of the National Natural Science Foundation of China (Grant No 60736033)Xi’an Applied Materials Innovation Fund of China (Grant No XA-AM-200703)the Open Fund of Key Laboratory of Wide Bandgap Semiconductors Material and Devices,Ministry of Education,China
文摘To reveal the internal physics of the low-temperature mobility of two-dimensional electron gas （2DEG） in Al- GaN/GaN heterostructures, we present a theoretical study of the strong dependence of 2DEG mobility on Al content and thickness of AlGaN barrier layer. The theoretical results are compared with one of the highest measured of 2DEG mobility reported for AlGaN/GaN heterostructures. The 2DEG mobility is modelled as a combined effect of the scat- tering mechanisms including acoustic deformation-potential, piezoelectric, ionized background donor, surface donor, dislocation, alloy disorder and interface roughness scattering. The analyses of the individual scattering processes show that the dominant scattering mechanisms are the alloy disorder scattering and the interface roughness scattering at low temperatures. The variation of 2DEG mobility with the barrier layer parameters results mainly from the change of 2DEG density and distribution. It is suggested that in AlGaN/GaN samples with a high Al content or a thick AlGaN layer, the interface roughness scattering may restrict the 2DEG mobility significantly, for the AlGaN/GaN interface roughness increases due to the stress accumulation in AlGaN layer.
文摘Thermoelectric properties of bulk and bilayer two-dimensional （2D） MoS2/MoSe2 het- erostructures are investigated using density functional theory in conjunction with semi- classical Boltzmann transport theory. It is predicted that the bulk 2D heterostructures could considerably enhance the thermoelectric properties as compared with the bulk MoSe2. The enhancement originates from the reduction in the band gap and the presence of interlayer van der Waals interactions. We therefore propose the 2D MoS2/MoSe2 heterostructures as a possible candidate material for thermoelectric applications.
基金supported by the National Natural Science Foundation of China (52173286, 52207249)Major basic research project of Natural Science Foundation of Shandong Province (ZR2023ZD12)+1 种基金the State Key Laboratory of Marine Resource Utilization in South China Sea (Hainan University) (MRUKF2023013)Open Program of Guangxi Key Laboratory of Information Materials (221024-K)。
文摘The inherent catalytic anisotropy of two-dimensional(2D) materials has limited the enhancement of LiO_(2) batteries(LOBs) performance due to the significantly different adsorption energies on 2D and edge surfaces.Tuning the adsorption strength in 2D materials to the reaction intermediates is essential for achieving high-performance LOBs.Herein,a MnS/MoS_(2) heterostructure is designed as a cathode catalyst by adjusting the adsorption behavior at the surface.Different from the toroidal-like discharge products on the MoS_(2) cathode,the MnS/MoS_(2) surface displays an improved adsorption energy to reaction species,thereby promoting the growth of the film-like discharge products.MnS can disturb the layer growth of MoS_(2),in which the stack edge plane features a strong interaction with the intermediates and limits the growth of the discharge products.Experimental and theoretical results confirm that the MnS/MoS_(2) heterostructure possesses improved electron transfer kinetics at the interface and plays an important role in the adsorption process for reaction species,which finally affects the morphology of Li_2O_(2),In consequence,the MnS/MoS_(2) heterostructure exhibits a high specific capacity of 11696.0 mA h g^(-1) and good cycle stability over 1800 h with a fixed specific capacity of 600 mA h g^(-1) at current density of100 mA g^(-1) This work provides a novel interfacial engineering strategy to enhance the performance of LOBs by tuning the adsorption properties of 2D materials.
文摘Since the successful fabrication of two-dimensional (2D) ferromagnetic (FM) monolayer CrI3 and Cr2Ge2Te6, 2D FM materials are becoming an exciting research topic in condensed matter physics and materials fields, as they provide a good platform to explore the fundamental physical properties of magnetic materials under 2D limit. In this review, we summarize the theoretical research progress of intrinsic 2D FM materials and related van der Waals heterostructures (vdWHs) including their electronic structures, magnetism, Curie temperature, valley polarization, and band alignment. Moreover, we also summarize recent researches on the methods that used to regulate the above properties of 2D FM materials and vdWHs, such as defects, doping, strain, electric field and interlayer coupling. These studies show that 2D FM materials have broad application prospects in spintronics and valleytronics. However, there are still many problems waiting to be solved on the way to practical application.
基金support from National Key Research and Development Program of China (2018YFA0704403)NSFC (62074064)Innovation Fund of WNLO
文摘Two-dimensional(2D)/quasi-2D organic-inorganic halide perovskites are regarded as naturally formed multiple quantum wells with inorganic layers isolated by long organic chains,which exhibit layered structure,large exciton binding energy,strong nonlinear optical effect,tunable bandgap via changing the layer number or chemical composition,improved environmental stability,and excellent optoelectronic properties.The extensive choice of long organic chains endows 2D/quasi-2D perovskites with tunable electron-phonon coupling strength,chirality,or ferroelectricity properties.In particular,the layered nature of 2D/quasi-2D perovskites allows us to exfoliate them to thin plates to integrate with other materials to form heterostructures,the fundamental structural units for optoelectronic devices,which would greatly extend the functionalities in view of the diversity of 2D/quasi-2D perovskites.In this paper,the recent achievements of 2D/quasi-2D perovskite-based heterostructures are reviewed.First,the structure and physical properties of 2D/quasi-2D perovskites are introduced.We then discuss the construction and characterizations of 2D/quasi-2D perovskite-based heterostructures and highlight the prominent optical properties of the constructed heterostructures.Further,the potential applications of 2D/quasi-2D perovskite-based heterostructures in photovoltaic devices,light emitting devices,photodetectors/phototransistors,and valleytronic devices are demonstrated.Finally,we summarize the current challenges and propose further research directions in the field of 2D/quasi-2D perovskite-based heterostructures.
基金supported by the National Natural Science Foundation of China(Grant Nos.51722204,91421110,51802145)the National Key Basic Research Program of China(Grant No.2014CB931702)+3 种基金the Sichuan Provincial Fund for Distinguished Young Academic and Technology Leaders(Grant No.2014JQ0011)the Science and Technology Support Program of Sichuan Province(Grant No.2018RZ0042,2016RZ0033,2018RZ0082)the Natural Science Foundation of Guangdong Province(2018A030310225)China Postdoctoral Science Foundation(Grant No.2018M643443).
文摘It is a rapidly developed subject in expanding the fundamental properties and application of two-dimensional(2D)materials.The weak van der Waals interaction in 2D materials inspired researchers to explore 2D heterostructures(2DHs)based broadband photodetectors in the far-infrared(IR)and middle-IR regions with high response and high detectivity.This review focuses on the strategy and motivation of designing 2DHs based high-performance IR photodetectors,which provides a wide view of this field and new expectation for advanced photodetectors.First,the photocarriers'generation mechanism and frequently employed device structures are presented.Then,the 2DHs are divided into semimetal/semiconductor 2DHs,semiconductor/semiconductor 2DHs,and multidimensional semi-2DHs;the advantages,motivation,mechanism,recent progress,and outlook are discussed.Finally,the challenges for next-generation photodetectors are described for this rapidly developing field.
基金the National Natural Science Foundation of China(nos.61505051,51902098,62090035,U19A2090,and 1217409)the Key Program of Science and Technology Department of Hunan Province(nos.2019XK2001 and 2020XK2001)+1 种基金the Science and Technology Innovation Program of Hunan Province(no.2021RC3061)the Natural Science Foundation of Hunan Province(nos.2021JJ20016 and 2021JJ30132).
文摘CONSPECTUS:Two-dimensional(2D)heterostructures have created many novel properties and triggered a variety of promising applications,thus setting off a boom in the modern semiconductor industry.As the first road to step into adequately exploring the properties and real applications,the material preparation process matters a lot.Adhering to the concept of epitaxial growth,chemical vapor deposition(CVD)shows great potential for the preparation of heterostructures for commercialization.
