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
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
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
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
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
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
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
This paper finds that the two-dimensional electron gas density in high Al-content A1GaN/GaN heterostructures exhibits an obvious time-dependent degradation after the epitaxial growth. The degradation mechanism was inv...This paper finds that the two-dimensional electron gas density in high Al-content A1GaN/GaN heterostructures exhibits an obvious time-dependent degradation after the epitaxial growth. The degradation mechanism was investigated in depth using Hall effect measurements,high resolution x-ray diffraction,scanning electron microscopy,x-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy.The results reveal that the formation of surface oxide is the main reason for the degradation,and the surface oxidation always occurs within the surface hexagonal defects for high Al-content AlGaN/GaN heterostructures.展开更多
Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. Whil...Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. While the carrier concentration reaches 1.32×10^13 cm^-2 and stays relatively unchanged with the decreasing temperature, the mobility of the 2DEG increases to 1.21 × 10^4 cm2/（V.s） at 2 K. The Shubnikov-de Haas （SdH） oscillations are observed in a magnetic field as low as 2.5 T at 2 K. By the measurements and the analyses of the temperature-dependent SdH oscillations, the effective mass of the 2DEC is determined. The ratio of the transport lifetime to the quantum scattering time is 9 in our sample, indicating that small-angle scattering is predominant.展开更多
A self-standing dual-electric field synergistic[TiO_(2)/polyvinylidene fluoride(PVDF)]//[g-C3 N4 tube/PVDF]Janus nanofibres(named as[TP]//[CTP]JNs)S-scheme heterostructure piezoelectric photocatalyst is designed and c...A self-standing dual-electric field synergistic[TiO_(2)/polyvinylidene fluoride(PVDF)]//[g-C3 N4 tube/PVDF]Janus nanofibres(named as[TP]//[CTP]JNs)S-scheme heterostructure piezoelectric photocatalyst is designed and constructed via conjugative electrospinning.Dual-fields of built-in electric fields supplied by S-scheme heterostructure and piezoelectric field formed by PVDF jointly boost separation and transfer of photo-induced charges.As a case study,piezoelectric photocatalytic efficiency of[TP]//[CTP]JNs for tetracycline hydrochloride(TCH)under ultrasonic united with simulated sunlight illumination is 93.35%(40 min),which is 1.39 times of the photocatalytic efficiency(light illumination only)and 5.32 times of piezoelectric catalytic efficiency(applying ultrasonic only),proving the advantages of the synergistic effect of piezoelectric catalysis and photocatalysis on contaminant degradation.The dynamic behaviors of photocatalysis and photo-generated charges are deeply revealed through fs-TA and TRPL decay spectra,and the degradation pathways of antibiotics are reasonably speculated by combining LCMS spectra with Fukui index.By the degradation ability,COMSOL simulation and DFT calculation,the structural advantage of Janus nanofibers is fully verified,and S-scheme charge transfer mechanism is confirmed by combining a series of sound ample experiments with theoretical calculations.Additionally,the construction mechanism of Janus nanofibers is proposed,and corresponding construction technique is established.展开更多
With a large number of researches being conducted on two?dimen?sional(2D)materials,their unique properties in optics,electrics,mechanics,and magnetics have attracted increasing attention.Accordingly,the idea of combin...With a large number of researches being conducted on two?dimen?sional(2D)materials,their unique properties in optics,electrics,mechanics,and magnetics have attracted increasing attention.Accordingly,the idea of combining distinct functional 2D materials into heterostructures naturally emerged that pro?vides unprecedented platforms for exploring new physics that are not accessible in a single 2D material or 3D heterostructures.Along with the rapid development of controllable,scalable,and programmed synthesis techniques of high?quality 2D heterostructures,various heterostructure devices with extraordinary performance have been designed and fabricated,including tunneling transistors,photodetectors,and spintronic devices.In this review,we present a summary of the latest progresses in fabrications,properties,and applications of di erent types of 2D heterostruc?tures,followed by the discussions on present challenges and perspectives of further investigations.展开更多
Two-dimensional （2D） materials, e.g., graphene, transition metal dichalcogenides （TMDs）, and black phosphorus （BP）, have demonstrated fascinating electrical and optical characteristics and exhibited great potent...Two-dimensional （2D） materials, e.g., graphene, transition metal dichalcogenides （TMDs）, and black phosphorus （BP）, have demonstrated fascinating electrical and optical characteristics and exhibited great potential in optoelectronic applications. High-performance and multifunctional devices were achieved by employing diverse designs, such as hybrid systems with nanostructured materials, bulk semiconductors and organics, forming 2D heterostructures. In this review, we mainly discuss the recent progress of 2D materials in high-responsive photodetectors, light-emitting devices and single photon emitters. Hybrid systems and van der Waals heterostructure-based devices are emphasized, which exhibit great potential in state-of-the-art applications.展开更多
Two-dimensional(2D) materials, such as graphene, transition metal dichalcogenides(TMDs), black phosphorus(BP),and related derivatives, have attracted great attention due to their advantages of flexibility, strong ligh...Two-dimensional(2D) materials, such as graphene, transition metal dichalcogenides(TMDs), black phosphorus(BP),and related derivatives, have attracted great attention due to their advantages of flexibility, strong light–matter interaction,broadband absorption, and high carrier mobility, and have become a powerful contender for next-generation infrared photodetectors. However, since the thickness of 2D materials is on the order of nanometers, the absorption of 2D materials is very weak, which limits the detection performance of 2D materials-based infrared photodetectors. In order to solve this problem, scientific researchers have tried to use optimized device structures to combine with 2D materials for improving the performance of infrared photodetectors. In this review, we review the progress of room-temperature infrared photodetectors with hybrid structure based on 2D materials in recent years, focusing mainly on 2D–nD(n = 0, 1, 2) heterostructures, the integration between 2D materials and on-chip or plasmonic structure. Finally, we summarize the current challenges and point out the future development direction.展开更多
Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from twodimensional(2D)materials.A revolutionary development is to flexibly construct ...Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from twodimensional(2D)materials.A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials.These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences.Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures;the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties.In this review,we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction,where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials.Afterward,we discuss the applications and experimental synthesis of lateral 2D heterostructures.Moreover,a perspective on lateral 2D heterostructures is given at the end.展开更多
Black phosphorous(BP),an excellent two-dimensional(2D)monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure,has been widely applied in ...Black phosphorous(BP),an excellent two-dimensional(2D)monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure,has been widely applied in various devices.As the essential building blocks for modern electronic and optoelectronic devices,high quality PN junctions based on semiconductors have attracted widespread attention.Herein,we report a junction field-effect transistor(JFET)by integrating narrow-gap p-type BP and ultra-wide gap n-typeβ-Ga2O3 nanoflakes for the first time.BP andβ-Ga2O3 form a vertical van der Waals(vdW)heterostructure by mechanically exfoliated method.The BP/β-Ga2O3 vdW heterostructure exhibits remarkable PN diode rectifying characteristics with a high rectifying ratio about 107 and a low reverse current around pA.More interestingly,by using the BP as the gate andβ-Ga2O3 as the channel,the BP/β-Ga2O3 JFET devices demonstrate excellent n-channel JFET characteristics with the on/off ratio as high as 107,gate leakage current around as low as pA,maximum transconductance(gm)up to 25.3μS and saturation drain current(IDSS)of 16.5μA/μm.Moreover,it has a pinch-off voltage of–20 V and a minimum subthreshold swing of 260 mV/dec.These excellent n-channel JFET characteristics will expand the application of BP in future nanoelectronic devices.展开更多
We report a large-scale, high-quality heterostructure composed of vertically-stacked graphene and two-dimensional(2D) germanium.The heterostructure is constructed by the intercalation-assisted technique.We first synth...We report a large-scale, high-quality heterostructure composed of vertically-stacked graphene and two-dimensional(2D) germanium.The heterostructure is constructed by the intercalation-assisted technique.We first synthesize large-scale,single-crystalline graphene on Ir(111) surface and then intercalate germanium at the interface of graphene and Ir(111).The intercalated germanium forms a well-defined 2D layer with a 2 × 2 superstructure with respect to Ir(111).Theoretical calculations demonstrate that the 2D germanium has a double-layer structure.Raman characterizations show that the 2D germanium effectively weakens the interaction between graphene and Ir substrate, making graphene more like the intrinsic one.Further experiments of low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy(XPS) confirm the formation of large-scale and high-quality graphene/2D-germanium vertical heterostructure.The integration of graphene with a traditional 2D semiconductor provides a platform to explore new physical phenomena in the future.展开更多
Graphene and transition metal dichalcogenides(TMDs), two-dimensional materials, have been investigated wildely in recent years. As a member of the TMD family, MoTe2 possesses a suitable bandgap of ~1.0 eV for near inf...Graphene and transition metal dichalcogenides(TMDs), two-dimensional materials, have been investigated wildely in recent years. As a member of the TMD family, MoTe2 possesses a suitable bandgap of ~1.0 eV for near infrared(NIR)photodetection. Here we stack the MoTe2 flake with two graphene flakes of high carrier mobility to form a graphene–MoTe2–graphene heterostructure. It exhibits high photo-response to a broad spectrum range from 500 nm to 1300 nm. The photoresponsivity is calculated to be 1.6 A/W for the 750-nm light under 2 V/0 V drain–source/gate bias, and 154 mA/W for the 1100-nm light under 0.5 V/60 V drain–source/gate bias. Besides, the polarity of the photocurrent under zero Vds can be efficiently tuned by the back gate voltage to satisfy different applications. Finally, we fabricate a vertical graphene–MoTe2–graphene heterostructure which shows improved photoresponsivity of 3.3 A/W to visible light.展开更多
The emergent two-dimensional(2D)material,tin diselenide(SnSe_(2)),has garnered significant consideration for its potential in image capturing systems,optical communication,and optoelectronic memory.Nevertheless,SnSe_(...The emergent two-dimensional(2D)material,tin diselenide(SnSe_(2)),has garnered significant consideration for its potential in image capturing systems,optical communication,and optoelectronic memory.Nevertheless,SnSe_(2)-based photodetection faces obstacles,including slow response speed and low normalized detectivity.In this work,photodetectors based on SnS/SnSe_(2)and SnSe/SnSe_(2)p−n heterostructures have been implemented through a polydimethylsiloxane(PDMS)−assisted transfer method.These photodetectors demonstrate broad-spectrum photoresponse within the 405 to 850 nm wavelength range.The photodetector based on the SnS/SnSe_(2)heterostructure exhibits a significant responsivity of 4.99×10^(3)A∙W^(−1),normalized detectivity of 5.80×10^(12)cm∙Hz^(1/2)∙W^(−1),and fast response time of 3.13 ms,respectively,owing to the built-in electric field.Meanwhile,the highest values of responsivity,normalized detectivity,and response time for the photodetector based on the SnSe/SnSe_(2)heterostructure are 5.91×10^(3)A∙W^(−1),7.03×10^(12)cm∙Hz^(1/2)∙W−1,and 4.74 ms,respectively.And their photodetection performances transcend those of photodetectors based on individual SnSe_(2),SnS,SnSe,and other commonly used 2D materials.Our work has demonstrated an effective strategy to improve the performance of SnSe_(2)-based photodetectors and paves the way for their future commercialization.展开更多
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.
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 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.
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.
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Project supported by the Major Program and State Key Program of National Natural Science of China (Grant Nos 60890191 and 60736033)the National Key Science & Technology Special Project (Grant No 2008ZX 01002)
文摘This paper finds that the two-dimensional electron gas density in high Al-content A1GaN/GaN heterostructures exhibits an obvious time-dependent degradation after the epitaxial growth. The degradation mechanism was investigated in depth using Hall effect measurements,high resolution x-ray diffraction,scanning electron microscopy,x-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy.The results reveal that the formation of surface oxide is the main reason for the degradation,and the surface oxidation always occurs within the surface hexagonal defects for high Al-content AlGaN/GaN heterostructures.
基金Project supported by the National Basic Research Program of China (Grant No.2011CB309606)
文摘Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. While the carrier concentration reaches 1.32×10^13 cm^-2 and stays relatively unchanged with the decreasing temperature, the mobility of the 2DEG increases to 1.21 × 10^4 cm2/（V.s） at 2 K. The Shubnikov-de Haas （SdH） oscillations are observed in a magnetic field as low as 2.5 T at 2 K. By the measurements and the analyses of the temperature-dependent SdH oscillations, the effective mass of the 2DEC is determined. The ratio of the transport lifetime to the quantum scattering time is 9 in our sample, indicating that small-angle scattering is predominant.
基金supported by the National Natural Science Foundation of China(No.52173155)the Natural Science Foundation of Jilin Province(Nos.YDZJ202101ZYTS130,YDZJ202101ZYTS059)the Natural Science Foundation of Chongqing(Nos.cstc2021jcyj-msxmX1076,cstc2021jcyj-msxmX0798).
文摘A self-standing dual-electric field synergistic[TiO_(2)/polyvinylidene fluoride(PVDF)]//[g-C3 N4 tube/PVDF]Janus nanofibres(named as[TP]//[CTP]JNs)S-scheme heterostructure piezoelectric photocatalyst is designed and constructed via conjugative electrospinning.Dual-fields of built-in electric fields supplied by S-scheme heterostructure and piezoelectric field formed by PVDF jointly boost separation and transfer of photo-induced charges.As a case study,piezoelectric photocatalytic efficiency of[TP]//[CTP]JNs for tetracycline hydrochloride(TCH)under ultrasonic united with simulated sunlight illumination is 93.35%(40 min),which is 1.39 times of the photocatalytic efficiency(light illumination only)and 5.32 times of piezoelectric catalytic efficiency(applying ultrasonic only),proving the advantages of the synergistic effect of piezoelectric catalysis and photocatalysis on contaminant degradation.The dynamic behaviors of photocatalysis and photo-generated charges are deeply revealed through fs-TA and TRPL decay spectra,and the degradation pathways of antibiotics are reasonably speculated by combining LCMS spectra with Fukui index.By the degradation ability,COMSOL simulation and DFT calculation,the structural advantage of Janus nanofibers is fully verified,and S-scheme charge transfer mechanism is confirmed by combining a series of sound ample experiments with theoretical calculations.Additionally,the construction mechanism of Janus nanofibers is proposed,and corresponding construction technique is established.
基金supported by NSF of China(Grant No.61775241)partly by the Innovation-driven Project(Grant No.2017CX019)the funding support from the Australian Research Council(ARC Discovery Projects,DP180102976)
文摘With a large number of researches being conducted on two?dimen?sional(2D)materials,their unique properties in optics,electrics,mechanics,and magnetics have attracted increasing attention.Accordingly,the idea of combining distinct functional 2D materials into heterostructures naturally emerged that pro?vides unprecedented platforms for exploring new physics that are not accessible in a single 2D material or 3D heterostructures.Along with the rapid development of controllable,scalable,and programmed synthesis techniques of high?quality 2D heterostructures,various heterostructure devices with extraordinary performance have been designed and fabricated,including tunneling transistors,photodetectors,and spintronic devices.In this review,we present a summary of the latest progresses in fabrications,properties,and applications of di erent types of 2D heterostruc?tures,followed by the discussions on present challenges and perspectives of further investigations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61422503 and 61376104)the Open Research Funds of Key Laboratory of MEMS of Ministry of Education of Chinathe Fundamental Research Funds for the Central Universities of China
文摘Two-dimensional （2D） materials, e.g., graphene, transition metal dichalcogenides （TMDs）, and black phosphorus （BP）, have demonstrated fascinating electrical and optical characteristics and exhibited great potential in optoelectronic applications. High-performance and multifunctional devices were achieved by employing diverse designs, such as hybrid systems with nanostructured materials, bulk semiconductors and organics, forming 2D heterostructures. In this review, we mainly discuss the recent progress of 2D materials in high-responsive photodetectors, light-emitting devices and single photon emitters. Hybrid systems and van der Waals heterostructure-based devices are emphasized, which exhibit great potential in state-of-the-art applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.61704061)
文摘Two-dimensional(2D) materials, such as graphene, transition metal dichalcogenides(TMDs), black phosphorus(BP),and related derivatives, have attracted great attention due to their advantages of flexibility, strong light–matter interaction,broadband absorption, and high carrier mobility, and have become a powerful contender for next-generation infrared photodetectors. However, since the thickness of 2D materials is on the order of nanometers, the absorption of 2D materials is very weak, which limits the detection performance of 2D materials-based infrared photodetectors. In order to solve this problem, scientific researchers have tried to use optimized device structures to combine with 2D materials for improving the performance of infrared photodetectors. In this review, we review the progress of room-temperature infrared photodetectors with hybrid structure based on 2D materials in recent years, focusing mainly on 2D–nD(n = 0, 1, 2) heterostructures, the integration between 2D materials and on-chip or plasmonic structure. Finally, we summarize the current challenges and point out the future development direction.
基金the National Key Research and Development Program of China (No. 2018YFA0306100)National Natural Science Foundation of China (No. 61604140)Thousand Talents Program
文摘Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from twodimensional(2D)materials.A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials.These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences.Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures;the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties.In this review,we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction,where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials.Afterward,we discuss the applications and experimental synthesis of lateral 2D heterostructures.Moreover,a perspective on lateral 2D heterostructures is given at the end.
基金supported by the National Natural Science Foundation of China(Grant No.61922082,61875223,61927813)the Natural Science Foundation of Jiangsu Province(Grant No.BK20191195)The support from the Vacuum Interconnected Nanotech Workstation(Nano-X)of Suzhou Institute of Nano-tech and Nano-bionics(SINANO),Chinese Academy of Sciences。
文摘Black phosphorous(BP),an excellent two-dimensional(2D)monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure,has been widely applied in various devices.As the essential building blocks for modern electronic and optoelectronic devices,high quality PN junctions based on semiconductors have attracted widespread attention.Herein,we report a junction field-effect transistor(JFET)by integrating narrow-gap p-type BP and ultra-wide gap n-typeβ-Ga2O3 nanoflakes for the first time.BP andβ-Ga2O3 form a vertical van der Waals(vdW)heterostructure by mechanically exfoliated method.The BP/β-Ga2O3 vdW heterostructure exhibits remarkable PN diode rectifying characteristics with a high rectifying ratio about 107 and a low reverse current around pA.More interestingly,by using the BP as the gate andβ-Ga2O3 as the channel,the BP/β-Ga2O3 JFET devices demonstrate excellent n-channel JFET characteristics with the on/off ratio as high as 107,gate leakage current around as low as pA,maximum transconductance(gm)up to 25.3μS and saturation drain current(IDSS)of 16.5μA/μm.Moreover,it has a pinch-off voltage of–20 V and a minimum subthreshold swing of 260 mV/dec.These excellent n-channel JFET characteristics will expand the application of BP in future nanoelectronic devices.
基金Project supported by the National Key Research&Development Program of China(Grant Nos.2016YFA0202300 and 2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.61390501,61888102,and 51872284)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB30000000 and XDB28000000)Beijing Nova Program,China(Grant No.Z181100006218023)the University of Chinese Academy of Sciences
文摘We report a large-scale, high-quality heterostructure composed of vertically-stacked graphene and two-dimensional(2D) germanium.The heterostructure is constructed by the intercalation-assisted technique.We first synthesize large-scale,single-crystalline graphene on Ir(111) surface and then intercalate germanium at the interface of graphene and Ir(111).The intercalated germanium forms a well-defined 2D layer with a 2 × 2 superstructure with respect to Ir(111).Theoretical calculations demonstrate that the 2D germanium has a double-layer structure.Raman characterizations show that the 2D germanium effectively weakens the interaction between graphene and Ir substrate, making graphene more like the intrinsic one.Further experiments of low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy(XPS) confirm the formation of large-scale and high-quality graphene/2D-germanium vertical heterostructure.The integration of graphene with a traditional 2D semiconductor provides a platform to explore new physical phenomena in the future.
基金Project supported by the National Natural Science Foundation of China(Grant No.21405109)the Seed Foundation of State Key Laboratory of Precision Measurement Technology and Instruments,China(Pilt No.1710)
文摘Graphene and transition metal dichalcogenides(TMDs), two-dimensional materials, have been investigated wildely in recent years. As a member of the TMD family, MoTe2 possesses a suitable bandgap of ~1.0 eV for near infrared(NIR)photodetection. Here we stack the MoTe2 flake with two graphene flakes of high carrier mobility to form a graphene–MoTe2–graphene heterostructure. It exhibits high photo-response to a broad spectrum range from 500 nm to 1300 nm. The photoresponsivity is calculated to be 1.6 A/W for the 750-nm light under 2 V/0 V drain–source/gate bias, and 154 mA/W for the 1100-nm light under 0.5 V/60 V drain–source/gate bias. Besides, the polarity of the photocurrent under zero Vds can be efficiently tuned by the back gate voltage to satisfy different applications. Finally, we fabricate a vertical graphene–MoTe2–graphene heterostructure which shows improved photoresponsivity of 3.3 A/W to visible light.
基金supported by the Jilin Scientific and Technological Development Program(Grant No.20230101286JC)National Natural Science Foundation of China(Grant Nos.61975051,6227503,and 52002110)Hebei Provincial Department of Education Innovation Ability Training Funding Project for graduate students.
文摘The emergent two-dimensional(2D)material,tin diselenide(SnSe_(2)),has garnered significant consideration for its potential in image capturing systems,optical communication,and optoelectronic memory.Nevertheless,SnSe_(2)-based photodetection faces obstacles,including slow response speed and low normalized detectivity.In this work,photodetectors based on SnS/SnSe_(2)and SnSe/SnSe_(2)p−n heterostructures have been implemented through a polydimethylsiloxane(PDMS)−assisted transfer method.These photodetectors demonstrate broad-spectrum photoresponse within the 405 to 850 nm wavelength range.The photodetector based on the SnS/SnSe_(2)heterostructure exhibits a significant responsivity of 4.99×10^(3)A∙W^(−1),normalized detectivity of 5.80×10^(12)cm∙Hz^(1/2)∙W^(−1),and fast response time of 3.13 ms,respectively,owing to the built-in electric field.Meanwhile,the highest values of responsivity,normalized detectivity,and response time for the photodetector based on the SnSe/SnSe_(2)heterostructure are 5.91×10^(3)A∙W^(−1),7.03×10^(12)cm∙Hz^(1/2)∙W−1,and 4.74 ms,respectively.And their photodetection performances transcend those of photodetectors based on individual SnSe_(2),SnS,SnSe,and other commonly used 2D materials.Our work has demonstrated an effective strategy to improve the performance of SnSe_(2)-based photodetectors and paves the way for their future commercialization.
