Two-dimensional(2D) semiconductors have captured broad interest as light emitters, due to their unique excitonic effects. These layer-blocks can be integrated through van der Waals assembly, i.e., fabricating homo-or ...Two-dimensional(2D) semiconductors have captured broad interest as light emitters, due to their unique excitonic effects. These layer-blocks can be integrated through van der Waals assembly, i.e., fabricating homo-or heterojunctions, which show novel emission properties caused by interface engineering. In this review, we will first give an overview of the basic strategies that have been employed in interface engineering, including changing components, adjusting interlayer gap, and tuning twist angle. By modifying the interfacial factors, novel emission properties of emerging excitons are unveiled and discussed. Generally, well-tailored interfacial energy transfer and charge transfer within a 2D heterostructure cause static modulation of the brightness of intralayer excitons. As a special case, dynamically correlated dual-color emission in weakly-coupled bilayers will be introduced, which originates from intermittent interlayer charge transfer. For homobilayers and type Ⅱ heterobilayers, interlayer excitons with electrons and holes residing in neighboring layers are another important topic in this review. Moreover, the overlap of two crystal lattices forms moiré patterns with a relatively large period, taking effect on intralayer and interlayer excitons. Particularly, theoretical and experimental progresses on spatially modulated moiré excitons with ultra-sharp linewidth and quantum emission properties will be highlighted. Moiré quantum emitter provides uniform and integratable arrays of single photon emitters that are previously inaccessible, which is essential in quantum many-body simulation and quantum information processing. Benefiting from the optically addressable spin and valley indices, 2D heterostructures have become an indispensable platform for investigating exciton physics, designing and integrating novel concept emitters.展开更多
Research on two-dimensional(2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since ...Research on two-dimensional(2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since the mechanical exfoliation of graphene in 2004. Starting from graphene, 2D materials now have become a big family with numerous members and diverse categories. The unique structural features and physicochemical properties of 2D materials make them one class of the most appealing candidates for a wide range of potential applications. In particular, we have seen some major breakthroughs made in the field of 2D materials in last five years not only in developing novel synthetic methods and exploring new structures/properties but also in identifying innovative applications and pushing forward commercialisation. In this review, we provide a critical summary on the recent progress made in the field of 2D materials with a particular focus on last five years. After a brief backgroundintroduction, we first discuss the major synthetic methods for 2D materials, including the mechanical exfoliation, liquid exfoliation, vapor phase deposition, and wet-chemical synthesis as well as phase engineering of 2D materials belonging to the field of phase engineering of nanomaterials(PEN). We then introduce the superconducting/optical/magnetic properties and chirality of 2D materials along with newly emerging magic angle 2D superlattices. Following that, the promising applications of 2D materials in electronics, optoelectronics, catalysis, energy storage, solar cells, biomedicine, sensors, environments, etc. are described sequentially. Thereafter, we present the theoretic calculations and simulations of 2D materials. Finally, after concluding the current progress, we provide some personal discussions on the existing challenges and future outlooks in this rapidly developing field.展开更多
The low-dimensional organic-inorganic halide perovskites with self-trapped exciton emission have promising prospects for single-phase white-light emitters. However, so far, these broadband white-light-emitting(BWLE) p...The low-dimensional organic-inorganic halide perovskites with self-trapped exciton emission have promising prospects for single-phase white-light emitters. However, so far, these broadband white-light-emitting(BWLE) perovskites were synthesized by trial-and-error testing spacing molecules. Here, we developed a steric hindrance regulation strategy to predictably synthesize BWLE perovskites. The molecules containing C–C(–NH_(2))–C groups were introduced into low-dimensional perovskites, which brings a large steric hindrance in-plane orientation. The bigger C–C(–NH_(2))–C bond angle would induce larger structural distortion in perovskites, which leads to the higher rate of self-trapping of excitons and the deeper self-trapping depth. The photoluminescence spectra of the synthesized perovskites can cover the cool-to-warm white light region. Overall, we fabricated a material library consisting of 40 kinds of BWLE compounds according to this strategy. Our findings develop a general strategy to synthesize BWLE perovskites and offer a material platform for optoelectronic applications.展开更多
Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials t...Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials that can be driven by facile nondestructive methods,such as temperature,are still rare.Here,we introduce ultrathin Cu_(9)S_(5)crystals grown by chemical vapor deposition(CVD)as an exemplary case.For the first time,their basic electrical properties were investigated based on Hall measurements,showing a record high hole carrier density of~1022 cm^(-3) among 2D semiconductors.Besides,an unusual and repeatable conductivity switching behavior at~250 K were readily observed in a wide thickness range of CVD-grown Cu_(9)S_(5)(down to 2 unit-cells).Confirmed by in-situ selected area electron diffraction,this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonalβphase and low-temperatureβ’phase with a superstructure.Our work provides new insights to understand the physical properties of ultrathin Cu_(9)S_(5)crystals,and brings new blood to the 2D materials family with reversible phase transitions.展开更多
Van der Waals heterojunctions are fast-emerging quantum structures fabricated by the controlled stacking of two-dimensional(2D)materials.Owing to the atomically thin thickness,their carrier properties are not only det...Van der Waals heterojunctions are fast-emerging quantum structures fabricated by the controlled stacking of two-dimensional(2D)materials.Owing to the atomically thin thickness,their carrier properties are not only determined by the host material itself,but also defined by the interlayer interactions,including dielectric environment,charge trapping centers,and stacking angles.The abundant constituents without the limitation of lattice constant matching enable fascinating electrical,optical,and magnetic properties in van der Waals heterojunctions toward next-generation devices in photonics,optoelectronics,and information sciences.This review focuses on the charge and energy transfer processes and their dynamics in transition metal dichalcogenides(TMDCs),a family of quantum materials with strong excitonic effects and unique valley properties,and other related 2D materials such as graphene and hexagonalboron nitride.In the first part,we summarize the ultrafast charge transfer processes in van der Waals heterojunctions,including its experimental evidence and theoretical understanding,the interlayer excitons at the TMDC interfaces,and the hot carrier injection at the graphene/TMDCs interface.In the second part,the energy transfer,including both Förster and Dexter types,are reviewed from both experimental and theoretical perspectives.Finally,we highlight the typical charge and energy transfer applications in photodetectors and summarize the challenges and opportunities for future development in this field.展开更多
Two-dimensional(2D)indium arsenide(InAs)is promising for future electronic and optoelectronic applications such as highperformance nanoscale transistors,flexible and wearable devices,and high-sensitivity broadband pho...Two-dimensional(2D)indium arsenide(InAs)is promising for future electronic and optoelectronic applications such as highperformance nanoscale transistors,flexible and wearable devices,and high-sensitivity broadband photodetectors,and is advantageous for its heterogeneous integration with Si-based electronics.However,the synthesis of 2D InAs single crystals is challenging because of the nonlayered structure.Here we report the van der Waals epitaxy of 2D InAs single crystals,with their thickness down to 4.8 nm,and their lateral sizes up to~37μm.The as-grown InAs flakes have high crystalline quality and are homogenous.The thickness can be tuned by growth time and temperature.Moreover,we explore the thickness-dependent optical properties of InAs flakes.Transports measurement reveals that 2D InAs possesses high conductivity and high carrier mobility.Our work introduces InAs to 2D materials family and paves the way for applying 2D InAs in high-performance electronics and optoelectronics.展开更多
基金supported by the Natural Science Foundation of China(22203042,21873048 and 22173044)。
文摘Two-dimensional(2D) semiconductors have captured broad interest as light emitters, due to their unique excitonic effects. These layer-blocks can be integrated through van der Waals assembly, i.e., fabricating homo-or heterojunctions, which show novel emission properties caused by interface engineering. In this review, we will first give an overview of the basic strategies that have been employed in interface engineering, including changing components, adjusting interlayer gap, and tuning twist angle. By modifying the interfacial factors, novel emission properties of emerging excitons are unveiled and discussed. Generally, well-tailored interfacial energy transfer and charge transfer within a 2D heterostructure cause static modulation of the brightness of intralayer excitons. As a special case, dynamically correlated dual-color emission in weakly-coupled bilayers will be introduced, which originates from intermittent interlayer charge transfer. For homobilayers and type Ⅱ heterobilayers, interlayer excitons with electrons and holes residing in neighboring layers are another important topic in this review. Moreover, the overlap of two crystal lattices forms moiré patterns with a relatively large period, taking effect on intralayer and interlayer excitons. Particularly, theoretical and experimental progresses on spatially modulated moiré excitons with ultra-sharp linewidth and quantum emission properties will be highlighted. Moiré quantum emitter provides uniform and integratable arrays of single photon emitters that are previously inaccessible, which is essential in quantum many-body simulation and quantum information processing. Benefiting from the optically addressable spin and valley indices, 2D heterostructures have become an indispensable platform for investigating exciton physics, designing and integrating novel concept emitters.
文摘Research on two-dimensional(2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since the mechanical exfoliation of graphene in 2004. Starting from graphene, 2D materials now have become a big family with numerous members and diverse categories. The unique structural features and physicochemical properties of 2D materials make them one class of the most appealing candidates for a wide range of potential applications. In particular, we have seen some major breakthroughs made in the field of 2D materials in last five years not only in developing novel synthetic methods and exploring new structures/properties but also in identifying innovative applications and pushing forward commercialisation. In this review, we provide a critical summary on the recent progress made in the field of 2D materials with a particular focus on last five years. After a brief backgroundintroduction, we first discuss the major synthetic methods for 2D materials, including the mechanical exfoliation, liquid exfoliation, vapor phase deposition, and wet-chemical synthesis as well as phase engineering of 2D materials belonging to the field of phase engineering of nanomaterials(PEN). We then introduce the superconducting/optical/magnetic properties and chirality of 2D materials along with newly emerging magic angle 2D superlattices. Following that, the promising applications of 2D materials in electronics, optoelectronics, catalysis, energy storage, solar cells, biomedicine, sensors, environments, etc. are described sequentially. Thereafter, we present the theoretic calculations and simulations of 2D materials. Finally, after concluding the current progress, we provide some personal discussions on the existing challenges and future outlooks in this rapidly developing field.
基金financial support from National Natural Science Foundation of China(21905154)and the Taishan Scholars Program.the Fundamental Research Funds for the Central Universities in China(020514380231021014380177)+3 种基金the National Natural Science Foundation of China(2217304421873048)the National Key R&D Program of China No.2020YFA0406104“Innovation&Entrepreneurship Talents Plan”of Jiangsu Province.
文摘The low-dimensional organic-inorganic halide perovskites with self-trapped exciton emission have promising prospects for single-phase white-light emitters. However, so far, these broadband white-light-emitting(BWLE) perovskites were synthesized by trial-and-error testing spacing molecules. Here, we developed a steric hindrance regulation strategy to predictably synthesize BWLE perovskites. The molecules containing C–C(–NH_(2))–C groups were introduced into low-dimensional perovskites, which brings a large steric hindrance in-plane orientation. The bigger C–C(–NH_(2))–C bond angle would induce larger structural distortion in perovskites, which leads to the higher rate of self-trapping of excitons and the deeper self-trapping depth. The photoluminescence spectra of the synthesized perovskites can cover the cool-to-warm white light region. Overall, we fabricated a material library consisting of 40 kinds of BWLE compounds according to this strategy. Our findings develop a general strategy to synthesize BWLE perovskites and offer a material platform for optoelectronic applications.
基金J.X.W.acknowledges financial support from the National Natural Science Foundation of China(NSFC)(No.92064005)Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure(No.SKL202211SIC)+6 种基金H.T.Y.acknowledges the support from the NSFC(Nos.51861145201,52072168,and 21733001)the National Key Research and Development Program of China(No.2018YFA0306200)J.W.H.acknowledges the support from the National Key Research and Development Program of China(No.2021YFA1202901)X.W.F.acknowledges financial support from the NSFC at grant(Nos.11974191 and 2217830)the National Key Research and Development Program of China at grant(No.2020YFA0309300)the Natural Science Foundation of Tianjin at grant(Nos.20JCZDJC00560 and 20JCJQJC00210)the 111 Project(No.B23045).
文摘Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials that can be driven by facile nondestructive methods,such as temperature,are still rare.Here,we introduce ultrathin Cu_(9)S_(5)crystals grown by chemical vapor deposition(CVD)as an exemplary case.For the first time,their basic electrical properties were investigated based on Hall measurements,showing a record high hole carrier density of~1022 cm^(-3) among 2D semiconductors.Besides,an unusual and repeatable conductivity switching behavior at~250 K were readily observed in a wide thickness range of CVD-grown Cu_(9)S_(5)(down to 2 unit-cells).Confirmed by in-situ selected area electron diffraction,this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonalβphase and low-temperatureβ’phase with a superstructure.Our work provides new insights to understand the physical properties of ultrathin Cu_(9)S_(5)crystals,and brings new blood to the 2D materials family with reversible phase transitions.
基金Agency for Science,Technology and Research,Grant/Award Number:1527300025Central University Basic Research Fund of China,Grant/Award Numbers:020514380231,021014380177+5 种基金National Natural Science Foundation of China,Grant/Award Numbers:12104006,21873048,92056204National Research Foundation,Grant/Award Number:NRFNRFI2016-08Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20180319Start up fundations from Anhui UniversityTsinghua UniversityState Key Laboratory of Low-Dimensional Quantum Physics。
文摘Van der Waals heterojunctions are fast-emerging quantum structures fabricated by the controlled stacking of two-dimensional(2D)materials.Owing to the atomically thin thickness,their carrier properties are not only determined by the host material itself,but also defined by the interlayer interactions,including dielectric environment,charge trapping centers,and stacking angles.The abundant constituents without the limitation of lattice constant matching enable fascinating electrical,optical,and magnetic properties in van der Waals heterojunctions toward next-generation devices in photonics,optoelectronics,and information sciences.This review focuses on the charge and energy transfer processes and their dynamics in transition metal dichalcogenides(TMDCs),a family of quantum materials with strong excitonic effects and unique valley properties,and other related 2D materials such as graphene and hexagonalboron nitride.In the first part,we summarize the ultrafast charge transfer processes in van der Waals heterojunctions,including its experimental evidence and theoretical understanding,the interlayer excitons at the TMDC interfaces,and the hot carrier injection at the graphene/TMDCs interface.In the second part,the energy transfer,including both Förster and Dexter types,are reviewed from both experimental and theoretical perspectives.Finally,we highlight the typical charge and energy transfer applications in photodetectors and summarize the challenges and opportunities for future development in this field.
基金supported by the National Key Basic Research Program of China(No.2021YFA1401400)the start-up funds of Shanghai Jiao Tong University,the National Natural Science Foundation of China(Nos.52103344,52031014,22022507,and 51973111)+1 种基金the National Key Research and Development Program of China(No.2017YFA0206301)Beijing National Laboratory for Molecular Sciences(No.BNLMS202004).
文摘Two-dimensional(2D)indium arsenide(InAs)is promising for future electronic and optoelectronic applications such as highperformance nanoscale transistors,flexible and wearable devices,and high-sensitivity broadband photodetectors,and is advantageous for its heterogeneous integration with Si-based electronics.However,the synthesis of 2D InAs single crystals is challenging because of the nonlayered structure.Here we report the van der Waals epitaxy of 2D InAs single crystals,with their thickness down to 4.8 nm,and their lateral sizes up to~37μm.The as-grown InAs flakes have high crystalline quality and are homogenous.The thickness can be tuned by growth time and temperature.Moreover,we explore the thickness-dependent optical properties of InAs flakes.Transports measurement reveals that 2D InAs possesses high conductivity and high carrier mobility.Our work introduces InAs to 2D materials family and paves the way for applying 2D InAs in high-performance electronics and optoelectronics.