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Split-off states in tunnel-coupled semiconductor heterostructures for ultrafast modulation of spin and optical polarization
摘要： We present a theoretical analysis of the split-off states emerging due to a tunnel coupling between a remote bound state and a semiconductor quantum well (QW). The on-site Coulomb repulsion and the spin splitting of the bound state have been considered. The split-off states emerge in the band gap of the QW and reveal themselves as two solitary peaks in the photoluminescence (PL) from the QW. The peaks have opposite circular polarization and their spectral position strongly depends on the tunnel coupling strength. We suggest a mechanism of ultrafast PL polarization switching by means of electrical modulation of the tunnel coupling by an external gate. The obtained results open a new possibility for the spin and optical polarization control in nanoscale systems.
关键词： split-off states,photoluminescence,optical polarization,semiconductor heterostructures,tunnel coupling,spin polarization
更新于2025-09-23 15:21:01
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Wafer-Scale Fabrication of 2D PtS <sub/>2</sub> /PtSe <sub/>2</sub> Heterojunctions for Efficient and Broadband Photodetection
摘要： The fabrication of van der Waals heterostructures have mainly extends to two-dimensional materials that are exfoliated from their bulk counterparts, which is greatly limited by high-volume manufacturing. Here, we demonstrate multilayered PtS2/PtSe2 heterojunctions covering a large area on SiO2/Si substrate with a maximum size of 2" in diameter, offering throughputs that can meet the practical application demand. Theoretical simulation was carried out to understand the electronic properties of the PtS2/PtSe2 heterojunctions. Zero-bias photoresponse in the heterojunctions is observed under laser illumination of different wavelengths (405 to 2200 nm). The PtS2/PtSe2 heterojunctions exhibit broadband photoresponse, high quantum efficiency at infrared wavelengths with lower bounds for the external quantum efficiencies (EQE) being 1.2% at 1064 nm, 0.2% at 1550 nm and 0.05% at 2200 nm, and also relatively fast response time at the dozens of millisecond level. The large area, broadband 2D heterojunction photodetector demonstrated in this work further corroborating the great potential of 2D materials in the future low-energy optoelectronics.
关键词： van der Waals heterostructures,self-driving operation,quantum efficiency,broadband photodetection,photoresponsivity,wafer-scale fabrication
更新于2025-09-23 15:21:01
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Electron quantum metamaterials in van der Waals heterostructures
摘要： In recent decades, scientists have developed the means to engineer synthetic periodic arrays with feature sizes below the wavelength of light. When such features are appropriately structured, electromagnetic radiation can be manipulated in unusual ways, resulting in optical metamaterials whose function is directly controlled through nanoscale structure. Nature, too, has adopted such techniques—for example in the unique colouring of butterfly wings—to manipulate photons as they propagate through nanoscale periodic assemblies. In this Perspective, we highlight the intriguing potential of designer structuring of electronic matter at scales at and below the electron wavelength, which affords a new range of synthetic quantum metamaterials with unconventional responses. Driven by experimental developments in stacking atomically layered heterostructures—such as mechanical pick-up/transfer assembly—atomic-scale registrations and structures can be readily tuned over distances smaller than characteristic electronic length scales (such as the electron wavelength, screening length and electron mean free path). Yet electronic metamaterials promise far richer categories of behaviour than those found in conventional optical metamaterial technologies. This is because, unlike photons, which scarcely interact with each other, electrons in subwavelength-structured metamaterials are charged and strongly interact. As a result, an enormous variety of emergent phenomena can be expected and radically new classes of interacting quantum metamaterials designed.
关键词： van der Waals heterostructures,nanoscale structure,electronic matter,electron quantum metamaterials,optical metamaterials
更新于2025-09-23 15:21:01
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Ultrafast dynamics in van der Waals heterostructures
摘要： Van der Waals heterostructures are synthetic quantum materials composed of stacks of atomically thin two-dimensional (2D) layers. Because the electrons in the atomically thin 2D layers are exposed to layer-to-layer coupling, the properties of van der Waals heterostructures are defined not only by the constituent monolayers, but also by the interactions between the layers. Many fascinating electrical, optical and magnetic properties have recently been reported in different types of van der Waals heterostructures. In this Review, we focus on unique excited-state dynamics in transition metal dichalcogenide (TMDC) heterostructures. TMDC monolayers are the most widely studied 2D semiconductors, featuring prominent exciton states and accessibility to the valley degree of freedom. Many TMDC heterostructures are characterized by a staggered band alignment. This band alignment has profound effects on the evolution of the excited states in heterostructures, including ultrafast charge transfer between the layers, the formation of interlayer excitons, and the existence of long-lived spin and valley polarization in resident carriers. Here we review recent experimental and theoretical efforts to elucidate electron dynamics in TMDC heterostructures, extending from timescales of femtoseconds to microseconds, and comment on the relevance of these effects for potential applications in optoelectronic, valleytronic and spintronic devices.
关键词： spin and valley polarization,charge transfer,valleytronic,transition metal dichalcogenide,Van der Waals heterostructures,excited-state dynamics,spintronic devices,interlayer excitons,optoelectronic
更新于2025-09-23 15:21:01
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Opportunities and challenges of interlayer exciton control and manipulation
摘要： Advances in van der Waals heterostructures allow the control of interlayer excitons by electrical and other means, promising exciting opportunities for high-temperature exciton condensation and valley–spin optoelectronics.
关键词： TMD bilayers,exciton condensation,van der Waals heterostructures,valley–spin optoelectronics,interlayer excitons
更新于2025-09-23 15:21:01
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Layered MoS2 defect-driven in-situ synthesis of plasmonic gold nanocrystals visualizes the planar size and interfacial diversity
摘要： Current defect theories significantly guide broadband research progresses, whereas the recognition of defect status remains challenging. Herein, MoS2 defect type, density and exposed state are visually identified with a reagent indicator of HAuCl4. Mo-terminated defects spontaneously reduce [AuCl4]- anions, and oxidized Mo species are dissociated. Consequently, MoS2 edges guide the epitaxial branch of Au nanocrystals (NCs), followed with sequential growths at their planar defects. The size-evolution processes of LaMer growth and planar packages of aggregative growth of Au/MoS2 nanoseeds result in the occupation of Au atomic layers on heterostructures. Consequently, shell-core hybrids are presented with localized surface plasmon resonance characteristics. The mechanism is systematically explored via the discriminated performance of plasmonic characteristics of Au nanostructures on semiconducting MoS2 substrates. With plasmonic identification, defect-associated size and interfacial diversities of MoS2 are visually information-rich. Tunable morphologies and synergistic optical characteristics of plasmonic semiconductor heterostructures inspire many more applications through the edge and planar defects intrinsic in layered MoS2.
关键词： heterostructures,gold nanocrystals,defect,MoS2,plasmonic
更新于2025-09-23 15:21:01
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Polarization and charge carrier density coupling in epitaxial PbZr <sub/>0.2</sub> Ti <sub/>0.8</sub> O <sub/>3</sub> /ZnO heterostructures
摘要： The integration of ferroelectric materials with semiconductor heterostructures can greatly enhance the functionality of electronic devices, provided the ferroelectric material retains a significant part of its switchable polarization. This work reports polarization switching in epitaxial PbZr0.2Ti0.8O3/ZnO/GaN heterostructures grown on c-cut sapphire single-crystal substrates. The electrical measurements of PbZr0.2Ti0.8O3/ZnO ferroelectric/semiconductor capacitors reveal an unexpected difference between a counterclockwise ferroelectric hysteresis loop and a clockwise C-V loop. A non-linear hysteretic behavior of the capacitance is observed in the voltage range that is at least 3 times narrower than the range of ferroelectric polarization switching voltages. This difference can be explained by charge injection effects at the interface between ferroelectrics and semiconductors. The interaction between electric polarization and the electronic structure of the heterojunction leads to capacitance and charge carrier concentrations that are switchable by polarization of the ferroelectric layer. These findings are important for both fundamental and applied research of switchable and highly tunable ferroelectric/semiconductor heterostructures.
关键词： ferroelectric materials,polarization switching,charge injection effects,capacitance,semiconductor heterostructures
更新于2025-09-23 15:21:01
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2D Material Optoelectronics for Information Functional Device Applications: Status and Challenges
摘要： Graphene and the following derivative 2D materials have been demonstrated to exhibit rich distinct optoelectronic properties, such as broadband optical response, strong and tunable light–mater interactions, and fast relaxations in the flexible nanoscale. Combining with optical platforms like fibers, waveguides, grating, and resonators, these materials has spurred a variety of active and passive applications recently. Herein, the optical and electrical properties of graphene, transition metal dichalcogenides, black phosphorus, MXene, and their derivative van der Waals heterostructures are comprehensively reviewed, followed by the design and fabrication of these 2D material-based optical structures in implementation. Next, distinct devices, ranging from lasers to light emitters, frequency convertors, modulators, detectors, plasmonic generators, and sensors, are introduced. Finally, the state-of-art investigation progress of 2D material-based optoelectronics offers a promising way to realize new conceptual and high-performance applications for information science and nanotechnology. The outlook on the development trends and important research directions are also put forward.
关键词： transition metal dichalcogenides,optoelectronics,MXene,van der Waals heterostructures,information devices,graphene,black phosphorus,2D materials
更新于2025-09-23 15:21:01
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Printed Higha??Density and Flexible Photodetector Arrays via Sizea??matched Heterogeneous Microa??/Nanostructure
摘要： Semiconductor/metal binary systems constitute the core components in electronic/photonic devices. The domain size of the heterostructure should be comparable to the charge diffusion length for superior photoelectric response. However, the fabrication of size-matched heterostructures is still a challenge, especially for printed devices. Here, a high-density photodetector array with lateral semiconductor/metal heterostructure is achieved via the template-assisted sequentially printing strategy. The Ag/PBDB-T:ITIC/Ag based lateral heterojunction that matches the charge diffusion length in the charge transfer process provides high light response sensitivity (D* = 3.41 × 1012 Jones, R = 12.9 A W?1). Moreover, the printed pixel interval can be decreased to 10 μm (106 pixels cm?2; resolution: 2.5 × 103 dpi). As the printing strategy can be implemented on soft substrates, the photodetector arrays are endowed with the flexibility. This work demonstrates a simple and effective strategy for chip-scale fabrication of flexible high-performance photodetectors, which validates the potential of printed heterogeneous micro-/nanostructures for integrated active electronics and optics.
关键词： flexible photodetector arrays,light imaging,sequential printing,heterostructures
更新于2025-09-23 15:21:01
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Highly Selective Photoreduction of CO <sub/>2</sub> with Suppressing H <sub/>2</sub> Evolution by Plasmonic Au/CdSea??Cu <sub/>2</sub> O Hierarchical Nanostructures under Visible Light
摘要： Here, the photocatalytic CO2 reduction reaction (CO2RR) with the selectivity of carbon products up to 100% is realized by completely suppressing the H2 evolution reaction under visible light (λ > 420 nm) irradiation. To target this, plasmonic Au/CdSe dumbbell nanorods enhance light harvesting and produce a plasmon-enhanced charge-rich environment; peripheral Cu2O provides rich active sites for CO2 reduction and suppresses the hydrogen generation to improve the selectivity of carbon products. The middle CdSe serves as a bridge to transfer the photocharges. Based on synthesizing these Au/CdSe–Cu2O hierarchical nanostructures (HNSs), efficient photoinduced electron/hole (e?/h+) separation and 100% of CO selectivity can be realized. Also, the 2e?/2H+ products of CO can be further enhanced and hydrogenated to effectively complete 8e?/8H+ reduction of CO2 to methane (CH4), where a sufficient CO concentration and the proton provided by H2O reduction are indispensable. Under the optimum condition, the Au/CdSe–Cu2O HNSs display high photocatalytic activity and stability, where the stable gas generation rates are 254 and 123 μmol g?1 h?1 for CO and CH4 over a 60 h period.
关键词： photocatalytic CO2 reduction,plasmonic heterostructures,visible light,H2 evolution
更新于2025-09-23 15:21:01