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2D Crystals in Three Dimensions: Electronic Decoupling of Single-Layered Platelets in Colloidal Nanoparticles
摘要： 2D crystals, single sheets of layered materials, often show distinct properties desired for optoelectronic applications, such as larger and direct band gaps, valley- and spin-orbit effects. Being atomically thin, the low amount of material is a bottleneck in photophysical and photochemical applications. Here, the formation of stacks of 2D crystals intercalated with small surfactant molecules is proposed. It is shown, using first principles calculations, that the very short surfactant methyl amine electronically decouples the layers. The indirect–direct band gap transition characteristic for Group 6 transition metal dichalcogenides is demonstrated experimentally by observing the emergence of a strong photoluminescence signal for ethoxide-intercalated WSe2 and MoSe2 multilayered nanoparticles with lateral size of about 10 nm and beyond. The proposed hybrid materials offer the highest possible density of the 2D crystals with electronic properties typical of monolayers. Variation of the surfactant’s chemical potential allows fine-tuning of electronic properties and potentially elimination of trap states caused by defects.
关键词： intercalates,photoluminescence,optoelectronics,2D materials,heterostructures
更新于2025-09-23 15:21:01
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Dependence of the photocatalytic reduction of bicarbonate to formic acid by Aua??TiO2 on Au morphology and its plasmonic vibrational mode
摘要： The effect of Au morphology and its plasmonic vibration mode on the photoactivity of Au-TiO2 nanostructures was evaluated. Here, Au nanoparticles with three distinct morphologies, i.e., nanooctahedra, nanocube, and nanorod, were successfully prepared and integrated into TiO2 nanoparticles. The nanocatalysts were used for photocatalytic conversion of bicarbonate to formic acid for solar fuel generation. Based on the result, it is found that the integration of Au and TiO2 resulted in a synergistic effect on the production of formic acid due to the presence of Au’s SPR phenomenon. Results also demonstrated that the shape of Au nanoparticles plays a pivotal role in the improvement of Au-TiO2 activity. From the photocatalytic experiment, Au NR-TiO2 was found to be the most active nanocatalyst with a formic acid yield of 5.14 mmol/g cat. By using spectroscopy techniques and near-field enhancement simulation, it is believed that the photocatalytic enhancement was due to non-radiative (hot electron transfer and storage) and radiative (near-field enhancement and far-field scattering) effects. However, the additional shape-dependent variation on activity was most likely due to the radiative effects instead of non-radiative ones.
关键词： heterostructures,bicarbonate,Plasmonic,TiO2,photoreduction,Au nanoparticles
更新于2025-09-23 15:21:01
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Theoretical characterization of strain and interfacial electronic effects in donor-acceptor bilayers of 2D transition metal dichalcogenides
摘要： Amine Slassi1, Jér?me Cornil1,* E-mail : jerome.cornil@umons.ac.be Bilayers of 2D Transition Metal Dichalcogenides 1Laboratory for Chemistry of Novel Materials, University of Mons, BE-7000 Mons, Belgium Theoretical Characterization of Strain and Interfacial Electronic Effects in Donor-Acceptor Two-dimensional (2D) materials and their van der Waals (vdW) stacked hetero-structures are promising candidates for highly efficient (opto)-electronic applications. The performance of vdW these properties are affected when building a bilayer. We focus on MoS2-based bilayers, including MoS2/MoS2, WS2/MoS2, MoSe2/MoS2 and WSe2/MoS2 structures. The impact of properties of two-dimensional transition metal dichalcogenide (TMDs) monolayers and the way vacancies on the interlayer interactions is also investigated. The main finding of our calculations first?principle calculations, we have explored systematically the structural and electronic is that changes in the properties of 2D monolayers upon building stack do occur and are driven by heterostructures in devices strongly depend on electronic processes at their interfaces. Here, using both strain effects and interfacial electronic processes.
关键词： defect vacancy,first-principles calculations,vdW heterostructures,electronic processes,strain effects
更新于2025-09-23 15:21:01
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Isostructural metal-insulator transition in VO <sub/>2</sub>
摘要： The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.
关键词： electronic phase transition,vanadium dioxide,metal-insulator transition,correlated materials,heterostructures
更新于2025-09-23 15:21:01
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Disassembly of 2D Vertical Heterostructures
摘要： As one of the most widely discussed fields, the assembly of nanomaterials has always been extensively studied. However, its inverse process, namely disassembly, is still limited in the ambit of biomolecules. Specifically, in the emerging 2D research field, disassembly still remains unexplored. Inspired by the disassembly of DNA molecules via breaking intermolecular hydrogen bonds, the disassembly of 2D vertical heterostructures (2DVHs) is first achieved through the weakening of the interlayer van der Waals interactions. As a demonstration, ReS2/WS2 VHs is successfully disassembled into individual building blocks. Density functional theory calculations are performed to study the disassembly of the 2DVHs, which simulate that 2DVHs are first activated by the disassembly promoters and then disassembled with weakened interlayer van der Waals interactions. Such a disassembly process demonstrates that it has great potential to be expanded as a general strategy to achieve the disassembly of other 2D superstructures.
关键词： heterostructures,disassembly,2D materials,van der Waals interaction,disassembly promoters
更新于2025-09-23 15:21:01
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Direct Silicon Heterostructures With Methylammonium Lead Iodide Perovskite for Photovoltaic Applications
摘要： We investigated the formation of photovoltaic (PV) devices using direct n-Si/MAPI (methylammonium lead tri-iodide) two-sided heterojunctions for the first time (as a possible alternative to two-terminal tandem devices) in which charge might be generated and collected from both the Si and MAPI. Test structures were used to establish that the n-Si/MAPI junction was photoactive and that spiro-OMeTAD acted as a “pinhole blocking” layer in n-Si/MAPI devices. Two-terminal “substrate” geometry devices comprising Al/n-Si/MAPI/spiro-OMeTAD/Au were fabricated and the effects of changing the thickness of the semitransparent gold electrode and the silicon resistivity were investigated. External quantum efficiency and capacitance–voltage measurements determined that the junction was one-sided in the silicon—and that the majority of the photocurrent was generated in the silicon, with there being a sharp cutoff in photoresponse above the MAPI bandgap. Construction of band diagrams indicated the presence of an upward valence band spike of up to 0.5 eV at the n-Si/MAPI interface that could impede carrier flow. Evidence for hole accumulation at this feature was seen in both Kelvin-probe transients and from unusual features in both current–voltage and capacitance–voltage measurements. The devices achieved a hysteresis-free best power conversion efficiency of 2.08%, VOC 0.46 V, JSC 11.77 mA/cm2, and FF 38.4%, demonstrating for the first time that it is possible to create a heterojunction PV device directly between the MAPI and n-Si. Further prospects for two-sided n-Si/MAPI heterojunctions are also discussed.
关键词： heterostructures,MAPI/silicon methylammonium lead iodide,methylammonium lead tri-iodide (MAPI),Heterojunctions,silicon
更新于2025-09-23 15:19:57
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Memristive Behavior Enabled by Amorphousa??Crystalline 2D Oxide Heterostructure
摘要： The emergence of memristive behavior in amorphous–crystalline 2D oxide heterostructures, which are synthesized by atomic layer deposition (ALD) of a few-nanometer amorphous Al2O3 layers onto atomically thin single-crystalline ZnO nanosheets, is demonstrated. The conduction mechanism is identified based on classic oxygen vacancy conductive channels. ZnO nanosheets provide a 2D host for oxygen vacancies, while the amorphous Al2O3 facilitates the generation and stabilization of the oxygen vacancies. The conduction mechanism in the high-resistance state follows Poole–Frenkel emission, and in the low-resistance state is fitted by the Mott–Gurney law. From the slope of the fitting curve, the mobility in the low-resistance state is estimated to be ≈2400 cm2 V?1 s?1, which is the highest value reported in semiconductor oxides. When annealed at high temperature to eliminate oxygen vacancies, Al is doped into the ZnO nanosheet, and the memristive behavior disappears, further confirming the oxygen vacancies as being responsible for the memristive behavior. The 2D heterointerface offers opportunities for new design of high-performance memristor devices.
关键词： zinc oxide,2D heterostructures,memristors,atomic layer deposition,oxygen vacancies
更新于2025-09-23 15:19:57
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Complementary doping of van der Waals materials through controlled intercalation for monolithically integrated electronics
摘要： Doping control has been a key challenge for electronic applications of van der Waals materials. Here, we demonstrate complementary doping of black phosphorus using controlled ionic intercalation to achieve monolithic building elements. We characterize the anisotropic electrical transport as a function of ion concentrations and report a widely tunable resistivity up to three orders of magnitude with characteristic concentration dependence corresponding to phase transitions during intercalation. As a further step, we develop both p-type and n-type field effect transistors as well as electrical diodes with high device stability and performance. In addition, enhanced charge mobility from 380 to 820 cm2/(V·s) with the intercalation process is observed and explained as the suppressed neutral impurity scattering based on our ab initio calculations. Our study provides a unique approach to atomically control the electrical properties of van der Waals materials, and may open up new opportunities in developing advanced electronics and physics platforms.
关键词： nanoelectronics,two-dimensional (2D) materials and heterostructures,tunable properties,diode,black phosphorus,FET
更新于2025-09-23 15:19:57
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Ultra-long carrier lifetime in neutral graphene-hBN van der Waals heterostructures under mid-infrared illumination
摘要： Graphene/hBN heterostructures are promising active materials for devices in the THz domain, such as emitters and photodetectors based on interband transitions. Their performance requires long carrier lifetimes. However, carrier recombination processes in graphene possess sub-picosecond characteristic times for large non-equilibrium carrier densities at high energy. An additional channel has been recently demonstrated in graphene/hBN heterostructures by emission of hBN hyperbolic phonon polaritons (HPhP) with picosecond decay time. Here, we report on carrier lifetimes in graphene/hBN Zener-Klein transistors of ~30 ps for photoexcited carriers at low density and energy, using mid-infrared photoconductivity measurements. We further demonstrate the switching of carrier lifetime from ~30 ps (attributed to interband Auger) down to a few picoseconds upon ignition of HPhP relaxation at finite bias and/or with infrared excitation power. Our study opens interesting perspectives to exploit graphene/hBN heterostructures for THz lasing and highly sensitive THz photodetection as well as for phonon polariton optics.
关键词： photodetectors,mid-infrared,phonon polaritons,van der Waals heterostructures,THz,Graphene,carrier lifetime,hBN
更新于2025-09-23 15:19:57
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MOVPE of Large-Scale MoS <sub/>2</sub> /WS <sub/>2</sub> , WS <sub/>2</sub> /MoS <sub/>2</sub> , WS <sub/>2</sub> /Graphene and MoS <sub/>2</sub> /Graphene 2D-2D Heterostructures for Optoelectronic Applications
摘要： Most publications on (opto)electronic devices based on 2D materials rely on single monolayers embedded in classical 3D semiconductors, dielectrics and metals. However, heterostructures of different 2D materials can be employed to tailor the performance of the 2D components by reduced defect densities, carrier or exciton transfer processes and improved stability. This translates to additional and unique degrees of freedom for novel device design. The nearly infinite number of potential combinations of 2D layers allows for many fascinating applications. Unlike mechanical stacking, metal-organic vapour phase epitaxy (MOVPE) can potentially provide large-scale highly homogeneous 2D layer stacks with clean and sharp interfaces. Here, we demonstrate the direct successive MOVPE of MoS2/WS2 and WS2/MoS2 heterostructures on 2” sapphire (0001) substrates. Furthermore, the first deposition of large-scale MoS2/graphene and WS2/graphene heterostructures using only MOVPE is presented and the influence of growth time on nucleation of WS2 on graphene is analysed.
关键词： MOVPE,WS2,MoS2,heterostructures,2D materials,graphene,optoelectronic applications
更新于2025-09-23 15:19:57