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Novel electronic structures and enhanced optical properties of boron phosphide/blue phosphorene and F4TCNQ/blue phosphorene heterostructures: a DFT + NEGF study
摘要： Blue phosphorene (Blue-p), an allotrope of black phosphorene, has attracted extensive interest due to its hexagonal crystal with a flat arranged layer of phosphorus atoms. However, the indirect band gap of Blue-p greatly hinders its applications in optoelectronics. By stacking both boron phosphide (BP) and the organic molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) with Blue-p, we construct BP/Blue-p and F4TCNQ/Blue-p heterostructures. We reveal that the BP/Blue-p heterostructure possesses a direct band gap of 0.605 eV and is tunable via in-plane strain and an external electric field. Moreover, it also has remarkable optical absorption in the UV region and enhanced transport properties. Furthermore, by doping with F4TCNQ, the F4TCNQ/Blue-p heterojunction displays type-II semiconducting properties with a flat valence band and Van Hove singularities at the Fermi level, which can be used to achieve extremely low in-band tunneling, yielding low static power dissipation and large drive currents in the ON regime of transistors. Due to the superior electronic, optical and transport properties, Blue-p-based heterostructures are promising candidates for electronic and optical device applications.
关键词： DFT,optical properties,electronic properties,transport properties,Blue phosphorene,heterostructures,boron phosphide,F4TCNQ,NEGF
更新于2025-09-23 15:19:57
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van der Waals heterostructures combining graphene and hexagonal boron nitride
摘要： As the first in a large family of 2D van der Waals (vdW) materials, graphene has attracted enormous attention owing to its remarkable properties. The recent development of simple experimental techniques for combining graphene with other atomically thin vdW crystals to form heterostructures has enabled the exploration of the properties of these so-called vdW heterostructures. Hexagonal boron nitride is the second most popular vdW material after graphene, owing to the new physics and device properties of vdW heterostructures combining the two. Hexagonal boron nitride can act as a featureless dielectric substrate for graphene, enabling devices with ultralow disorder that allow access to the intrinsic physics of graphene, such as the integer and fractional quantum Hall effects. Additionally, under certain circumstances, hexagonal boron nitride can modify the optical and electronic properties of graphene in new ways, inducing the appearance of secondary Dirac points or driving new plasmonic states. Integrating other vdW materials into these heterostructures and tuning their new degrees of freedom, such as the relative rotation between crystals and their interlayer spacing, provide a path for engineering and manipulating nearly limitless new physics and device properties.
关键词： quantum Hall effect,graphene,moiré superlattices,polaritons,hexagonal boron nitride,van der Waals heterostructures
更新于2025-09-19 17:15:36
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Interlayer interactions in 2D WS <sub/>2</sub> /MoS <sub/>2</sub> heterostructures monolithically grown by <i>in situ</i> physical vapor deposition
摘要： The understanding of the interlayer interactions in vertical heterostructures of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is essential to exploit their advanced functions for next-generation optoelectronics and electronics. Here we demonstrate a monolithic stacking of TMDC heterostructures with 2D MoS2 and WS2 layers via in situ physical vapor deposition. We find that the kinetically sputtered atoms are able to overcome the interlayer van der Waals forces between the vertical layers, leading to a substantial number of randomly oriented stacks with various twist angles. Our X-ray photoelectron spectroscopy results reveal a type II heterojunction for 2D WS2/MoS2, showing a band alignment with a conduction band offset of 0.41 eV and a valence band offset of 0.25 eV. In particular, we observed a remarkable interlayer coupling and associated exciton relaxation at the hetero-interface due to the misoriented stacks. By analyzing the band structures and charge densities of the vertical stacks using first-principles calculations, we reveal that the interlayer coupling is a function of the interlayer distance and is relatively insensitive to the angle of misorientation.
关键词： band alignment,2D materials,physical vapor deposition,interlayer coupling,heterostructures
更新于2025-09-19 17:15:36
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Light from van der Waals quantum tunneling devices
摘要： The understanding of and control over light emission from quantum tunneling has challenged researchers for more than four decades due to the intricate interplay of electrical and optical properties in atomic scale volumes. Here we introduce a device architecture that allows for the disentanglement of electronic and photonic pathways—van der Waals quantum tunneling devices. The electronic properties are defined by a stack of two-dimensional atomic crystals whereas the optical properties are controlled via an external photonic architecture. In van der Waals heterostructures made of gold, hexagonal boron nitride and graphene we find that inelastic tunneling results in the emission of photons and surface plasmon polaritons. By coupling these heterostructures to optical nanocube antennas we achieve resonant enhancement of the photon emission rate in narrow frequency bands by four orders of magnitude. Our results lead the way towards a new generation of nanophotonic devices that are driven by quantum tunneling.
关键词： van der Waals heterostructures,inelastic electron tunneling,nanophotonics,light emission,quantum tunneling,optical antennas
更新于2025-09-19 17:15:36
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Symmetric Ultrafast Writing and Erasing Speeds in Quasi-Nonvolatile Memory via van der Waals Heterostructures
摘要： Due to the large gap in timescale between volatile memory and nonvolatile memory technologies, quasi-nonvolatile memory based on 2D materials has become a viable technology for filling the gap. By exploiting the elaborate energy band structure of 2D materials, a quasi-nonvolatile memory with symmetric ultrafast write-1 and erase-0 speeds and long refresh time is reported. Featuring the 2D semifloating gate architecture, an extrinsic p–n junction is used to charge or discharge the floating gate. Owing to the direct injection or recombination of charges from the floating gate electrode, the erasing speed is greatly enhanced to nanosecond timescale. Combined with the ultrafast write-1 speed, symmetric ultrafast operations on the nanosecond timescale are achieved, which are ≈106 times faster than other memories based on 2D materials. In addition, the refresh time after a write-1 operation is 219 times longer than that of dynamic random access memory. This performance suggests that quasi-nonvolatile memory has great potential to decrease power consumption originating from frequent refresh operations, and usher in the next generation of high-speed and low-power memory technology.
关键词： symmetric ultrafast operations,van der Waals heterostructures,quasi-nonvolatile memory
更新于2025-09-19 17:15:36
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Ag-Functionalized CuWO <sub/>4</sub> /WO <sub/>3</sub> nanocomposites for solar water splitting
摘要： Ag-Functionalized CuWO4/WO3 heterostructures were successfully prepared via a polyvinyl pyrrolidone (PVP)-assisted sol–gel (PSG) route. Thin films prepared via electrophoretic deposition were used as photoanodes for photoelectrochemical (PEC) water splitting. Compared to pristine CuWO4 and WO3 films, a significant enhancement of the photocurrent (3–4 times) at the thermodynamic potential for oxygen evolution (0.62 V vs. Ag/AgCl, pH 7) was obtained for the Ag-functionalized CuWO4/WO3 photoanodes. The obtained enhancement is shown to be derived from a synergic contribution of heterostructure formation (CuWO4/WO3) and improvements of light utilization by Ag-induced surface plasmon resonance (SPR) effects. Accordingly, a photocurrent of 0.205 mA cm?2 at 0.62 V vs. Ag/AgCl under neutral conditions (without hole scavengers) under front-side simulated AM1.5G illumination was achieved. A detailed analysis of the obtained PEC data alongside performed impedance measurements suggests that charge separation is significantly improved for the prepared Ag-functionalized CuWO4/WO3 photoanodes. Our work offers beneficial insights to design new plasmonic metal/heterostructured nanocomposites for energy conversion applications.
关键词： nanocomposites,surface plasmon resonance,photoelectrochemical,CuWO4/WO3,solar water splitting,Ag-functionalized,heterostructures
更新于2025-09-19 17:15:36
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Hierarchical WO3/ZnWO4 1D fibrous heterostructures with tunable in-situ growth of WO3 nanoparticles on surface for efficient low concentration HCHO detection
摘要： Hierarchical WO3/ZnWO4 1D fibrous heterostructures with tunable in-situ growth of WO3 nanoparticles on surface have been fabricated by the original one-step electrospinning technology combined with subsequent calcination process. Phase composition and morphology can be transformed from bead-like WO3 fibers to hierarchical WO3/ZnWO4 1D composites with the introduction of ZIF-8 into the precursor solution, which was mainly attributed to the combination of nucleation competition and crystal planes matching mechanisms during heat treatment. Compared with pure WO3 and WO3/ZnWO4-10%, WO3/ZnWO4-5% displayed the highest specific surface area value evaluated to be 268.57, indicating the prominent enhanced absorption behavior for targeted organic species. It is found that WO3/ZnWO4-5% composites have a response about 44.5 for 5 ppm HCHO, which was almost 8 times higher than that of sensor based on pure WO3 nanofibers at the optimal operating temperature. Meanwhile, the fast response/recovery time (12/14 s) and excellent stability characteristics (recycling, long-term, and humidity stability) towards HCHO can be also observed for WO3/ZnWO4-5% samples. The enhanced gas-sensing mechanism based on WO3/ZnWO4 composites can be ascribed to the synergistic effect of effective heterojunctions, large specific surface area, multiple reaction sites, and unique surface/interface electron transmission. The design and construction of hierarchical WO3/ZnWO4 1D materials attest to the significant potential of their use as novel gas sensors for detecting low concentration HCHO.
关键词： electrospinning,gas sensors,in-situ growth,HCHO,WO3/ZnWO4 heterostructures
更新于2025-09-19 17:15:36
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Waveguide-integrated van der Waals heterostructure photodetector at telecom wavelengths with high speed and high responsivity
摘要： Intensive efforts have been devoted to the exploration of new optoelectronic devices based on two-dimensional transition-metal dichalcogenides (TMDCs) owing to their strong light–matter interaction and distinctive material properties. In particular, photodetectors featuring both high-speed and high-responsivity performance are of great interest for a vast number of applications such as high-data-rate interconnects operated at standardized telecom wavelengths. Yet, the intrinsically small carrier mobilities of TMDCs become a bottleneck for high-speed application use. Here, we present high-performance vertical van der Waals heterostructure-based photodetectors integrated on a silicon photonics platform. Our vertical MoTe2–graphene heterostructure design minimizes the carrier transit path length in TMDCs and enables a record-high measured bandwidth of at least 24 GHz under a moderate bias voltage of –3 V. Applying a higher bias or employing thinner MoTe2 flakes boosts the bandwidth even to 50 GHz. Simultaneously, our device reaches a high external responsivity of 0.2 A W–1 for incident light at 1,300 nm, benefiting from the integrated waveguide design. Our studies shed light on performance trade-offs and present design guidelines for fast and efficient devices. The combination of two-dimensional heterostructures and integrated guided-wave nano photonics defines an attractive platform to realize high-performance optoelectronic devices, such as photodetectors, light-emitting devices and electro-optic modulators.
关键词： transition-metal dichalcogenides,photodetectors,silicon photonics,van der Waals heterostructures,two-dimensional materials
更新于2025-09-19 17:13:59
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Fabrication of ZnSe/InP Heterojunctions on Flat and Shaped Surfaces of InP Laser Crystals
摘要： We have studied the growth of zinc selenide layers on flat and shaped indium phosphide surfaces. The growth rate of zinc selenide has been shown to depend on substrate orientation. It has been shown that the present results can be useful in designing mesa stripe structures for quantum electronic instruments. We have fabricated mesa stripe laser diodes operating on the absorption band of methane and suitable for producing fiber-optic signal transmission systems.
关键词： methane,semiconductor heterostructures,zinc selenide,laser diodes
更新于2025-09-19 17:13:59
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Graphene-TMD Van der Waals Heterostucture Plasmonics
摘要： The collective excitations of electrons in the bulk or at the surface, viz. plasmons, play an important role in the properties of materials, and have generated the field of “plasmonics”. We report the observation of a highly unusual plasmon mode on the surface of Van der Waals heterostructures (vdWHs) of graphene monolayer on 2D transition metal dichalcogenide (Gr-TMD) substrate. Since the exponentially decaying fields of surface plasmon wave propagating along interface is highly sensitive to the ambient refractive index variations, such heterostructures are useful for ultra-sensitive bio-sensing.
关键词： Van der Waals heterostructures,Bio-sensing,Surface plasmon
更新于2025-09-19 17:13:59