- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
2D Material-Based Vertical Double Heterojunction Bipolar Transistors with High Current Amplification
摘要： The heterojunction bipolar transistor (HBT) differs from the classical homojunction bipolar junction transistor in that each emitter-base-collector layer is composed of a different semiconductor material. 2D material (2DM)-based heterojunctions have attracted attention because of their wide range of fundamental physical and electrical properties. Moreover, strain-free heterostructures formed by van der Waals interaction allows true bandgap engineering regardless of the lattice constant mismatch. These characteristics make it possible to fabricate high-performance heterojunction devices such as HBTs, which have been difficult to implement in conventional epitaxy. Herein, NPN double HBTs (DHBTs) are constructed from vertically stacked 2DMs (n-MoS2/p-WSe2/n-MoS2) using dry transfer technique. The formation of the two P–N junctions, base-emitter, and base-collector junctions, in DHBTs, was experimentally observed. These NPN DHBTs composed of 2DMs showed excellent electrical characteristics with highly amplified current modulation. These results are expected to extend the application field of heterojunction electronic devices based on various 2DMs.
关键词： 2D materials,tungsten diselenide,P–N junction,heterojunction bipolar transistor,molybdenum disulfide
更新于2025-09-23 15:23:52
-
Spatial Separation of Carrier Spin by the Valley Hall Effect in Monolayer WSe <sub/>2</sub> Transistors
摘要： We investigate the valley Hall effect (VHE) in monolayer WSe2 field-effect transistors using optical Kerr rotation measurements at 20 K. While studies of the VHE have so far focused on n-doped MoS2, we observe the VHE in WSe2 in both the n- and p-doping regimes. Hole doping enables access to the large spin-splitting of the valence band of this material. The Kerr rotation measurements probe the spatial distribution of the valley carrier imbalance induced by the VHE. Under current flow, we observe distinct spin-valley polarization along the edges of the transistor channel. From analysis of the magnitude of the Kerr rotation, we infer a spin-valley density of 44 spins/μm, integrated over the edge region in the p-doped regime. Assuming a spin diffusion length less than 0.1 μm, this corresponds to a spin-valley polarization of the holes exceeding 1%.
关键词： magneto-optical Kerr effect,Tungsten diselenide,valleytronics,spintronics
更新于2025-09-23 15:23:52
-
Gate-Tunable Thermal Metal–Insulator Transition in VO <sub/>2</sub> Monolithically Integrated into a WSe <sub/>2</sub> Field-Effect Transistor
摘要： Vanadium dioxide (VO2) shows promise as a building block of switching and sensing devices because it undergoes an abrupt metal-insulator transition (MIT) near room temperature, where the electrical resistivity changes by orders of magnitude. A challenge for versatile applications of VO2 is to control the MIT by gating in the field-effect device geometry. Here, we demonstrate a gate-tunable abrupt switching device based on a VO2 microwire that is monolithically integrated with a two-dimensional (2D) tungsten diselenide (WSe2) semiconductor by van der Waals stacking. We fabricated the WSe2 transistor using the VO2 wire as the drain contact, titanium as the source contact, and hexagonal boron nitride as the gate dielectric. The WSe2 transistor was observed to show ambipolar transport, with higher conductivity in the electron branch. The electron current increases continuously with gate voltage below the critical temperature of the MIT of VO2. Near the critical temperature, the current shows an abrupt and discontinuous jump at a given gate voltage, indicating that the MIT in the contacting VO2 is thermally induced by gate-mediated self-heating. Our results have paved the way for the development of VO2-based gate-tunable devices by the van der Waals stacking of 2D semiconductors, with great potential for electronic and photonic applications.
关键词： 2D materials,field-effect transistor,tungsten diselenide,phase-change materials,vanadium dioxide,metal-insulator transition,van der Waals heterostructures
更新于2025-09-23 15:22:29
-
Hybrid Single-Layer/Bulk Tungsten Diselenide Transistors by Lithographic Encoding of Material Thickness in Chemical Vapor Deposition
摘要： whose bulk-like (3D) portion can be used for metal contacts and efficient charge injection into the metal dichalcogenide (TMD) transistors; because of the small number of charge carriers in a 2D demonstrate that lithographic pre-patterning of a growth substrate prior to chemical vapor deposition of a TMD film can shape the TMD material into nanoscale hybrid 2D/3D structures enhanced reduction of performance compared to conventional bulk Schottky Barriers. Here we single-layer (2D) areas which serve as transistor channels with excellent mobilities and on-off Schottky-like barriers are an important limitation of the performance of single-layer transition semiconductor, the screening of metal contacts is inefficient leading to large depletion zones and devices (through 300nm of oxide) at realistic operation temperatures near 100°C using ratios. We observe mobilities of nearly 100 cm2V-1s-1 with an on/off ratio >105 for bottom-gated TMD growth. Bulk-like 3D WSe2 is observed to grow at the location of the hafnia, while 2D comparatively long channels (>5 microns) and absent other contact optimization. Our process involves lithographic patterning of a hafnium (IV) dioxide film onto the SiO2/Si substrate prior to allows us to extract Schottky barrier heights and other fundamental properties of our hybrid single-layer material is grown in regions of bare SiO2. Systematic evaluation of transport data devices.
关键词： Tungsten Diselenide,Schottky-Barrier,Transition Metal Dichalcogenides,2D Materials
更新于2025-09-23 15:21:01
-
Nonvolatile Programmable WSe <sub/>2</sub> Photodetector
摘要： Optoelectronic devices with nonvolatile memory are an important component in a wide variety of applications ranging from optoelectronic random-access-memories, with the advantage of using optical stimuli as an added parameter, to complex artificial neuromorphic networks that pretend to mimic the working schemes of the human brain. In the past few years, 2D materials have been proposed as attractive candidates to build such optoelectronic devices with memory due to their excellent optoelectronic properties and high sensitivity to external electric fields. Here, a WSe2 monolayer p–n junction working as a nonvolatile programmable photodetector is reported, that, enabled by a split-gate configuration with embedded charge-trapping layers, is capable of retaining custom responsivity values over time, prior configuration by the user. Once configured, this photodetector can operate without external applied bias voltage as a self-driven photodetector, as well as without external back-gate voltage thanks to the charge stored in the floating gates. Furthermore, the device shows a remarkable performance, with open-circuit voltage around 1 V at approximately 270 W m?2 white light, fill factor higher than 30%, and fast response times. This programmable photodetector sets a new concept as a building block in more complex image-sensing systems.
关键词： programmable photodetector,tungsten-diselenide,2D materials,photodetectors,floating gates,nonvolatile memories
更新于2025-09-23 15:19:57
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Toward Coupling Color Centers in Single Crystal Diamond to Two-Dimensional Materials
摘要： Individual nitrogen vacancy (NV) color centers in diamond are bright, photo-stable, atomic-sized dipole emitters [1]. Consequently, they represent optimal candidates for novel scanning near field microscopy techniques [2]. Here, NV centers form one member of a F¨orster Resonance Energy Transfer (FRET) pair. Due to their broadband emission (> 100 nm), NVs are versatile donors for FRET to systems absorbing in the near infrared spectral range. Highly-promising applications include, e.g., nanoscale imaging of fluorescent molecules or nanomaterials like graphene [2]. Critical parameters for FRET are the NV’s quantum efficiency, charge state stability and NV-sample-distance. Previous experiments used NVs in nanodiamond for FRET [2], however these NVs might suffer from quenching, instability and badly controlled surface termination. We here address this issue by using shallowly implanted NV centers in optimized cylindrical nanostructures [3] used as scanning probes in our homebuilt combination of a confocal and an atomic force microscope. In recent years, two-dimensional materials especially monolayers of semiconducting materials are of major interest in research. Particularly, dichalcogenides like, e.g., tungsten diselenide (WSe2) are promising candidates for a varity of applications [4]. WSe2 emits photons at a wavelength of around 750 nm while absorbing photons below 700 nm [4] which renders WSe2 as a promising FRET partner for NV centers. Here, we present first results towards demonstrating the interaction of NV color centers in single crystal diamond with WSe2. We envisage using quenching of the NV center sued as a donor in FRET in close proximity to the 2D material as a valuable sensing ressource.
关键词： F¨orster Resonance Energy Transfer (FRET),tungsten diselenide (WSe2),nitrogen vacancy (NV) color centers,diamond,two-dimensional materials
更新于2025-09-11 14:15:04
-
Quantum Multibody Interactions in Halide-Assisted Vapor-Synthesized Monolayer WSe <sub/>2</sub> and Its Integration in a High Responsivity Photodetector with Low-Interface Trap Density
摘要： Among the two-dimensional (2D) transitional-metal dichalcogenides, monolayer (1L) tungsten diselenide (WSe2) has recently attracted a great deal of interest because of its direct band gap and tunable charge transport behavior, making it attractive for a variety of electronic and optoelectronic applications. Controlled and efficient synthesis of 1L WSe2 using chemical vapor deposition (CVD) is often challenging because of the high temperatures required to generate a steady flux of tungsten atoms in the vapor phase from the oxide precursors. Here, the use of halide-assisted low-pressure CVD with NaCl helps to reduce the growth temperature to ～750 °C, which is lower than the typical temperatures needed with conventional CVD for realizing 1L WSe2. Moreover, we experimentally probed the quantum multibody interactions in 1L WSe2 ascribed to excitons, trions, and other localized states by analyzing the temperature-dependent photoluminescence spectra, where such multibody interactions govern the intrinsic electronic and optoelectronic properties of 1L WSe2 for device platforms. The role of the metal?2D semiconductor interface is also critical to realize high-performance devices. In this study, a 1L WSe2-based photodetector was fabricated using Al contacts, which shows a high photoresponsivity, and the interface-state density Dit of the Al/WSe2 junction was computed to be the lowest reported to date ～3.45 × 1012 cm?2 eV?1. Our work demonstrates the tremendous potential of WSe2 to open avenues for state-of-the-art electronic, optoelectronic, and quantum-optoelectronic devices using scalable synthesis routes.
关键词： transitional-metal dichalcogenides,photodetector,tungsten diselenide (WSe2),two-dimensional (2D) materials,quantum multibody interactions,interface-state density,chemical vapor deposition (CVD)
更新于2025-09-11 14:15:04
-
High-performance WSe2 photodetector based on laser-induced p-n junction
摘要： Two-dimensional (2D) heterojunctions exhibit many unique features in nanoelectronic and optoelectronic devices. However, heterojunction engineering requires complicated alignment process and some defects are inevitably introduced during material preparation. In this work, a laser scanning technique is used to construct a lateral WSe2 p-n junction. The laser-scanned region shows a p-type behavior and the adjacent region is electrically n-doped with a proper gate voltage. The laser-oxidized product WOx is found to be responsible for this p-type doping. After laser scanning, WSe2 displays a change from ambipolar to unipolar p-type property. A significant photocurrent emerges at the p-n junction. Therefore, a self-powered WSe2 photodetector can be fabricated based on this junction, which presents a large photoswitching ratio of 106, high photoresponsivity of 800 mA W-1 and short photoresponse time with long-term stability and reproducibility. Therefore, this selective laser-doping method is prospective in future electronics applications.
关键词： photodetector,p-n junction,laser-doping,tungsten diselenide,oxidation product
更新于2025-09-11 14:15:04
-
Hole Conduction of Tungsten Diselenide Crystalline Transistors by Niobium Dopant
摘要： In spite of its ambipolar character, tungsten diselenide (WSe2) is known as one of a few p-type materials among transition metal dichalcogenides and is currently being used as a fundamental building block of homo- and hetero-junctions to meet the essential requirement of electronic devices. Many studies have solved the hole transport of WSe2 by contact engineering; however, another route is shown by an effective p-doping strategy for achieving reliable p-type transistor. Diverse characterization methods confirm the transition of the Fermi level from near midgap in intrinsic WSe2 to lower half bandgap with niobium substitutional doping, leading to a nondegenerate doping level exceeding a 1017–1018 cm?3 hole concentration. As a consequence, current on/off ratio and swing parameter have improved correspondingly as expected. The WSe2 transistors (with and without doping) are examined by the Zerbst-type method to conduct the transient data analysis enabling the systemic characterization of the generation lifetime and surface generation velocity of WSe2. It is demonstrated that the lifetime for WSe2 is commonly in the 0.5–0.1 μs range. The generation velocity is ≈10 000-fold slower than that of the typical crystalline silicon, which is attributed to the ultrathin body nature of the materials.
关键词： p-type,niobium doping,tungsten diselenide,transistors,lifetime
更新于2025-09-10 09:29:36
-
PVP intercalated metallic WSe<sub>2</sub> as NIR photothermal agents for efficient tumor ablation
摘要： Transition metal dichalogenides (TMDCs) with unique layered structures hold promising potential as transducers for photothermal therapy. However, the low photothermal conversion efficiency and poor stability in some cases limit their practical applications. Herein, we demonstrate the fabrication of an ultrathin homogeneous hybridized TMDC nanosheets and their use for highly efficient photothermal tumor ablation. In particular, the nanosheets were composed of metallic WSe2 intercalated with polyvinylpyrrolidone (PVP), which was facilely prepared through a solvothermal process from the mixture of selenourea crystals, WCl6 powder along with PVP polymeric nanogel. Our characterizations revealed the obtained nanosheets exhibited excellent photothermal conversion efficiency, improved biocompatibility and physiological stability attributing to the combined merits of metallic phase of WSe2 and hydrophilic PVP insertion. Both the histological analysis of vital organs and in-vitro/in-vivo tests confirmed the nanosheets as actively effective and biologically safe in this phototherapeutic technique. Findings from this non-invasive experiment clearly emphasize the explorable therapeutic efficacy of layered-based hybrid agents in future cancer treatment planning procedures.
关键词： Solvothermal synthesis,intercalation,metallic tungsten diselenide,photothermal therapy
更新于2025-09-10 09:29:36