Recent demonstrations of magnetization switching induced by in-plane current in heavy metal/ferromagnetic heterostructures (HMFHs) have drawn great attention to spin torques arising from large ...spin-orbit coupling (SOC). Given the intrinsic strong SOC, topological insulators (TIs) are expected to be promising candidates for exploring spin-orbit torque (SOT)-related physics. Here we demonstrate experimentally the magnetization switching through giant SOT induced by an in-plane current in a chromium-doped TI bilayer heterostructure. The critical current density required for switching is below 8.9 × 10(4) A cm(-2) at 1.9 K. Moreover, the SOT is calibrated by measuring the effective spin-orbit field using second-harmonic methods. The effective field to current ratio and the spin-Hall angle tangent are almost three orders of magnitude larger than those reported for HMFHs. The giant SOT and efficient current-induced magnetization switching exhibited by the bilayer heterostructure may lead to innovative spintronics applications such as ultralow power dissipation memory and logic devices.
For the first time, high quality In2Te3 nanowires were synthesized via a chemical vapor deposition (CVD) method. The synthesized In2Te3 nanowires are single crystals grown along the 132 direction ...with a uniform diameter of around 150 nm and an average length of tens of micrometers. Further, two kinds of photodetectors made by 1D In2Te3 nanostructures synthesized by CVD and solvothermal (ST) methods respectively were fabricated. To our best knowledge, this is the first time photoresponse properties of In2Te3 nanowire have been studied. The CVD grown nanowire device shows better performance than the ST device, which demonstrates a fast, reversible, and stable photoresponse and also a broad light detection range from 350 nm to 1090 nm, covering the UV–visible–NIR region. The excellent performance of the In2Te3 nanowire photodetectors will enable significant advancements of the next-generation photodetection and photosensing applications.
Two-dimensional materials (2DMs) are competitive candidates in replacing or supplementing conventional semiconductors owing to their atomically uniform thickness. However, current conventional ...micro/nanofabrication technologies realize hardly ultrashort channel and integration, especially for sub-10 nm. Meanwhile, experimental device performance associated with the scaling of dimension needs to be investigated, due to the short channel effects. Here, we show a novel and universal technological method to fabricate sub-10 nm gaps with sharp edges and steep sidewalls. The realization of sub-10 nm gaps derives from a corrosion crack along the cleavage plane of Bi2O3. By this method, ultrathin body field-effect transistors (FETs), consisting of 8.2 nm channel length, 6 nm high-k dielectric, and 0.7 nm monolayer MoS2, exhibit no obvious short channel effects. The corresponding current on/off ratio and subthreshold swing reaches to 106 and 140 mV/dec, respectively. Moreover, integrated circuits with sub-10 nm channel are capable of operating as digital inverters with high voltage gain. The results suggest our technological method can be used to fabricate the ultrashort channel nanopatterns, build the experimental groundwork for 2DMs FETs with sub-10 nm channel length and 2DMs integrated circuits, and offer new potential opportunities for large-scale device constructions and applications.
Two-dimensional (2D) magnetic materials provide an ideal platform for the application in spintronic devices due to their unique spin states in nanometer scale. However, recent research on the ...exfoliated monolayer magnetic materials suffers from the instability in ambient atmosphere, which needs extraordinary protection. Hence the controllable synthesis of 2D magnetic materials with good quality and stability should be addressed. Here we report for the first time the van der Waals (vdW) epitaxial growth of one-unit-cell-thick air-stable ferrimagnet Cr2S3 semiconductor via a facile chemical vapor deposition method. Single crystal Cr2S3 with the domain size reaching to 200 μm is achieved. Most importantly, we observe the as grown Cr2S3 with a Néel temperature (T N) of up to 120 K and a maximum saturation magnetic momentum of up to 65 μemu. As the temperature decreases, the samples show a transition from soft magnet to hard magnet with the highest coercivity of 1000 Oe. The one-unit-cell-thick Cr2S3 devices show a p-type transfer behavior with an on/off ratio over 103. Our work highlights Cr2S3 monolayer as an ideal magnetic semiconductor for 2D spintronic devices. The vdW epitaxy of nonlayered magnets introduces a new route for realizing magnetism in 2D limit and provides more application potential in the 2D spintronics.
Due to the novel physical properties, high flexibility, and strong compatibility with Si‐based electronic techniques, 2D nonlayered structures have become one of the hottest topics. However, the ...realization of 2D structures from nonlayered crystals is still a critical challenge, which requires breaking the bulk crystal symmetry and guaranteeing the highly anisotropic crystal growth. CdTe owns a typical wurtzite crystal structure, which hinders the 2D anisotropic growth of hexagonal‐symmetry CdTe. Here, for the first time, the 2D anisotropic growth of ultrathin nonlayered CdTe as thin as 4.8 nm via an effective van der Waals epitaxy method is demonstrated. The anisotropic ratio exceeds 103. Highly crystalline nanosheets with uniform thickness and large lateral dimensions are obtained. The in situ fabricated ultrathin 2D CdTe photodetector shows ultralow dark current (≈100 fA), as well as high detectivity, stable photoswitching, and fast photoresponse speed (τrising = 18.4 ms, τdecay = 14.7 ms). Besides, benefitting from its 2D planar geometry, CdTe nanosheet exhibits high compatibility with flexible substrates and traditional microfabrication techniques, indicating its significant potential in the applications of flexible electronic and optoelectronic devices.
The synthesis of large‐size ultrathin single‐crystalline CdTe nanosheets as thin as 4.8 nm via van der Waals epitaxy is demonstrated for the first time. The fabricated ultrathin CdTe photodetector shows not only ultralow dark current, high detectivity, stable photoswitching, and ultrafast photoresponse speed, but also high compatibility with flexible substrates and traditional microfabrication techniques.
For increasing scalability and reducing cost, transition metal dichalcogenides‐based electrocatalysts presently have been proposed as substitutes for noble metals to generate hydrogen, but these ...alternatives usually suffer from inferior performance. Here, a Ravenala leaf‐like WxC@WS2 heterostructure is grown via carbonizing WS2 nanotubes, whose outer walls being partially unzipped along with the Wx C “leaf‐valves” attached to the inner tubes during the carbonization process. This heterostructure exhibits a catalytic activity for hydrogen evolution reaction with low overpotential of 146 mV at 10 mA cm−2 and Tafel slope of 61 mV per decade, outperforming the performance of WS2 nanotubes and WxC counterparts under the same condition. Density functional theory calculations are performed to unravel the underlying mechanism, revealing that the charge distribution between WxC and WS2 plays a key role for promoting H atom adsorption and desorption kinetics simultaneously. This work not only provides a potential low‐cost alternative for hydrogen generation but should be taken as a guide to optimize the catalyst structure and composition.
Here, a Ravenala leaf‐like WxC@WS2 heterostructure with WxC “leaf‐valves” attached to the inner WS2 tubes is grown. Its catalytic activity for hydrogen evolution reaction outperforms that of WS2 and WxC counterparts under the same condition. Theoretical calculations reveal the charge distribution at the interface between WxC and WS2 plays a key role for promoting H atom adsorption and desorption kinetics simultaneously.
2D metal‐semiconductor heterostructures based on transition metal dichalcogenides (TMDs) are considered as intriguing building blocks for various fields, such as contact engineering and ...high‐frequency devices. Although, a series of p–n junctions utilizing semiconducting TMDs have been constructed hitherto, the realization of such a scheme using 2D metallic analogs has not been reported. Here, the synthesis of uniform monolayer metallic NbS2 on sapphire substrate with domain size reaching to a millimeter scale via a facile chemical vapor deposition (CVD) route is demonstrated. More importantly, the epitaxial growth of NbS2‐WS2 lateral metal‐semiconductor heterostructures via a “two‐step” CVD method is realized. Both the lateral and vertical NbS2‐WS2 heterostructures are achieved here. Transmission electron microscopy studies reveal a clear chemical modulation with distinct interfaces. Raman and photoluminescence maps confirm the precisely controlled spatial modulation of the as‐grown NbS2‐WS2 heterostructures. The existence of the NbS2‐WS2 heterostructures is further manifested by electrical transport measurements. This work broadens the horizon of the in situ synthesis of TMD‐based heterostructures and enlightens the possibility of applications based on 2D metal‐semiconductor heterostructures.
The edge‐epitaxial growth of 2D (two‐dimensional) NbS2‐WS2 metal‐semiconductor heterostructures is demonstrated. Both lateral and vertical NbS2‐WS2 heterostructures are achieved. The synthesis of monolayer NbS2 with domain size reaching to a millimeter scale is also realized. This work broadens the horizon of the synthesis of heterostructures and enlightens the possibility of applications based on metal‐semiconductor heterostructures.
Solvent-resistant nanofiltration (SRNF) is considered an emerging process capable of replacing conventional energy-consuming methods of separating organic mixtures in diverse industrial fields. This ...study optimized the performance of polypyrrole (PPy) composite SRNF membranes by varying the polymerization conditions, including the types and concentrations of oxidants and pyrrole concentrations, forming integral selective layers on hydrolyzed polyacrylonitrile (PAN-H) support membranes with better separation properties. The PAN-H support was partially hydrolyzed as indicated by the FTIR spectrum and was compatible with the PPy selective layer, as demonstrated by the apparent lack of an interfacial phase observed in the cross-sections of the composite membranes. The PPy/PAN-H composite SRNF membrane fabricated by reacting 0.5molL−1 (NH4)2S2O8 and 5.0wt% pyrrole exhibited a Rose Bengal (RB) rejection of 99.2% in isopropanol (IPA), with a relatively high solvent permeance. For the first time, graphene oxide (GO) was incorporated into the PPy/PAN-H composite SRNF membrane by dispersing GO into the pyrrole ethanol solution before polymerization. GO led to a significant enhancement in solvent permeance without compromising RB rejection. Compared with pure PPy/PAN-H composite SRNF membranes, the methanol (MeOH), ethanol (EtOH), and isopropanol (IPA) permeances of the GO-PPy/PAN-H membrane were approximately 945%, 635% and 302% higher, respectively. In a long term experiment, the GO-PPy/PAN-H composite SRNF membrane exhibited a constant IPA permeance of 1.21Lm−2h−1bar−1 and an RB rejection of approximately 99.0%. Therefore, the newly developed GO-PPy/PAN-H composite SRNF membranes in this study have significant potential for practical applications.
Display omitted
•PPy composite SRNF membranes were prepared on a PAN-H support.•The effects of polymerization conditions were investigated in detail.•Oxidant types, concentrations and monomer concentrations were optimized.•The performances of PPy membranes were greatly improved by the GO incorporation.
Nanomaterials have gained plenty of research interest because of their excellent performance, which is derived from their small size and special structure. In practical applications, to acquire ...nanomaterials with high performance, many methods have been used to modulate the structure and components of materials. To date, ion beam techniques have extensively been applied for modulating the performance of various nanomaterials. Energetic ion beams can modulate the surface morphology and chemical components of nanomaterials. In addition, ion beam techniques have also been used to fabricate nanomaterials, including 2D materials, nanoparticles, and nanowires. Compared with conventional methods, ion beam techniques, including ion implantation, ion irradiation, and focused ion beam, are all pure physical processes; these processes do not introduce any impurities into the target materials. In addition, ion beam techniques exhibit high controllability and repeatability. Here, recent progress in ion beam techniques for nanomaterial surface modification is systematically summarized and existing challenges and potential solutions are presented.
Ion beam techniques are wildly applied in nanomaterial synthesis and surface modification. Compared with conventional methods, ion beam techniques exhibit high controllability and repeatability. This Review focuses on the recent progress of ion beam techniques for nanomaterial surface modification.
Despite great progress in synthesis and application of graphene-like materials, it remains a considerable challenge to prepare two-dimensional (2D) nanostructures of nonlayered materials that may ...bring us surprising physical and chemical properties. Here, we propose a general strategy for the growth of 2D nonlayered materials by van der Waals epitaxy (vdWE) growth with two conditions: (1) the nonlayered materials satisfy 2D anisotropic growth and (2) the growth is implemented on the van der Waals substrates. Large-scale ultrathin 2D Pb1–x Sn x Se nanoplates (∼15–45 nm) have been produced on mica sheets by applying this strategy. Benefiting from the 2D geometry of Pb1–x Sn x Se nanoplates and the flexibility of mica sheet, flexible photodetectors that exhibit fast, reversible, and stable photoresponse and broad spectra detection ranging from UV to infrared light (375, 473, 632, 800, and 980 nm) are in situ fabricated based on Pb1–x Sn x Se nanoplates. We anticipate that more nonlayered materials will be developed into 2D nanostructures through vdWE, enabling the exploitation of novel electronic and optoelectronic devices.
PDF
