Two-step Chemical Vapor Deposition Research Articles

Synthesis of Epitaxial MoS2/MoO2 Core-Shell Nanowires by Two-Step Chemical Vapor Deposition with Turbulent Flow and Their Physical Properties.

MoO2 nanowires (NWs), MoO2/MoS2 core-shell NWs, and MoS2 nanotubes (NTs) were synthesized by the turbulent flow chemical vapor deposition of MoO2 using MoO3, followed by sulfurization in the sulfur gas flow. The involvement of MoO x suboxide is suggested by density functional theory (DFT) calculations of the surface energies of MoO2. The thickness of the MoS2 layers can be controlled by precise tuning of sulfur vapor flow and temperatures. MoS2 had an armchair-type winding topology due to the epitaxial relation with the MoO2 NW surface. A single ∼ few-layer MoO2/MoS2 core-shell structure showed photoluminescence after the treatment with a superacid. The resistivities of an individual MoO2 NW and a MoS2 NT were measured, and they showed metallic and semiconducting resistivity-temperature relationships, respectively.

(Invited) From Bulk to Nanostructured Perovskites

The dimensionality of semiconductors has a crucial role in determining their properties. Recently, metal halide perovskites have been demonstrated with many exciting applications, attracting wide attention to further their development for advanced optoelectronics, such as photovoltaics, photodetectors, light-emitting diodes, and lasers. At length scales down to nanoscale regimes, surface features as well as quantum confinement effects become dominant in regulating the material properties of perovskite materials. In past years, our group focus on the synthesis and characterization of metal halide perovskites with different configurations, ranging from bulk films, microplates, nanosheets, to nanowires. The corresponding physical properties and device applications were also systematically studied based on their widely tunable dimensionality, morphologies, and compositions.Specifically, for perovskite bulk films, surface defects and bulk structural order significantly affect their device performance. Through optimizing processing techniques, self-assembled quasi-2D perovskite films with graded phase distribution were successfully prepared. Gradient type-II band alignments along the out-of-plane direction of perovskites with spontaneous separation of photo-generated electrons and holes are obtained, which is later employed to construct self-powered vertical-structure photodetectors for the first time. Without any driving voltage, the device exhibited impressive performance with the responsivity up to 444 mA/W and ultrashort response time down to 52 µs. In addition, to assess the intrinsic material properties of crystalline perovskites, freestanding MAPbI3 nanosheets and lead-free Cs3Sb2I9 microplates were fabricated by two-step chemical vapor deposition method, in which excellent optoelectronic performance (e.g., responsively of MAPbI3 nanosheet is measured to be 40 A/W) together with ultra-fast response speed (down to 58 µs) and superior thermal stability were obtained.For nanostructured perovskites, understanding the dimensional features and their impact on the materials and devices is becoming increasingly important. Lately, we reported the direct vapor-liquid-solid growth of single-crystalline all-inorganic lead halide perovskite (i.e., CsPbX3; X = Cl, Br, or I) NWs. These NWs exhibited high-performance photodetection with the responsivity exceeding 4489 A/W and detectivity over 7.9 × 1012 Jones toward the visible light regime. Field-effect transistors based on individual CsPbX3 NWs were also fabricated to show the impressive carrier mobility of 3.05 cm2/Vs, being higher than other all-inorganic perovskite devices. Besides, the realization of high-mobility CsPbBr3 NW devices is reported via a simple surface charge transfer doping strategy. After MoO3 decoration and device fabrication, the hole mobility of CsPbBr3/MoO3 core-shell NW device is significantly enhanced to 23.3 cm2/Vs. All these results provide important guidelines for the further improvement of these perovskite nanostructures for practical utilization.

High performance near-infrared MoTe2/Ge heterojunction photodetector fabricated by direct growth of Ge flake on MoTe2 film substrate

We demonstrated a feasible strategy to fabricate MoTe2/Ge heterojunction by direct growth of Ge flake on a MoTe2 film substrate with a two-step chemical vapor deposition method. A thin transition layer (∼4 nm) mainly composed of polycrystalline germanium at the MoTe2/Ge interface was verified during the Ge flake growth. The MoTe2/Ge heterojunction-based photodetector exhibits both the response speed with a rise/fall time of 7/4 μs and the photoresponsivity and detectivity with 4.87 A W−1 and 5.02 × 1011 Jones under zero bias in the near-infrared regime, respectively. The characteristics of device performance imply its practical applicability as building block for potential near-infrared integrated photonics.

Epitaxy of NiTe2 on WS2 for the p-Type Schottky Contact and Increased Photoresponse.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have great potential applications in the electronic and optoelectronic devices. Nevertheless, due to the difficulty in the efficient doping of atomic-thickness TMDCs or Fermi level pinning (FLP) effects at the metal/semiconductor interface, most TMDC devices exhibit the n-type conduction polarity, which significantly limits their functional applications based on the p-n junction. Here, 2D semi-metal NiTe2 nanosheets were epitaxially grown on the WS2 monolayer by a two-step chemical vapor deposition route. The microstructure and optical characterizations confirm that the vertically stacked NiTe2/WS2 heterostructures are formed by van der Waals epitaxy. Interestingly, p-type WS2 field-effect transistors can be obtained with the hole mobility of ∼4.22 cm2/V·s, when the epitaxial NiTe2 sheets act as the source/drain electrodes. This is attributed to the decreased FLP effect and hence the low potential barrier for holes at the van der Waals contacts. Furthermore, the photodetectors based on the heterostructures show a 2 orders of magnitude increase in the switch ratio, responsivity, and detectivity and a 1 order of magnitude increase in the rise and decay speeds relative to those based on pristine WS2. This work paves the way to realize the p-type contact for monolayer WS2 with significantly enhanced optoelectronic performance.

Composition gradient-enabled circular photogalvanic effect in inogranic halide perovskites

Inversion symmetry breaking could lead to the creation of a Rashba–Dresselhauls magnetic field, which plays the key role in spintronic devices. In this work, we propose and develop a composition gradient engineering approach that breaks inversion symmetry into inorganic halide perovskites with strong spin–orbit coupling. We synthesize epitaxial CsPbBrxCl(3−x) with Br/Cl composition gradient by a two-step chemical vapor deposition approach. Through optoelectronic measurements, we show the presence of circular photogalvanic effects (CPGEs), evidencing a Rashba-like spin polarized band structure. By spatially resolved photoluminescence spectra, we find that the observed CPGE is likely a cumulative result of inversion symmetry-broken interfaces featured by abrupt and stepwise composition gradient between the pristine and separated daughter phases. Our work suggests an avenue in engineering the spintronic property of halide perovskites for information processing.

Nanosheet MoS2-Decorated MoO2 on Porous Carbon as Electrodes for Efficient Hydrogen Evolution

To optimize the disadvantage of low conductivity and few active sites of MoS2-based catalysts, in situ growth on carbonized wood (CW) through coupling of conductive materials and MoS2 can be a proven strategy. Herein, a three-dimensional self-supporting electrode with a heterostructure of nanosheet MoS2-decorated MoO2 grown on CW (MoS2-MoO2/CW) is prepared for the hydrogen evolution reaction (HER) via a simple two-step chemical vapor deposition strategy. The coupling of MoS2 and MoO2 with excellent electrical conductivity and the rational design of three-dimensional self-supporting electrodes are the key factors to improve the catalytic performance. The designed MoS2-MoO2/CW electrode has a potential of 148 mV at a current density of 10 mA cm–2, a low Tafel slope of 86.7 mV dec–1, and outstanding long-term stability in 0.5 M H2SO4. Consequently, wood-based porous carbon electrodes with a heterogeneous structure of nanosheet MoS2-decorated MoO2 can provide meaningful references for MoS2-based electrocatalysts.

Effect of PyC Inner Coating on Preparation of 3C-SiC Coating on Quartz Glass by Chemical Vapor Reaction

The cubic polycrystal of SiC (3C-SiC) coating on the quartz glass (QG) surface was successfully prepared via a two-step chemical vapor deposition (CVD) by introducing a thin PyC coating as a buffer layer. Through combining the intake system of CVD PyC and CVD SiC, the SiC/PyC composite coating can be in-situ prepared on the QG without halfway in-and-out chamber. The results showed that the SiC/PyC composite coating possesses highly uniform, dense, and continuous features, while the pure SiC coating exhibits many cracks, implying that the internal stress between the SiC coating and the QG can be relieved by adding the PyC buffer coating. The average hardness of the SiC/PyC/QG is measured to be 46.8 GPa, and its calculated modulus is 416.3 GPa by using a nanoindentation technique. Compared to the pure QG, the friction coefficient of the SiC/PyC/QG is slightly increased to 1.47 vs. 1.45. Moreover, the SiC/PyC/QG displays the excellent anti-acid corrosion in the 5%HF and 5%HCl mixed solution with the weight loss of about 33% lower than the pure QG after 8 h acid test at 80°C.

Strong interfacial coupling in vertical WSe2/WS2 heterostructure for high performance photodetection

Two-dimensional van der Waals (vdWs) heterostructures have shown great potential in the field of electronic and optoelectronic applications over the recent decade. However, the controlled preparation of high-quality vdWs heterostructures remains a great challenge ascribing to the incompatibility of different material synthesis processes. Here, we report a two-step chemical vapor deposition method for the growth of high quality WS2 on a WSe2 template with a very low temperature of ∼550 °C, where WO3 nanosheets formed in the first step are further employed as the precursor for synthesis of the top WS2 layer in the second step. Such low growth temperatures in the second step also enable the effective protection of bottom WSe2 during the WS2 growth process and, therefore, result in high-quality WSe2/WS2 heterostructures. Photoluminescence characterizations are further conducted, where significant interlayer exciton emission is observed, indicating strong interlayer coupling in the heterostructure. Based on the obtained WSe2/WS2 heterostructure, dual-channel photosensitive devices were further designed and systematically studied, where high photoresponsivity (3 A/W) as well as fast response speed (<1 ms) are obtained. The developed WO3-assisted growth technique would provide an effective reference for the controlled synthesis of high quality vdWs heterostructures and promote further applications in high-performance optoelectronic devices.

Monolayer MoS2 of high mobility grown on SiO2 substrate by two-step chemical vapor deposition

We report a novel two-step ambient pressure chemical vapor deposition (CVD) pathway to grow high-quality MoS2 monolayer on the SiO2 substrate with large crystal size up to 110 μm. The large specific surface area of the pre-synthesized MoO3 flakes on the mica substrate compared to MoO3 powder could dramatically reduce the consumption of the Mo source. The electronic information inferred from the four-probe scanning tunneling microscope (4P-STM) image explains the threshold voltage variations and the n-type behavior observed in the two-terminal transport measurements. Furthermore, the direct van der Pauw transport also confirms its relatively high carrier mobility. Our study provides a reliable method to synthesize high-quality MoS2 monolayer, which is confirmed by the direct 4P-STM measurement results. Such methodology is a key step toward the large-scale growth of transition metal dichalcogenides (TMDs) on the SiO2 substrate and is essential to further development of the TMDs-related integrated devices.

Synthesis and characterization of large-sized monolayer MoS2 nanoflakes by sulfurization of exfoliated MoO3 powder

We demonstrate a novel approach based on sulfurization of MoO3 powder pre-exfoliated on the SiO2/Si substrate to synthesize high crystalline quality and large-sized monolayer MoS2 films uniformly covering the whole substrate. The surface morphology, thickness, crystalline quality, and luminescence mechanism of the MoS2 films were characterized by the optical microscopy, Raman spectroscopy, and photoluminescence spectroscopy. The results reveal that MoS2 films directly synthesized on the bare SiO2/Si substrate by our method have high surface coverage superior over those of one-step chemical vapor deposition (CVD) method and exhibit uniform monolayer with larger lateral length up to ∼120 µm compared to those of the traditional two-step CVD method. Our proposed growth strategy opens up new pathways for CVD synthesis of high crystalline quality and large-sized uniform monolayer MoS2 films and can also be utilized for synthesizing other two-dimensional materials.

High-performance CdS@CsPbBr3 core–shell microwire heterostructure photodetector

A core–shell heterojunction has been developed to fabricate efficient optoelectronic devices by optimizing the light absorption and promoting the generation and extraction of charge carriers. Herein, the CdS@CsPbBr3 core–shell microwire (MW) heterojunction was structured via a two-step chemical vapor deposition and was further used to fabricate a UV–Vis photodetector. The photodetector performance is greatly dependent on the thickness of the CsPbBr3 shell. Growth time of 60 min could produce about 80 nm thick CsPbBr3 shell with excellent coverage and adhesion, resulting in optimized performance parameters. As compared with bare cadmium sulfide (CdS) MW photodetector, the CdS@CsPbBr3 core–shell MW heterojunction photodetector exhibits relatively high ratio of photocurrent and dark current (104), much higher light responsivity (319.79 A W−1) and faster response time (6.6 ms). The responsivity is 3.3 times to the value of bare CdS photodetector and the photocurrent increases nearly 10 times. The significant performance parameters mainly result from the formation of a type-II energy band structure and the reduction of the defects states on CdS surface, leading to the obviously improved carriers transport process. The results indicate that the CdS@CsPbBr3 core–shell MW heterojunction is a promising potential candidate to construct high-performance electronic and optoelectronic devices.

In-situ strain engineering on the emission and photoresponse of epitaxial vertical and horizontal CsPbBr3 triangular nanoplates

CsPbBr3 perovskite has attracted significant attention due to its enhanced stability, structural diversity, and excellent properties. Here, vertical and horizontal CsPbBr3 triangular nanoplates (TPs) with side lengths up to several tens of microns have been grown by a two-step chemical vapour deposition for the first time. The vertical CsPbBr3 TPs exhibits two emission peaks at 524 nm and 532 nm due to different spatial morphology and reducing interfacial stress, which is different from horizontal CsPbBr3 TPs emitting only a single emission peak at 524 nm. In addition, the carrier lifetime of vertical perovskite increase ∼40% compared with horizontal perovskite due to fewer contributions of edge trapping and surface trap states. This work provides a method to regulate the properties of CsPbBr3 through in-situ strain engineering, holding great potential in electronic and optoelectronic devices.

Free-standing Si3N4 nanowires@pyrolytic carbon membranes decorated with metal oxide nanoarrays for flexible hybrid supercapacitors

To satisfy the increasing requirement of flexible energy storage devices, various free-standing flexible conductive substrates were developed to construct high-performance supercapacitor electrodes. In this work, free-standing, flexible and conductive Si3N4 nanowires (NWs)@pyrolytic carbon (PyC) membrane, served as nanoscale substrate, was fabricated by a two-step chemical vapor deposition (CVD) method. NiCo2O4 nanosheets (NSs) and Fe2O3 nanorods (NRs) were finally grown on Si3N4NWs@PyC membrane substrates, which were directly served as the positive and negative electrodes, respectively. The membrane electrodes possesss the structural advantages, such as the interwoven network structure of nanowires substrates and array structure of active materials, which guarantee the excellent electrochemical performance of electrodes. Additionally, the flexible solid-state hybrid supercapacitor (HSC) assembled by Si3N4NWs@PyC@NiCo2O4NSs and Si3N4NWs@PyC@Fe2O3NRs, delivered a high energy density of 74.3 Wh kg−1 at a power density of 0.8 kW kg−1, excellent cycling stability (Capacitance retention of 84.6% after 4000 cycles), and good flexibility. Impressively, this work provides a new thinking about the structural design of high-performance supercapacitor electrodes as well as expands the application field of ceramic nanowires macrostructures.

Chemical vapor deposited WS2/MoS2 heterostructure photodetector with enhanced photoresponsivity

Two-dimensional transition metal dichalcogenides (TMDCs) have attracted great interest due to their unique semiconductor properties. Among all TMDC materials, MoS2 and WS2 are promising for composing heterostructures. However, traditional TMDC heterostructure fabrication depends on transfer process, with drawbacks of interface impurity and small size. In this work, a two-step chemical vapor deposition (CVD) process was applied to synthesize large-scale WS2/MoS2 heterostructure. Surface morphology and crystal structure characterizations demonstrate the high-quality WS2/MoS2 heterostructure. The WS2/MoS2 heterostructure photodetector fabricated by photolithography exhibits an enhanced photoresponsivity up to 370 A W−1 in comparison with single WS2 or MoS2 devices. This study suggests a direct CVD growth of large-scale TMDC heterostructure films with clean interface. The built-in electric field at interface contributes to the separation of photo-generated electron–hole pairs, leading to enhanced photocurrent and responsivity, and showing promising potentials in photo-electric applications.

Growth of Single-Walled Carbon Nanotubes from Solid Carbon Nanoparticle Seeds via Cap Formation Engineering with a Two-Step Growth Process and Water Vapor Supply.

Solid carbon nanoparticles are promising growth seeds to prepare single-walled carbon nanotubes (SWCNTs) at high temperatures, at which the SWCNT crystallinity should be improved significantly but conventional metal catalyst nanoparticles are unstable and suffer from aggregation. The noncatalytic nature of solid carbon nanoparticles, however, makes SWCNT growth inefficient, resulting in a limited growth yield. In this study, we develop a two-step chemical vapor deposition process to efficiently synthesize high-crystallinity SWCNTs at high temperatures from solid carbon nanoparticles obtained from nanodiamond. Based on thermodynamic considerations, the growth conditions are separately adjusted to supply different growth driving forces which are suitable for the formation of the initial cap structures and for the stationary elongation of SWCNTs. This process, called cap formation engineering, improves the nucleation density of the cap structures. We examined the changes in crystallinity, amorphous carbon deposition, diameter, and yield of SWCNTs with respect to the synthesis conditions. By controlling the initial growth conditions, high-quality SWCNTs are grown with improved yield. With the addition of water vapor as the etchant, deposition of amorphous carbon at high temperatures was further prevented. The results provide a pathway for precise growth control of SWCNTs from unconventional solid growth seeds.

Edge assisted epitaxy of CsPbBr3 nanoplates on Bi2O2Se nanosheets for enhanced photoresponse

Bi2O2Se has been proved to be a promising candidate for electronic and optoelectronic devices due to their unique physical properties. However, it is still a great challenge to construct the heterostructures with direct epitaxy of hetero semiconductor materials on Bi2O2Se nanosheets. Here, a two-step chemical vapor deposition (CVD) route was used to directly grow the CsPbBr3 nanoplate-Bi2O2Se nanosheet heterostructures. The CsPbBr3 nanoplates were selectively grown on the Bi2O2Se nanosheet along the edges, where the dangling bonds provide the nucleation sites. The epitaxial relationships between CsPbBr3 and Bi2O2Se were determined as [200]Bi2O2Se||[110]CsPbBr3 and [110]Bi2O2Se||[200]CsPbBr3 by transmission electron microscopy characterization. The photoluminescence (PL) results reveal that the formation of heterostructures results in the remarkable PL quenching due to the type-I band arrangement at CsPbBr3/Bi2O2Se interface, which was confirmed by ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe measurements, and makes the photogenerated carriers transfer from CsPbBr3 to Bi2O2Se. Importantly, the photodetectors based on the heterostructures exhibit a 4-time increase in the responsivity compared to those based on the pristine Bi2O2Se sheets, and the fast rise and decay time in microsecond. These results indicate that the direct epitaxy of the CsPbBr3 plates on the Bi2O2Se sheet may improve the optoelectronic performance of Bi2O2Se based devices.

Controllable growth of 2H-1 T′ MoS2/ReS2 heterostructures via chemical vapor deposition

Two-dimensional (2D) 2H-1 T′ heterojunctions based on transition-metal dichalcogenides have attracted great attention due to their special interface structures and novel properties. Understanding the growth mechanism and the interface structures is essential for their controllable growth. In this work, we successfully synthesize lateral and vertical MoS2/ReS2 heterojunctions by using a two-step chemical vapor deposition (CVD) method, and deeply explore the evolution of the structure. It is found that the growth mode of heterojunction undergoes a transition from lateral epitaxy to vertical stacking under a high Re/S ratio during the growth. Furthermore, the interface structure is greatly determined by the edge shape of MoS2 core. Two kinds of structures, with the b-axis of 1 T′ ReS2 shell parallel to the (100) and (010) plane of MoS2 core respectively, are observed. Meanwhile, by comparing with MoS2 monolayer, MoS2/ReS2 heterostructures possess a reduced emission intensity due to the carrier transfer. This work provides a robust and controllable strategy for the synthesis of heterostructures with different phase structures.

Photoemission oscillation in epitaxially grown van der Waals β-In2Se3WS2 heterobilayer bubbles* *Project supported by the National Natural Science Foundation of China (Grant Nos. 51732010 and 51972280), the Natural Science Foundation of Hebei Province, China (Grant No. E2019203233), the Research Program of the College Science & Technology of Hebei Province, China (Grant No. ZD2020121).

Thin films of millimeter-scale continuous monolayer WS2 have been grown on SiO2/Si substrate, followed by the deposition of β-In2Se3 crystals on monolayer WS2 to prepare In2Se3/WS2 van de Waals heterostructures by a two-step chemical vapor deposition (CVD) method. After the growth of In2Se3 at elevated temperatures, high densities of In2Se3/WS2 heterostructure bubbles with monolayer to multilayer β-In2Se3 crystals atop are observed. Fluorescence of the resultant β-In2Se3/WS2 heterostructure is greatly enhanced in intensity upon the formation of bubbles, which are evidenced by the Newton’s rings in optical image owing to constructive and destructive interference. In photoluminescence (PL) mapping images of monolayer β-In2Se3/monolayer WS2 heterobilayer bubble, significant oscillatory behavior of emission intensity is demonstrated due to constructive and destructive interference. However, oscillatory behaviors of peak position are also observed and come from a local heating effect induced by an excitation laser beam. The oscillatory mechanism of PL is further verified by changing the exterior pressure of bubbles placed in a home-made vacuum chamber. In addition, redshifted in peak position and broadening in peak width are observed due to strain effect during decreasing the exterior pressure of bubbles.

Designing New-Generation Piezoelectric Transducers by Embedding Superior Graphene-Based Thermal Regulators.

Cascaded-piezoelectric-transducers (CPETs) is a key component in modern energy-conversion fields, possessing versatile applications in ultrasonic scalpels, acoustic levitation, and sonar. However, serious self-heating inevitably occurs inside high-power CPETs, severely limiting their practical applications in broader fields. To tackle this, multidirectional heat-escape channels of multidimensional (multi-D, 3D/2D) graphene films are introduced in designing new-type thermal regulators. A porous AlN-ceramic thermal-sink is creatively selected as a template for directly synthesizing graphene via a two-step chemical vapor deposition strategy. This perfect combination of 3D/2D-graphene and the AlN ceramic can integrate their complementary advantages in uniformizing, transmitting, and releasing heat. Amazingly, in the new-generation CPETs embedded with these graphene-based thermal regulators, the self-heating-induced temperature rise can be substantially reduced by ≈60% (far exceeding actual demand standard). As another kernel parameter, electroacoustic-energy-conversion efficiency is dramatically improved in the new-generation CPETs. Briefly, this research realizes the first synthesis of a novel multi-D-graphene/AlN-ceramic hybrid, and propels its brand-new application directions in new-generation energy-conversion- and thermal-management-related territories.

One-Step Synthesis of NbSe2/Nb-Doped-WSe2 Metal/Doped-Semiconductor van der Waals Heterostructures for Doping Controlled Ohmic Contact.

van der Waals heterostructures (vdWHs) of metallic (m-) and semiconducting (s-) transition-metal dichalcogenides (TMDs) exhibit an ideal metal/semiconductor (M/S) contact in a field-effect transistor. However, in the current two-step chemical vapor deposition process, the synthesis of m-TMD on pregrown s-TMD contaminates the van der Waals (vdW) interface and hinders the doping of s-TMD. Here, NbSe2/Nb-doped-WSe2 metal-doped-semiconductor (M/d-S) vdWHs are created via a one-step synthesis approach using a niobium molar ratio-controlled solution-phase precursor. The one-step growth approach synthesizes Nb-doped WSe2 with a controllable doping concentration and metal/doped-semiconductor vdWHs. The hole carrier concentration can be precisely controlled by controlling the Nb/(W + Nb) molar ratio in the precursor solution from ∼3 × 1011/cm2 at Nb-0% to ∼1.38 × 1012/cm2 at Nb-60%; correspondingly, the contact resistance RC value decreases from 10 888.78 at Nb-0% to 70.60 kΩ.μm at Nb-60%. The Schottky barrier height measurement in the Arrhenius plots of ln(Isat/T2) versus q/KBT demonstrated an ohmic contact in the NbSe2/WxNb1-xSe2 vdWHs. Combining p-doping in WSe2 and M/d-S vdWHs, the mobility (27.24 cm2 V-1 s-1) and on/off ratio (2.2 × 107) are increased 1238 and 4400 times, respectively, compared to that using the Cr/pure-WSe2 contact (0.022 cm2 V-1 s-1 and 5 × 103, respectively). Together, the RC value using the NbSe2 contact shows 2.46 kΩ.μm, which is ∼29 times lower than that of using a metal contact. This method is expected to guide the synthesis of various M/d-S vdWHs and applications in future high-performance integrated circuits.