Novel and Enhanced Optoelectronic Performances of Multilayer MoS2–WS2 Heterostructure Transistors

Van der Waals heterostructures designed by assembling isolated two‐dimensional (2D) crystals have emerged as a new class of artificial materials with interesting and unusual physical properties. Here, the multilayer MoS₂–WS₂ heterostructures with different configurations are reported and their optoelectronic properties are studied. It is shown that the new heterostructured material possesses new functionalities and superior electrical and optoelectronic properties that far exceed the one for their constituents, MoS₂ or WS₂. The vertical transistor exhibits a novel rectifying and bipolar behavior, and can also act as photovoltaic cell and self‐driven photodetector with photo‐switching ratio exceeding 10³. The planar device also exhibits high field‐effect ON/OFF ratio (>10⁵), high electron mobility of 65 cm²/Vs, and high photo­responsivity of 1.42 A/W compared to that in isolated multilayer MoS₂ or WS₂ nanoflake transistors. The results suggest that formation of MoS₂–WS₂ heterostructures could significantly enhance the performance of optoelectronic devices, thus open up possibilities for future nanoelectronic, photovoltaic, and optoelectronic applications.     

Transition‐Metal‐Carbide (Mo2C) Multiperiod Gratings for Realization of High‐Sensitivity and Broad‐Spectrum Photodetection

A novel hybrid phototransistor consisting of molybdenum carbide (Mo₂C) and molybdenum disulfide (MoS₂) is proposed. By exploiting the interface properties of MoS₂ and Mo₂C, a highly sensitive and broad‐spectral response photodetector is fabricated. The underlying mechanism of the enhanced performance is the efficient hot carrier injection from Mo₂C to MoS₂. The strong coupling of MoS₂ and Mo₂C at the interface provides the significantly low Schottky barrier height (≈70 meV), which gives rise to the significantly efficient hot carrier transfer from Mo₂C to MoS₂. The grating of metallic Mo₂C produces plasmonic resonance, which provides hot carriers to the MoS₂ channel. By adjusting the grating period of Mo₂C (400–1000 nm), the optimal photoresponse of light can be controlled, from visible to NIR. By integrating various Mo₂C multigrating periods (400–1000 nm) with MoS₂, a novel photodetector is demonstrated with high responsivity (R > 10³ A W^?1) and light‐to‐dark current ratio (>10²) over a broad spectral range (405–1310 nm). The proposed novel hybrid photodetector, 2D semiconductors with multigrating 2D metallic stripes, exhibits high sensitivity and broad spectral detection of light and can overcome the inherent weakness of conventional 2D photodetectors, paving the way forward for next‐generation photoelectric devices.     

Dependence of Photocurrent Enhancements in Quantum Dot (QD)‐Sensitized MoS2 Devices on MoS2 Film Properties

This report demonstrates highly efficient nonradiative energy transfer (NRET) from alloyed CdSeS/ZnS semiconductor nanocrystal quantum dots (QDs) to MoS₂ films of varying layer thicknesses, including pristine monolayers, mixed monolayer/bilayer, polycrystalline bilayers, and bulk‐like thicknesses, with NRET efficiencies of over 90%. Large‐area MoS₂ films are grown on Si/SiO₂ substrates by chemical vapor deposition. Despite the ultrahigh NRET efficiencies there is no distinct increase in the MoS₂ photoluminescence intensity. However, by studying the optoelectronic properties of the MoS₂ devices before and after adding the QD sensitizing layer photocurrent enhancements as large as ≈14‐fold for pristine monolayer devices are observed, with enhancements on the order of ≈2‐fold for MoS₂ devices of mixed monolayer and bilayer thicknesses. For the polycrystalline bilayer and bulk‐like MoS₂ devices there is almost no increase in the photocurrent after adding the QDs. Industrially scalable techniques are specifically utilized to fabricate the samples studied in this report, demonstrating the viability of this hybrid structure for commercial photodetector or light harvesting applications.     

MoS2/Si Heterojunction with Vertically Standing Layered Structure for Ultrafast,High‐Detectivity,Self‐Driven Visible–Near Infrared Photodetectors

As an interesting layered material, molybdenum disulfide (MoS₂) has been extensively studied in recent years due to its exciting properties. However, the applications of MoS₂ in optoelectronic devices are impeded by the lack of high‐quality p–n junction, low light absorption for mono‐/multilayers, and the difficulty for large‐scale monolayer growth. Here, it is demonstrated that MoS₂ films with vertically standing layered structure can be deposited on silicon substrate with a scalable sputtering method, forming the heterojunction‐type photodetectors. Molecular layers of the MoS₂ films are perpendicular to the substrate, offering high‐speed paths for the separation and transportation of photo‐generated carriers. Owing to the strong light absorption of the relatively thick MoS₂ film and the unique vertically standing layered structure, MoS₂/Si heterojunction photodetectors with unprecedented performance are actualized. The self‐driven MoS₂/Si heterojunction photodetector is sensitive to a broadband wavelength from visible light to near‐infrared light, showing an extremely high detectivity up to ≈10¹³ Jones (Jones = cm Hz^1/2 W^?1), and an ultrafast response speed of ≈3 μs. The performance is significantly better than the photodetectors based on mono‐/multilayer MoS₂ nanosheets. Additionally, the MoS₂/Si photodetectors exhibit excellent stability in air for a month. This work unveils the great potential of MoS₂/Si heterojunction for optoelectronic applications.     

Novel Ω‐Shaped Core–Shell Photodetector with High Ultraviolet Selectivity and Enhanced Responsivity

The design of nanostructure plays an important role in performance enhancement of low‐dimensional optoelectronic devices. Herein, a novel photodetector (PD) based on electrospun SnO₂ nanofibers with Ω‐shaped ZnO shell (SnO₂@ZnO) is fabricated. With 87.4% transmittance at 550 nm, SnO₂@ZnO PD exhibits a high photo‐to‐dark current ratio up to 10⁴ at around 280 nm. Owing to the additional Ω‐shaped ZnO shell, SnO₂@ZnO PD possesses a responsivity of nearly 100 A W^?1 under 5 V bias and the illumination of 250 nm light, which is 30‐time enhancement of pristine SnO₂ PD. The enhancement is mainly attributed to type‐II energy band structure. Furthermore, by changing the direction of incident light, SnO₂@ZnO PD has a high UV selectivity with an UV–vis rejection ratio (R _{250 nm}/R _{400 nm}) as much as 2.0 × 10³ at 5 V bias under back illumination, which is fourfold higher than that under face illumination. The UV selectivity improvement may be attributed to light confinement in the Ω‐shaped structure. With both theoretical simulations and experimental comparisons, it is demonstrated that the unique compact Ω‐shaped nanostructure does contribute to photon trapping and gaining process, especially in back‐illumination configuration. The approach can be easily extended to other materials, preparing novel building blocks for optoelectronic devices.     

High‐Performance Transition Metal Dichalcogenide Photodetectors Enhanced by Self‐Assembled Monolayer Doping

Most doping research into transition metal dichalcogenides (TMDs) has been mainly focused on the improvement of electronic device performance. Here, the effect of self‐assembled monolayer (SAM)‐based doping on the performance of WSe₂‐ and MoS₂‐based transistors and photodetectors is investigated. The achieved doping concentrations are ≈1.4 × 10¹¹ for octadecyltrichlorosilane (OTS) p‐doping and ≈10¹¹ for aminopropyltriethoxysilane (APTES) n‐doping (nondegenerate). Using this SAM doping technique, the field‐effect mobility is increased from 32.58 to 168.9 cm² V^?1 s in OTS/WSe₂ transistors and from 28.75 to 142.2 cm² V^?1 s in APTES/MoS₂ transistors. For the photodetectors, the responsivity is improved by a factor of ≈28.2 (from 517.2 to 1.45 × 10⁴ A W^?1) in the OTS/WSe₂ devices and by a factor of ≈26.4 (from 219 to 5.75 × 10³ A W^?1) in the APTES/MoS₂ devices. The enhanced photoresponsivity values are much higher than that of the previously reported TMD photodetectors. The detectivity enhancement is ≈26.6‐fold in the OTS/WSe₂ devices and ≈24.5‐fold in the APTES/MoS₂ devices and is caused by the increased photocurrent and maintained dark current after doping. The optoelectronic performance is also investigated with different optical powers and the air‐exposure times. This doping study performed on TMD devices will play a significant role for optimizing the performance of future TMD‐based electronic/optoelectronic applications.     

High Responsivity Phototransistors Based on Few‐Layer ReS2 for Weak Signal Detection

2D transition metal dichalcogenides are emerging with tremendous potential in many optoelectronic applications due to their strong light–matter interactions. To fully explore their potential in photoconductive detectors, high responsivity is required. Here, high responsivity phototransistors based on few‐layer rhenium disulfide (ReS₂) are presented. Depending on the back gate voltage, source drain bias and incident optical light intensity, the maximum attainable photoresponsivity can reach as high as 88 600 A W^?1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS₂. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement due to the existence of trap states in the few‐layer ReS₂ flakes. It further enables the detection of weak signals, as successfully demonstrated with weak light sources including a lighter and limited fluorescent lighting. Our studies underscore ReS₂ as a promising material for future sensitive optoelectronic applications.     

Irradiation of Transition Metal Dichalcogenides Using a Focused Ion Beam: Controlled Single‐Atom Defect Creation

Manipulation and structural modifications of 2D materials for nanoelectronic and nanofluidic applications remain obstacles to their industrial‐scale implementation. Here, it is demonstrated that a 30 kV focused ion beam can be utilized to engineer defects and tailor the atomic, optoelectronic, and structural properties of monolayer transition metal dichalcogenides (TMDs). Aberration‐corrected scanning transmission electron microscopy is used to reveal the presence of defects with sizes from the single atom to 50 nm in molybdenum (MoS₂) and tungsten disulfide (WS₂) caused by irradiation doses from 10¹³ to 10¹⁶ ions cm^?2. Irradiated regions across millimeter‐length scales of multiple devices are sampled and analyzed at the atomic scale in order to obtain a quantitative picture of defect sizes and densities. Precise dose value calculations are also presented, which accurately capture the spatial distribution of defects in irradiated 2D materials. Changes in phononic and optoelectronic material properties are probed via Raman and photoluminescence spectroscopy. The dependence of defect properties on sample parameters such as underlying substrate and TMD material is also investigated. The results shown here lend the way to the fabrication and processing of TMD nanodevices.     

Hollow Spherical Nanoshell Arrays of 2D Layered Semiconductor for High‐Performance Photodetector Device

Well‐defined hollow spherical nanoshell arrays of 2D transitional metal dichalcogenide (TMDC) nanomaterials for MoSe₂ and MoS₂ are grown via chemical vapor deposition technique for the first time. The hollow sphere arrays display the uniform dimensions of ≈450 nm with the shell thickness of ≈10 nm. The unique hollow sphere architecture with increased active surface area is forecasted to supply more efficient route to improve light‐harvesting efficiency through repeated light reflection and scattering inside the hollow structure without decay of response and recovery speed, because exceptional “SP–SP” junction barriers conducting mechanism can facilitate carriers tunneling and transport during the electron transfer procedure within the present particular structure. The MoSe₂ hollow sphere photodetector exhibits an outstanding responsivity (8.9 A W^?1), which is tenfold higher than that for MoSe₂ compact film (0.9 A W^?1), fast response and recovery speed, and good durability under illumination wavelength of 365 nm. Meanwhile, MoSe₂ hollow sphere arrays on flexible polyethylene terephthalate substrates reveal excellent bending stability. Therefore, this research indicates that unique hollow sphere architecture of 2D TMDC materials will be an anticipated avenue for efficient photodetector devices with far‐ranging capability.     

Low‐Power Nonvolatile Charge Storage Memory Based on MoS2 and an Ultrathin Polymer Tunneling Dielectric

Low‐power, nonvolatile memory is an essential electronic component to store and process the unprecedented data flood arising from the oncoming Internet of Things era. Molybdenum disulfide (MoS₂) is a 2D material that is increasingly regarded as a promising semiconductor material in electronic device applications because of its unique physical characteristics. However, dielectric formation of an ultrathin low‐k tunneling on the dangling bond‐free surface of MoS₂ is a challenging task. Here, MoS₂‐based low‐power nonvolatile charge storage memory devices are reported with a poly(1,3,5‐trimethyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) tunneling dielectric layer formed via a solvent‐free initiated chemical vapor deposition (iCVD) process. The surface‐growing polymerization and low‐temperature nature of the iCVD process enable the conformal growing of low‐k (≈2.2) pV3D3 insulating films on MoS₂. The fabricated memory devices exhibit a tunable memory window with high on/off ratio (≈10⁶), excellent retention times of 10⁵ s with an extrapolated time of possibly years, and an excellent cycling endurance of more than 10³ cycles, which are much higher than those reported previously for MoS₂‐based memory devices. By leveraging the inherent flexibility of both MoS₂ and polymer dielectric films, this research presents an important milestone in the development of low‐power flexible nonvolatile memory devices.     

Large‐Area,Flexible Broadband Photodetector Based on ZnS–MoS2 Hybrid on Paper Substrate

Flexible broadband photodetectors based on 2D MoS₂ have gained significant attention due to their superior light absorption and increased light sensitivity. However, pristine MoS₂ has absorption only in visible and near IR spectrum. This paper reports a paper‐based broadband photodetector having ZnS–MoS₂ hybrids as active sensing material fabricated using a simple, cost effective two‐step hydrothermal method wherein trilayer MoS₂ is grown on cellulose paper followed by the growth of ZnS on MoS₂. Optimization in terms of process parameters is done to yield uniform trilayer MoS₂ on cellulose paper. UV sensing property of ZnS and broadband absorption of MoS₂ in visible and IR, broadens the range from UV to near IR. ZnS plays the dual role for absorption in UV and in the generation of local electric fields, thereby increasing the sensitivity of the sensor. The fabricated photodetector exhibits a higher responsivity toward the visible light when compared to UV and IR light. Detailed studies in terms of energy band diagram are presented to understand the charge transport mechanism. This represents the first demonstration of a paper‐based flexible broadband photodetector with excellent photoresponsivity and high bending capability that can be used for wearable electronics, flexible security, and surveillance systems, etc.     

High‐Sensitivity Floating‐Gate Phototransistors Based on WS2 and MoS2

In recent years, 2D layered materials have been considered as promising photon absorption channel media for next‐generation phototransistors due to their atomic thickness, easily tailored single‐crystal van der Waals heterostructures, ultrafast optoelectronic characteristics, and broadband photon absorption. However, the photosensitivity obtained from such devices, even under a large bias voltage, is still unsatisfactory until now. In this paper, high‐sensitivity phototransistors based on WS₂ and MoS₂ are proposed, designed, and fabricated with gold nanoparticles (AuNPs) embedded in the gate dielectric. These AuNPs, located between the tunneling and blocking dielectric, are found to enable efficient electron trapping in order to strongly suppress dark current. Ultralow dark current (10^?11 A), high photoresponsivity (1090 A W^?1), and high detectivity (3.5 × 10¹¹ Jones) are obtained for the WS₂ devices under a low source/drain and a zero gate voltage at a wavelength of 520 nm. These results demonstrate that the floating‐gate memory structure is an effective configuration to achieve high‐performance 2D electronic/optoelectronic devices.     

Fast,Self‐Driven,Air‐Stable,and Broadband Photodetector Based on Vertically Aligned PtSe2/GaAs Heterojunction

Group‐10 layered transitional metal dichalcogenides including PtS₂, PtSe₂, and PtTe₂ are excellent potential candidates for optoelectronic devices due to their unique properties such as high carrier mobility, tunable bandgap, stability, and flexibility. Large‐area platinum diselenide (PtSe₂) with semiconducting characteristics is far scarcely investigated. Here, the development of a high‐performance photodetector based on vertically aligned PtSe₂‐GaAs heterojunction which exhibits a broadband sensitivity from deep ultraviolet to near‐infrared light, with peak sensitivity from 650 to 810 nm, is reported. The I_light/I_dark ratio and responsivity of photodetector are 3 × 10⁴ and 262 mA W^?1 measured at 808 nm under zero bias voltage. The response speed of τ_r/τ_f is 5.5/6.5 µs, which represents the best result achieved for Group‐10 TMDs based optoelectronic device thus far. According to first‐principle density functional theory, the broad photoresponse ranging from visible to near‐infrared region is associated with the semiconducting characteristics of PtSe₂ which has interstitial Se atoms within the PtSe₂ layers. It is also revealed that the PtSe₂/GaAs photodetector does not exhibit performance degradation after six weeks in air. The generality of the above good results suggests that the vertically aligned PtSe₂ is an ideal material for high‐performance optoelectronic systems in the future.     

Controlled Synthesis of 2D Palladium Diselenide for Sensitive Photodetector Applications

Palladium diselenide (PdSe₂), a thus far scarcely studied group‐10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer‐scale and homogeneous 2D PdSe₂ film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe₂ with thickness of 1.2–20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe₂ exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe₂ layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W^?1) and specific detectivity (≈10¹³ Jones). By decorating the device with black phosphorus quantum dots, the device performance can be further optimized. These results suggest the as‐selenized PdSe₂ is a promising material for optoelectronic application.     

Charge Photogeneration in Few‐Layer MoS2

The 2D semiconductor MoS₂ in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub‐ps and ms time scales is used to study the photoexcitation dynamics in few‐layer MoS₂. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS₂ photovoltaic and photodetector devices are made.     

Enhancement of photodetection based on perovskite/MoS2 hybrid thin film transistor

Perovskite/MoS₂ hybrid thin film transistor photodetectors consist of few-layered MoS₂ and CH₃NH₃PbI₃ film with various thickness prepared by two-step vacuum deposition. By implementing perovskite CH₃NH₃PbI₃ film onto the MoS₂ flake, the perovskite/MoS₂ hybrid photodetector exhibited a photoresponsivity of 10⁴A/W and fast response time of about 40 ms. Improvement of photodetection performance is attributed to the balance between light absorption in the perovskite layer and an effective transfer of photogenerated carriers from perovskite entering the MoS₂ channel. This work may provide guidance to develop high-performance hybrid structure optoelectronic devices.     

Strategy Toward Semiconducting Ti3C2Tx-MXene: Phenylsulfonic Acid Groups Modified Ti3C2Tx as Photosensitive Material for Flexible Visual Sensory-Neuromorphic System

The excellent electronic and electrochemical properties make 2D MXenes suitable candidates for sensors, batteries, and supercapacitors. However, the metallic-like behavior of MXenes hinders their potential for optoelectronic devices such as photodetectors. In this study, the band gap of metalloid Ti₃C₂T_x MXene is successfully opened to 1.53 eV with phenylsulfonic acid groups and realized a transistor and high-performance near-infrared photodetector array for a flexible vision sensory-neuromorphic system. The phenylsulfonic acid groups modified Ti₃C₂T_x MXene (S-Ti₃C₂T_x)-based flexible photodetector has a maximum responsivity of 8.50×10² A W⁻¹ and a detectivity of 3.69×10¹¹ Jones under 1064 nm laser irradiation. Moreover, the fabricated flexible vision sensory-neuromorphic system for image recognition realizes a high recognition rate >0.99, leading to great potential in the field of biological visual simulation and biomimetic eye. Besides conventional devices with Au as the conductive electrodes, all Ti₃C₂T_x MXene-based devices are also fabricated with S-Ti₃C₂T_x as the photosensitive material and unmodified Ti₃C₂T_x as the conductive electrodes, exhibiting comparable optoelectronic performances.     

Self‐Assembly of Flexible Free‐Standing 3D Porous MoS2‐Reduced Graphene Oxide Structure for High‐Performance Lithium‐Ion Batteries

Flexible freestanding electrodes are highly desired to realize wearable/flexible batteries as required for the design and production of flexible electronic devices. Here, the excellent electrochemical performance and inherent flexibility of atomically thin 2D MoS₂ along with the self‐assembly properties of liquid crystalline graphene oxide (LCGO) dispersion are exploited to fabricate a porous anode for high‐performance lithium ion batteries. Flexible, free‐standing MoS₂–reduced graphene oxide (MG) film with a 3D porous structure is fabricated via a facile spontaneous self‐assembly process and subsequent freeze‐drying. This is the first report of a one‐pot self‐assembly, gelation, and subsequent reduction of MoS₂/LCGO composite to form a flexible, high performance electrode for charge storage. The gelation process occurs directly in the mixed dispersion of MoS₂ and LCGO nanosheets at a low temperature (70 °C) and normal atmosphere (1 atm). The MG film with 75 wt% of MoS₂ exhibits a high reversible capacity of 800 mAh g^?1 at a current density of 100 mA g^?1. It also demonstrates excellent rate capability, and excellent cycling stability with no capacity drop over 500 charge/discharge cycles at a current density of 400 mA g^?1.     

Atomic Vacancy Control and Elemental Substitution in a Monolayer Molybdenum Disulfide for High Performance Optoelectronic Device Arrays

Defect engineering of 2D transition metal dichalcogenides (TMDCs) is essential to modulate their optoelectrical functionalities, but there are only a few reports on defect‐engineered TMDC device arrays. Herein, the atomic vacancy control and elemental substitution in a chemical vapor deposition (CVD)‐grown molybdenum disulfide (MoS₂) monolayer via mild photon irradiation under controlled atmospheres are reported. Raman spectroscopy, photoluminescence, X‐ray, and ultraviolet photoelectron spectroscopy comprehensively demonstrate that the well‐controlled photoactivation delicately modulates the sulfur‐to‐molybdenum ratio as well as the work function of a MoS₂ monolayer. Furthermore, the atomic‐resolution scanning transmission electron microscopy directly confirms that small portions (2–4 at% corresponding to the defect density of 4.6 × 10¹² to 9.2 × 10¹³ cm^?2) of sulfur vacancies and oxygen substituents are generated in the MoS₂ while the overall atomic‐scale structural integrity is well preserved. Electronic and optoelectronic device arrays are also realized using the defect‐engineered CVD‐grown MoS₂, and it is further confirmed that the well‐defined sulfur vacancies and oxygen substituents effectively give rise to the selective n‐ and p‐doping in the MoS₂, respectively, without the trade‐off in device performance. In particular, low‐percentage oxygen‐doped MoS₂ devices show outstanding optoelectrical performance, achieving a detectivity of ≈10¹³ Jones and rise/decay times of 0.62 and 2.94 s, respectively.     

Patterned Growth of P‐Type MoS2 Atomic Layers Using Sol–Gel as Precursor

2D layered MoS₂ has drawn intense attention for its applications in flexible electronic, optoelectronic, and spintronic devices. Most of the MoS₂ atomic layers grown by conventional chemical vapor deposition techniques are n‐type due to the abundant sulfur vacancies. Facile production of MoS₂ atomic layers with p‐type behavior, however, remains challenging. Here, a novel one‐step growth has been developed to attain p‐type MoS₂ layers in large scale by using Mo‐containing sol–gel, including 1% tungsten (W). Atomic‐resolution electron microscopy characterization reveals that small tungsten oxide clusters are commonly present on the as‐grown MoS₂ film due to the incomplete reduction of W precursor at the reaction temperature. These omnipresent small tungsten oxide clusters contribute to the p‐type behavior, as verified by density functional theory calculations, while preserving the crystallinity of the MoS₂ atomic layers. The Mo containing sol–gel precursor is compatible with the soft‐lithography techniques, which enables patterned growth of p‐type MoS₂ atomic layers into regular arrays with different shapes, holding great promise for highly integrated device applications. Furthermore, an atomically thin p–n junction is fabricated by the as‐prepared MoS₂, which shows strong rectifying behavior.