Doping Of MoS2 Research Articles

Tunable, stable, and reversible n-type doping of MoS2 via thermal treatment in N-methyl-2-pyrrolidone

Here, we report a highly stable and reversible n-type doping of monolayer MoS2 using thermal treatment in N-methyl-2-pyrrolidone (NMP). The Raman and photoluminescence spectroscopic measurements as well as the device performance of the MoS2 transistors suggested a stronger n-type doping effect with increasing time and temperature of the thermal treatment in NMP. Within the given time (5–60 min) and temperature (50 °C–110 °C), the surface treatment in NMP provided an electron concentration from 6 × 1010 to 2 × 1012 cm−2. Owing to the n-type doping effect, the thermal treatment in NMP reduced the contact resistance and enhanced the field-effect mobility of the MoS2 transistors. The n-type doping via thermal treatment in NMP remained effective for more than 12 months in ambient air, and could be completely removed after immersion in isopropanol. These results demonstrate that thermal treatment in NMP can be a facile and effective route to achieve stable and reversible doping of two-dimensional materials including MoS2 for their applications in high-performance electronics and optoelectronics.

Manganese and oxygen dual-doping MoS2 boosts reduction and adsorption activity toward efficient recovery of gold(I) from thiosulfate solutions

The necessity for application of molybdenum disulfide (MoS2) in photocatalytic reduction field required speedy improvement with high reduction and adsorption performance. Here, manganese (Mn) and oxygen (O) dual-doping strategy were taken for demonstrating that enhancing photocatalytic reduction could achieve simultaneous modulation of the reduction and adsorption parameters by optimizing the electronic configuration and hydrophilicity ability in MoS2. Benefiting from the Mn and O dual-doping collective effect, the developed Mn,O-MoS2 exhibited outstanding photocatalytic reduction and recovery performances of gold(I) from thiosulfate leaching solutions with reduction capacity of 1386.98 mg/g and the corresponding recovery of 92.50%. Besides, Mn and O atoms dual doping in MoS2 accelerated the recovery rate, which was 3 folds higher compared with that of MoS2. Experimental and first-principle approaches suggested that the reduction and adsorption ability of MoS2 were strengthened through tuning the electronic structure and surface property with Mn and O dopants: (1) Mn atoms notably enhanced the conductivity and optimized the electronic structure for facilitating the reduction performance; (2) The incorporated O atoms greatly promoted the adsorption of [Au(S2O3)2]3- by improving the affinity of water molecules and Mn,O-MoS2. The work provides a promising strategy to manipulate two-dimensional materials for various applications about catalysts and adsorbent.

MoS2 Defect Healing for High-Performance Chemical Sensing of Polycyclic Aromatic Hydrocarbons.

The increasing population and industrial development are responsible for environmental pollution. Among toxic chemicals, polycyclic aromatic hydrocarbons (PAHs) are highly carcinogenic contaminants resulting from the incomplete combustion of organic materials. Two-dimensional materials, such as transition metal dichalcogenides (TMDCs), are ideal sensory scaffolds, combining high surface-to-volume ratio with physical and chemical properties that are strongly susceptible to environmental changes. TMDCs can be integrated in field-effect transistors (FETs), which can operate as high-performance chemical detectors of (non)covalent interaction with small molecules. Here, we have developed MoS2-based FETs as platforms for PAHs sensing, relying on the affinity of the planar polyaromatic molecules for the basal plane of MoS2 and the structural defects in its lattice. X-ray photoelectron spectroscopy analysis, photoluminescence measurements, and transfer characteristics showed a notable reduction in the defectiveness of MoS2 and a p-type doping upon exposure to PAHs solutions, with a magnitude determined by the correlation between the ionization energies (EI) of the PAH and that of MoS2. Naphthalene, endowed with the higher EI among the studied PAHs, exhibited the highest output. We observed a log-log correlation between MoS2 doping and naphthalene concentration in water in a wide range (10-9-10-6 M), as well as a reversible response to the analyte. Naphthalene concentrations as low as 0.128 ppb were detected, being below the limits imposed by health regulations for drinking water. Furthermore, our MoS2 devices can reversibly detect vapors of naphthalene with both an electrical and optical readout, confirming that our architecture could operate as a dual sensing platform.

Esaki Diode Behavior in Highly Uniform MoS2/Silicon Carbide Heterojunctions

AbstractThe heterogeneous integration with 2D materials enables new functionalities and novel devices in state‐of‐the‐art bulk (3D) semiconductors. In this work, highly uniform MoS2 heterostructures with silicon carbide (4H‐SiC) are obtained by a facile synthesis method, highly compatible with semiconductor fab processing, i.e., the sulfurization of predeposited very‐thin (≈1.2 nm) Mo films at a temperature of 700 °C. Current–voltage characteristics of MoS2/n+‐4H‐SiC junctions collected by conductive atomic force microscopy show a pronounced negative differential resistance even at room temperature, which is a typical manifestation of band‐to‐band tunneling between degenerately p+‐/n+‐doped semiconductors. Here, the degenerate p+‐type doping of MoS2, with Nholes ≈ 4 × 1019 cm−3 evaluated by Raman mapping, is ascribed to the significant MoO3 content in the film, as demonstrated by X‐ray photoelectron spectroscopy analyses. Furthermore, atomic resolution transmission electron microscopy analyses reveal the presence of an ultrathin (≈1 nm) SiO2 tunneling barrier between MoS2 and 4H‐SiC, formed during the sulfurization process. The observation of Esaki diode behavior in MoS2 heterojunctions with 4H‐SiC opens new perspectives for this material system as a platform for ultrafast low‐power consumption digital applications.

MoS2 doping and concentration optimization for application-specific design of P3HT-viologen-based solid state electrochromic device

Methods to improve the performance of solid state electrochromic devices (ECDs) need to be explored and the dynamic doping process must be optimized to achieve ideal device performance. Molybdenum disulphide (MoS2) doped ECD has been fabricated by using two conducting polymeric films, i.e. polythiophene (P3HT) and ethyl viologen (EV), to investigate the role of 2D material doping on the overall device performance. Hydrothermally grown MoS2 nanoflowers, characterized using x-ray diffraction, electron microscopy and Raman spectroscopy were used for this purpose. Furthermore, the effect of MoS2 dopant concentration on the performance of an EV/P3HT-based ECD was studied systematically. The prepared solid-state ECD shows improved electrochromic performance in terms of switching speed, color contrast and coloration efficiency while switching its color from one state to the other (magenta and blue) under a very small external bias (±1.4 V). The transition from colored to bleached state is fastest for the highest (0.3 wt%) MoS2-doped ECD, whereas the color contrast and coloration efficiency is maximum for the lowest (0.1 wt%) MoS2-doped device. The variation in electrochromic parameters as a function of dopant (MoS2) concentration reveals that an appropriate concentration must be chosen depending on the requirement

Compact Super Electron-Donor to Monolayer MoS2.

The surface functionalization of two-dimensional (2D) materials with organic electron donors (OEDs) is a powerful tool to modulate the electronic properties of the material. Here we report a novel molecular dopant, Me-OED, that demonstrates record-breaking molecular doping to MoS2, achieving a carrier density of 1.10 ± 0.37 × 1014 cm-2 at optimal functionalization conditions; the achieved carrier density is much higher than those by other OEDs such as benzyl viologen and an OED based on 4,4'-bipyridine. This impressive doping power is attributed to the compact size of Me-OED, which leads to high surface coverage on MoS2. To confirm, we study tBu-OED, which has an identical reduction potential to Me-OED but is significantly larger. Using field-effect transistor measurements and spectroscopic characterization, we estimate the doping powers of Me- and tBu-OED are 0.22-0.44 and 0.11 electrons per molecule, respectively, in good agreement with calculations. Our results demonstrate that the small size of Me-OED is critical to maximizing the surface coverage and molecular interactions with MoS2, enabling us to achieve unprecedented doping of MoS2.

A High‐Speed Photodetector Fabricated with Tungsten‐Doped MoS2 by Ion Implantation

AbstractMolybdenum disulfide (MoS2) is a promising 2D semiconductor material for its unique characteristics such as tunable bandgap, high electrical conductivity, and strong light–matter interaction. Presently, many efforts have been made to modulate its properties, such as surface engineering, strain introduction, doping, and so on. Recently, it has been proved that substitutional metal doping is an effective approach to tune the energy bandgap of the aimed material and improve the performance of the device. Conventional metal doping methods will inevitably introduce impurities or defects and cannot control doping regions. Ion implantation is widely used in traditional semiconductor modification processes due to its high efficiency, controllability, and homogeneity. But it is rarely applied to 2D materials because of the damage caused during the implantation process. Here, the SiO2 substrate is implanted by tungsten ion implantation and then the tungsten doping of MoS2 is successfully achieved by chemical vapor deposition (CVD) growth process, while avoiding direct implantation damage to it. The W‐doped MoS2 photodetectors show a high‐speed response with a rise/fall time of 210 ms/160 ms. This work provides a novel doping strategy for metal doping of 2D materials and opens a new avenue to modify 2D materials properties.

RF Sputtered Nb-Doped MoS2 Thin Film for Effective Detection of NO2 Gas Molecules: Theoretical and Experimental Studies.

Doping plays a significant role in affecting the physical and chemical properties of two-dimensional (2D) dichalcogenide materials. Controllable doping is one of the major factors in the modification of the electronic and mechanical properties of 2D materials. MoS2 2D materials have gained significant attention in gas sensing owing to their high surface-to-volume ratio. However, low response and recovery time hinder their application in practical gas sensors. Herein, we report the enhanced gas response and recovery of Nb-doped MoS2 gas sensor synthesized through physical vapor deposition (PVD) toward NO2 at different temperatures. The electronic states of MoS2 and Nb-doped MOS2 monolayers grown by PVD were analyzed based on their work functions. Doping with Nb increases the work function of MoS2 and its electronic properties. The Nb-doped MoS2 showed an ultrafast response and recovery time of trec = 30/85 s toward 5 ppm of NO2 at their optimal operating temperature (100 °C). The experimental results complement the electron difference density functional theory calculation, showing both physisorption and chemisorption of NO2 gas molecules on niobium substitution doping in MoS2.

Bilayer MoS2 on silicon for higher terahertz amplitude modulation

The terahertz (THz) amplitude modulation has been experimentally demonstrated by employing bilayer molybdenum disulfide (MoS2) on high-resistivity silicon (Si). The Raman spectroscopy and x-ray photoelectron spectra confirm the formation of bilayer MoS2 film. The THz transmission measurements are carried out using a continuous wave (CW) frequency-domain THz system. This reveals the higher modulation depth covering wide THz spectra of 0.1–1 THz at low optical pumping power. The modulation depth up to 72.3% at 0.1 THz and 62.8% at 0.9 THz under low power optical excitation is achieved. After annealing, the strong built-in electric field is induced at the MoS2–Si interface due to p-type doping in MoS2. This improves modulation depth to 86.4% and 79.7%, respectively. The finite-difference time-domain (FDTD) based numerical simulations match well with the experimental results. The higher modulation depth at low optical power, broadband response, low insertion losses, and simplicity in the design are the key attributes of this THz modulator.

Electrospun PCL/MoS2 Nanofiber Membranes Combined with NIR-Triggered Photothermal Therapy to Accelerate Bone Regeneration.

Electrospun nanofiber membranes have been widely used for guided bone regeneration (GBR). For assistance in bone healing, photothermal therapy which renders moderate heat stimulation to defect regions by near-infrared (NIR) light irradiation has attracted much attention in recent years. Combined with photothermal therapy, novel electrospun poly(ε-caprolactone)/molybdenum disulfide (PCL/MoS2 ) nanofiber membranes are innovatively synthesized as GBR for bone therapy, wherein the exfoliated MoS2 nanosheets served as osteogenic enhancers and NIR photothermal agents. With the doping of MoS2 , the mechanical properties of nanofiber membranes got improved with the degradation unaffected. The composite PCL/MoS2 membranes show enhanced cell growth and osteogenic performance compared with PCL alone. Under NIR-triggered mild photothermal therapy, osteogenesis and bone healing are accelerated by using PCL/MoS2 nanofiber membranes for growth of bone mesenchymal stem cells in vitro and repair of rat tibia bone defect in vivo. The novel nanofiber membranes may be developed as intelligent GBR in the therapy of bone defects.

Substitutional Doping of MoS2 for Superior Gas-Sensing Applications: A Proof of Concept.

Two-dimensional layered materials (like MoS2 and WS2) those are being used as sensing layers in chemoresistive gas sensors suffer from poor sensitivity and selectivity. Mere surface functionalization (decorating of material surface) with metal nanoparticles (NPs) might not improve the sensor performance significantly. In this respect, doping of the layered material can play a significant role. Here, we report a simple yet effective substitutional doping technique to dope MoS2 with noble metals. Through various material characterization techniques like X-ray diffraction, scanning tunneling spectroscopy images, and selected area electron diffraction pattern, we were able to put forward the difference between surface decoration and substitutional doping by Au at S-vacancy sites of MoS2. Lattice strain was found to exist in the Au-doped MoS2 samples, while being absent in the Au NP-decorated samples. Surface chemistry studies performed using X-ray photoelectron spectroscopy showed a shift of Mo 3d peaks to lower binding energies, thus realizing p-type doping due to Au. The blue shift of the peaks as observed in Raman spectroscopy further confirmed the p-type doping. We found that gold-doped MoS2 was more sensitive and selective toward ammonia (with a response of 150% for 500 ppm of ammonia at 90 °C) as compared to gold NP-decorated MoS2. The advantages of substitutional doping and the gas-sensing mechanism were also explained by the density functional theory study. From the first principles study, it was found that the adsorption of Au atoms on the S-vacancy site of a monolayer of the MoS2 sheet was thermodynamically favorable with the adsorption energy of 2.39 eV. We also successfully doped MoS2 with Pt using the same technique. It was found that Pt-doped MoS2 gives huge response toward humidity (60,000% at 80% relative humidity). Thus, various noble metal doping of MoS2 selectively improved the sensing response toward specific analytes. From this work, we believe that this method could also be useful to dope other layered nanomaterials to design gas sensors with improved selectivity.

Development of novel MoS2 hydrovoltaic nanogenerators for electricity generation from moving NaCl droplet

Competence of two-dimensional (2D) material e.g. MoS2 for developing efficient seawater energy harvester has been investigated as sea water stores huge amount of clean energy in its dynamic form. Hydrovoltaic nanogenerators has been fabricated using MoS2 monolayer grown by pulsed laser deposition (PLD) technique. Fabricated MoS2 nanogenerators are found to generate voltage>7 V by the dynamic flow of NaCl electrolyte over MoS2 monolayer. Good quality large area growth of MoS2 monolayer using PLD technique was confirmed by Raman spectroscopy, Photoluminescence (PL), in-situ RHEED and XPS. Obtained high voltage from MoS2 hydrovoltaic nanogenerators has been explained using equivalent circuit model considering dynamic charging and discharging process in formed electric double layer with successive movement of NaCl droplet. Substrate dependent nanogenerator performance was investigated and it was concluded that unintentional doping of MoS2 provided by underlying substrates is crucial for enhancing the power generation. Present work opens the possibility of using MoS2 monolayer as practical nanogenerator for energy harvesting from sea water (0.6 M NaCl) as demonstrated.

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS2 Exfoliated on Gold and Transferred to an Insulating Substrate.

Gold-assisted mechanical exfoliation currently represents a promising method to separate ultralarge (centimeter scale) transition metal dichalcogenide (TMD) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between Au and chalcogen atoms is key to achieving this nearly perfect 1L exfoliation yield. On the other hand, it may significantly affect the doping and strain of 1L TMDs in contact with Au. In this paper, we systematically investigated the morphology, strain, doping, and electrical properties of large area 1L MoS2 exfoliated on ultraflat Au films (0.16–0.21 nm roughness) and finally transferred to an insulating Al2O3 substrate. Raman mapping and correlative analysis of the E′ and A1′ peak positions revealed a moderate tensile strain (ε ≈ 0.2%) and p-type doping (n ≈ −0.25 × 1013 cm–2) of 1L MoS2 in contact with Au. Nanoscale resolution current mapping and current–voltage (I–V) measurements by conductive atomic force microscopy (C-AFM) showed direct tunneling across the 1L MoS2 on Au, with a broad distribution of tunneling barrier values (ΦB from 0.7 to 1.7 eV) consistent with p-type doping of MoS2. After the final transfer of 1L MoS2 on Al2O3/Si, the strain was converted to compressive strain (ε ≈ −0.25%). Furthermore, an n-type doping (n ≈ 0.5 × 1013 cm–2) was deduced by Raman mapping and confirmed by electrical measurements of an Al2O3/Si back-gated 1L MoS2 transistor. These results provide a deeper understanding of the Au-assisted exfoliation mechanism and can contribute to its widespread application for the realization of novel devices and artificial vdW heterostructures.

Robust ferromagnetism in Mn and Co doped 2D-MoS2 nanosheets: Dopant and phase segregation effects

We investigate the structural and ferromagnetic properties of Mo1-xMnxS2 and Mo1-xCoxS2 (x = 0, 0.025, 0.05, 0.075, 0.1 and 0.25) nanosheets synthesized by a wet chemical process. X-ray diffraction (XRD) patterns confirm the 2H polytype of MoS2 for both pristine and doped nanosheets. From X-ray absorption near-edge spectral (XANES) studies, Mn doping in MoS2 is found to be very ineffective even for x up to 0.25 and is found to be in Mn4+ oxidation state. Cobalt doping in MoS2 is very effective and found in a mixed oxidation state of 2+/3+. For x > 0.05, Co9S8 secondary phase is discerned in XRD. XANES and extended X-ray absorption fine structure study further confirm the absence of Co, Mn clusters. All the MoS2 nanosheets are multi-layered (~10 to 20 layers) as discerned from Raman and high-resolution transmission electron microscopy (HRTEM) studies. HRTEM images also show the presence of planar and edge defects in MoS2 nanosheets. These defects arise from the bends, tears, folds and edges of the nanosheets. In addition to these defects, sulphur vacancy point defects are predominant as evidenced from electron paramagnetic resonance signal at g = 2.03. Pristine MoS2 nanosheets exhibit weak ferromagnetism [magnetization (MS) = 19 × 10−3 emu/g and 1.3 × 10−3 emu/g at T = 5 K and 300 K] mostly arising from the planar defects. While the magnetization increases roughly 6 (3) times higher for Mn-doped MoS2 compared to the pristine MoS2 nanosheets at 300 K (5 K). For Co-doped MoS2 nanosheets 7 times increase in MS is found at 300 K, however, the changes are minimal at 5 K. A small change in MS for Mo1-xMnxS2 nanosheets is due to ineffective Mn substitution at Mo sites. On the contrary, Co doped samples exhibit strong paramagnetic contribution at 5 K. Despite effective substitution of Co in MoS2, the saturation magnetization values obtained after subtracting the paramagnetic component are slightly less compared to Mn doped samples. This is most probably due to the dominant antiferromagnetic interaction and the Co9S8 phase segregation. Thus, our experiments show that controlled Mn and Co doping in the low concentration (x < 0.05) is a promising candidate for enabling ferromagnetism in MoS2 nanosheets for spintronics and sensor applications.

Adsorption and dissociation of [formula omitted] on [formula omitted] doped with p-block elements

Nitrogen dioxide (NO2) is a chemical compound produced in large amounts as a byproduct of combustion in vehicles and industrial processes. In its gas form, it is harmful to both human health and the environment causing acid rain, greenhouse effects, and a variety of respiratory symptoms. Hence, significant effort has been put into its detection and removal including studies on low-dimensional layered materials. Those have shown that molecules of NO2 have a good affinity for surfaces of molybdenum disulfide (MoS2). This allows for NO2 detection, however, the interaction is too weak for its effective accumulation or subsequent catalysis. Consequently, this work investigates, employing density functional theory, doping of MoS2 for enhanced NO2 adsorption, and the extent to which it affects the molecule. The results show that the strength of molecule-substrate interaction depends on the changes in the orbital population of the dopant. This results in different adsorption configurations with varying energies and molecule-substrate charge transfers. The changes allow Cl-MoS2 to be more suitable for detection, and Ge-MoS2 accumulation of NO2. Also, due to the interaction strength, the Si and P doped monolayers facilitate dissociation of NO2 into NO. Thus, tuning the potential of MoS2 for surface catalysis.

Ni-doped MoS2 modified graphitic carbon nitride layered hetero-nanostructures as highly efficient photocatalysts for environmental remediation

Highly efficient and cost-effective photocatalysts are among the most prominent targets in the field of environmental remediation and clean energy production. Here, we report that 2D/2D layer heterostructures composed of exfoliated Ni-doped MoS2 nanosheets and g-C3N4 layers can carry out photocatalytic Cr(VI) reduction in aqueous solutions with outstanding activity, exhibiting apparent QYs as high as 29.6 % and 23.7 % at 375 and 410 nm. We show that Ni doping of MoS2 markedly increases the photochemical activity, which, together with electrochemical, spectroscopic and theoretical DFT studies, arises from the enhanced carrier density and mobility at the Ni-MoS2/g-C3N4 interface. In addition to the favorable charge transport properties, delineation of the photoinduced oxidation reactions by gas monitoring techniques reveals that the high efficiency also arises from fast water oxidation kinetics. The results of this work mark an important step forward in understanding and designing low-cost and earth-abundant catalysts for detoxification of Cr(VI)-contaminated industrial effluents.

The effect of Cl- and N-doped MoS2 and WS2 coated on epitaxial graphene in gas-sensing applications

In this study, epitaxial graphene (EG) was grown on a 6H-SiC (0001) substrate via the thermal decomposition of SiC. Undoped and Cl- or N-doped molybdenum disulfide (MoS2) and tungsten disulfide (WS2) ultrathin films were spin-coated on the graphene surface. The scanning electron microscopy (SEM) images and topological atomic force microscopy (AFM) analysis showed good distribution of thin MoS2 and WS2 flakes on the EG surface. The X-ray photoelectron spectroscopy (XPS) confirmed the presence of Mo-related peaks of 3d5/2 and 3d3/2 at ~ 232.2 eV and 235.1 eV, respectively. It also represented peaks of W 4f7/2 and 5p5/2 at around 36.1 eV and 37.9 eV, respectively. Moreover, XPS results showed peaks at around 167.4 eV and 168.4 eV corresponding to S 2p for MoS2 and WS2, respectively. The XPS results also confirmed the presence of dopant elements in MoS2 and WS2 flakes. We fabricated sensors using undoped and chlorine- or nitrogen-doped MoS2 and WS2 ultrathin films for gas-sensing applications. These sensors were surveyed for ammonia (NH3) and nitrogen dioxide (NO2) gas sensing. As in NO2, both undoped sensors react with a decrease in relative sensor responses to NH3, hence showing n-type behavior. Doping MoS2 and WS2 with chlorine led to a higher response vis-à-vis the nitrogen-doped sensors. The absolute relative response of Cl-doped WS2 and MoS2 was about 3.5 and 1.8 times more than that of their undoped counterparts toward NH3. A change of direction with a slightly smaller response (approximately × 0.8), however, could also be observed in the doping of MoS2 and WS2 with nitrogen. When exposed to NO2, the Cl-doped WS2 sensor response was 1.2 more than the N-doped one, while for MoS2 these values changed in the range of 1.2 – 1.6 for different flows of gas.

Plasmon Triggered, Enhanced Light–Matter Interactions in Au–MoS2 Coupled System with Superior Photosensitivity

Enhanced light–matter interactions by integrating plasmonic Au nanostructures as a light harvester on two-dimensional (2D) MoS2 carrier sink layers are reported, leading to broadband optical absorption and significantly enhanced Raman scattering intensity. The calculations of electronic band structure using density functional theory analysis and optical simulations elucidate the metal induced doping in MoS2 and the enhancement of electromagnetic field through localized surface plasmon resonance at the Au/MoS2 interface by forming a number of hot spots, corroborating the spectroscopic results. The ultrafast time-domain results reveal a 200-fold enhancement in the carriers’ lifetime for nanohybrids, as compared to the control sample, which is attributed to the efficient transfer of hot electrons from Au to MoS2. Fabricated metal–semiconductor–metal photodetectors using hybrid nanostructures exhibit a 20-fold enhancement of photoresponsivity (∼1.5 A/W at 640 nm) as compared to pristine MoS2 and a remarkably high peak detectivity (∼4.75 × 1013 Jones at 3 V), which are promising for broadband and multicolor photodetection, making them attractive for large area 2D materials-based nanophotonic devices.

Interfacial Charge Transfer Induced Electronic Property Tuning of MoS2 by Molecular FunctionalizationSupported by the National Natural Science Foundation of China (Grant No. 22002031), the Natural Science Foundation of Zhejiang Province (Grant No. LY18F010019), and the Innovation Project in Hangzhou for Returned Scholar.

The modulation of electrical properties of MoS2 has attracted extensive research interest because of its potential applications in electronic and optoelectronic devices. Herein, interfacial charge transfer induced electronic property tuning of MoS2 are investigated by in situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy measurements. A downward band-bending of MoS2-related electronic states along with the decreasing work function, which are induced by the electron transfer from Cs overlayers to MoS2, is observed after the functionalization of MoS2 with Cs, leading to n-type doping. Meanwhile, when MoS2 is modified with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4-TCNQ), an upward band-bending of MoS2-related electronic states along with the increasing work function is observed at the interfaces. This is attributed to the electron depletion within MoS2 due to the strong electron withdrawing property of F 4-TCNQ, indicating p-type doping of MoS2. Our findings reveal that surface transfer doping is an effective approach for electronic property tuning of MoS2 and paves the way to optimize its performance in electronic and optoelectronic devices.

Fabrication of heterogeneous interface and phosphorus doping in MoS2 for efficient hydrogen evolution in both acid and alkaline electrolytes

Reasonable design of non-precious metal electrocatalysts with high catalytic activity plays a crucial role in promoting the sustainable development of hydrogen energy. Herein, to improve both the active sites and intrinsic conductivity of molybdenum disulfide (MoS2), a facile ionic liquid-assisted hydrothermal method and subsequent phosphorization treatment are fabricated for advanced electrochemical hydrogen evolution reaction (HER) performance. The obtained P-CoS1.097@MoS2/CC heterostructure exhibits a low overpotential of 98 mV and 88 mV at the current density of 10 mA cm−2 in 0.5 M H2SO4 and 1 M KOH, respectively. The remarkable performance is due to the synergistic effects of the constructed heterogeneous interface between CoS1.097 and MoS2 as well as sulfur vacancies generated by the phosphorus doping. Therefore, fast electron transfer and large number of catalytic active sites can be achieved by means of such advantageous strategy. This research paves the way for the development of MoS2-based catalysts through the cooperative design of doping and interface engineering toward efficient HER process.