Molybdenum Disulfide Films Research Articles

Piezoelectric-enhanced MoS2@PVDF-HFP composite for photocatalytic degradation of tetracycline

In this work, composite films of molybdenum disulfide (MoS2) with poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) were fabricated using aqueous phase transformation and hydrothermal methods, aiming at efficiently degrading tetracycline hydrochloride (TC). The findings revealed that the degradation efficiency of TC by MoS2@PVDF-HFP, when subjected to a combined photocatalysis process involving a simulated pressure electric field and aeration, reached a remarkable 96.11% within 1 hour-surpassing the performance observed under individual conditions. The changes in the electron density cloud on the films surface induced by the pressure electric field and the acceleration of electron transfer rate between contact interfaces were evident. Notably, the composite films exhibited a stable performance with a TC removal rate of 90.23% after five cycles, including a relatively stable degree of mineralization. We employed Density Functional Theory (DFT) to investigate the changes in the state density of MoS2@PVDF-HFP under different conditions, such as compressive stress, tension, and no force. This further clarified the mechanism of piezoelectric coupling photocatalysis promoting induced charge transfer on the films surface. The research findings presented in this paper provide a promising avenue for the application of piezoelectric field-assisted photocatalysis in enhancing material performance.

Electronic Barriers Behavioral Analysis of a Schottky Diode Structure Featuring Two-Dimensional MoS2

This research presents a comprehensive study of a Schottky diode fabricated using a gold wafer and a bilayer molybdenum disulfide (MoS2) film. Through detailed simulations, we investigated the electric field distribution, potential profile, carrier concentration, and current–voltage characteristics of the device. Our findings confirm the successful formation of a Schottky barrier at the Au/MoS2 interface, characterized by a distinct nonlinear I–V relationship. Comparative analysis revealed that the Au/MoS2 diode significantly outperforms a traditional W/Si structure in terms of rectification performance. The Au/MoS2 diode exhibited a current density of 1.84 × 10−9 A/cm2, substantially lower than the 3.62 × 10−5 A/cm2 in the W/Si diode. Furthermore, the simulated I–V curves of the Au/MoS2 diode closely resembled the ideal diode curve, with a Pearson correlation coefficient of approximately 0.9991, indicating an ideality factor near 1. A key factor contributing to the superior rectification performance of the Au/MoS2 diode is its higher Schottky barrier height of 0.9 eV compared to the 0.67 eV of W/Si. This increased barrier height is evident in the band diagram analysis, which further elucidates the underlying physics of Schottky barrier formation in the Au/MoS2 junction. This research provides insights into the electronic properties of Schottky contacts based on two-dimensional MoS2, particularly the relationship between electronic barriers, system dimensions, and current flow. The demonstration of high-ideality-factor Au/MoS2 diodes contributes to the design and optimization of future electronic and optoelectronic devices based on 2D materials. These findings have implications for advancements in semiconductor technology, potentially enabling the development of smaller, more efficient, and flexible devices.

MoS2high temperature sensitive element with a single Si3N4protective layer.

Temperature sensors find extensive applications in industrial production, defense, and military sectors. However, conventional temperature sensors are limited to operating temperatures below 200°C and are unsuitable for detecting extremely high temperatures. In this paper, a method for thermal protection of molybdenum disulfide (MoS2) films is proposed and a MoS2 high temperature sensor is prepared. By depositing a monolayer of Si3N4 onto MoS2, not only is the issue of high-temperature oxidation effectively addressed, but also the contamination by impurities that could potentially compromise the performance of MoS2 is prevented. Moreover, the width of the Schottky barrier of metal/MoS2 is reduced by using PECVD deposition of 400 nm Si3N4 to form an ohmic contact, which improves the electrical performance of the device by three orders of magnitude. The sensor exhibits a positive temperature coefficient measurement range of 25 to 550°C, with a maximum temperature coefficient of resistance (TCR) of 0.32%·°C-1. The thermal protection method proposed in this paper provides a new idea for the fabrication of high-temperature sensors, which is expected to be applied in the high-temperature field.&#xD.

Frictional properties and environmental adaptability of Ti-MoS2/WC multilayer films

Magnetron-sputtered molybdenum disulfide films are extensively utilized as solid lubricating coatings in space applications as a result of their low friction coefficient and minimal contamination. However, MoS2-based films are sensitive to hygrothermal and oxidation environment, and are easily oxidized to form MoO3, which results in high friction and wear of the films, significantly reducing their operational lifespan. Especially when the spacecraft adopts the launching mode of coastal launch or ocean platform, the performance deterioration caused by oxidation of MoS2 films during transportation, storage and launch is more serious. Therefore, to enhance the frictional performance and oxidation resistance of the films in humid and salt spray environments, the Ti-MoS2/WC multilayer films with preferred (002) crystal plane orientation were prepared, achieving a friction coefficient of 0.009 in a vacuum environment and a wear rate of 1.1×10-7 mm3/N∗m. In particular, the film can maintain this extremely low coefficient of friction even after exposure to moisture or salt spray. These findings demonstrate that the dual doping of Ti and WC and the design of multilayer structures enable MoS2 films to achieve outstanding frictional performance and oxidation resistance. This is crucial for designing MoS2 films with excellent environmental adaptability.

Molybdenum Disulfide (MoS2) Film Formation and Friction Properties of Molybdenum Phosphate Additive in Combined Condition with Zinc Dialkyldithiophosphate (ZnDTP)

This article describes experimental studies on low friction film formation of molybdenum phosphate (MoP) in combination with zinc dialkyldithiophosphate (ZnDTP). The spinning type friction tests were conducted, and in the test procedure, the test using ZnDTP containing oil was conducted following the test using MoP oil. The results showed that after switching to ZnDTP, the friction coefficient steeply decreased and reached approximately 0.06 in 1,353 ppm of sulfur concentration, and minimum friction coefficient depended on the concentration of sulfur in the oil with ZnDTP. Moreover, it is shown that the friction coefficient gradually increased, and that the coefficient at 1 h after switching to ZnDTP corresponded to that in ZnDTP alone. Raman spectroscopy demonstrated that, at 5 min after switching to ZnDTP, the molybdenum disulfide (MoS2) film was formed on the contact surface. Also, energy dispersive x-ray spectroscopy (EDX) analysis results indicated that at 1 h after switching to ZnDTP, the film derived from ZnDTP was composed of phosphorus, oxygen, and sulfur. These results suggest the film formation mechanism of MoS2: molybdenum oxide, such as iron (II) molybdate (FeMoO4), formed in the test of MoP, was then transformed into MoS2 by sulfur or a sulfur containing compound from ZnDTP decomposition.

Rapid synthesis of MoS2 for transistors and memristors

This study presents a rapid synthesis method using carbon fibers, converting ammonium tetrathiomolybdate to molybdenum disulfide films with controllable thickness (1–5 nm) and smooth surface (200 pm on average) in tens of seconds. Electronic devices based on these multilayers exhibit promising performance: memristors operate at an average of 1.5 V; field-effect transistors display electron mobility ranging from 0.1 to 0.4 cm2/V·s with a 103 on/off ratio. The electrical performance can be enhanced by optimizing annealing recipes. This scalable, time-efficient method holds the potential for large-scale production of multilayer two-dimensional semiconductors for electronics.

CVD growth of large-area, continuous, and defect-free MoS2 multilayer films from solution-cast seed nanoflakes

Defects in transition metal dichalcogenides are among the primary source of their chemical reactivity, including their response to water. The CVD growth of defect-free continuous molybdenum disulfide (MoS2) films has been particularly challenging. In this work, we demonstrate the growth of large-area continuous films of MoS2 using solution-cast MoS2 seed nanoflakes, both with and without the assistance of alkali halide. The MoS2 seed nanoflakes serve as nucleation sites for the in-plane growth of few-layer MoS2, which is accompanied by localized vertical growth of MoS2 particles. For films grown with the combination of seed and NaCl, very low oxygen content was observed together with the stoichiometric ratio of Mo: S being close to the ideal value of 1: 2. These films show humidity-insensitive electrical response over a wide interval (5%–95% RH). This is attributed to very low concentrations of edge and basal-plane defects, leading to low water dissociation and restricted proton transport.

Eight In. Wafer-Scale Epitaxial Monolayer MoS2.

Large-scale, high-quality, and uniform monolayer molybdenum disulfide(MoS2) films are crucial for their applications in next-generation electronics and optoelectronics. Epitaxy is a mainstream technique for achieving high-quality MoS2 films and is demonstrated at a wafer scale up to 4-in. In this study, the epitaxial growth of 8-in. wafer-scale highly oriented monolayer MoS2 on sapphire is reported as with excellent spatial homogeneity, using a specially designed vertical chemical vapor deposition (VCVD) system. Field effect transistors (FETs) based on the as-grown 8-in. wafer-scale monolayer MoS2 film are fabricated and exhibit high performances, with an average mobility and an on/off ratio of 53.5 cm2 V-1 s-1 and 107, respectively. In addition, batch fabrication of logic devices and 11-stage ring oscillators are also demonstrated, showcasing excellent electrical functions. This work may pave the way of MoS2 in practical industry-scale applications.

Effect of vacuum atomic oxygen irradiation on tribological properties of MoS2/WC multilayer films

The adaptability of molybdenum disulfide (MoS2) films in space environments is crucial for aerospace applications. However, atomic oxygen (AO) in low Earth orbit can damage the friction and wear performance of MoS2 films, leading to a reduction in the service life of the film. To enhance the resistance of the film to atomic oxygen irradiation, we constructed a nano-multilayer structure composed of MoS2-WC-MoS2. Studies have shown that MoS2/WC multilayer films exhibit an ultra-low friction coefficient of 0.010 due to their (002) preferred orientation. Even after high-dose AO irradiatione at 1.84 × 1020 atoms·cm−2, the film still maintains a friction coefficient of 0.009. This is attributed to the presence of MeOX nanoparticles in the MoS2 transfer film at the friction interface after AO irradiation, and the existence of MeOX nanoparticles plays a key role in maintaining ultra-low friction of the film. These findings are of great significance for extending the service life of molybdenum disulfide films in space environments and enhancing their resistance to atomic oxygen irradiation.

Thermal investigation of Pd interface with molybdenum disulfide

The thermal stability of molybdenum disulfide (MoS2) films, and particularly of the 1T-MoS2 metallic phase, plays a crucial role in their applicability across diverse technological fields. In this research, we successfully achieved a phase transition of multilayer MoS2 nanosheets from the semiconducting 2H phase to the metallic 1T phase through Pd substitution of Mo atoms on non-stoichiometric (sulfur-rich) MoS2 substrates and MoS2 hybrids with reduced graphene oxide (MoS2-rGO). This investigation involved studying the thermal stability of MoS2 thin films with mixed 1T-2H phases, up to 500 °C, in an ultra-high vacuum (UHV) environment. Our findings indicate that the 1T phase transforms to the 2H semiconducting stable phase at different temperatures, depending on the surface chemistry. In sulfur-rich substrates, the 1T phase remains present up to approximately 400 °C, while it vanishes on the stoichiometric MoS2-rGO films. Notably, enhanced thermal stability of the 1T phase is achieved with a sulfur surplus, regardless of the presence of rGO. Furthermore, during annealing, we observed Pd sintering, accompanied by a chemical state change from metallic Pd0 to Pd2+. These results elucidate the stability of 1T-MoS2 within an acceptable temperature range for the catalytic process and energy applications involving MoS2.

Post-annealing in ultra-high vacuum or nitrogen plasma for MoS2 thin films deposited by magnetron sputtering

The thin films of amorphous molybdenum disulfide were deposited at room temperature by magnetron sputtering technique. Post-annealing process in ultra-high vacuum (∼10−8 Pa) or nitrogen plasma environments at the temperatures of 300, 400, 500, and 700 °C have been first proposed to enhance the microstructure and optical properties of MoS2 thin films. The phase transformation of MoS2 thin films from amorphous to polycrystalline was characterized by in situ reflection high-energy electron diffraction during the post-annealing process. The microstructure of MoS2 thin films was also analyzed by Raman spectrum and X-ray diffractometer after the post-annealing process. In addition, the thermal analysis of the differential scanning calorimeter and optical measurement of photoreflectance confirmed the phase transformation of MoS2 thin films. The analysis of photoreflectance also estimated the exciton transition at the bandgap energy of 2.038 eV at 0 K, attributed by the crystalline MoS2 film annealed at 700 °C in ultra-high vacuum. The surface chemical composition of MoS2 thin films has been identified by X-ray photoelectron spectroscopy, but the desulfurization of MoS2 was observed after post-annealing in ultra-high vacuum. Moreover, the preferred orientation of (004) plane in the MoS2 films was performed as the increase in post-annealing temperature.

Enhancing mechanical performance and high-temperature lubrication enabled by MoS2/WB2 nanolayered films

Molybdenum disulfide (MoS2) films are widespread application in aerospace, nuclear, mechanical, and electronic fields owing to their unique structural characteristics and inherent interlayer slip. However, their utility is hindered by environmental susceptibility, particularly oxidation at elevated temperatures and in humid environments, limiting their effectiveness. Herein, we report a nanocomposite integrating MoS2 with WB2 by periodic alternating arrangement, synthesized using magnetron sputtering technology. This nanolayered architecture effectively harnesses the synergistic properties of both materials, imparting exceptional mechanical properties, superior environmental adaptability and efficient high-temperature lubrication. Methodical experiments and atomistic simulations reveal the incorporation of WB2 promotes preferential growth of MoS2 along the (002) plane, yielding an impressive hardness-to-elastic modulus ratio of approximately 0.1. The resultant film demonstrates notable achievements: a minimal friction coefficient of 0.056 and a specific wear rate of 1.88 × 10−7 mm3 N−1 m−1 in humid air. These findings are primarily stem from the interaction between MoS2 nanosheets and metal-oxide nanoparticles at the sliding interface. Remarkably, even at 400 °C, the engineered MoS2/WB2 nanocomposite achieves low friction and wear under high contact stress, outperforming conventional MoS2-based materials. This innovative design, complemented by insights into the high-temperature friction mechanism, holds promise for advancing the development of robust and high-temperature-resistant lubricants.

Tribological properties of graphene quantum dot hybrid polyethylene glycol lubricated molybdenum disulfide films

Herein, molybdenum disulfide (MoS2) films were obtained by magnetron sputtering, and graphene quantum dots (GQDs) prepared by the hydrothermal method were used as additives for polyethylene glycol (PEG) lubricants to investigate the tribological mechanisms under solid-liquid composite lubrication. The friction coefficient of GQDs hybridized PEG lubricated MoS2 solid-liquid composite films was reduced by 69.23%, and the wear rate was reduced by 79.31% as compared to solid lubrication (MoS2 film). This solid-liquid complex lubrication occurs mainly as abrasive wear. GQDs form a uniform and dense amorphous carbon film on the corresponding balls to protect the wear between the friction pair. This work demonstrates the great potential of zero-dimensional and two-dimensional materials for solid-liquid composite lubrication.

Low-temperature synthesis of uniform monolayer molybdenum disulfide films

Monolayer molybdenum disulfide (MoS2) has garnered significant attention owing to its potential applications in electronics and optoelectronics. Nevertheless, existing methods for the chemical vapor deposition growth of MoS2 demand elevated synthesis temperatures and involve transfer procedures, thereby restricting its effectiveness in device manufacturing. In this study, we present the direct growth of 1-in. (∼25 mm) monolayer MoS2 films on SiO2 and other substrates under low-temperature conditions (360 °C). We employed a highly reactive substance, MoO2Cl2, as the molybdenum source for growth, which significantly reduces the growth temperature of MoS2. Simultaneously, a transitional temperature zone was implemented to further lower the growth temperature of MoS2. Experimental results from multiple tests on the produced MoS2 films indicated excellent uniformity and relatively large grain size (∼5 μm) at the low growth temperature, ensuring its promising applicability Furthermore, we fabricated field-effect transistors on the SiO2, achieving a mobility of 14.3 cm2 V−1 s−1 and an Ion/Ioff ratio exceeding 105. Our method offers a versatile approach for the low-temperature growth of MoS2, paving the way for future developments in silicon process-compatible applications.

Enhanced environmental adaptability of sandwich-like MoS2/Ag/WC nanomultilayer films via Ag nanoparticle diffusion-dominated defect repair.

Robustness and environmental adaptability are crucial for molybdenum disulfide (MoS2) films to minimize friction and wear in industrial applications. However, current sputtered MoS2 films suffer from inherent defects, including insufficient hardness, poor crystallinity, and susceptibility to oxidation, thereby limiting their longevity and reliability. Here, we present a sandwich-like nanomultilayer architecture comprising alternating MoS2 and tungsten carbide (WC) layers integrated with Ag nanoparticles. This architecture demonstrates robust corrosion resistance, effectively protecting the MoS2 within the film for over 18 months of air exposure and exhibiting minimal corrosion during 21 days of salt spray tests. The remarkable environmental stability of the sandwich-like MoS2/Ag/WC nanomultilayer film is attributed to the creation of numerous heterogeneous interfaces and the spontaneous diffusion and repair of Ag atoms through defect channels of the film, impeding the penetration of corrosive agents. Furthermore, during the frictional process, Ag, characterized by its inherent high mobility and ductility, facilitates the formation of a dense tribofilm on its counterpart ball, encapsulating formed metal oxides to prevent adhesive wear. As a result, the film exhibits a significantly reduced wear rate (1.25 × 10-7 mm3 N-1 m-1) even after long-term salt spray corrosion and air exposure. This study offers a general route for designing MoS2-based materials toward long-lifetime and environmental adaptability via self-repair mechanisms.

Quantifying photoluminescence variability in monolayer molybdenum disulfide films grown by chemical vapour deposition

Monolayer molybdenum disulfide (MoS2) is a promising candidate for inclusion in optoelectronic technologies, owing to its two-dimensional (2D) nature and resultant novel photoluminescence (PL). Chemical vapour deposition (CVD) is an important method for the preparation of large-area films of monolayer MoS2. The PL character of as-prepared monolayer MoS2 must be well understood to facilitate detailed evaluation of any process-induced effects during device fabrication. We comparatively explore the PL emission from four different commercially available CVD-grown MoS2 monolayer films. We characterize the samples via Raman and PL spectroscopy, using both single-spot and mapping techniques, while atomic force microscopy (AFM) is applied to map the surface structure. Via multipeak fitting, we decompose the PL spectra into constituent exciton and trion contributions, enabling an assessment of the quality of the MoS2 monolayers. We find that the PL character varies significantly from sample to sample. We also reveal substantial inhomogeneity of the PL signal across each individual MoS2 film. We attribute the PL variation to non-uniform MoS2 film morphologies that result from the nucleation and coalescence processes during the CVD film development. Understanding the large variability in starting PL behaviour is vital to optimize the optoelectronic properties for MoS2-based devices.

Superlubricity of molybdenum disulfide film

Superlubricity is an ideal state with zero contact friction between two frictional interfaces. It has become a hot research topic for many scientists in the past 20 years, and the field spans the complex hot research directions of physics, chemistry, mechanics, and materials. The concept of superlubricity was introduced in 1990, and the understanding of the process of realizing superlubricity is vital for controlling the tribological properties of materials and promoting the development of tribology. This review focuses on the fundamental properties of molybdenum disulfide (MoS2) films and the influence of the environment on affecting MoS2 films. As a result, some methods for realizing superlubricity by MoS2 films are proposed. The key to achieving superlubricity with MoS2 is summarized. Finally, an outlook on the application of MoS2 films is given.

Tribological properties of Ti/Pb-MoS2-Graphene composite films under high environment temperature

For purpose of enhancing the tribological properties of molybdenum disulfide (MoS2) films, Ti/Pb doping and graphene dripping have been synchronously introduced to restrain the oxidation and wear under the environment temperature of 25, 100, 200, 300 and 400 °C. The MoS2, Ti-MoS2, Pb-MoS2 and Ti/Pb-MoS2 films have been prepared on the GCr15 steel substance by magnetron sputtering; and then graphene has been doped on the surface of the MoS2-based films to investigate the synergistic effects of graphene and MoS2-based films on the tribological performances tested by the UMT multifunctional friction and wear tester. Experimental results show the friction coefficient and wear rate of the MoS2-based films increase with the rising of the environment temperature. Wear mechanisms of tested under various temperatures are the co-action of oxidation wear and abrasive wear. Comparing the MoS2-graphene composite film, the Ti, Pb or Ti/Pb doped MoS2-graphene composite films tested under the environment temperature of below 400 ℃ show a low friction coefficient (less than 0.1) and a low wear rate, which is owing to the redox reaction of graphene and metal (Ti and Pb).

Hierarchically Organized MoS2 Films as Promising Electrodes for Flexible Supercapacitors

The formation of hierarchically organized MoS2 films on various substrates by a hydrothermal method was studied. The influence of synthesis conditions and the substrate (a glass or a flexible carbon paper substrate) on the crystal structure of sulfide films was determined using X-ray powder diffraction (XRD). Scanning electron microscopy (SEM) showed that the films on glass substrates comprised structurally different elements, namely a continuous dense layer of spherical nanoparticles on the surface of which hierarchically organized globular agglomerates of two types are arranged. A molybdenum disulfide shell about 1.5 μm thick, consisting of hierarchically organized nanosheets less than 10 nm thick, was formed on the surface of carbon fibers that make up the carbon paper. Elemental mapping was used to evaluate the homogeneity of the MoS2 film formed on the carbon paper. Atomic force microscopy (AFM) showed that an individual carbon fiber modified with a sulfide film had a mean square roughness of about 13 nm (over an area of about 100 μm2). According to Kelvin-probe force microscopy (KPFM) data, the electron work function of the material was 4.53 eV. The electrochemical characteristics of the manufactured flexible electrode based on a hierarchically organized molybdenum disulfide film were investigated. The specific capacitance and the stability of functional and microstructural properties of the manufactured supercapacitor electrode in 2000 charge–discharge cycles were evaluated. Thus, the proposed strategy is promising for the fabrication of efficient hierarchically organized MoS2 electrodes for flexible supercapacitors.

Synthesis of binder-free nanostructured MoS2 films for optoelectronic applications

The binder-free polycrystalline nanostructured molybdenum disulfide (MoS2) films are synthesized on glass substrates placed at 15, 16 and 17 cm with respect to source material by powder vapor transport technique. The X-rays diffraction analysis confirms the development of different diffraction planes related to MoS2 and Mo2S3 phases. The formation of surface morphologies (nano-boxes and nano-fibers) of MoS2 films is associated with increasing substrate distances. The changes in reflectance (0.18–0.09), refractive index (2.52–1.91), energy band gap (1.62–2 eV), Urbach energy (0.61–1.11 eV), dielectric constant (7-5.6), dissipation factor (0.04–0.06), surface/volume energy loss functions (0.0017–0.005/0.002–0.005), optical & electrical conductivities (1.23–2.04 × 1014 s−1 and 9.86–6.70 × 1019 S m−1), single oscillator energy (5.70–3.36 eV), dispersion energy (26.45–5.80 eV), nonlinear and static refractive index (0.041–1.58 × 10−5, 5.64–2.72), linear & nonlinear optical susceptibilities (0.37–0.14 and 0.011–6.16 × 10−6) are strongly associated with increasing substrate distances. Results indicate that the synthesized MoS2 films can be used in optoelectronic and solar cell devices.