Letteratura scientifica selezionata sul tema "TMDs@SWCNTs Hybrid Heterostructure"

In today's world of technological innovation, semiconductors play a crucial role. To satisfy the escalating demand for enhanced functionalities, new concepts of mixed-dimensional heterostructure have emerged. By combining two-dimensional (2D) nanomaterials with one-dimensional (1D) nanomaterials, the resulting hybrid Van der Waals heterostructures will have improved performances due to synergistic effects. Transition Metal Chalcogenides (TMDs) and Single-Walled Carbon Nanotubes (SWCNTs) promise enhanced performances in multiple eras, notably in gas sensing. Their unique properties, like ultra-high surface-to-volume ratio, and thermal, electrical, and mechanical stability, make them suitable for such activity. [1] [2] The purpose is to create a gas sensor that has low dimensions with superior performance in terms of sensitivity, selectivity, and stability. Gas sensors that are based on high-quality WS2@SWCNTs and MoS2@SWCNTs heterostructures were fabricated using a bottom-up dry approach, employing a sequential growth method that combines Chemical Vapor Deposition and Molecular Beam Epitaxy techniques. The as-grown materials exhibit high crystalline structures and high purity at the interfaces, as demonstrated by various characterization techniques such as Raman spectroscopy, SEM, TEM, and Photoemission Analysis techniques, which are usually challenging to achieve. Additionally, a difference in electronic properties was observed. Since the electronic properties of WS2 and MoS2 are intrinsically different, an opposite type of doping was expected where the WS2@SWCNTs have proven to be an n-type semiconductor and MoS2@SWCNTs are a p-type semiconductor. This achievement opens the door to further scientific exploration and advancement. To assess their performance, various tests, including humidity sensing, temperature, and blue light excitation, have been conducted. These tests reveal interesting stability under high temperatures and elevated relative humidity conditions, with a good response recovery. Further measurements will be performed to evaluate the selectivity, sensibility, and ability to perform monitoring functioning of TMDs@SWCNTs nanosensors in the presence of different byproduct gas molecules.

Transition metal dichalcogenides (TMDs) have attracted widespread attention due to their excellent electrochemical and catalytic properties. In this work, a tungsten (W)-modulated molybdenum selenide (MoSe2)/graphene heterostructure was investigated for application in electrochemistry. MoSe2/graphene heterojunctions with low-doped W compositions were synthesized by a one-step hydrothermal catalysis approach. Based on the conducted density functional theory (DFT) calculations, it was determined that inserting a small amount of W (≈5%) into the MoSe2/graphene heterostructure resulted in the modification of its lattice structure. Additionally, an increase in the distance between layers (≈8%) and a decrease in the adsorption energy of the potassium ions (K+) (≈−1.08 eV) were observed following W doping. Overall, the electrochemical performance of the MoSe2/graphene hybrid was enhanced by the presence of W. An all-solid-state supercapacitor device prepared using electrodes based on the W-doped MoSe2/graphene composite achieved excellent capacitance of 444.4 mF cm−2 at 1 mV s−1. The results obtained herein revealed that the MoSe2/graphene hybrid exhibiting low W composition could be valuable in the field of energy storage and isoelectronic doping of TMDs.

Transition metal dichalcogenides (TMDs) are the auspicious inexpensive electrocatalysts for the hydrogen evolution reaction (HER) which has been broadly studied owing to their remarkable enactment, however the drought of factors understanding were highly influenced to hinder their electrocatalytic behavior. Recently, transition metal carbide (TMC) has also emerged as an attractive electrode material due to their excellent ionic and electronic transport behavior. In this work, Mo2C@WS2 hybrids have been fabricated through a simple chemical reaction method. Constructed heterostructure electrocatalyts presented the small Tafel slope of 59 and 95 mV per decade and low overpotential of 93 mV and 98 @10 mA·cm−2 for HER in acidic and alkaline solution, respectively. In addition, 24-h robust stability with the improved interfacial interaction demonstrated the suitability of hybrid electrocatalyst for HER than their pure form of Mo2C and WS2 structures. The derived outcomes describe the generated abundant active sites and conductivity enhancement in TMC/TMD heterostructure along with the weaken ion/electron diffusion resistance for efficient energy generation applications.

Abstract A mismatch of atomic registries between single-layer transition metal dichalcogenides (TMDs) in a two-dimensional (2D) van der Waals heterostructure produces a moiré superlattice with a periodic potential, which can be fine-tuned by introducing a twist angle between the materials. This approach is promising both for controlling the interactions between the TMDs and for engineering their electronic band structures, yet direct observation of the changes to the electronic structure introduced with varying twist angle has so far been missing. Here, we probe heterobilayers comprised of single-layer MoS2 and WS2 with twist angles ranging from 2∘ to 20∘ and determine the twist angle-dependent evolution of the electronic band structure using micro-focused angle-resolved photoemission spectroscopy. We find strong interlayer hybridization between MoS2 and WS2 electronic states at the Γ ˉ -point of the Brillouin zone, leading to a shift of the valence band maximum in the heterostructure. Replicas of the hybridized states are observed at the center of twist angle-dependent moiré mini Brillouin zones. We confirm that these replica features arise from the inherent moiré potential by comparing our experimental observations with density functional theory calculations of the superlattice dispersion. Our direct visualization of these features underscores the potential of using twisted heterobilayer semiconductors to engineer hybrid electronic states and superlattices that alter the electronic and optical properties of 2D heterostructures for a wide range of twist angles.

Two-dimensional (2D) materials, such as Graphene, h-BN and MoS2, are promising candidates in a number of advanced device applications, owing to their exceptional electrical, optical and mechanical properties. Scalable growth of high quality 2D materials is crucial for their adoption in technological applications the same way the arrival of high-quality silicon single crystals was to the semiconductor industry. While CVD growth of wafer-scale monolayer graphene and TMDs has been demonstrated, considerable challenges still remain. In this talk, we first report a CVD method to grow fluorine rich 2D polymer (2DP-F) on varies substrates for low-k dielectrics in 2D TMDs based devices. Using precursors with low vaporize temperature, a uniform and ultra-flat 2DP-F film with controlled thickness can be deposited on silicon oxide wafer, glass, sapphire and mica substrates. Dielectric properties and relevant mechanical properties were carefully characterized. These 2DP-F films were then used as the substrate for transition metal dichalcogenides (TMDs) based devices, and significant improvements in device performances were found, possibly owing to the ultra-smooth and dangling bond free surface of 2DP-F that can significantly reduce the interfacial scattering of carriers. Next, we show that atomically thin Cs3Bi2I9, an all-inorganic lead-free perovskite derivative with strong optical activity can be successfully synthesized by vapor growth method. Reducing the dimensionality of such perovskites could utilize the materials’ advantages for solid-state information devices like valleytronics. By breaking the inversion symmetry, 2D Cs3Bi2I9 flakes with odd-layer number exhibited persistent, optically addressable valley polarization. This study potentially opens generalizable CVD method for growing a broad range of 2D perovskites towards cost-effective and energy-efficient integrated device applications. Finally, we report a two-step vapor phase growth process for the creation of high-quality vdW heterostructures based on perovskites and TMDCs, such as 2D Cs3Bi2I9/MoSe2, with a large lattice mismatch. Supported by experimental and theoretical investigations, we discover that the Cs3Bi2I9/MoSe2 vdW heterostructure possesses hybrid band alignments consisting of type-I and type-II heterojunctions because of the existence of defect energy levels in Cs3Bi2I9. More importantly, we demonstrate that the type-II heterojunction in the Cs3Bi2I9/MoSe2 vdW heterostructure not only shows a higher interlayer exciton density, but also exhibits a longer interlayer exciton lifetime than traditional 2D TMDCs based type-II heterostructures. Such vdW heterostructures provide promising platforms for exploring novel physics and cutting-edge optoelectronics and valleytronics applications.

In this work, a facile oxidation strategy was developed to prepare novel tungsten disulfide/tungsten trioxide (WS2/WO3) heterostructures for adsorbing organic dyes efficiently by combining the hydrophilic property of WO3 and the superior dye affinity of WS2. The structural and elemental properties of the synthesized hybrid materials were systematically investigated, and the results demonstrated the retained flower-like morphology of the primitive WS2 and the successful introduction of WO3. Furthermore, surface properties such as a superior hydrophilicity and negative-charged potential were also demonstrated by a water contact angle characterization combined with a Zeta potential analysis. The performance of the obtained WS2/WO3 hybrid materials for removing Rhodamine B (RhB) from wastewater was evaluated. The results showed that the maximum adsorption capacity of the newly synthesized material could reach 237.1 mg/g. Besides, the adsorption isotherms were also simulated by a statistical physics monolayer model, which revealed the non-horizontal orientation of adsorbates and endothermic physical interaction. Finally, the adsorption mechanism and the recyclability revealed that the partial oxidation strategy could contribute to a higher adsorption capacity by modulating the surface properties and could be applied as a highly efficient strategy to design other transition metal dichalcogenides (TMDs) heterostructures for removing organic dyes from wastewater.

Abstract A UV-Visible broadband photodetector (PD) based on single walled carbon nanotube (SWCNT)/Zinc Oxide nanowire (ZnO NW) hybrid is being reported. This work focuses on designing a stable, fast, efficient and reliable hybrid broadband PD by surface modification of ZnO NWs using SWCNT. The study shows that spectral response of the hybrid heterostructure (HS) spans beyond the UV spectrum and into the visible region which is due to the integration of SWCNTs. Photoluminescence (PL) study reveals surface plasmon (SP) mediated resonance phenomenon resulting in an increase in PL intensity. High nanotube charge carrier mobility and conductivity allows the hybrid HS to attain high values of spectral responsivity (Rλ=187.77 A/W), external quantum efficiency (EQE=5.82×104 %), specific detectivity (D*=7.04×1011 Jones) and small noise equivalent power (NEP=4.77×10-12 W) values for the SWCNT/ZnO NW hybrid HS. The device also gives quick rise (trise=0.43 s) and fall (tfall=0.60 s) time values.

L'évolution des technologies silicium atteint ses limites intrinsèques, entraînant un besoin d'innovations en matériaux et architectures pour la miniaturisation, la sensibilité et le faible consommation d'énergie dans les dispositifs électroniques.Les dichalcogénures de métaux de transition (TMDs), avec leur épaisseur atomique et leurs propriétés optoélectroniques uniques, suscitent un vif intérêt pour des applications telles que la photodétection et la détection de gaz. Cependant, la synthèse de TMDs de haute cristallinité, contrôlée par épitaxie par faisceau moléculaire (MBE), demeure un défi, limitant souvent les performances dans les applications pratiques. En parallèle, les nanotubes de carbone monoparoi (SWCNTs) offrent des propriétés uniques telles qu'une grande surface spécifique, une conductivité ajustable et une stabilité mécanique qui peuvent améliorer la fonctionnalité des dispositifs lorsqu'ils sont intégrés aux TMDs. La combinaison de ces matériaux dans une configuration hiérarchique ouvre des perspectives pour des dispositifs multifonctionnels performants. Cette thèse explore la synthèse et la caractérisation d'hétérostructures van der Waals (vdW) hybrides TMDs@SWCNTs de haute cristallinité et leur mise en œuvre dans des dispositifs. La croissance de TMDs (disulfure de molybdène (MoS₂) et disulfure de tungstène (WS₂)) par MBE a été investiguée. L'épitaxie par van der Waals de ces TMDs (MoS₂ et WS₂) a montré la capacité de former des structures de haute cristallinité sur de substrats à désaccord de maille (quartz et C-sapphire) sans compromettre l'intégrité du matériau. Nous avons exploré une approche novatrice basée sur des techniques ultra- vide (UHV), dans un réacteur construit maison, associant successivement le dépôt chimique en phase vapeur et à filament chaud (HF-CVD) avec la MBE, et permettant une croissance hautement contrôlée sur des substrats en quartz. Nous avons réussi à synthétiser des structures hybrides TMDs@SWCNTs qui exhibent une haute cristallinité, une épaisseur uniforme allant jusqu'à 10 nm, et un contact interfacial précis. Le rôle fondamental des SWCNTs dans le mécanisme de croissance de WS₂ et MoS₂ a été élucidé à travers des caractérisations poussées, in-situ/opérando et ex-situ, ce qui a permis de proposer un mécanisme de croissance basé sur les résultats expérimentaux obtenus. La caractérisation détaillée des matériaux, incluant la spectroscopie Raman, les techniques de spectroscopie électronique de surface et la microscopie électronique en transmission (TEM), met en évidence la croissance de haute cristallinité des couches de TMD sur les modèles de SWCNT, tout en prouvant le transfert de charge entre ces matériaux. En tant que canaux actifs, ces hétérostructures ont démontré d'excellentes propriétés optiques, atteignant une responsivité (~8,1 × 10³ A/W) et une détectivité (~2,91 × 10¹³ Jones) élevées pour la détection de la lumière proche de l'ultraviolet. De plus, la forte densité de sites exposés en bord de TMDs améliore l'adsorption des molécules de gaz et accélère la réponse dans les applications de détection. Des tests d'exposition à l'humidité ont montré la stabilité de ces hétérostructures, attribuée aux interactions électroniques à l'interface TMDs@SWCNTs. En outre, les hétérostructures présentent des propriétés électroniques intrinsèques contrastées et des effets de dopage ajustables (dopage P et N), soulignant leur polyvalence. Les travaux présentés ici mettent en évidence le potentiel des hétérostructures TMDs@SWCNTs en tant que matériaux innovants et performants pour les capteurs de gaz et les photodétecteurs de nouvelle génération. En approfondissant la compréhension des dynamiques de nucléation et de croissance des nanostructures hybrides, cette recherche ouvre la voie à l'intégration des TMDs et des SWCNTs dans des dispositifs de détection polyvalents en élargissant ainsi le champ des applications potentielles
The evolution of Si-based technologies is approaching intrinsic limits, driving the need for innovative materials and architectures that support advanced miniaturization, high sensitivity, and low-power operation in electronic devices. Among the promising candidates are transition metal dichalcogenides (TMDs), whose atomic-scale thickness and unique optoelectronic properties, have garnered attention for applications such as photodetection and gas sensing. However, achieving high-crystallinity TMDs synthesis, with controlled growth parameters, via molecular beam epitaxy (MBE), remains challenging, often limiting performance in practical applications. In parallel, single-walled carbon nanotubes (SWCNTs) offer unique properties, such as high specific surface area, tunable conductivity, and mechanical stability, that can enhance device functionality when integrated with TMDs. Combining the merit of these two classes of materials in a hierarchical arrangement can unlock a new realm of multifunctional devices with enhanced performance.This thesis explores the synthesis and characterization of high crystalline TMDs@SWCNTs van der Waals (vdW) hybrid heterostructures and their implementation in device structures.TMDs (molybdenum disulfide (MoS2) and tungsten disulfide (WS2) growth by MBE were investigated. The van der Waals epitaxial growth of these TMDs (MoS2 and WS2) has demonstrated high crystalline structures on large lattice-mismatched substrates (quartz and C-sapphire) without compromising material integrity. We explored a novel approach based on ultra-high vacuum techniques (UHV), in a home-built reactor, through sequential Hot-filament chemical vapor deposition (HF-CVD) /MBE offering highly controlled growth on quartz substrates. We achieved the synthesis of TMDs@SWCNTs hybrid structures that exhibit high crystallinity, uniform thickness up to 10 nm, and precise interfacial bonding. The fundamental role of SWCNTs in the growth mechanisms of WS2 and MoS2 is elucidated through comprehensive in-situ/operando and ex-situ characterizations, leading to a proposed growth mechanism based on the obtained experimental results.Detailed material characterization, including Raman spectroscopy, surface electron spectroscopy techniques, and transmission electron microscopy (TEM), demonstrates the structural integrity and high crystallinity of the TMD layers grown on SWCNT templates, while also confirming the charge transfer between these materials. Integrated as an active channel into a device, the as-grown heterostructures have proven remarkable optical properties, achieving high Responsivity (~8.1 × 103 A/W) and Detectivity (~2.91 × 1013 Jones) for detecting near-ultraviolet light. Additionally, the synthesized TMDs@SWCNTs exhibit a high density of exposed edge sites on TMD nanoflakes, that enhance the adsorption of target gas molecules and facilitate faster response in sensing applications. Environmental humidity exposure testing further demonstrated the stability of these heterostructures, which is attributed to the distinctive electronic interactions at the TMD-SWCNT interface. Moreover, the heterostructures display contrasting intrinsic electronic properties and tunable doping effects (p and n doping), underscoring their versatility and possibility to be integrated into multifunctional devices.The work presented here underscores the potential of TMDs@SWCNTs heterostructures as scalable, high-performance materials for next-generation gas sensors and photodetectors. By advancing the understanding of nucleation and growth dynamics of hybrid nanostructures, this research paves the way for integrating TMDs and SWCNTs into versatile sensing platforms with superior response characteristics, laying a foundation for applications spanning environmental monitoring and optoelectronics