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One-step growth of centimeter-scale doped multilayer MoS <sub/>2</sub> films by pulsed laser-induced synthesis
摘要： Recently, two-dimensional MoS2 has attracted interest for applications in electronics, optics, energy storage, and catalysis. Furthermore, n-type or p-type doping of MoS2 can result in improved film properties, thereby expanding the range of applicability. However, the rapid preparation of large-scale MoS2 films and the e?ective doping of such films remain challenging. Herein, we report on a one-step growth method called pulsed laser-induced synthesis (PLIS) that can resolve these challenges and can quickly (5–10 min) prepare centimeter-scale MoS2 films directly and selectively on a substrate. A continuous length of up to 1.412 cm can be achieved with MoS2 films prepared by the described in situ doping of noble metals (Au, Pt, and Pd) to convert MoS2 into a p-type semiconductor was realized, consistent with the results obtained from first-principles calculations. The STEM images reveal that the phenomena of surface modification and cation substitution occur in the doped MoS2 films. The doped MoS2 films were further processed into a p-type field effect transistor with an on/off ratio of 105. Importantly, this technique can be applied to other transition metal dichalcogenides (TMDCs) while employing various doping elements; this scheme provides an innovative method for upscaling production and large-area doping of TMDC thin films.
关键词： TMDCs,MoS2,field effect transistor,doping,pulsed laser-induced synthesis
更新于2025-09-23 15:21:01
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Interplay of charge transfer and disorder in optoelectronic response in Graphene/hBN/MoS<sub>2</sub> van der Waals heterostructures
摘要： Strong optoelectronic response in the binary van der Waals heterostructures of graphene and transition metal dichalcogenides (TMDCs) is an emerging route towards high-sensitivity light sensing. While the high sensitivity is an effect of photogating of graphene due to inter-layer transfer of photo-excited carriers, the impact of intrinisic defects, such as traps and mid-gap states in the chalcogen layer remain largely unexplored. Here we employ graphene/hBN (hexagonal boron nitride)/MoS2 (molybdenum disulphide) trilayer heterostructures to explore the photogating mechanism, where the hBN layer acts as interfacial barrier to tune the charge transfer timescale. We find two new features in the photoresponse: First, an unexpected positive component in photoconductance upon illumination at short times that preceeds the conventional negative photoconductance due to charge transfer, and second, a strong negative photoresponse at infrared wavelengths (up to 1720 nm) well-below the band gap of single layer MoS2. Detailed time and gate voltage-dependence of the photoconductance indicates optically-driven charging of trap states as possible origin of these observations. The responsivity of the trilayer structure in the infrared regime was found to be extremely large (> 108 A/W at 1550 nm using 20 mV source drain bias at 180 K temperature and ≈ ?30 V back gate voltage). Our experiment demonstrates that interface engineering in the optically sensitive van der Waals heterostructures may cast crucial insight onto both inter- and intra-layer charge reorganization processes in graphene/TMDC heterostructures.
关键词： defects and disorders in TMDCs,monolayer MoS2,phototransistor,graphene,infrared photodetection,Van der Waals heterostructures
更新于2025-09-23 15:19:57
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Laser annealing towards high-performance monolayer MoS2 and WSe2 field effect transistors
摘要： The transition metal dichalcogenides (TMDCs) have been intensively investigated as one of promising nanoelectronic and optoelectronic materials. However, the pervasive adsorbates on the surface of monolayer TMDCs, including oxygen and water molecules from the ambient environments, predominately degrade the device performance, thus hindering the precise applications. In this work, we report the effect of laser irradiation on the transport and photoresponse of monolayer MoS2 and WSe2 devices, and this laser annealing process is demonstrated as one straightforward approach to remove the physically adsorbed contaminations. Compared with vacuum pumping and in-situ thermal annealing treatments, the field-effect transistors after the laser annealing show more than one order of magnitude higher on-state current, and no apparent degradation of device performance at low temperature. The mobility of monolayer WSe2 devices can be enhanced by 3-4 times, and for single-layered MoS2 devices with the commonly used SiO2 as the back-gate, the mobility increases by 20 times, reaching 37 cm2 ? V?1 ? s?1. The efficient cleaning effect of the laser annealing is also supported by the reduction of channel and contact resistances revealed by the transmission line experiment. Further, the enhanced photocurrent by a factor of 10 has been obtained in the laser annealed device. These findings pave the way for the high-performance monolayer TMDCs-based electronic and optoelectronic devices with the clean surface and intrinsic properties.
关键词： TMDCs,monolayer MoS2,photoresponse,field-effect transistors,laser annealing,monolayer WSe2
更新于2025-09-19 17:13:59
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Synthesis of Monolayer MoSe2 with Controlled Nucleation via Reverse-Flow Chemical Vapor Deposition
摘要： Two-dimensional (2D) layered semiconductor materials, such as transition metal dichalcogenides (TMDCs), have attracted considerable interests because of their intriguing optical and electronic properties. Controlled growth of TMDC crystals with large grain size and atomically smooth surface is indeed desirable but remains challenging due to excessive nucleation. Here, we have synthesized high-quality monolayer, bilayer MoSe2 triangular crystals, and continuous thin films with controlled nucleation density via reverse-flow chemical vapor deposition (CVD). High crystallinity and good saturated absorption performance of MoSe2 have been systematically investigated and carefully demonstrated. Optimized nucleation and uniform morphology could be achieved via fine-tuning reverse-flow switching time, growth time and temperature, with corresponding growth kinetics proposed. Our work opens up a new approach for controllable synthesis of monolayer TMDC crystals with high yield and reliability, which promote surface/interface engineering of 2D semiconductors towards van der Waals heterostructure device applications.
关键词： controlled growth,transition metal dichalcogenides (TMDCs),MoSe2,reverse-flow chemical vapor deposition (CVD)
更新于2025-09-16 10:30:52
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Site-selective Atomic Layer Precision Thinning of MoS2 via Laser-Assisted Anisotropic Chemical Etching
摘要： Various exotic optoelectronic properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) strongly depend on their number of layers, and typically manifest in ultra-thin few- or mono-layer formats. Thus, precise manipulation of thickness and shape is essential to fully access their potential in optoelectronic applications. Here, we demonstrate site-selective atomic layer precision thinning of exfoliated MoS2 flake by laser. The oxidation mediated anisotropic chemical etching initiated from edge defects and progressed by controlled scanning of the laser beam. Thereby, the top-most layer can be preferentially removed in designed patterns without damaging the bottom flake. In addition, we could monitor the deceleration of the thinning by in-situ reflectance measurement. The apparent slow-down of the thinning rate is attributed to the sharp reduction in the temperature of the flake due to thickness dependent optical properties. Fabrication of monolayer stripes by laser thinning suggests potential applications in non-linear optical gratings. The proposed thinning method would offer a unique and rather straightforward way to obtain arbitrary shape and thickness of TMDCs flake for various optoelectronic applications.
关键词： Laser Thinning,Single layer precision thinning,Non-linear optical grating,Anisotropic chemical etching,TMDCs,MoS2
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Miramar Beach, FL, USA (2019.8.19-2019.8.21)] 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - 2D TMDCs-Based NIR Photodetector on a Silicon Microring Cavity
摘要： Here, we report a photodetector (PD) based on heterogeneous integration of Few-layer MoTe2 integrated on MRR by using our developed 2D printer technique. The device is realized in a two-terminal in-plane electrode configuration without applying external gating, showing a responsivity of (~0.1 A/W).
关键词： TMDCs,micro-ring resonator,photonic integration,2D materials,photodetector
更新于2025-09-11 14:15:04
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Accelerated synthesis of atomically-thin 2D quantum materials by a novel laser-assisted synthesis technique
摘要： Two-dimensional (2D) layered materials including transition metal dichalcogenides (TMDCs) have recently been at the heart of the quantum materials and information sciences research due to unusual properties associated with their firmly defined dimensionalities. Many efforts have focused on developing new methods for the accelerated growth and discovery of 2D materials, including physical and chemical vapor deposition techniques. However, the synthesis of these multi-component crystals in the gas phase has been extremely challenging due to complex and uncontrolled gas-phase reactions and flow dynamics. Here, we demonstrate a novel laser-assisted synthesis technique (LAST), which significantly reduces the existing growth complexities and notably accelerates the growth of 2D materials. This approach facilitates the growth of various 2D materials directly from stoichiometric powders by laser vaporization process. We show that directed laser heating allows pressure-independent decoupling of the growth and evaporation kinetics enabling the use of stoichiometric powder as precursors for the growth of high-quality 2D materials including MoS2, MoSe2, WSe2, and WS2. A comprehensive experimental study was conducted to identify the system behavior, including the evaporation and growth parameters as well as the process-property relationships. This method presents a general yet simple approach for accelerating the discovery of emerging quantum materials.
关键词： TMDCs,2D materials,Laser-assisted synthesis,Stoichiometric 2D precursor
更新于2025-09-11 14:15:04
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Atomic scale depletion region at one dimensional MoSe <sub/>2</sub> -WSe <sub/>2</sub> heterointerface
摘要： Lateral heterojunctions based on two dimensional (2D) transition metal dichalcogenides (TMDCs) potentially realize monolayer devices exploiting 2D electronic structures and the functions introduced by the presence of 1D heterointerfaces. Electronic structures of a lateral MoSe2-WSe2 junction have been unveiled using scanning tunneling microscopy and spectroscopy. A smooth and narrow depletion region exists despite a defect-rich heterointerface deviating from the preferred zigzag orientations of the TMDC lattice. From the characteristics of the depletion region, a high carrier concentration and high internal electric fields are inferred, offering to benefit designs of lateral TMDC devices.
关键词： depletion region,MoSe2-WSe2,heterointerface,scanning tunneling microscopy,scanning tunneling spectroscopy,TMDCs
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Design Guidelines and Limitations of Multilayer Two-dimensional Vertical Tunneling FETs for UltraLow Power Logic Applications
摘要： New designs for vertical 2D-materials-based TFETs are proposed in this paper adopting asymmetric layer numbers for the top and bottom layer with undoped source/drain using Black Phosphorus as an example. The results show that abrupt turn-on and Ion/Ioff > 105 can be sustained when the channel length is down to sub-5 nm. The results are benchmarked against other TFETs based on promising 2D materials homo-/hetero-structures, meanwhile, the limitations, as well as guidelines, are presented.
关键词： DFT,tunnel FETs,Non-equilibrium Green’s Function,TMDCs,black phosphorus,Two-dimensional Materials Heterojunctions
更新于2025-09-04 15:30:14