Far-Infrared Signatures for a Two-Steps Pressure-Driven Metallization in Transition Metal Dichalcogenides. (arXiv:2301.11448v1 [cond-mat.mtrl-sci])

2023-01-30T02:29:26+00:00January 30th, 2023|Categories: Publications|Tags: , |

We present a high-pressure investigation of the semiconductor-to-metal transition in MoS2 and WS2 carried out by synchrotron-based far-infrared spectroscopy, to reconcile the controversial estimates of the metallization pressure found in the literature and gain new insight into the mechanisms ruling this electronic transition. Two spectral descriptors are found indicative of the onset of metallicity and of the origin of the free carriers in the metallic state: the absorbance spectral weight, whose abrupt increase defines the metallization pressure threshold, and the asymmetric lineshape of the E1u peak, whose pressure evolution, interpreted within the Fano model, suggests the electrons in the metallic state originate from n-type doping levels. Combining our results with those reported in the literature, we hypothesize a two-step mechanism is at work in the metallization process, in which the pressure-induced hybridization between doping and conduction band states drives an early metallic behaviour, while the band-gap closes at higher pressures.

Published in: "arXiv Material Science".

Selective surface modification and layer thinning of MoS2 via ultraviolet light irradiation in ionic solution. (arXiv:2301.10417v1 [cond-mat.mtrl-sci])

2023-01-26T02:29:18+00:00January 26th, 2023|Categories: Publications|Tags: |

The electrical and optoelectronic properties of transition-metal dichalcogenides (TMDs), such as MoS2, are highly dependent on carrier doping and layer thickness. The ability to selectively control these two critical characteristics is of great importance to develop TMD-based multifunctional device applications, which remains challenging. Here, we report a strategy for controllable surface modification and layer thinning of MoS2 via ultraviolet (UV) light irradiation in a silver ionic solution environment. The results show that by adjusting UV irradiation time, nanostructured silver ultrathin films (~2.9 nm) are uniformly deposited on monolayer MoS2 and can lead to controllable p-type doping effect, while the thickness of MoS2 from few-layer to bulk crystals could be thinned down to the atomic monolayer limit. Both silver nanostructure deposition and layer thinning process have been evidenced to initiate from the edges of MoS2, and independent of the edge type, thus revealing a unique UV light-assisted defect-induced surface modification and layer thinning mechanism. Overall, this study provides a new methodology for selective control of doping and layer thickness in TMDs, paving the way for developing novel 2D nanoelectronics and integrated optoelectronics.

Published in: "arXiv Material Science".

Excitation-Dependent High-Lying Excitonic Exchange via Interlayer Energy Transfer from Lower-to-Higher Bandgap 2D Material. (arXiv:2301.05644v1 [cond-mat.mtrl-sci])

2023-01-16T02:29:21+00:00January 16th, 2023|Categories: Publications|Tags: , , , , |

High light absorption (~15%) and strong photoluminescence (PL) emission in monolayer (1L) transitionmetal dichalcogenide (TMD) makes it an ideal candidate for optoelectronic applications. Competing interlayer charge (CT) and energy transfer (ET) processes control the photocarrier relaxation pathways in TMD heterostructures (HSs). In TMDs, long-distance ET can survive up to several tens of nm, unlike the CT process. Our experiment shows that an efficient ET occurs from the 1L WSe2 to 1L MoS2 with ~9 nm interlayer hBN, due to the resonant overlapping of the high-lying excitonic states between the two TMDs, resulting in enhanced HS MoS2 PL emission. This type of ET from the lower-to-higher optical bandgap material has never been observed. With increasing temperature, the ET process becomes weaker due to the increased electron-phonon scattering, destroying the enhanced MoS2 emission. Our work provides a new insight into the long-distance ET process and its effect on the photocarrier relaxation pathways.

Published in: "arXiv Material Science".

Strain Induced Enhanced Photocatalytic Activities in Layered Two Dimensional C2N/MoS2 Heterostructure: A Meta-GGA Study. (arXiv:2301.03809v1 [cond-mat.mtrl-sci])

2023-01-11T02:29:30+00:00January 11th, 2023|Categories: Publications|Tags: , , |

The improved photocatalytic water splitting using 2D materials has technological importance for economically viable renewable energy. The present study focuses on the effect of uniaxial, biaxial, and vertical strain on the energy gap and band edge positions of C2N/MoS2 van der Waals heterostructures through first-principles density functional theory using PBE and SCAN functionals. The calculations establish that SCAN functional provides comparatively much better results as compared to the PBE for the band gap and band alignment study. The heterostructure exhibits a type- II band alignment which is beneficial for the efficient separation of charge carriers. For a good photocatalyst, the band edge positions should straddle the water redox potentials. It is observed that for both compressive and tensile vertical strain, the water redox potential values lie within the valence band maximum (VBM) and conduction band minimum (CBM) of the heterostructure. On the other hand, for uniaxial and biaxial strain, the system can be used as a useful photocatalyst only for larger compressive strain, whereas for tensile strain, the energy gap between VBM and CBM keeps on decreasing and lie within the water oxidation/reduction potential. Our study also establishes that the meta-GGA SCAN functional shows similar results as compared to the computationally expensive hybrid HSE functionals. The present work can be extremely useful for experimentalists to design artificial heterostructure devices for better performance in photocatalytic water splitting.

Published in: "arXiv Material Science".

Correlated carrier dynamics in a superconducting van der Waals heterostructure. (arXiv:2301.03473v1 [cond-mat.supr-con])

2023-01-10T02:29:41+00:00January 10th, 2023|Categories: Publications|Tags: , , |

The study of Berezinskii-Kosterlitz-Thouless transitions in clean, layered two-dimensional superconductors promises to provide insight into a host of novel phenomena like re-entrant vortex-dynamics, underlying unconventional metallic phases, and topological superconductivity. In this letter, we report the study of charge carrier dynamics in a novel 2-dimensional superconducting van der Waals heterostructure comprising monolayer MoS2 and few-layer NbSe2 (15 nm). Using low-frequency conductance fluctuation spectroscopy, we show that the superconducting transition in the system is percolative. We present a phenomenological picture of different phases across the transition correlating with the evaluated noise. The analysis of the higher-order statistics of fluctuation reveals non-Gaussian components around the transition indicative of long-range correlation in the system.

Published in: "arXiv Material Science".

Catalytic action of two-dimensional layered materials (WS2, and MoS2) on hydrogen sorption properties of MgH2. (arXiv:2301.02897v1 [cond-mat.mtrl-sci])

2023-01-10T02:29:30+00:00January 10th, 2023|Categories: Publications|Tags: , , |

The present study reports the catalytic action of two-dimensional (2D) layered materials (MoS2 and WS2) for improving the de/re-hydrogenation kinetics of MgH2. The MgH2 start desorbing at 277 C with a hydrogen storage capacity of 5.95 wt% in the presence of WS2 catalyst whereas onset desorption temperature of MgH2 catalyzed by MoS2 is 330 C. The MgH2-WS2 absorbed hydrogen ~ 3.72 wt% within 1.3 minutes at 300 C under 13 atm hydrogen pressure and it desorbed ~5.57 wt% within 20 minutes at 300 C under 1 atm hydrogen pressure. We have performed 25 cycles of dehydrogenation (under 1 atm hydrogen pressure at 300 C) and re-hydrogenation (under 13 atm hydrogen pressure at 300 {deg}C) to ensure cyclic stability of catalyzed version of MgH2 where MgH2-WS2 shows better cyclic stability than MgH2-MoS2. MgH2-WS2 also shows the lower reaction activation energy ~117 kJ/mol as compare to other catalyzed and uncatalyzed samples. On the other hand, these catalysts (WS2 and MoS2) do not have any impact on the thermodynamical parameters that is change in enthalpy.

Published in: "arXiv Material Science".

In situ Imaging of an Anisotropic Layer-by-Layer Phase Transition in Few-Layer MoTe2. (arXiv:2301.02694v1 [cond-mat.mtrl-sci])

2023-01-10T02:29:29+00:00January 10th, 2023|Categories: Publications|Tags: , , |

Understanding the phase transition mechanisms in two-dimensional (2D) materials is a key to precisely tailor their properties at the nanoscale. Molybdenum ditelluride (MoTe2) exhibits multiple phases at room temperature, making it a promising candidate for phase-change applications. Here, we fabricate lateral 2H-Td interfaces with laser irradiation and probe their phase transitions from micro- to atomic scales with in situ heating in the transmission electron microscope (TEM). By encapsulating the MoTe2 with graphene protection layers, we create an in situ reaction cell compatible with atomic resolution imaging. We find that the Td-to-2H phase transition initiates at phase boundaries at low temperatures (200-225 degree C) and propagates anisotropically along the b-axis in a layer-by-layer fashion. We also demonstrate a fully reversible 2H-Td-2H phase transition cycle, which generates a coherent 2H lattice containing inversion domain boundaries. Our results provide insights on fabricating 2D hetero-phase devices with atomically sharp and coherent interfaces.

Published in: "arXiv Material Science".

Charges‐Enhanced Molybdenum Disulfide Nanozyme Activity for Ultrasound‐Mediated Cascade‐Catalytic Tumor Ferroptosis

2023-01-05T13:07:58+00:00January 5th, 2023|Categories: Publications|Tags: |

Deficient catalytic activity of nanozyme and insufficient endogenous H2O2 in tumor microenvironment (TME) are major obstacles for nanozyme-mediated catalytic tumor therapy. Herein, since electron transfer is the basic essence of catalysis-mediated redox reaction, we explored the contributing factors of enzymatic activity based on positive and negative charges, which are experimentally and theoretically demonstrated to enhance the peroxidase (POD)-like activity of MoS2 nanozyme. Hence, an acidic TME-responsive and ultrasound-mediated cascade nanocatalyst (BTO/MoS2@CA) is presented by making few-layer MoS2 nanosheets grown on the surface of piezoelectric tetragonal barium titanate (T-BTO) and modified with pH-responsive cinnamaldehyde (CA). The integration of pH-responsive CA-mediated H2O2 self-supply, ultrasound-mediated charges enhanced enzymatic activity and GSH depletion enables out-of-balance redox homeostasis, leading to effective tumor ferroptosis with minimal side effects.

Published in: "Angewandte Chemie International Edition".

Synergistic Photon Management and Strain-Induced Band Gap Engineering of Two-Dimensional MoS2 Using Semimetal Composite Nanostructures. (arXiv:2301.01164v1 [cond-mat.mes-hall])

2023-01-04T02:29:57+00:00January 4th, 2023|Categories: Publications|Tags: |

2D MoS2 attracts increasing attention for its application in flexible electronics and photonic devices. For 2D material optoelectronic devices, light absorption of the molecularly thin 2D absorber would be one of the key limiting factors in device efficiency, and conventional photon management techniques are not necessarily compatible with them. In this paper, we show two semimetal composite nanostructures for synergistic photon management and strain-induced band gap engineering of 2D MoS2: (1) pseudo-periodic Sn nanodots, (2) conductive SnOx (x15x enhancement in absorption at {lambda}=650-950 nm under Sn nanodots, and 20-30x at {lambda}=700-900 nm under SnOx (x

Published in: "arXiv Material Science".

Single-material MoS$_{2}$ thermoelectric junction enabled by substrate engineering. (arXiv:2301.00974v1 [cond-mat.mtrl-sci])

2023-01-04T02:29:53+00:00January 4th, 2023|Categories: Publications|Tags: |

To realize a thermoelectric power generator, typically a junction between two materials with different Seebeck coefficient needs to be fabricated. Such difference in Seebeck coefficients can be induced by doping, which renders difficult when working with two-dimensional (2d) materials. Here, we employ substrate effects to form a thermoelectric junction in ultra-thin few-layer MoS2 films. We investigated the junctions with a combination of scanning photocurrent microscopy and scanning thermal microscopy. This allows us to reveal that thermoelectric junctions form across the substrate-engineered parts. We attribute this to a gating effect induced by interfacial charges in combination with alterations in the electron-phonon scattering mechanisms. This work demonstrates that substrate engineering is a promising strategy to develop future compact thin-film thermoelectric power generators.

Published in: "arXiv Material Science".

Edge-based 2D alpha-In2Se3-MoS2 ferroelectric field effect device. (arXiv:2301.00568v1 [cond-mat.mtrl-sci])

2023-01-03T02:29:27+00:00January 3rd, 2023|Categories: Publications|Tags: , , |

Heterostructures based on two dimensional (2D) materials offer the possibility to achieve synergistic functionalities which otherwise remain secluded by their individual counterparts. Herein ferroelectric polarization switching in alpha-In2Se3 has been utilized to engineer multilevel non-volatile conduction states in partially overlapping alpha-In2Se3-MoS2 based ferroelectric semiconducting field effect device. In particular, we demonstrate how the intercoupled ferroelectric nature of alpha-In2Se3 allows to non-volatilely switch between n-i and n-i-n type junction configurations based on a novel edge state actuation mechanism, paving the way for sub-nanometric scale non-volatile device miniaturization. Furthermore the induced asymmetric polarization enables enhanced photogenerated carriers separation resulting in extremely high photoresponse of 1275 AW-1 in the visible range and strong non-volatile modulation of the bright A- and B- excitonic emission channels in the overlaying MoS2 monolayer. Our results show significant potential to harness the switchable polarization in partially overlapping alpha-In2Se3-MoS2 based FeFETs to engineer multimodal non-volatile nanoscale electronic and optoelectronic devices.

Published in: "arXiv Material Science".

Charges‐Enhanced Molybdenum Disulfide Nanozyme Activity for Ultrasound‐Mediated Cascade‐Catalytic Tumor Ferroptosis

2022-12-31T13:07:44+00:00December 31st, 2022|Categories: Publications|Tags: |

Deficient catalytic activity of nanozyme and insufficient endogenous H2O2 in tumor microenvironment (TME) are major obstacles for nanozyme-mediated catalytic tumor therapy. Herein, since electron transfer is the basic essence of catalysis-mediated redox reaction, we explored the contributing factors of enzymatic activity based on positive and negative charges, which are experimentally and theoretically demonstrated to enhance the peroxidase (POD)-like activity of MoS2 nanozyme. Hence, an acidic TME-responsive and ultrasound-mediated cascade nanocatalyst (BTO/MoS2@CA) is presented by making few-layer MoS2 nanosheets grown on the surface of piezoelectric tetragonal barium titanate (T-BTO) and modified with pH-responsive cinnamaldehyde (CA). The integration of pH-responsive CA-mediated H2O2 self-supply, ultrasound-mediated charges enhanced enzymatic activity and GSH depletion enables out-of-balance redox homeostasis, leading to effective tumor ferroptosis with minimal side effects.

Published in: "Angewandte Chemie International Edition".

Achiral dielectric metasurfaces for spectral and polarization control of valley specific light emission from monolayer MoS2. (arXiv:2212.09147v1 [physics.optics])

2022-12-20T02:29:37+00:00December 20th, 2022|Categories: Publications|Tags: |

Two-dimensional transition metal dichalcogenides host robust excitons with a valley degree of freedom that can be optically accessed and manipulated for quantum information processing. Here, we demonstrate enhancement and spectral control of valley exciton emission in MoS2 via coupling with dielectric metasurfaces composed of arrays of Si nano-disks. By varying the disk diameter, we tune the frequencies of Mie scattering modes of the disks to match the exciton frequency in MoS2. Photoluminescence (PL) intensity of MoS2 is enhanced by over 30 times on the metasurface in contrast to that on flat sapphire substrate, attributed to enhancement of both excitation and emission resulting from the metasurface optical near field coupling. The MoS2 emission spectra are also markedly modified via the coupling of neutral excitons, trions and defect bound excitonic states with the metasurface Mie modes. Finally, we show how the metasurface enhances the valley polarized PL from both excitons and trions by over an order of magnitude at cryogenic temperatures (100K). The observed disk-diameter dependent enhancement shows excellent agreement with the calculated Purcell factor of our metasurfaces. Our study provides a Si-compatible photonic design to improve the recombination dynamics of valley polarized excitons and trions for a variety of on-chip valleytronic applications.

Published in: "arXiv Material Science".

Exciton lifetime and optical linewidth profile via exciton-phonon interactions: Theory and first-principles calculations for monolayer MoS$_2$. (arXiv:2212.08451v1 [cond-mat.mtrl-sci])

2022-12-19T02:29:19+00:00December 19th, 2022|Categories: Publications|Tags: , |

Exciton dynamics dictate the evolution of photoexcited carriers in photovoltaic and optoelectronic devices. However, interpreting their experimental signatures is a challenging theoretical problem due to the presence of both electron-phonon and many-electron interactions. We develop and apply here a first-principles approach to exciton dynamics resulting from exciton-phonon coupling in monolayer MoS2 and reveal the highly selective nature of exciton-phonon coupling due to the internal spin structure of excitons, which leads to a surprisingly long lifetime of the lowest energy bright A exciton. Moreover, we show that optical absorption processes rigorously require a second-order perturbation theory approach, with photon and phonon treated on an equal footing, as proposed by Toyozawa and Hopfield. Such a treatment, thus far neglected in first-principles studies, gives rise to off-diagonal exciton-phonon coupling matrix elements, which are critical for the description of dephasing mechanisms, and yields exciton linewidths in excellent agreement with experiment.

Published in: "arXiv Material Science".

Quantitative Imaging of Intrinsic and Extrinsic Strain in Transition Metal Dichalcogenide Moir’e Bilayers. (arXiv:2212.07006v1 [cond-mat.mtrl-sci])

2022-12-15T02:29:28+00:00December 15th, 2022|Categories: Publications|Tags: , |

The accumulation of strain plays a key role in defining the electronic structure of two-dimensional materials. In moir’e superlattices, including those of transition metal dichalcogenides(TMDs), strain may arise intrinsically due to spontaneous intralayer lattice relaxation, as well as from the extrinsic stretching of one or both layers. Imaging of TMD moir’es has so far established a qualitative understanding of lattice relaxation in terms of interlayer stacking energies, and quantification of strain has relied exclusively on theoretical simulations. Here, we develop interferometric four-dimensional scanning transmission electron microscopy to quantitatively map strain fields in small-angle twisted bilayer MoS2 and WSe2/MoS2 heterobilayers with sub-nanometer resolution. These strain maps quantify how local rotations govern the intrinsic reconstruction process for twisted homobilayers, and reveal that local in-plane dilations dominate in heterobilayers possessing a sufficiently large lattice constant mismatch. Extrinsic uniaxial heterostrain, which introduces a lattice constant difference in twisted homobilayers, leads to further accumulation and redistribution of reconstruction strain, demonstrating another route to modify the moir’e potential landscape.

Published in: "arXiv Material Science".

Deformable Molecular Crystal on 2D Crystal: A New Way to Build Nanoscale Periodic Trapping Sites for Interlayer Excitons. (arXiv:2212.06796v1 [cond-mat.mes-hall])

2022-12-14T04:30:26+00:00December 14th, 2022|Categories: Publications|Tags: , , |

The nanoscale moir’e pattern formed at 2D transition metal dichalcogenide crystal (TMDC) heterostructures provides periodic trapping sites for excitons, which is essential for realizing various exotic phases such as artificial exciton lattices, Bose-Einstein condensates, and exciton insulators. At organic molecule/TMDC heterostructures, similar periodic potentials can be formed via other degrees of freedom. We utilize the structure deformability of a 2D molecular crystal as a degree of freedom to create a periodic nanoscale potential that can trap interlayer excitons (IXs). Specifically, two semiconducting molecules, PTCDI and PTCDA, which possess similar bandgaps and ionization potentials but form different lattice structures on MoS2, are investigated.The PTCDI lattice on MoS2 is distorted geometrically, which lifts the degeneracy of the two molecules within the crystal’s unit cell. The degeneracy lifting results in a spatial variation of the molecular orbital energy, with an amplitude and periodicity of ~ 0.2 eV and ~ 2 nm, respectively. On the other hand, no such energy variation is observed in PTCDA/MoS2, where the PTCDA lattice is much less distorted. The periodic variation in molecular orbital energies provides effective trapping sites for IXs. For IXs formed at PTCDI/MoS2, rapid spatial localization of the electron in the organic layer towards the interface is observed, which demonstrate the effectiveness of these interfacial IX’s traps.

Published : "arXiv Mesoscale and Nanoscale Physics".

Unveiling the complex structure-property correlation of defects in 2D materials based on high throughput datasets. (arXiv:2212.02110v1 [cond-mat.mtrl-sci])

2022-12-06T02:29:50+00:00December 6th, 2022|Categories: Publications|Tags: , , , , |

Modification of physical properties of materials and design of materials with on-demand characteristics is at the heart of modern technology. Rare application relies on pure materials–most devices and technologies require careful design of materials properties through alloying, creating heterostructures of composites or controllable introduction of defects. At the same time, such designer materials are notoriously difficult for modelling. Thus, it is very tempting to apply machine learning methods for such systems. Unfortunately, there is only a handful of machine learning-friendly material databases available these days. We develop a platform for easy implementation of machine learning techniques to materials design and populate it with datasets on pristine and defected materials. Here we describe datasets of defects in represented 2D materials such as MoS2, WSe2, hBN, GaSe, InSe, and black phosphorous, calculated using DFT. Our study provides a data-driven physical understanding of complex behaviors of defect properties in 2D materials, holding promise for a guide to the development of efficient machine learning models. In addition, with the increasing enrollment of datasets, our database could provide a platform for designing of materials with predetermined properties.

Published in: "arXiv Material Science".

Explore of exfoliable multifunctional high-k two-dimensional oxides. (arXiv:2212.01731v1 [cond-mat.mtrl-sci])

2022-12-06T02:29:43+00:00December 6th, 2022|Categories: Publications|Tags: , |

As the continuing down-scaling of field-effect transistors (FETs) in more-than-Moore integrated circuits, finding new functional two-dimensional (2D) materials with a higher dielectric constant (high-k) serve as gate dielectrics is critical. Here, we identify dozens of binary 2D oxides by screening potentially exfoliable bulk metal oxides despite of their non-layered structures followed by simulation of the exfoliation process. For dynamically stable materials, we fully characterize their static dielectric constants and electronic structures, among which GeO2(011)/(101)/(1-11) 2D oxides exhibit unusually high k values (85-99), being much higher than the k of the currently highly regarded 2D dielectrics CaF2 (k ~6) and b{eta}-Bi2SeO5 (k ~22), together with band gap of 3.3 eV. We further design 2D high-k oxides/2D semiconductors (such as MoS2) heterostructures, and determine by DFT calculations whether they can form Van der Waals interfaces to evaluate their compatibility as gate dielectrics in 2D FETs. In addition to dielectric properties, we also explore magnetic and mechanical properties of potentially exfoliable 2D oxides, revealing a number of functional materials that can be studied experimentally, notably including ferromagnetic half semiconductors, non-magnetic spintronic materials, flexible high-k 2D oxides, and auxetic monolayers.

Published in: "arXiv Material Science".

Efficient Multiple Exciton Generation in Monolayer MoS2. (arXiv:2212.01587v1 [cond-mat.mtrl-sci])

2022-12-06T02:29:36+00:00December 6th, 2022|Categories: Publications|Tags: , |

Utilizing the excess energy of photoexcitation that is otherwise lost as thermal effects can improve the efficiency of next-generation light-harvesting devices. Multiple exciton generation (MEG) in semiconducting materials yields two or more excitons by absorbing a single high-energy photon, which can break the Shockley-Queisser limit for the conversion efficiency of photovoltaic devices. Recently, monolayer transition metal dichalcogenides (TMDs) have emerged as promising light-harvesting materials because of their high absorption coefficient. Here, we report efficient MEG with low threshold energy and high (86%) efficiency in a van der Waals (vdW) layered material, MoS2. Through different experimental approaches, we demonstrate the signature of exciton multiplication and discuss the possible origin of decisive MEG in monolayer MoS2. Our results reveal that vdW-layered materials could be a potential candidate for developing mechanically flexible and highly efficient next generation solar cells and photodetectors.

Published in: "arXiv Material Science".

Ultrafast response of spontaneous photovoltaic effect in 3R-MoS2-based heterostructures. (arXiv:2211.06746v1 [cond-mat.mes-hall])

2022-11-15T04:30:26+00:00November 15th, 2022|Categories: Publications|Tags: , , |

Rhombohedrally stacked MoS2 has been shown to exhibit spontaneous polarization down to the bilayer limit and can sustain a strong depolarization field when sandwiched between graphene. Such a field gives rise to a spontaneous photovoltaic effect without needing any p-n junction. In this work, we show the photovoltaic effect has an external quantum efficiency of 10% for devices with only two atomic layers of MoS2 at low temperatures, and identify a picosecond-fast photocurrent response, which translates to an intrinsic device bandwidth at ~ 100-GHz level. To this end, we have developed a non-degenerate pump-probe photocurrent spectroscopy technique to deconvolute the thermal and charge-transfer processes, thus successfully revealing the multi-component nature of the photocurrent dynamics. The fast component approaches the limit of the charge-transfer speed at the graphene-MoS2 interface. The remarkable efficiency and ultrafast photoresponse in the graphene-3R-MoS2 devices support the use of ferroelectric van der Waals materials for future high-performance optoelectronic applications.

Published : "arXiv Mesoscale and Nanoscale Physics".

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