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Elastic Properties and Fracture Behaviors of Biaxially Deformed, Polymorphic MoTe <sub/>2</sub>
摘要： Biaxial deformation of suspended membranes widely exists and is used in nanoindentation to probe elastic properties of structurally isotropic two-dimensional (2D) materials. However, elastic properties and particularly fracture behaviors of anisotropic 2D materials remain largely unclarified in the case of biaxial deformation. MoTe2 is a polymorphic 2D material with both isotropic (2H) and anisotropic (1T’ and Td) phases, thereby an ideal system of single-stoichiometric materials to study these critical issues. Here we report the elastic properties and fracture behaviors of biaxially-deformed, polymorphic MoTe2, by combining temperature-variant nanoindentation and first-principles calculations. It is found that due to similar atomic bonding, the effective moduli of the three phases deviate by less than 15 %. However, the breaking strengths of distorted 1T’ and Td phases are only half the value of 2H phase due to their uneven distribution of bonding strengths. Fractures of both isotropic 2H and anisotropic 1T’ phases obey the theorem of minimum energy, forming triangular and linear fracture patterns, respectively, along the orientations parallel to Mo-Mo zigzag chains. Our findings not only provide a reference database for the elastic behaviors of versatile MoTe2 phases, but also illuminate a general strategy to the mechanical investigation of any isotropic and anisotropic 2D materials.
关键词： elastic properties,phase transition,MoTe2,nanoindentation
更新于2025-11-14 17:04:02
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Band Alignment of MoTe <sub/>2</sub> /MoS <sub/>2</sub> Nanocomposite Films for Enhanced Nonlinear Optical Performance
摘要： Band alignment is a key issue for the optoelectronics based on 2D layered transition metal dichalcogenides (TMDs) heterostructures. Herein, band alignment of MoTe2/MoS2 mixed heterostructure is measured with high-resolution X-ray photoelectron spectroscopy. The MoTe2/MoS2 heterostructure belongs to type-II heterostructure with the conduction band offset of 0.46 eV and the valence band offset of 0.9 eV. The stronger saturable absorption is observed in MoTe2/MoS2 heterostructure film compared with that of pure MoTe2 and MoS2 nanofilms at the same condition. An energy-level model combined with Runge–Kutta algorithm is used to understand the enhancement mechanism. It is found that the interlayer transition from MoTe2/MoS2 heterojunction plays an important role in the nonlinear optical enhancement. Meanwhile, band structure of MoTe2/MoS2 heterostructure is calculated by the first principles. The contributions of the MoTe2 and MoS2 to the heterojunction are almost equal and the valence band maximum and conduction band minimum exist in MoTe2 and MoS2 separately. This structure can form the interlayer carriers easily. The results suggest that the band alignment of TMDs paves the way for the type-II heterostructure for enhanced nonlinear response in the development of optical modulator, ultrafast laser mode lockers, saturable absorbers, and optical switches.
关键词： molybdenum disulfide (MoS2),band alignment,saturable absorption,heterostructure,molybdenum telluride (MoTe2)
更新于2025-09-23 15:23:52
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Low Frequency Noise Characteristics in Multilayer MoTe2 FETs with Hydrophobic Amorphous Fluoropolymers
摘要： This paper investigates the low-frequency noise (LFN) properties of multilayer MoTe2 field effect transistors (FETs) before and after hydrophobic amorphous polymer (CYTOP) encapsulation in the subthreshold and linear regimes. Noise spectrum density of drain current (SID) shows that the low-frequency noise in multilayer MoTe2 FETs nicely fits to a 1/fγ power law with γ～1 in the frequency range of 10 Hz to 200 Hz. From the dependence of SID on the drain current, carrier number fluctuation(Δn) is considered as a dominant low frequency noise mechanism from all operation regimes in multilayer MoTe2 FETs. Extracted trap density(Nt) based on McWhorter model in this study was reduced at least more than one order level, as compared to multilayered MoTe2 FETs without CYTOP passivation.
关键词： CYTOP,1/f noise,MoTe2 FETs
更新于2025-09-23 15:23:52
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Millimeter-scale single-crystalline semiconducting MoTe <sub/>2</sub> via solid-to-solid phase transformation
摘要： Among the Mo- and W-based two-dimensional (2D) transition metal dichalcogenides (TMDCs), MoTe2 is particularly interesting for phase-engineering applications, because it has the smallest free energy difference between the semiconducting 2H phase and metallic 1T’ phase. In this work, we reveal that, under the proper circumstance, Mo and Te atoms can rearrange themselves to transform from a polycrystalline 1T’ phase into a single-crystalline 2H phase in a large scale. We manifest the mechanisms of the solid-to-solid transformation by conducting the density functional theory calculations, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The phase transformation is well described by the time-temperature-transformation diagram. By optimizing the kinetic rates of nucleation and crystal growth, we have synthesized single-crystalline 2H-MoTe2 domain with a diameter of 2.34 mm, centimeter-scale 2H-MoTe2 thin film with a domain size up to several hundred micrometers, and the seamless 1T’-2H MoTe2 coplanar homojunction. The 1T’-2H MoTe2 homojunction provides an elegant solution for ohmic contact of 2D semiconductors. The controlled solid-to-solid phase transformation in 2D limit provides a new route to realize wafer-scale single-crystalline 2D semiconductor and coplanar heterostructure for 2D circuitry.
关键词： 1T’-2H interface,phase transformation,single crystal,MoTe2 film
更新于2025-09-23 15:23:52
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Importance of electron correlations in understanding photoelectron spectroscopy and Weyl character of
摘要： We study the role of electron correlations in the presumed type-II Weyl semimetallic candidate γ-MoTe2 by employing density functional theory (DFT) where the on-site Coulomb repulsion (Hubbard U) for the Mo 4d states is included within the DFT+U scheme. We show that pure DFT calculations fail to describe important features of the light-polarization dependence of the angular resolved photoemission intensity which can be accounted for by including the role of the Hubbard U. At the same time, while pure DFT calculations cannot explain the angular dependence of the Fermi surface as revealed by quantum oscillation experiments (a fact which had raised doubt about the presence of the Weyl physics in γ-MoTe2), inclusion of such on-site Coulomb repulsion can. We find that while the number of Weyl points (WPs) and their position in the Brillouin zone change as a function of U, a pair of such WPs very close to the Fermi level survive the inclusion of these important corrections. Our calculations suggest that the Fermi surface of γ-MoTe2 is in the vicinity of a correlations-induced Lifshitz transition, which can be probed experimentally and its interplay with the Weyl physics might be intriguing.
关键词： electron correlations,Lifshitz transition,angular resolved photoemission,MoTe2,DFT+U,Hubbard U,quantum oscillation,Weyl semimetal,photoelectron spectroscopy
更新于2025-09-23 15:23:52
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van der Waals Epitaxy of High-Mobility Polymorphic Structure of Mo <sub/>6</sub> Te <sub/>6</sub> Nanoplates/MoTe <sub/>2</sub> Atomic Layers with Low Schottky Barrier Height
摘要： High contact resistance between two-dimensional (2D) transition metal dichalcogenides (TMDs) and metal electrodes is a practical barrier for applications of 2D TMDs to conventional devices. A promising solution to this is polymorphic integration of 1T′-phase semi-metallic and 2H-phase semiconducting TMD crystals, which can lower the Schottky barrier of the TMDs. Here, we demonstrate the van der Waals epitaxy of density-controlled single isolated 1T′-Mo6Te6 nanoplates on 2H-MoTe2 atomic layers by using metal-organic chemical vapor deposition. Importantly, in situ grown 1T′-Mo6Te6 nanoplates significantly reduce the contact resistance of the 2H-MoTe2 atomic layers, providing a record high mobility of 1,139 cm2/Vs for Pd/1T′-Mo6Te6/2H-MoTe2 back-gated field-effect transistors (FETs), along with a low Schottky barrier height (q?b) of 8.7 meV. These results lead to the possibility of ameliorating the high contact resistance faced by other TMDs, and furthermore, offer polymorphic structures for realizing higher mobility TMD devices.
关键词： 1T′-2H polymorphs,MOCVD,transition metal dichalcogenides,Mo6Te6,MoTe2
更新于2025-09-23 15:22:29
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[IEEE 2019 IEEE International Conference on Power, Electrical, and Electronics and Industrial Applications (PEEIACON) - Dhaka, Bangladesh (2019.11.29-2019.12.1)] 2019 IEEE International Conference on Power, Electrical, and Electronics and Industrial Applications (PEEIACON) - A Numerical Analysis of N-MoTe <sub/>2</sub> in Back Contact of CdTe Solar Cell
摘要： Thin-film PV cells with low-cost attractive materials are more appropriate over high-cost silicon-based solar cells as free renewable energy sources. Cadmium Telluride (CdTe) PV cells are widely investigated as one of the ultra-thin film PV cells. They have broadly researched to increase efficiency by improving different front contact and back contact material. the effect of unintentionally formed n-type Molybdenum Telluride (n-MoTe2) in the back contact interface between the Cadmium Telluride (CdTe) absorber layer and Mo layer has been investigated from a numerical analysis by the facilitation of AMPS-1D software. The variation of short circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and efficiency (η) are analyzed by changing four parameters like (i) layer thickness (ii) operating temperature (iii) donor concentration and (iv) sun intensity. From the numerical analysis a moderate performance is observed, where the efficiency of the solar cell is found about 16.532%, Jsc is 21.298 mAcm-2, Voc is 0.99 V and FF is 0.863 for the layer thickness, donor concentration, operating temperature and sun intensity at 60 nm, 1×1016cm-3, 350K, and 1.1 suns respectively.
关键词： numerical analysis,CdTe,Thin film PV cells,MoTe2
更新于2025-09-23 15:21:01
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Two-dimensional series connected photovoltaic cells defined by ferroelectric domains
摘要： Recently, a large amount of effort has been devoted to bringing p- and n-type two-dimensional (2D) materials in close contact to promise a p–n junction for photodetectors and photovoltaic devices. However, all solar cells based on 2D materials are single p–n junctions so far, where the open circuit voltage is usually limited by the bandgap of semiconductor materials. Here, by using a scanning-probe domain patterning method to polarize the ferroelectric ?lm, we demonstrate a series connected MoTe2 photovoltaic cell with an additive open circuit voltage and output electrical power. The nonvolatile MoTe2 p–n diodes exhibit a recti?cation ratio of 100. As a photodetector, the device presents a responsivity of 220 mA/W and an external quantum ef?ciency of 41% without any gate or bias voltages. The open circuit voltage increases linearly with the number of series connected p–n junctions and can be beyond the bandgap of the multilayer MoTe2.
关键词： photovoltaic cells,MoTe2,open circuit voltage,two-dimensional materials,ferroelectric domains
更新于2025-09-23 15:19:57
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Controlled Growth of Large-scale Uniform 1Ta?2 MoTe2 Crystals with Tunable Thickness and its photodetector application
摘要： The monoclinic phase 1T′ MoTe2 exhibits inversion symmetry as an anisotropic semi-metal, dictating its interesting quantum transport phenomenon and other novel physical properties. However, large-scale controlled growth of uniform MoTe2 crystal still remain great challenges, hindering its further fundamental research and applications for novel devices. Here, we report a modified growth method to synthesizing few-layer 1T′ MoTe2 crystals with large-scale uniformity by assistance of molecular sieves. The theoretical simulations demonstrated that due to the temperature-dependent formation energies of different edges, the edge of (010) orientation shown high thermodynamic stability than the (100) orientation, and results in the anisotropic growth behavior of 1T' MoTe2 while the temperature changes. The photoresponse of tri-layer 1T' MoTe2 based devices shown a wide spectrum reponse from 532 nm to 1550 nm. The photo-response time of 1T' MoTe2 crystal demonstrate that it supposes to be the synergistic mechanism of photo-conductive and photo-radiatation effect. Our findings not only provide a method for the controllable growth of anisotropic two-dimensional materials at wafer scale, but also explore a wide spectrum photodetector with the MoTe2-based device.
关键词： anisotropic growth,1T′ MoTe2,wide spectrum photodetector,molecular sieves
更新于2025-09-23 15:19:57
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Ultrahigh sensitive near-infrared photodetectors based on MoTe2/germanium heterostructure
摘要： The efficient near-infrared light detection of the MoTe2/germanium (Ge) heterojunction has been demonstrated. The fabricated MoTe2/Ge van der Waals heterojunction shows excellent photoresponse performances under the illumination of a 915 nm laser. The photoresponsivity and specific detectivity can reach to 12,460 A/W and 3.3 × 1012 Jones, respectively. And the photoresponse time is 5 ms. However, the MoTe2/Ge heterojunction suffers from a large reverse current at dark due to the low barrier between MoTe2 and Ge. Therefore, to reduce the reverse current, an ultrathin GeO2 layer deposited by ozone oxidation has been introduced to the MoTe2/Ge heterojunction. The reverse current of the MoTe2/GeO2/Ge heterojunction at dark was suppressed from 0.44 μA/μm2 to 0.03 nA/μm2, being reduced by more than four orders of magnitude. The MoTe2/Ge heterojunction with the GeO2 layer also exhibits good photoresponse performances, with a high responsivity of 15.6 A/W, short response time of 5 ms, and good specific detectivity of 4.86 × 1011 Jones. These properties suggest that MoTe2/Ge heterostructure is one of the promising structures for the development of high performance near-infrared photodetectors.
关键词： near-infrared,MoTe2,heterojunction,Ge,photodetector
更新于2025-09-12 10:27:22