MoTe2 Research Articles

Performance analysis of p-MoTe2/n-MoSe2 -based bifacial solar cells with p+-N:Cu2O as BSF layer by SCAPS-1D

Photovoltaic solar cells (PVSC) with Molybdenum telluride (MoTe2) have received considerable attention because of their wide range of absorption, along with the absence of dangling bonds at their surface. Here, MoTe2-based PVSC with a preliminary device structure of Al/ITO/n-MoSe2/p-MoTe2/Pt was designed and estimated its performance by using the solar cell capacitance simulator in one dimension software program (SCAPS-1D). The effect of different parameters like thickness, doping density, and interface defect density of each layer was also investigated. Our investigation reveals that a moderate thickness of ∼1000 nm of MoTe2 and 500 nm of MoSe2, a higher concentration of more than 1017 cm−3 for both layers and moderate defect density of below 1014 cm−3 are favorable for the better PVSC device. The effect of integrating of p + -N:Cu 2 O layer in the MoTe2-based PVSC as a back surface field (BSF) layer was also taken into account to improve the device performance. We also evaluated the output parameters of the optimized Al/ITO /n-MoSe 2 /p-MoTe 2 /p + -N:Cu 2 O/Pt PVSC with different series and shunt resistance, back-metal work function, and working temperature. Our analysis shows that minimum series resistance, higher shunt resistance, lower working temperature, and a high back-metal work function of more than 5.35 eV are advantageous for superior PVSC due to low recombination losses, low electrical losses, and better transport of charge carriers. The best performance of 28.75% with Jsc of 34.11 mA cm−2, Voc of 0.98 V, and FF of 86.3%, was achieved by optimizing all parameters. To further improve the device performance, the bifacial mode of optimized Al/ITO /n-MoSe 2 /p-MoTe 2 /p + -N:Cu 2 O/Pt was considered and the PV performance of the proposed bifacial-PVSC has been also studied by using SCAPS-1D. Compared to the mono-facial device, a bifacial-PVSC device shows better performance with the bifacial factor of 77.5%, bifacial gain of 14.78%, and a higher PCE of 32.17%.

Spacer effects on the performance of MoTe2/MoSe2 and MoTe2/WSe2 heterostructure double gate MOSFET

In this work, the spacer effects (both low and high-k) on the dc and noise characteristics of heterostructure molybdenum ditelluride (MoTe2/MoSe2 and MoTe2/WSe2) double gate (DG) MOSFET is analyzed. To study the device characteristics, a hybrid methodology that uses both QuantumWise ATK and Sentaurus TCAD tool is used. The performance metrics of the device such as on-current (Ion), Ion/Ioff ratio, subthreshold swing (SS), threshold voltage are obtained. The noise performance of the device is also studied (with/without spacer) using impedance field method. Noise parameters such as noise power spectral density (SID) and noise figure (function of both frequency and bias) has also been simulated and noise components such as G-R noise, flicker noise and white noise are obtained. The simulation results shows that the introduction of spacer material enhances the dc performance of the device and influences its noise characteristics.

Electronic structure and optical properties of alkali metal X (X=Li, Na, K, Rb, Cs) adsorbed in the Te vacancy-deficient molybdenum ditelluride system: A first-principles study

In the framework of density functional theory, based on first principles, the plane wave pseudopotential technique was utilized to investigate the electrical and optical properties of MoTe2 adjusted by alkali metal X adsorption on Te vacancy defects (X[Formula: see text]=[Formula: see text]Li, Na, K, Rb, Cs). The adsorption of alkali metals on Te vacancy-deficient MoTe2 monolayers has been computationally analyzed. Charge transfer, electronic structure, and optical properties of alkali metal adsorption were systematically studied. It is shown that the MoTe2 bandgap is significantly reduced under Te vacancies. Te vacancies are frequently active sites in TMDs materials. With the adsorption of alkali metal atoms X (X = Li, Na, K, Rb, Cs) in the Te vacancy MoTe2 system, Li atoms have the most substantial geometrical deformation and the minor adsorption energy and can improve the adsorption properties more effectively. The MoTe2 system undergoes a change from semiconductor to metal after adsorption. Regarding optical properties, firm absorption and reflection peaks appeared, and a blueshift phenomenon was observed in the mountains. It is expected that these discoveries are likely to guide the use of molybdenum ditelluride in optoelectronics.

Non-equilibrium Green's function analysis of charge plasma-based source-drain electrode P-type MoTe2 MOSFET for high sensitivity hydrogen sensing

—The paper presents a novel P-type molybdenum ditelluride (MoTe2) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) designed for high sensitivity hydrogen sensing applications. Through the utilization of palladium at the source-drain charge plasma electrode, P+ regions at both ends are generated, obviating the necessity for low-dimensional MoTe2 doping. Simultaneously, the inclusion of palladium on both regions act as the sensing area, resulting in notably heightened sensitivity. The study employs Non-Equilibrium Green's Function (NEGF) formalism to investigate the carrier transport properties of the device. The results provide valuable insights into less explored area of p-type MOSFET performance as Hydrogen(H2) gas sensor and its potential.

Biaxial tensile-compressive deformation on the electronic structure and optical properties of doped with different concentrations F–MoTe2: A first-principles study

Under the framework of density functional theory based on the first principles, the plane wave pseudopotential method was used to investigate the effects of biaxial stretch-compression deformation on the electrical structure and optical characteristics of molybdenum telluride systems doped with various fluorine atom concentrations. Electrical structure, density of states, charge transfer, and optical characteristics were calculated and thoroughly investigated in the molybdenum ditelluride system. The results demonstrate that the band gap shrinks with increasing fluorine atom doping concentration of fluorine atoms, and n-type doping occurs for different doping concentrations of halogen fluorine atoms. The semiconductor-quasi-metal transition occurs in the MoTe2 system when the doping concentration reaches 16.67%. After that, the fluorine atoms with 4% doping concentration were deformed by stretching and compression, and the semiconductor started to transition to quasi-metal as the amount of stretching increased. The deformation of the system changed considerably when the stretching amount was 14%. Compression induces a direct-to-indirect bandgap transition, transforming semiconductors into metals. Significant changes in electronic energy band diagrams and density of states diagrams. In terms of optical qualities, the absorption spectra of the entire system are blue-shifted during stretching and compression. The reflectance spectra are red-shifted and then blue-shifted.

Two-dimensional molybdenum ditelluride waveguide-integrated near-infrared photodetector

Low-cost, small-sized, and easy integrated high-performance photodetectors for photonics are still the bottleneck of photonic integrated circuits applications and have attracted increasing attention. The tunable narrow bandgap of two-dimensional (2D) layered molybdenum ditelluride (MoTe2) from ∼0.83 to ∼1.1 eV makes it one of the ideal candidates for near-infrared (NIR) photodetectors. Herein, we demonstrate an excellent waveguide-integrated NIR photodetector by transferring mechanically exfoliated 2D MoTe2 onto a silicon nitride (Si3N4) waveguide. The photoconductive photodetector exhibits excellent responsivity (R), detectivity (D*), and external quantum efficiency at 1550 nm and 50 mV, which are 41.9 A W−1, 16.2 × 1010 Jones, and 3360%, respectively. These optoelectronic performances are 10.2 times higher than those of the free-space device, revealing that the photoresponse of photodetectors can be enhanced due to the presence of waveguide. Moreover, the photodetector also exhibits competitive performances over a broad wavelength range from 800 to 1000 nm with a high R of 15.4 A W−1 and a large D* of 59.6 × 109 Jones. Overall, these results provide an alternative and prospective strategy for high-performance on-chip broadband NIR photodetectors.

Bending deformation modulation of the optoelectronic properties of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, O): a first-principles study.

A first-principles approach based on density functional theory was used to explore the effect of bending deformation on the electrical structure of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, and O). The study included alternate doping of nonmetallic atoms, as well as a comparison of the effects of intrinsic bending deformation and nonmetallic doping deformation. The results demonstrate that boron atom doping raises the Fermi energy level. Examining the energy band structure indicates that the intrinsic molybdenum ditelluride is a direct band gap semiconductor, which is transformed from a direct band gap to an indirect band gap after doping. We selected boron-doped systems for bending deformation and compared them with the intrinsic systems. With increasing deformation, all systems start to shift from semiconductor to metal. When the deformation reaches 8°, the energy levels fill and the electron energy increases. The intrinsically bent systems transition from direct band gap to indirect band gap and eventually to metal. The indirect band gap semiconductor-to-metal transition process occurs after the bending deformation of the boron-doped atoms. The analytical results show that the absorption and reflection peaks of the molybdenum ditelluride system are blue-shifted after the bending deformation of the boron-doped atoms. Under fundamental principles, this research depends on the density functional theory framework (DFT) using the CASTEP module in the Materials-Studio software. The plane-wave pseudopotential approach with modified gradient approximation and the Perdew-Burke-Ernzerhof (PBE) generalized function is used for structure optimization and total energy calculations of the X-doped (X = B, C, N, O) MoTe2 system at different shape variables. Geometry optimization of the 27-atom superlattice MoTe2 was carried out, followed by alternative doping of tellurium atoms in the molybdenum ditelluride with B, C, N, and O. In this paper, the intrinsic bending deformation and B-doping of molybdenum ditelluride were selected for deformation analysis. Intrinsic bending deformations and boron-doped molybdenum ditelluride with bending angles ranging from 2° to 8° were employed for deformation investigation. In Fig.1, pink is used to represent doped B atoms, orange is used to describe Te atoms, and green is used to represent Mo atoms. For the degree of deformation of molybdenum ditelluride, in this paper, it is expressed by the bending angle, i.e., the angle of the plane of molybdenum ditelluride after bending and deformation of a single layer of molybdenum ditelluride concerning the angle of the plane folded for the deformed plane. How to do it: For ease of presentation, the atomic chains are set to different colors. The purple part on both sides of the figure is bent and deformed, 3-5 atoms are fixed appropriately, and the middle part is deformed. On this basis, the bending deformation of intrinsically doped and boron-doped MoTe2 is comparatively analyzed. The effect of boron-doped atoms on the structure of MoTe2 is systematically investigated to study its structural stability and electronic structure. Fig.1 a1 and a2 The main and side views of intrinsic MoTe2; b1 and (b2) the main and side views of MoTe2 doped with boron atoms bent by 8°.

Temperature-dependent failure of atomically thin MoTe2.

In this study, we investigated the mechanical responses of molybdenum ditelluride (MoTe2) using molecular dynamics (MD) simulations. Our key focus was on the tensile behavior of MoTe2 with trigonal prismatic phase (2H-MoTe2) which was investigated under uniaxial tensile stress for both armchair and zigzag directions. Crack formation and propagation were examined to understand the fracture behavior of such material for varying temperatures. Additionally, the study also assesses the impact of temperature on Young's modulus and fracture stress-strain of a monolayer of 2H-MoTe2. The investigation was done using molecular dynamics (MD) simulations using Stillinger-Weber (SW) potentials. The tensile behavior was simulated for temperature for 10K and then from 100 to 600K with a 100-K interval. The crack propagation and formation of 10K and 300K 2H-MoTe2 for both directions at different strain rates was analyzed using Ovito visualizer. All the simulations were conducted using a strain rate of 10-4ps-1. The results show that the fracture strength of 2H-MoTe2 in the armchair and zigzag direction at 10K is 16.33 GPa (11.43 N/m) and 13.71429 GPa (9.46 N/m) under a 24% and 18% fracture strain, respectively. The fracture strength of 2H-MoTe2 in the armchair and zigzag direction at 600K is 10.81 GPa (7.56 N/m) and 10.13 GPa (7.09 N/m) under a 12.5% and 12.47% fracture strain, respectively.

High-Performance Flexible Broadband Photoelectrochemical Photodetector Based on Molybdenum Telluride.

Flexible broadband photodetectors are desired but challenging to be fabricated for next-generation wearable intelligent optoelectronic devices. Considering the narrow bandgap and strong light absorption, molybdenum telluride (MoTe2) based photoelectrochemical photodetectors are successfully assembled by liquid phase exfoliation accompanied with the electrophoretic deposited method. This MoTe2-based photodetector shows a broadband detection in ultraviolet-near-infrared band, long-term stability within 18000s, and fast response in millisecond-level (response time≈19ms, recovery time≈26ms). More importantly, even though the MoTe2 photodetector is bent and twisted at a high degree for several hundred times, it still shows excellent flexibility with stable on-off switching characteristics. Additionally, this photodetector displays a good response for rotation angles in the range from 0° to 360°, and the extracted Iph maintain almost the same value approximately 0.97µAcm-2, suggesting an omnidirectional detection capability. This work demonstrates the proposed flexible photoanode shows a great potential in future broadband omnidirectional detection systems.

Giant Optical Anisotropy in a Covalent Molybdenum Tellurite via Oxyanion Polymerization.

Large birefringence is a crucial but hard-to-achieve optical parameter that is a necessity for birefringent crystals in practical applications involving modulation of the polarization of light in modern opto-electronic areas. Herein, an oxyanion polymerization strategy that involves the combination of two different types of second-order Jahn-Teller distorted units is employed to realize giant anisotropy in a covalent molybdenum tellurite. Mo(H2O)Te2O7 (MTO) exhibits a record birefringence value for an inorganic UV-transparent oxide crystalline material of 0.528 @ 546nm, which is also significantly larger than those of all commercial birefringent crystals. MTO has a UV absorption edge of 366nm and displays a strong powder second-harmonic generation response of 5.4 times that of KH2PO4. The dominant roles of the condensed polytellurite oxyanions [Te8O20]8- in combination with the [MoO6]6- polyhedra in achieving the giant birefringence in MTO are clarified by structural analysis and first-principles calculations. The results suggest that polymerization of polarizability-anisotropic oxyanions may unlock the promise of birefringent crystals with exceptional birefringence.

Strain-enhanced dynamic ranges in two-dimensional MoS2 and MoTe2 nanomechanical resonators

Two-dimensional (2D) materials are promising for atomic-scale, ultralow-power, and highly tunable resonant nanoelectromechanical systems (NEMS) in sensing, communications, and computing. Toward these applications, a broad and controllable linear dynamic range (DR) is desirable for increasing the signal-to-noise ratio (SNR) and reliability. Here, we develop a comprehensive strain-enhanced DR model for 2D NEMS resonators, which is experimentally verified through the tuning of DRs in 2D molybdenum disulfide (MoS2) and molybdenum ditelluride (MoTe2) NEMS resonators using gate-induced strain. We find that the resonance frequency, quality factor, and nonlinear coefficient are all tuned by the gate voltage, which enhance the DR together. Through the guidance of the DR tuning model, we demonstrate DR enhancement by up to 26.9 dB (from 69.5 to 96.4 dB) in a 2D MoS2 NEMS resonator by properly tuning the gate voltage, leading to a theoretical mass resolution of 26 yg (1 yg = 10−24 g). To accurately extract the DR, we further differentiate the quality factors for thermomechanical resonances and for resonances at the largest linear amplitude. This gate-enhanced DR model is also verified using a MoTe2 resonator, with DR enhancement of 7 dB (91.2 to 98.2 dB). The results provide a promising pathway for accurately predicting and optimizing the DRs in NEMS resonators, toward enhanced sensitivity and SNR in mass sensing, radio frequency signal processing, memory, and computing applications.

Photoinduced growth of the crystalline phase of tellurium on a 1T′-MoTe2 matrix

Due to the growing demand for miniaturization and energy efficiency in modern electronic devices, there is a renewed interest for optoelectronic memories and sensors based on 2D materials. In particular, the molybdenum ditelluride (MoTe2) is one of the most promising materials for applications in nonvolatile phase-change memory devices, as its properties can be controlled by visible-light illumination. Among the several ways to synthesize MoTe2, the molybdenum oxide tellurization through isothermal close space sublimation (CSS) annealing in gas atmosphere is a simple and low-cost effective method for large-scale production of devices based on this layered material. Therefore, the understanding of the physical properties of MoTe2 thin films produced by this technique is crucial for future applications. Surprisingly, our results indicate that there is a photoinduced growth of the crystalline phase of tellurium on the 1T′-MoTe2 matrix even when the power density of the laser is low. From Raman spectroscopy investigations, we were able to show that nanometer-sized tellurium crystallites work as seed sites for the photocrystallization of tellurium. By assuming that the overall crystallization process is described by a kinetic approach that is based on the Kolmogorov–Johnson–Mehl–Avrami theory, our results indicate that the process is governed by an anisotropic organization of the tellurium atoms in helical structures during the crystal growth.

New design and optimization of half-tandem quantum dot solar cell: Over 30% power conversion efficiency using nanostructure oriented core-shell

We achieve 30.64% power conversion efficiency (PCE) by comprehensive design and optimization of half-tandem quantum dot (QD) solar cell using nanostructure-oriented core-shell to improve open circuit voltage (Voc) in QD solar cell (QDSC) for first time. In this study, we have used coupling of optical and electrical equations to calculate solar cell parameters. The aim of this study was to optimize the reference structure including PbS quantum dots (PbS-QDs) treated with tetrabutylammonium iodide (PbS-TBAI), Magnesium Zinc Oxide (MgZnO) and PbS ethanedithiol (PbS-EDT) for active layer (AL), electron transport layer (ETL) and hole transport layer (HTL) respectively. At first, the structure was enhanced into half-tandem solar cell by adding Molybdenum Ditelluride (MoTe2) as the second absorber layer to cover the infrared region. Furthermore, the structure was optimized in four steps: (i) adding a Spiro-OMeTAD layer to reduce the series resistance (Rs) and prevent electrons from entering aluminum metal contact, (ii) adding a core-shell (CFTS – SnS) nanostructure, (iii) optimizing ETL, and (iv) investigating the effect of core-shell nanostructure angle. As a final result, the values of short circuit current (Jsc), Voc, PCE, fill factor (FF) and series resistance were obtained 25.25 mA/cm2, 1.49 V, 30.64 %, 0.78 and 2.8 Ω/cm2, respectively.

3D Flower-like Nanospheres Constructed by Transition Metal Telluride Nanosheets as Sulfur Immobilizers for High-Performance Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries hold immense promise as next-generation energy storage systems, owing to their exceptionally high theoretical capacity, abundant resources, eco-friendliness, and affordability. Nevertheless, their practical application is impeded by the shuttling effect of sodium polysulfides (NaPSs) and sluggish sulfur redox kinetics. In this study, an advanced strategy by designing 3D flower-like molybdenum telluride (MoTe2) as an efficient catalyst to promote sulfur redox for RT Na-S batteries is presented. The unique 3D flower-like MoTe2 effectively prevents NaPS shuttling and simultaneously offers abundant active catalytic sites facilitating polysulfide redox. Consequently, the obtained MoTe2/S cathode delivers an outstanding initial reversible capacity of 1015mAhg-1 at 0.1C, along with robust cycling stability of retaining 498mAhg-1 at 1C after 500 cycles. In addition, pouch cells are fabricated with the MoTe2 additive to deliver an ultrahigh initial discharge capacity of 890mAhg-1 and remain stable over 40 cycles under practically necessary conditions, demonstrating the potential application in the commercialization of RT Na-S batteries.

Electrochemical Synthesis of Molybdenum Ditelluride (MoTe2) and Its Potential Application as Negative Electrode Material for Sodium Ion Battery

With the rapid expansion in energy demands and depletion of fossil fuel reservoirs, the importance of clean energy production and storage has increased drastically. The renewable energy recourses are cost effective, sustainable and carbon dioxide emission free alternatives. Nevertheless, this energy is not always available and needs to be stored. Lithium-ion batteries (LIBs) are rapidly used in various applications such as powering electronics, electric vehicles and grid energy storage. However, the source of lithium is extremely limited in earth crust, during mining it pollutes the environment and it is costly. Therefore, attention has been shifted towards development of sodium ion batteries (SIBs) which have wide reserves and low precursor cost and thus is considered as an appropriate choice for solar and wind energy development. The prime problem encountered in development of large-scale SIBs is the low effectiveness of appropriate anode material because of large size and sluggish kinetics of Na ions which limits the specific capacity as well as energy density.Metal tellurides have emerged as a promising material for use as negative electrode in sodium-ion batteries due to its unique layered crystal structure, high intrinsic conductivity, and high trap density. Molybdenum ditelluride has more electric conductivity than selenides and sulfides. Other metals except molybdenum in the group takes part in alloying mechanism that leads to higher volume expansion and poor cycling stability.In this study, we describe the synthesis of MoTe2 on copper and aluminium substrate by using predeposited molybdenum and electrodeposited tellurium at relatively low temperature of 450°C. Further we characterized the samples by X-Ray Diffraction, Raman Spectroscopy and Field Emission Scanning Electron Microscope for structural, elemental, and morphological properties, respectively. The synthesized material was used as negative electrode in sodium ion coin cell. The electrochemical performance of the coin cell will be correlated with the structural and electronic property of MoTe2.

Four-phonon scattering and thermal transport in 2H–MoTe2

Among two-dimensional (2D) transition metal dichalcogenides, molybdenum ditelluride (MoTe2) is of great interest to achieving unique functionalities in diverse electronic, photonic, and phononic devices. Despite extensive studies over the past decade, the thermal transport properties and mechanisms of MoTe2 remain largely unclear. Here, we grow few-layer (7L, 10L, and 17L) single-crystalline 2H–MoTe2 and measure their in-plane thermal conductivities using an optothermal Raman technique. The room-temperature values range from 4 to 9 W m−1 K−1, substantially lower than theoretical predictions considering only three-phonon scattering. By employing first-principles calculations and machine learning-assisted molecular dynamics simulations, we reveal that four-phonon scattering could suppress the thermal conductivity of 2H–MoTe2 by 80%, which agrees with experimental measurement and is mainly attributed to the flexural acoustic modes. Thickness-dependent suppression is observed owing to the varying reflection symmetry. Our work highlights higher-order phonon-phonon interactions in 2D materials and offers guidance for the thermal design of emerging devices.

Directionally-Resolved Phononic Properties of Monolayer 2D Molybdenum Ditelluride (MoTe2) under Uniaxial Elastic Strain.

Understanding the phonon characteristics of two-dimensional (2D) molybdenum ditelluride (MoTe2) under strain is critical to manipulating its multiphysical properties. Although there have been numerous computational efforts to elucidate the strain-coupled phonon properties of monolayer MoTe2, empirical validation is still lacking. In this work, monolayer 1H-MoTe2 under uniaxial strain is studied via in situ micro-Raman spectroscopy. Directionally dependent monotonic softening of the doubly degenerate in-plane E2g1 phonon mode is observed with increasing uniaxial strain, where the E2g1 peak red-shifts -1.66 ± 0.04 cm-1/% along the armchair direction and -0.80 ± 0.07 cm-1/% along the zigzag direction. The corresponding Grüneisen parameters are calculated to be 1.09 and 0.52 along the armchair and zigzag directions, respectively. This work provides the first empirical quantification and validation of the orientation-dependent strain-coupled phonon response in monolayer 1H-MoTe2 and serves as a benchmark for other prototypical 2D transition-metal tellurides.

Fourier‐Transform Infrared Spectroscopy of MoTe2 Thin Films

Molybdenum ditelluride (MoTe2), a member of the transition metal dichalcogenide family, holds significant promise in optoelectronic applications. To harness its full potential, it is imperative to understand its fundamental optical properties, including refractive indices. Herein, measurements of the transmittance and reflectance spectra of thin MoTe2 layers are conducted featuring hexagonal and monoclinic structures across the far‐infrared (IR) and mid‐IR spectral regions. These spectra are fitted, allowing to extract the complex refractive index and optical conductance. In the semiconducting hexagonal phase, both the conductance and extinction coefficient remain negligible below 3000 cm−1 and increase at higher energies. Conversely, the monoclinic phase exhibits a conductance peak in the far‐IR region and a continuous increase from 1000 to 6000 cm−1. The findings are compared with existing theoretical and experimental results to provide further insights into MoTe2's optical behavior.

Li adsorption and diffusion on the surfaces of molybdenum dichalcogenides MoX2 (X = S, Se, Te) monolayers for lithium-ion batteries application: a DFT study.

We study some of the most high performance electrode materials for lithium-ion batteries. These comprise molybdenum dichalcogenide MoX2 (molybdenum disulfide MoS2, molybdenum diselenide MoSe2, molybdenum ditelluride MoTe2). The stability is studied by calculating cohesive energy and formation energy. Structural, electronic, and electrical properties are well defined, and these structures show a direct gap. Lithium adsorption at different sites, theoretical storage capacity, and lithium diffusion path are determined. Our study findings suggest that the adsorption of Li on the preferred site on the surface of the MoX2 monolayer maintains its semiconductor behavior. Comparing the activation energy barrier of these structures with other monolayers such as graphene or silicene, we found that MoX2 shows low lithium diffusion energy and good storage capacity, which indicates that the MoX2 is well suited as an anode material for lithium-ion batteries. Our research can offer new ideas for experimental and theoretical design and new anode materials for lithium-ion batteries (LIB). The studies were performed with Quantum ESPRESSO package based on density functional theory (DFT), plane waves, and pseudopotentials (PWSCF) to calculate the physical properties of MoX2 (X = S, Se, Te), lithium adsorption, and diffusion on their surfaces and the storage capacity of these structures. The BoltzTraP code is used to calculate thermoelectric properties.

Torsional deformation modulation of the electronic structure and optical properties of molybdenum ditelluride systems doped with halogen atoms X (X = F, Cl, Br, I): a first-principles study.

Using a first-principles plane-wave pseudopotential technique within the context of density-functional theory, the electronic structure and optical properties of the molybdenum ditelluride system doped with halogen atoms X (X = F, Cl, Br, I) were investigated. The electronic structure, density of states, charge transfer, and optical properties of halogen atom X doped on MoTe2 monolayer are systematically calculated and analyzed. It shows that the Fermi energy level is shifted upward after doping with halogen atoms. With F-MoTe2 doping, the geometrical distortion is the most pronounced, the charge transfer number is the highest, and the semiconductor shifts from a direct band gap to an indirect band gap. When the torsional deformation is between 1° and 5°, the F-doped MoTe2 system stays an indirect band gap semiconductor and transitions to quasi-metal at 6°. It is shown that the torsional deformation can modulate the electronic properties of the doped structure and realize the semiconductor-metal transition. The F-doped system has a strong absorption peak reflection peak after torsion, and with the increase of torsion angle, the absorption peak is red-shifted, and the reflection peak is blue-shifted. Moreover, the absorption and reflection peaks start to decrease with the rise of the torsion angle. We apply the generalized gradient approximation plane-wave pseudopotential technique based on Perdew-Burke-Ernzerhof (PBE) generalized functions, under the first principles of the density-functional theory framework. The overall optimization of the intrinsic molybdenum ditelluride structure and the halogen atom X-doped molybdenum ditelluride structure was carried out. Then, the F-doped molybdenum ditelluride system was selected for torsional deformation with torsion angles from 1° to 6° for computational analysis. To make the presentation more accessible, the atoms in the F-doped molybdenum ditelluride system were colored differently. The pink chain edge atoms were first reversed by θ°. Then, the blue chain edge atoms were reversed by θ° in the other direction. The middle row of atoms was adjusted accordingly to the different twisting angles of the two sides by doing the corresponding torsion with the torsion angle θ°/2 and fixing the individual atoms. The calculation employs the Monkhorst-Pack particular K-point sampling method. The 3 × 3 × 1 inverted-space K-point grid is utilized for material structure optimization calculations in each model, and the 9 × 9 × 1 K-point grid is used for material electronic structure calculations. A 15 Å vacuum layer is put on the crystal surface of vertical monolayer molybdenum ditelluride supercells to avoid interactions with adjoining cells.