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We demonstrated a feasible strategy to fabricate MoTe2/Ge heterojunction by direct growth of Ge flake on a MoTe2 film substrate with a two-step chemical vapor deposition method. A thin transition layer (∼4 nm) mainly composed of polycrystalline germanium at the MoTe2/Ge interface was verified during the Ge flake growth. The MoTe2/Ge heterojunction-based photodetector exhibits both the response speed with a rise/fall time of 7/4 μs and the photoresponsivity and detectivity with 4.87 A W−1 and 5.02 × 1011 Jones under zero bias in the near-infrared regime, respectively. The characteristics of device performance imply its practical applicability as building block for potential near-infrared integrated photonics. [ABSTRACT FROM AUTHOR]

We report the fabrication of high performance MoTe2/Si heterojunction photodiodes by direct growth of MoTe2 patterns on a commercial Si substrate by a feasible chemical vapor deposition method. The devices exhibit an ultrafast response speed with a rise/fall time of 5/8 μs, a broadband (400–1550 nm) photoresponse, a high on/off ratio of ∼104, and self-powered photo-detection with a zero bias responsivity of 0.26 A W−1 and a detectivity of 2 × 1013 Jones at 700 nm wavelength. The devices further show high stability in air for one month. This investigation offers the feasibility to fabricate high performance MoTe2/Si photodiodes for future vital optoelectronic applications. [ABSTRACT FROM AUTHOR]

Weyl semimetal Td‐phase WTe2 possesses the spin‐resolved band structure with strong spin–orbit coupling, holding promises as a useful spin source material. The noncentrosymmetric crystalline structure of Td‐WTe2 endows the generation of the out‐of‐plane polarized spin, which is of great interest in magnetic memory applications. Previously, WTe2 was explored in spin devices based on mechanically exfoliated single crystal flakes with a size of micrometers. For practical spintronics applications, it is highly desirable to implement wafer‐scale thin films. In this work, centimeter‐scale chemical vapor deposition (CVD) grown Td‐WTe2 thin films are used and the spin current generation is studied by the spin torque ferromagnetic resonance (ST‐FMR) technique. The in‐plane and out‐of‐plane spin conductivities of 7.36 × 103 (ℏ/2e) (Ωm)–1 and 1.76 × 103 (ℏ/2e) (Ωm)–1, respectively, are found in CVD‐growth 5 nm‐WTe2. The current‐induced magnetization switching in WTe2/NiFe is demonstrated at room temperature in the domain wall motion regime, which may invigorate potential spintronic device innovations based on Weyl semimetals. [ABSTRACT FROM AUTHOR]

Atom‐thick 2D metal telluride atomic crystals (2D MTACs) display many fascinating physical properties for potential applications in multiple fields. In this review, recent advances in the preparation, physical properties and applications of 2D MTACs are presented. First, three kinds of the most available preparation methods for 2D single crystal MTACs have been summarized, including single crystal‐based mechanical exfoliation, molecular beam epitaxy, and chemical vapor deposition. Second, the recent progress on abundant physical properties of 2D MTACs is briefly introduced, including surface electronic properties, optoelectronic properties, electronic transport, and thermoelectric properties, ferroelectric properties, superconducting properties, and ferromagnetic properties. Third, the potential electronics, spintronics, optoelectronics and energy applications of 2D MTACs are presented. Finally, some significant challenges and opportunities in 2D MTACs are briefly addressed. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenides (TMDs) have emerged as an ideal alternative to silicon in advanced electronics. Especially, MoTe2 attracts peculiar attention since it offers a unique opportunity of resolving critical electrical contacts. Currently, although MoTe2‐based coplanar semiconductor‐metal circuitry realized by epitaxial growth and chemical assembly has been demonstrated, while still suffers from the requirement of extremely accurate synthesis process control. Here, a facile strategy is demonstrated to fabricate large scale and high performance MoTe2 transistors with a 1T'/2H vertical homojunction structure by combining a spatial and phase controlled MoTe2 scalable synthesis and a scalable universal transfer method with water‐soluble poly‐vinylpyrrolidone and poly‐(vinyl alcohol) bilayer mediator. Both high quality 1T'‐ and 2H‐ MoTe2 with controlled dimensions can be scalable synthesized via a shadow mask assisted chemical vapor deposition method. These as‐synthesized MoTe2 patterns can be successfully transferred to a wide range of substrates at a high yield >80% with well‐retained properties to construct transistors with a complex vertical 1T'/2H‐MoTe2/HfAlO2 structure. The devices exhibit an on/off current ratio surpassing 104 and a typical mobility of ≈29 cm2 V−1 s−1. The developed scaled strategy of combining both scalable MoTe2 synthesis and transfer offers a feasible way for potential MoTe2‐based large‐scale electronics. [ABSTRACT FROM AUTHOR]

Quasi-one-dimensional (1D)/two-dimensional (2D) ZrTe3 attracts intense interest as a typical charge density wave (CDW)-bearing material. However, the conventional chemical vapor transport (CVT) synthesis of bulk ZrTe3 is limited by high time consumption, even up to weeks, and low morphological controllability, so it is highly desirable to develop feasible methods for fast and controlled ZrTe3 growth, and so far, these have not been demonstrated. In this work, we first demonstrated that ZrTe3 nanoribbons can be grown directly by a modified chemical vapor deposition (CVD) method. The growth time is significantly reduced to less than 90 min, and the size of ZrTe3 nanoribbons can be well tuned by controlling the growth time and growth temperature. Moreover, differing from most of the other transition metal trichalcogenides (TMTCs), we reveal that ZrTe3 nanoribbons exhibit both competing and synergistic magnetic properties originating from their intrinsic diamagnetism and unexpected ferromagnetism, which can be attributed to their structural imperfection and edge-states due to the reduced dimensionality. Such observable ferromagnetism might favor the exploration of their spin-electronic applications. [ABSTRACT FROM AUTHOR]

Molybdenum telluride (MoTe2), as a member of the family of transition metal dichalcogenides (TMDs), gains increasing attention due to its interesting properties such as phase transition. However, it is still challenging to directly grow large area, few-layer, two-dimensional 1T′ and 2H phases of MoTe2 simultaneously on one substrate and to construct a 1T′–2H phase heterostructure. In this work, we have developed a novel facile strategy to achieve large area, phase-controlled growth of few-layer, two-dimensional MoTe2 and lateral 1T′–2H MoTe2 heterostructures on one SiO2/Si substrate directly by special substrate position arrangement during chemical vapor deposition and tuning the cooling rate after growth. We found that a slow cooling rate after film growth is essential for the production of a uniform large-area 2H-MoTe2 film, whereas discrete regions of 2H MoTe2 are preferred to grow under the conditions of a fast cooling rate. Furthermore, the substrate location also plays a crucial role in controlling the synthesis of 1T′ and 2H phases. The resulted few-layer MoTe2 shows a carrier mobility comparable with that of the mechanical exfoliated ones. Our findings pave the way for the study of the physical properties and phase related devices of the MoTe2 and MoTe2 based 1T′–2H heterostructures. [ABSTRACT FROM AUTHOR]

Abstract We present a layered-carbon/PbSO 4 composite additive for the negative active material (NAM) of lead-acid batteries to improve their high rate charge/discharge performance. The layered-carbon/PbSO 4 composite, consisting of graphene-like two-dimensional carbon decorated with fine PbSO 4 particles, is prepared by a simple chemical vapor deposition (CVD) method and a subsequent ion exchange process. In the synthesis process, potassium carbonate functions as template to promote the generation of layered carbon sheets in CVD process and as template in ion exchange process to in situ produce PbSO 4 nanoparticles. The composite can effectively enhance the electronic conductivity and the ionic conductivity of NAM, and resist the tendency to sulfation during high-rate partial-state-of-charge (HRPSoC) operation. Moreover, the PbSO 4 deposits on the layered-carbon can not only make the carbonaceous additive be uniformly mixed with the NAM, but also inhibit the hydrogen evolution of the layered-carbon. As a result, the specific capacity, rate performance, and HRPSoC cycling performance of the NAM are significantly enhanced. The NAM with 2 wt% composite additive (the content of layered-carbon in NAM is 0.1 wt%) delivers a high initial specific discharge capacity of 160 mAh g−1 at 0.1 C rate, and 61 mAh g−1 at a high rate of 10 C rate, which is 30% higher than that of the Ref one. The cell with composite additives has achieved a HRPSoC cycle life of 160,000 cycles, which is 3 times longer than the Ref cell. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

• The 2H-MoTe 2 /β-Ga 2 O 3 (01) heterojunction has a type I band alignment, with valence and conduction band offsets of 0.16 eV and 3.56 eV, respectively. • The heterojunction diodes exhibit the rectifying ratio of 105 and on-current density of up to 1 mA/cm2. • Abnormal build-in potential in the heterojunction diode could be attributed to an interfacial layer of MoO X evidenced by TEM and XPS measurements. Beta phase gallium oxide (β-Ga 2 O 3) has attracted wide attention due to its unique material property; however, the lack of p-type doping hinders its practical application. Here, we report a 2H-MoTe 2 /β-Ga 2 O 3 (2 - 01) vertical p-n heterojunction diode via chemical vapor deposition, which exhibited excellent rectification characteristics with a rectifying ratio of 105, and an on-current density of up to 1 mA/cm2. The depletion comes from strain-free interface of the 2H-MoTe 2 and β-Ga 2 O 3 (2 - 01) by van der Waals force. The band offsets and the interface element distribution of the heterojunction were investigated by the X-ray photoelectron spectroscopy and transmission electron microscope. The valence and conduction band offsets between the 2H-MoTe 2 and β-Ga 2 O 3 were consequently determined to be 0.16 eV and 3.56 eV, with a nested gap (type I) band alignment. Moreover, an abnormal build-in potential was observed in the 2H-MoTe 2 /β-Ga 2 O 3 p-n heterojunction diode which could be attributed to the formation of an interfacial layer of MoO X. These observations in the 2H-MoTe 2 /β-Ga 2 O 3 heterojunction show the great potential in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Two dimensional layered materials show great potential in memristor applications. MoTe 2 shows unique properties and is an important 2D material. However, MoTe 2 - based memristor has been rarely studied so far. Herein, a facile method is developed to control phase in large area MoTe 2 and MoTe 2-x O x /MoTe 2 heterostructures by precursor thickness in chemical vapor deposition. The memristive behavior of MoTe 2 is highly influenced by phase and oxidization states in MoTe 2-x O x /MoTe 2 heterostructures. The original 2H and 1 T' MoTe 2 doesn't have memristive property while the surface oxidized 2H-MoTe 2 based MoTe 2-x O x /MoTe 2 heterostructures behave excellent and stable memristive behavior for at least 3000 cycles. 1 T' -MoTe 2 based heterostructures still show no memristive behavior. In addition, we compare the effect of metal electrode (Ag electrode and Al electrode) on heterostructures based memristor. The pulse tests about memristor from oxidized 2H-MoTe 2 based heterostructures show a good mimic of biological synapses in neuromorphic system. • A facile method is developed to control phase in large area MoTe 2 and MoTe 2-x O x /MoTe 2 heterostructures by precursor thickness in CVD. • The memristive behavior of MoTe 2 is highly influenced by phase and oxidization states in MoTe 2-x O x /MoTe 2 heterostructures. • The pulse test about memristor from oxidized 2H-MoTe 2 based heterostructure show a good mimic of biological synapses in neuromorphic system. [ABSTRACT FROM AUTHOR]