High-quality ultrathin single-crystalline SnSe2 flakes are synthesized under atmospheric-pressure chemical vapor deposition for the first time. A high-performance photodetector based on the individual SnSe2 flake demonstrates a high photoresponsivity of 1.1 × 10(3) A W(-1), a high EQE of 2.61 × 10(5)%, and superb detectivity of 1.01 × 10(10) Jones, combined with fast rise and decay times of 14.5 and 8.1 ms, respectively.

Three isomorphous compounds M(CHOO)3[NH2(CH3)2] (M = Mn(1 x Mn), Co(2 x Co), Ni(3 x Ni)) have been synthesized in solvothermal conditions. Single-crystal X-ray diffraction shows that they are all crystallized in the trigonal space group R c with small differences in the lattice parameters. Bridged by the three-atom single-bridge CHOO-, M ions form a three-dimensional distorted perovskite-like structure with dimethylamine (DMA) cations located in the cages of the network. Based on the magnetic data, these three 3D compounds are weak ferromagnets with the critical temperature Tc = 8.5 K (1 x Mn), 14.9 K (2 x Co), and 35.6 K (3 x Ni), and for 2 x Co and 3 x Ni, spin reorientation might take place at 13.1 and 14.3 K, respectively. At 1.8 K, hysteresis loops can be observed for all three compounds with the coercivity field ca. 90 Oe (1 x Mn), 920 Oe (2 x Co), and 320 Oe (3 x Ni). The canting angles are estimated to be 0.08 degrees, 0.5 degrees, and 0.6 degrees for 1 x Mn, 2 x Co, and 3.Ni, respectively. The magnetic coupling between MnII ions in 1.Mn was estimated based on the model developed by Rushbrook and Wood for a Heisenberg antiferromagnet on a simple cubic lattice and the best fit gives J = -0.23 cm(-1). At the same time, according to molecular field theory of antiferromagnetism, the J values for compounds 1 x Mn, 2 x Co, and 3 x Ni were estimated to be -0.32 cm(-1), -2.3 cm(-1), and -4.85 cm(-1), respectively. The spin cant in these compounds may originate from the noncentrosymmetric character of the three-atom single-bridge CHOO-. Furthermore, amorphous materials 4 x Mn238, 5 x Mn450, 6 x Co320, and 7 x Ni300 were prepared from precursors 1-3 under an argon atmosphere at different temperatures according to the thermogravimetric analyses. As an interesting result, 5 x Mn450 was confirmed to be an amorphous form of Mn3O4 with a considerably large coercivity field HC = 4.1 kOe at 30 K compared to that value (250 Oe) for bulk Mn3O4.

Subcentimeter single-crystalline graphene grains, with diameter up to 5.9 mm, have been successfully synthesized by tuning the nucleation density during atmospheric pressure chemical vapor deposition. Morphology studies show the existence of a single large nanoparticle (>~20 nm in diameter) at the geometric center of those graphene grains. Similar size particles were produced by slightly oxidizing the copper surface to obtain oxide nanoparticles in Ar-only environments, followed by reduction into large copper nanoparticles under H2/Ar environment, and are thus explained to be the main constituent nuclei for graphene growth. On this basis, we were able to control the nanoparticle density by adjusting the degree of oxidation and hydrogen annealing duration, thereby controlling nucleation density and consequently controlling graphene grain sizes. In addition, we found that hydrogen plays dual roles on copper morphology during the whole growth process, that is, removing surface irregularities and, at the same time, etching the copper surface to produce small nanoparticles that have only limited effect on nucleation for graphene growth. Our reported approach provides a highly efficient method for production of graphene film with long-range electronic connectivity and structure coherence.

2D SnS2 nanosheets have been attracting intensive attention as one potential candidate for the modern electronic and/or optoelectronic fields. However, the controllable large‐size growth of ultrathin SnS2 nanosheets still remains a great challenge and the photodetectors based on SnS2 nanosheets suffer from low responsivity, thus hindering their further applications so far. Herein, an improved chemical vapor deposition route is provided to synthesize large‐size SnS2 nanosheets, the side length of which can surpass 150 μm. Then, ultrathin SnS2 nanosheet‐based phototransistors are fabricated, which achieve high photoresponsivities up to 261 A W−1 (with a fast rising time of 20 ms and a falling time of 16 ms) in air and 722 A W−1 in vacuum, respectively. Furthermore, the effects of back‐gate voltage and air adsorbates on the optoelectronic properties of the SnS2 nanosheet have been systematically investigated. In addition, a high‐performance flexible photodetector based on SnS2 nanosheet is also fabricated with a high responsivity of 34.6 A W−1.

Monolayer of 2D transition metal dichalcogenides, with a thickness of less than 1 nm, paves a feasible path to the development of ultrathin memristive synapses, to fulfill the requirements for constructing large-scale high density 3D stacking neuromorphic chips. Herein, memristive devices based on monolayer n-MoS on p-Si substrate with a large self-rectification ratio, exhibiting photonic potentiation and electric habituation, are successfully fabricated. Versatile synaptic neuromorphic functions, such as potentiation/habituation, short-term/long-term plasticity, and paired-pulse facilitation, are successfully mimicked based on the inherent persistent photoconductivity performance and the volatile resistive switching behavior. These findings demonstrate the potential applications of ultrathin transition metal dichalcogenides for memristive synapses. These memristive synapses with the combination of photonic and electric neuromorphic functions have prospective in the applications of synthetic retinas and optoelectronic interfaces for integrated photonic circuits based on mixed-mode electro-optical operation.

As a direct-band-gap transition metal dichalcogenide (TMD), atomic thin MoS has attracted extensive attention in photodetection, whereas the hitherto unsolved persistent photoconductance (PPC) from the ungoverned charge trapping in devices has severely hindered their employment. Herein, we demonstrate the realization of ultrafast photoresponse dynamics in monolayer MoS by exploiting a charge transfer interface based on surface-assembled zinc phthalocyanine (ZnPc) molecules. The formed MoS/ZnPc van der Waals interface is found to favorably suppress the PPC phenomenon in MoS by instantly separating photogenerated holes toward the ZnPc molecules, away from the traps in MoS and the dielectric interface. The derived MoS detector then exhibits significantly improved photoresponse speed by more than 3 orders (from over 20 s to less than 8 ms for the decay) and a high responsivity of 430 A/W after AlO passivation. It is also demonstrated that the device could be further tailored to be 2-10-fold more sensitive without severely sacrificing the ultrafast response dynamics using gate modulation. The strategy presented here based on surface-assembled organic molecules may thus pave the way for realizing high-performance TMD-based photodetection with ultrafast speed and high sensitivity.

Rhenium disulfide (ReS 2 ) is attracting more and more attention for its thickness-depended direct band gap. As a new appearing 2D transition metal dichalcogenide, the studies on synthesis method via chemical vapor deposition (CVD) is still rare. Here a systematically study on the CVD growth of continuous bilayer ReS 2 film and single crystalline hexagonal ReS 2 flake, as well as their corresponding optoelectronic properties is reported. Moreover, the growth mechanism has been proposed, accompanied with simulation study. High-performance photodetector based on ReS 2 flake shows a high responsivity of 604 A·W −1 , high external quantum efficiency of 1.50 × 10 5 %, and fast response time of 2 ms. ReS 2 film-based photodetector exhibits weaker performance than the flake one; however, it still demonstrates a much faster response time (≈10 3 ms) than other reported CVD-grown ReS 2 -based photodetector (≈10 4 -10 5 ms). Such good properties of ReS 2 render it a promising future in 2D optoelectronics.

A molecular‐scale gap array is introduced into a single‐layer graphene sheet by a lithographic dash‐line cutting process. Electrically active molecules are then covalently wired into these point contacts in high yield, thus forming stable molecular devices that for example are able to reversibly switch their conductance by chemical treatment.