Correlating Nanocrystalline Structure with Electronic Properties in 2D Platinum Diselenide

Platinum diselenide (PtSe₂) is a 2D material with outstanding electronic and piezoresistive properties. The material can be grown at low temperatures in a scalable manner, which makes it extremely appealing for many potential electronics, photonics, and sensing applications. Here, the nanocrystalline structure of different PtSe₂ thin films grown by thermally assisted conversion (TAC) is investigated and is correlated with their electronic and piezoresistive properties. Scanning transmission electron microscopy for structural analysis, X-ray photoelectron spectroscopy (XPS) for chemical analysis, and Raman spectroscopy for phase identification are used. Electronic devices are fabricated using transferred PtSe₂ films for electrical characterization and piezoresistive gauge factor measurements. The variations of crystallite size and their orientations are found to have a strong correlation with the electronic and piezoresistive properties of the films, especially the sheet resistivity and the effective charge carrier mobility. The findings may pave the way for tuning and optimizing the properties of TAC-grown PtSe₂ toward numerous applications.     

Photoactive Electro-Controlled Visual Perception Memory for Emulating Synaptic Metaplasticity and Hebbian Learning

In bionic technology, it has become an innovative process imitating the functionality and structuralism of human biological systems to exploit advanced artificial intelligent machines. Bionics plays a significant role in environmental protection, especially for its low energy loss. By fusing the concept of receptor-like sensing component and synapse-like memory, the photoactive electro-controlled optical sensory memory (PE-SM) is proposed and realized in a single device, which endows a simple methodology of reducing power consumption by photoactive electro-control. The PE-SM is the system built with the stacked atomically thick materials, in which rhenium diselenide serves as a robust photosensor, hexagonal boron nitride serves as a tunneling dielectric, and graphene serves as a charge-storage layer. With the features of the PE-SM, it performs synaptic metaplasticities under optical spikes. In addition, a simulated spiking neural network composed of 24 × 24 PE-SMs is further presented in an unsupervised machine learning environment, performing image recognition via the Hebbian rule. The PE-SM not only improves the neuromorphic computing efficiency but also simplifies the circuit-size structure. Eventually, the concept of photoactive electro-control can extend to other photosensitive 2D materials and provide a new approach of constructing either visual perception memory or photonic synaptic devices.     

WSe2场效应晶体管的源漏接触特性研究

二硒化钨(WSe2)具有双极导电特性,可以通过外界掺杂或改变源漏金属来调节载流子传输类型,是一类特殊的二维纳米材料,有望在未来集成电路中成为硅(Si)的替代材料.文章采用理论与实验相结合的方式系统分析了 WSe2场效应晶体管中的源漏接触特性对器件导电类型及载流子传输特性的影响,通过制备不同金属作为源漏接触电极的WSe2场效应晶体管,发现金属/WSe2接触的实际肖特基接触势垒高低极大地影响了晶体管的开态电流.源漏金属/WSe2接触特性不仅取决于接触前理想的费米能级差,还受到界面特性,特别是费米能级钉扎效应的影响.     

Phenyl Selenosulfides as Cathode Materials for Rechargeable Lithium Batteries

The Se? Se bond in an organo‐diselenide (RSeSeR, R is an organic group) can break in a 2e^? reduction reaction, but it has limited capacity as a cathode material for rechargeable lithium‐ion batteries. To increase its capacity, redox active species (e.g., sulfur) can be added in the middle of the selenium atoms. Herein, phenyl diselenide (PDSe, PhSeSePh) is mixed with sulfur to form two hybrid compounds with 1:1 and 1:2 molar ratios, which almost double and triple the capacity of PDSe, respectively. Theoretical calculations suggest that phenyl selenosulfide (PDSe‐S, PhSe‐S‐SePh) and phenyl selenodisulfide (PDSe‐S₂, PhSe‐SS‐SePh) can form via addition reactions, which is supported by mass spectrometry analysis. The hybrid materials exhibit three highly reversible redox plateaus and enhanced cycling stability due to the reduced solubility of the discharge products. PDSe‐S and PDSe‐S₂ show initial capacities of 252 and 330 mAh g^?1, respectively, followed by stable cycling performance with a capacity retention of >73% after 200 cycles at C/5 rate. In addition, they show steady rate capabilities. This study reports a novel strategy to increase the electrochemical performance of organo‐diselenide by addition of sulfur.     

Improved performance in ZnO/CdS/CuGaSe2 thin‐film solar cells

We report the growth and characterization of improved efficiency wide‐bandgap ZnO/CdS/CuGaSe₂ thin‐film solar cells. The CuGaSe₂ absorber thickness was intentionally decreased to better match depletion widths indicated by drive‐level capacitance profiling data. A total‐area efficiency of 9·5% was achieved with a fill factor of 70·8% and a V_oc of 910 mV. Published in 2003 by John Wiley & Sons, Ltd.     

株冶锌冶炼Ⅰ系统硫酸锌溶液净化生产实践

主要论述了株冶集团锌Ⅰ系统硫酸锌溶液净化除杂的机理及实践效果,并对之加以评论及探讨,指出了生产实践中存在的问题,提出了相应的解决措施。     

Growth of iron diselenide nanorods on graphene oxide nanosheets as advanced electrocatalyst for hydrogen evolution reaction

Advanced electrocatalysts for the fabrication of sustainable hydrogen from water splitting are innermost to energy research. Herein, we report the growth of iron diselenide (FeSe₂) nanorods on graphene oxide (GO) sheets using two-step process viz., simple hydrothermal reduction and followed by wet chemical process. The orthorhombic phase of FeSe₂ incorporated GO nanosheet was developed as a low-cost and efficient electrocatalyst for hydrogen evolution reaction (HER) by water splitting. The phase purity, crystalline structure, surface morphology and elemental composition of the synthesized samples have been investigated by UV–visible absorption spectroscopy (UV–vis), fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDS). Voltammetry and Tafel polarization methods have been utilized to assess the performance of various weight ratio of GO nanosheet in FeSe₂ nanorods towards H₂ evolution. Detailed electrochemical investigations revealed that the 30% FeSe₂/GO composite showed a tremendous electrocatalytic HER activity in acidic medium with high cathodic current density of 9.68 mA/cm² at η = 250 mV overpotential and with a Tafel slope of 64 mV/dec. The 30% FeSe₂/GO composite offers a high synergistic effect towards HER activity, which is mainly due to high electrochemical active catalytic sites, low charge-transfer resistance and enhanced electrocatalytic performances of H₂ production. The present analysis revealed the possible application of FeSe₂/GO composite as a promising low-cost alternative to platinum based electrocatalysts for H₂ production.     

Novel routes to polyelectrolytes and reactive polymers via ROMP

Various derivatives of norbornene and 7‐oxanorbornenedicarboxylic acid have been synthesized and polymerized via Ring Opening Metathesis Polymerization (ROMP). The introduction of tetrahydropyranyl moieties as protection groups opened a way for the synthesis of polyelectrolytes through well‐defined transition metal alkylidene catalysts that are usually deactivated by reactions with acidic protons. The incorporation of methacrylate groups in the polycarboxylic acids was achieved either by copolymerization of methacrylate functionalized norbornene or 7‐oxanorbornene derivatives, or by the polymer analogous reaction of the polycarboxylic acids with glycidyl methacrylate (GMA). These materials are soluble in water as well as in ethanol and undergo cross‐linking reactions initiated by UV light. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 47–60, 2000     

Ring opening metathesis polymerization of dicyclopentadiene catalyzed by titanium tetrachloride adduct complexes with nitrogen‐containing ligands

Ring opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) catalyzed by titanium tetrachloride adduct complexes such as TiCl₄ · 2L [L = pyridine (1), 2‐methylpyridine (2), 2,4,6‐trimethylpyridine (3), 3‐aminopyridine (4), 2‐hyroxypyridine (5)] and CH₃Li as cocatalyst was reported. The polymer was characterized by IR and ¹H‐NMR methods. Five influencing factors were also discussed. The catalyst systems TiCl₄ · 2L/CH₃Li (L = 2‐methylpyridine, 2,4,6‐trimethylpyridine) appeared to be very active for the ROMP of DCPD. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3247–3251, 2000     

Preparation and properties of ester or cyano group substituted ring-opening polymers and their hydrogenated derivatives

Ester or cyano substituted tetracyclo [4.4.0.1^2,5.1^7,10]dodec-3-enes (1) were synthesized and their metathesis ring-opening polymerization was examined. The tungsten-based ternary catalyst system polymerized them very well. The polymers showed high glass transition temperatures (T_g) and no evidence of crystallization (e.g., the T_g of the polymer derived from 8-methyl-8-methoxycarbonyl substituted monomer (1a) was 207°C, and colorless transparent films could be casted from the solution of the polymer). The stability of these high T_g polymers were too unstable, so practical thermal molding methods could not be applied to them. The hydrogenation of these polymers with a palladium catalyst decreased T_g and greatly increased thermal stability. The physical and thermal properties of the hydrogenated polymers were thoroughly investigated. Monomer 1 was successfully copolymerized with other cyclic olefins. The resultant copolymers were hydrogenated, giving thermally stable polymers. In all cases examined in this study, a decrease of T_g by hydrogenation was about 35°C, regardless of the monomer structure. These results indicate that the main-chain mobility is the major contribution to the decrease of T_g. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 367–375, 1997