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A three-dimensional Zn <sup>II</sup> coordination network based on 5,5′-methylenebis(2,4,6-trimethylisophthalic acid) and 2,7-bis(1 <i>H</i> -imidazol-1-yl)fluorene: synthesis, structure and luminescence properties
摘要： In recent years, coordination polymers constructed from multidentate carboxylate ligands and N-containing ligands have attracted much attention since these ligands can adopt a rich variety of coordination modes which can lead to crystalline products with intriguing structures and interesting properties. A new coordination polymer, namely poly[[diaqua[μ-2,7-bis(1H-imidazol-1-yl)fluorene-κ2N3:N3′][μ-5,5′-methylenebis(2,4,6-trimethylisophthalato)-κ2O1:O1′]zinc(II)] hemihydrate], {[Zn(C23H22O8)(C19H14N4)(H2O)2]·0.5H2O}n, 1, was prepared by the self-assembly of Zn(NO3)2·6H2O with 5,5′-methylenebis(2,4,6-trimethylisophthalic acid) (H4BTMIPA) and 2,7-bis(1H-imidazol-1-yl)fluorene (BIF) under solvothermal conditions. The structure of 1 was determined by elemental analysis, single-crystal X-ray crystallography, powder X-ray diffraction, IR spectroscopy and thermogravimetric analysis. Each ZnII ion is six-coordinated by two O atoms from two H2BTMIPA2? ligands, by two N atoms from two BIF ligands and by two water molecules, forming a distorted octahedral ZnN2O4 coordination geometry. Adjacent ZnII ions are linked by H2BTMIPA2? ligands and BIF ligands, leading to the formation of a two-dimensional (2D) (4,4)-sql network, and intermolecular hydrogen-bonding interactions connect the 2D layer structure into the three-dimensional (3D) supramolecular structure. Each 2D layer contains two kinds of helices with the same direction, which are opposite in adjacent layers. The luminescence properties of complex 1 in the solid state have also been investigated.
关键词： crystal structure,fluorescence properties,two-dimensional coordination polymer,supramolecular,5,5′-methylenebis(2,4,6-trimethylisophthalic acid,zinc(II),2,7-bis(1H-imidazol-1-yl)fluorene,hydrogen bonding
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Design Guidelines and Limitations of Multilayer Two-dimensional Vertical Tunneling FETs for UltraLow Power Logic Applications
摘要： New designs for vertical 2D-materials-based TFETs are proposed in this paper adopting asymmetric layer numbers for the top and bottom layer with undoped source/drain using Black Phosphorus as an example. The results show that abrupt turn-on and Ion/Ioff > 105 can be sustained when the channel length is down to sub-5 nm. The results are benchmarked against other TFETs based on promising 2D materials homo-/hetero-structures, meanwhile, the limitations, as well as guidelines, are presented.
关键词： DFT,tunnel FETs,Non-equilibrium Green’s Function,TMDCs,black phosphorus,Two-dimensional Materials Heterojunctions
更新于2025-09-04 15:30:14
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[Springer Theses] Properties of Synthetic Two-Dimensional Materials and Heterostructures || Properties of Atomically Thin WSe2 Grown Via Metal-Organic Chemical Vapor Deposition
摘要： Two-dimensional tungsten diselenide (WSe2) is of interest for the next-generation electronic and optoelectronic devices due to its bandgap of 1.65 eV and also its excellent transport properties. However, technologies based on 2D WSe2 cannot be realized without a scalable synthesis process. The first part of this chapter focuses on the scalable synthesis for large-area, mono, and few-layer WSe2 via metal organic chemical vapor deposition (MOCVD) using tungsten hexacarbonyl (W(CO)6) and dimethylselenium ((CH3)2Se). In addition to the excellent scalability of production, this technique allows for the precise control of vapor-phase chemistry, which is not obtainable though the physical vapor reaction using powder precursors. Growth parameters such as temperature, pressure, Se to W ratio, and selection of the substrates for the growth play important roles on the resultant structure. With optimized conditions, domain size >8 μm is yielded.
关键词： electronic devices,WSe2,epitaxial growth,MOCVD,two-dimensional materials
更新于2025-09-04 15:30:14
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Langmuir–Hinshelwood and Light-Intensity Dependence Analyses of Photocatalytic Oxidation Rates by Two-Dimensional-Ladder Kinetic Simulation
摘要： Though photocatalytic reactions gather enormous attention, dependences of light intensity and reactant concentration have not been concurrently expressed clearly. In the previously reported studies, a quadratic formula equation obtained from the conventional analysis using the concentration of electron?hole pairs has been modified. In this report we numerically simulated the reaction with a two-dimensional(2D)-ladder kinetics without using electron?hole concentrations. In fundamental processes, (i) photoabsorption, (ii) reduction, (iii) oxidation, and (iv) recombination, were treated as the transitions between the states of each powder characterized by the numbers of possessing negative and positive charges. Through the numerical 2D-ladder simulation with various rate constants, the light-intensity (I) dependence of the oxidation rate was found to be fully expressed by involving the square of the intrinsic quantum yield into the square root part of the well-known quadratic formula equation. The square root dependence of the reaction rate, r ∝ I1/2, could be expected only when the rate of the reduction is extremely smaller than the recombination rate at the normal light intensity. Then, the resultant equations obtained with this 2D-ladder simulation were transformed to the equation for Langmuir?Hinshelwood kinetics with two parameters, rL and KL, which correspond to the intrinsic oxidation rate and the adsorption equilibrium constant of the reactant, respectively. Light-intensity dependence of KL was expressed by adding two terms proportional to I2 to both the adsorption and desorption rate constants. The reported experimental data sets of the decomposition rates for phenol and 4-chlorophenol were fitted with the proposed equation, and then from the obtained parameter values the formation rate of (cid:129)O2? could be estimated and found to be compatible to that which has been experimentally measured. Thus, the present analytical treatment is actually the simple and useful method to understand the dependencies of reactant concentration and light-intensity on the photocatalytic oxidation rates.
关键词： reactant concentration,photocatalytic reactions,light intensity,Langmuir?Hinshelwood kinetics,two-dimensional-ladder kinetics
更新于2025-09-04 15:30:14
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Photon Noise Suppression by a Built-in Feedback Loop
摘要： Visionary quantum photonic networks need transform-limited single photons on demand. Resonance fluorescence on a quantum dot provides the access to a solid-state single photon source, where the environment is unfortunately the source of spin and charge noise that leads to fluctuations of the emission frequency and destroys the needed indistinguishability. We demonstrate a built-in stabilization approach for the photon stream, which relies solely on charge carrier dynamics of a two-dimensional hole gas inside a micropillar structure. The hole gas is fed by hole tunneling from field-ionized excitons and influences the energetic position of the excitonic transition by changing the local electric field at the position of the quantum dot. The standard deviation of the photon noise is suppressed by nearly 50% (noise power reduction of 6 dB) and it works in the developed micropillar structure for frequencies up to 1 kHz. This built-in feedback loop represents an easy way for photon noise suppression in large arrays of single photon emitters and promises to reach higher bandwidth by device optimization.
关键词： semiconductor heterostructure,single photon source,two-dimensional hole gas,Quantum dots,quantum optics,resonance fluorescence
更新于2025-09-04 15:30:14
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Wafer-sized ultrathin gallium and indium nitride nanosheets through the ammonolysis of liquid metal derived oxides
摘要： We report the synthesis of centimeter sized ultrathin GaN and InN. The synthesis relies on the ammonolysis of liquid metal derived two-dimensional (2D) oxide sheets that were squeeze-transferred onto desired substrates. Wurtzite GaN nanosheets featured typical thicknesses of 1.3 nm, an optical bandgap of 3.5 eV and a carrier mobility of 21.5 cm2V-1s-1, while the InN featured a thickness of 2.0 nm. The deposited nanosheets were highly crystalline, grew along the (001) direction and featured a thickness of only three unit cells. The method provides a scalable approach for the integration of 2D morphologies of industrially important semiconductors into emerging electronics and optical devices.
关键词： ultrathin indium nitride,ultrathin gallium nitride,ammonolysis,two-dimensional materials,liquid metal derived oxides
更新于2025-09-04 15:30:14
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EuO epitaxy by oxygen scavenging on SrTiO <sub/>3</sub> (001): Effect of SrTiO <sub/>3</sub> thickness and temperature
摘要： The EuO/SrTiO3 heterojunction is a promising combination of a ferromagnetic material and a two-dimensional electron system. We explore the deposition of Eu metal on SrTiO3/Si pseudo-substrates, with varying SrTiO3 (STO) thickness, under ultrahigh vacuum conditions. By varying the thickness of the STO layer (2-10 nm) and the deposition temperature (20-300 °C), we investigate the process by which oxygen is scavenged from STO by Eu. In situ x-ray photoelectron spectroscopy is used to investigate the electronic structure of the nominal Eu/STO/Si stack. We ?nd that as a result of Eu deposition, epitaxial EuO is formed on thick STO (6-10 nm), leaving behind a highly oxygen-de?cient SrTiO3-δ layer of ～4 nm in thickness. However, if the thickness of the STO layer is comparable to or less than the scavenging depth, the crystal structure of STO is disrupted and a solid state reaction between Eu, Si, and STO occurs when the deposition is done at a high temperature (300 °C). On the other hand, at a low temperature (20 °C), only a 1-2 nm-thick EuO interlayer is grown, on top of which the Eu metal appears to be stable. This study elucidates the growth process under different conditions and provides a better understanding and control of this system.
关键词： SrTiO3,epitaxy,EuO,two-dimensional electron system,oxygen scavenging,ferromagnetic material
更新于2025-09-04 15:30:14
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Stark shift of excitons and trions in two-dimensional materials
摘要： The effect of an external in-plane electric ?eld on neutral and charged exciton states in two-dimensional (2D) materials is theoretically investigated. These states are argued to be strongly bound, so that electron-hole dissociation is not observed up to high electric ?eld intensities. Trions in the anisotropic case of monolayer phosphorene are demonstrated to be especially robust under electric ?elds, so that ?elds as high as 100 kV/cm yield no signi?cant effect on the trion binding energy or probability density distribution. Polarizabilities of excitons are obtained from the parabolicity of numerically calculated Stark shifts. For trions, a fourth order Stark shift is observed, which enables the experimental veri?cation of hyperpolarizability in 2D materials, as observed in the highly excited states of the Rydberg series of atoms and ions.
关键词： Stark shift,polarizability,two-dimensional materials,electric field,excitons,trions,hyperpolarizability
更新于2025-09-04 15:30:14
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Reversible and selective ion intercalation through the top surface of few-layer MoS2
摘要： Electrochemical intercalation of ions into the van der Waals gap of two-dimensional (2D) layered materials is a promising low-temperature synthesis strategy to tune their physical and chemical properties. It is widely believed that ions prefer intercalation into the van der Waals gap through the edges of the 2D flake, which generally causes wrinkling and distortion. Here we demonstrate that the ions can also intercalate through the top surface of few-layer MoS2 and this type of intercalation is more reversible and stable compared to the intercalation through the edges. Density functional theory calculations show that this intercalation is enabled by the existence of natural defects in exfoliated MoS2 flakes. Furthermore, we reveal that sealed-edge MoS2 allows intercalation of small alkali metal ions (e.g., Li+ and Na+) and rejects large ions (e.g., K+). These findings imply potential applications in developing functional 2D-material-based devices with high tunability and ion selectivity.
关键词： defects,MoS2,electrochemical control,two-dimensional materials,ion intercalation
更新于2025-09-04 15:30:14