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Determination of Phase Transition and Electro-optical Behaviors of Quantum Dot Doped Polymer Dispersed Liquid Crystal
摘要： This paper describes our research into phase transition, electro-optical and dielectric behaviors of polymer dispersed liquid crystal (PDLC) and cadmium selenide sulphide/zinc sulphide quantum dot (QD) doped PDLC (PDLC/QD). The PDLC was prepared with nematic liquid crystal (E63) and UV-curable photopolymer (NOA65) by using a polymerization induced phase separation technique. Dielectric properties of composites were investigated with a dielectric/impedance analyzer at 1 kHz–10 MHz frequency range. Electro-optical measurements of investigated samples were carried out using an electro-optical switching method. Phase transition temperature of PDLC and PDLC/QD composites was also determined, using a differential scanning calorimeter. The results showed that the introduction of QD signi?cantly changes the physical properties of PDLC, and these changes could become a focus of interest for future applications.
关键词： quantum dot,electro-optical and dielectric behaviors,Polymer dispersed liquid crystal,phase transition
更新于2025-09-16 10:30:52
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Evidence for Ferroelectricity of All-Inorganic Perovskite CsPbBr3 Quantum Dots
摘要： The ferroelectric-optical combination of properties in halide perovskites has attracted tremendous interests because of its potential for optoelectronic and energy applications. However, very few reports focus on the ferroelectricity of all-inorganic halide perovskites quantum dots. Herein, we report a excellent ferroelectricity in CsPbBr3 quantum dots (QDs) with a saturation polarization of 0.25 μC/cm2. Differential scanning calorimeter (DSC), X-ray diffraction (XRD), transmission electronic microscopy (TEM) revealed that the mechanism of ferroelectric-paraelectric switching of CsPbBr3 QDs can be attributed to the phase transition from cubic phase (????3??) to orthorhombic phase (Pna21). In the orthorhombic CsPbBr3, the distortion of octahedral [PbBr6]4- structural units and the off-center Cs+ generated the slightly separated centres of positive charge and negative charge, resulting in the ferroelectric properties. The variable temperature emission spectrum from 328 K to 78 K exhibits green luminescence and the gradually red shift due to the phase transition. This finding opens up a avenue to explore the ferroelectric-optical properties of inorganolead halide perovskites for high-performance multifunctional materials.
关键词： CsPbBr3 quantum dots,all-inorganic perovskite,phase transition,optoelectronic applications,ferroelectricity
更新于2025-09-16 10:30:52
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Inlaid ReS <sub/>2</sub> Quantum Dots in Monolayer MoS <sub/>2</sub>
摘要： Two-dimensional (2D) transition metal dichalcogenides (TMDs) are prospective materials for quantum devices owing to their inherent 2D confinements. They also provide a platform to realize even lower-dimensional in-plane electron confinement, e.g., 0D quantum dots, for exotic physical properties. However, fabrication of such laterally confined monolayer (1L) nanostructure in 1L crystals remains challenging. Here we report the realization of 1L ReS2 quantum dots epitaxially inlaid in 1L MoS2 by a two-step chemical vapor deposition method combining with plasma treatment. The lateral lattice mismatch between ReS2 and MoS2 leads to size-dependent crystal structure evolution and in-plane straining of the 1L ReS2 nanodots. Optical spectroscopies reveal the abnormal charge transfer between the 1L ReS2 quantum dots and the MoS2 matrix, most likely resulting from electron trapping in the 1L ReS2 quantum dots. This study may shed light on the realization of in-plane quantum-confined devices in 2D materials for potential applications in quantum information.
关键词： chemical vapor deposition,phase transition,2D materials,phase engineering,transition metal dichalcogenide alloy
更新于2025-09-12 10:27:22
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Phase-transition modulated, high-performance dual-mode photodetectors based on WSe <sub/>2</sub> /VO <sub/>2</sub> heterojunctions
摘要： Photodetectors based on two-dimensional (2D) transition metal dichalcogenides (TMDs) can only be operated in a single photovoltaic or photoconductive mode, showing either high detectivity or high responsivity, but not both. An effort to develop a photodetector that can dynamically switch its working mode is indispensable for practical applications. In this article, we demonstrate a high performance, phase-transition modulated, dual-mode photodetector based on WSe2/VO2 heterojunction. Enabled by the insulator-to-metal transition of VO2, the WSe2/VO2 heterojunction can be regulated from a type-II heterojunction to a Schottky junction, showing a tunable built-in electric field at the heterojunction interface. This resulted in the dynamic switch of carrier transport and photoresponse in the heterojunction. With this dual-mode function, the new photodetector can have both a high detectivity and a large responsivity, surpassing the current performance of single mode 2D TMDs photodetectors. With a direct laser writing and erasing technique, the photoresponse of a WSe2/VO2 device can be locally modulated as desired. This dual mode detection of the WSe2/VO2 photodetector deepens the fundamental understanding of charge transfer in heterojunctions and favors versatile applications in photodetection.
关键词： Photodetectors,Phase-transition,2D materials,WSe2/VO2 heterojunction,Dual-mode
更新于2025-09-12 10:27:22
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Surface Engineering of MoS <sub/>2</sub> via Laser‐Induced Exfoliation in Protic Solvents
摘要： With excellent performance in the hydrogen evolution reaction (HER), molybdenum disulfide (MoS2) is considered a promising nonprecious candidate to substitute Pt-based catalysts. Herein, pulsed laser irradiation in liquid is used to realize one-step exfoliation of bulk 2H-MoS2 to ultrastable few-layer MoS2 nanosheets. Such prepared MoS2 nanosheets are rich in S vacancies and metallic 1T phase, which significantly contribute to the boosted catalytic HER activity. Protic solvents play a pivotal role in the production of S vacancies and 2H-to-1T phase transition under laser irradiation. MoS2 exfoliated in an optimal solvent of formic acid exhibits outstanding HER activity with an overpotential of 180 mV at 10 mA cm?2 and Tafel slope of 54 mV dec?1.
关键词： molybdenum disulfide,sulfur vacancy,solvent effect,phase transition,laser exfoliation in liquid
更新于2025-09-11 14:15:04
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Electron-hole superfluidity controlled by a periodic potential
摘要： We propose controlling an electron-hole super?uid in semiconductor coupled quantum wells and double layers of a two-dimensional (2D) material by an external periodic ?eld. This can be created either by the gates periodically located and attached to the quantum wells or double layers of the 2D material or by the moiré pattern of two twisted layers. The dependence of the electron-hole pairing order parameter on the temperature, the charge carrier density, and the gate parameters is obtained by minimization of the mean-?eld free energy. The second-order phase transition between super?uid and electron-hole plasma, controlled by the external periodic gate ?eld, is analyzed for different parameters.
关键词： mean-?eld free energy,semiconductor coupled quantum wells,electron-hole super?uid,phase transition,external periodic ?eld,two-dimensional material
更新于2025-09-11 14:15:04
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Macroscopically aligned carbon nanotubes for flexible and high-temperature electronics, optoelectronics, and thermoelectrics
摘要： With excellent performance in the hydrogen evolution reaction (HER), molybdenum disulfide (MoS2) is considered a promising nonprecious candidate to substitute Pt-based catalysts. Herein, pulsed laser irradiation in liquid is used to realize one-step exfoliation of bulk 2H-MoS2 to ultrastable few-layer MoS2 nanosheets. Such prepared MoS2 nanosheets are rich in S vacancies and metallic 1T phase, which significantly contribute to the boosted catalytic HER activity. Protic solvents play a pivotal role in the production of S vacancies and 2H-to-1T phase transition under laser irradiation. MoS2 exfoliated in an optimal solvent of formic acid exhibits outstanding HER activity with an overpotential of 180 mV at 10 mA cm?2 and Tafel slope of 54 mV dec?1.
关键词： molybdenum disulfide,sulfur vacancy,solvent effect,phase transition,laser exfoliation in liquid
更新于2025-09-11 14:15:04
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Atom-photon bound states and non-Markovian cooperative dynamics in coupled-resonator waveguides
摘要： We study the properties of atom-photon bound states and single-photon cooperative dynamics in a waveguide system which consists of a finite-bandwidth channel with model dispersion and an ensemble of two-level atoms whose size is ignorable when compared with the lattice constant. The bound states are formed by all atoms and a localized photonic excitation. We find that the effect of atomic collection is equivalent to the case of one atom by rescaling the coupling strength with the square root of the atom number, as far as the eigenenergy equation is concerned. Besides, it is found there is a quantum phase transition when more than one type of atom are present. The characteristic lengths and wave functions are analyzed near the phase transition point. The exact analytical results for the cooperative dynamics at the single excitation level are obtained and we point out the dark state in this system leads to a universal population trapping in the time evolution process. This type of trapping obeys a simple law that is only associated with the atom number. A direct conclusion that results from the trapping law is that the single-photon cooperative emission is suppressed when the number of atoms is large enough.
关键词： coupled-resonator waveguides,quantum phase transition,non-Markovian cooperative dynamics,atom-photon bound states,dark state
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 8th International Conference Nanomaterials: Application & Properties (NAP) - Zatoka, Ukraine (2018.9.9-2018.9.14)] 2018 IEEE 8th International Conference Nanomaterials: Application & Properties (NAP) - Theoretical Model of the Processes of Nanostructuring the Material Surface under the Influence of Laser Radiation
摘要： The transition between different structural states of a surface of a solid after influence of laser radiation can be presented by the self-consistent behavior of three parameters: the relaxation field, the fields of stress and the concentration of relaxation zones. Within the framework of the Lorentz system, the transition between stable states of formations on the surface of a solid was presented. The dependence of the stationary value of the order parameter, at which the formation of relaxation zones is possible, was obtained. The intermittent version of the formation of relaxation zones was examined using the mechanism of first order phase transition.
关键词： phase transition,nanostructure,residual deformation,relaxation parameter
更新于2025-09-11 14:15:04
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Barkhausen effect in the first order structural phase transition in type-II Weyl semimetal MoTe <sub/>2</sub>
摘要： We report the first observation of the non-magnetic Barkhausen effect in van der Waals layered crystals, specifically, during transitions between the Td and 1T′ phases in type-II Weyl semimetal MoTe2. Thinning down the MoTe2 crystal from bulk material to about 25 nm results in a drastic strengthening of the hysteresis in the phase transition, with the difference in critical temperature increasing from ~40 K to more than 300 K. The Barkhausen effect appears for thin samples and the temperature range of the Barkhausen zone grows approximately linearly with reducing sample thickness, pointing to a surface origin of the phase pinning effects. The distribution of the Barkhausen jumps shows a power law behavior, with its critical exponent α = 1.27, in good agreement with existing scaling theory. Temperature-dependent Raman spectroscopy on MoTe2 crystals of various thicknesses shows results consistent with our transport measurements.
关键词： Barkhausen effect,2D materials,MoTe2,structural phase transition
更新于2025-09-11 14:15:04