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Phase relation between supercooled liquid and amorphous silicon
摘要： The phase relation between supercooled liquid silicon (l-Si) and amorphous silicon (a-Si) is discussed based on experimental results. Electrostatically levitated l-Si samples were supercooled down to low temperatures, 300 K below the melting temperature (Tcl: 1683 K), and solidified accompanied by the release of latent heat. It was found that solidified Si samples melted again at 1480 K caused by the latent heat. Also, it was found that the Si samples that rapidly quenched near the solidification temperature contained a large amount of a-Si with tetrahedral coordination. These two findings show that the supercooled l-Si samples solidified into a-Si and a-Si melted, confirming the idea of a first-order phase transition between two metastable phases proposed by Turnbull et al. [Metall. Mater. Trans. A 29, 1825 (1998)].
关键词： supercooled liquid silicon,electrostatic levitation,amorphous silicon,latent heat,phase transition
更新于2025-09-19 17:13:59
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Strain-induced structural phase transition, electric polarization and unusual electric properties in photovoltaic materials CsMI <sub/>3</sub> (M = Pb, Sn)
摘要： The structural phase transition, ferroelectric polarization, and electric properties have been investigated for photovoltaic films CsMI3 (M = Pb, Sn) epitaxially grown along (001) direction based on the density functional theory. The calculated results indicate that the phase diagrams of two epitaxial CsPbI3 and CsSnI3 films are almost identical, except critical transition strains varying slightly. The epitaxial tensile strains induce two ferroelectric phases Pmc21, and Pmn21, while the compressive strains drive two paraelectric phases P212121, P21212. The larger compressive strain enhances the ferroelectric instability in these two films, eventually rendering them another ferroelectric state Pc. Whether CsPbI3 or CsSnI3, the total polarization of Pmn21 phase comes from the main contribution of B-position cations (Pb or Sn), whereas, for Pmc21 phase, the main contributor is the I ion. Moreover, the epitaxial strain effects on antiferrodistortive vector, polarization and band gap of CsMI3 (M = Pb, Sn) are further discussed. Unusual electronic properties under epitaxial strains are also revealed and interpreted.
关键词： structural phase transition,electric properties,photovoltaic films,ferroelectric polarization,epitaxial strain,density functional theory,CsMI3
更新于2025-09-19 17:13:59
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Realization of near-infrared active Fano-resonant asymmetric metasurface by precisely controlling the phase transition of Ge2Sb2Te5
摘要： Realization of near-infrared active Fano-resonant asymmetric metasurface by precisely controlling the phase transition of Ge2Sb2Te5
关键词： Ge2Sb2Te5,metasurface,phase transition,near-infrared,Fano resonance
更新于2025-09-19 17:13:59
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Modification characteristics of filamentary traces induced by loosely focused picosecond laser in sapphire
摘要： The ability of loosely focused picosecond laser to induce filamentation (4.8 times the Rayleigh length) in sapphire was confirmed. The morphology and microstructure of the filamentary traces under typical pulse energy were studied, in which the colorful birefringence phenomenon and damage defects were detected in sapphire. Irreversible ceramic-like polycrystalline microstructures were formed in filamentary traces, and the phase transition from α-Al2O3 to γ-Al2O3 directly reflected the thermal effect of picosecond laser filamentation. According to the filamentary characteristics, a continuous filamentary channel with a uniform diameter of 33 μm and a length of 7443 μm was obtained by gradually raising the focal position. The research provides first-hand information for the high throughput micro-cutting, micro drilling and thin slicing of sapphire based on ultrafast laser non-linear effects.
关键词： Phase transition,Modification,Picosecond laser,Filamentation,Sapphire
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - High Responsivity and Low NEP of Room-Temperature Terahertz Antenna-Coupled Microbolometers with Meander Titanium Thermistor
摘要： In this paper, we first formulate the confinement-escape problem of a defender and an evader who attempts escaping from a circular region, which differs from the traditional pursuit-evasion problems. In our setting of the confinement-escape problem, the defender is restricted to move and patrol on the circle, trying to prevent possible escape of the evader who is initially located inside the circle. We describe and characterize some general properties of the problem, and then design two bio-inspired control strategies for the evader and the defender, respectively. In addition, we illustrate some possible motion patterns of the system, investigate the escaping time as a function of the relative-initial-positions of the agents, as well as the winning sets of the two players, respectively, under different system-parameters. To that end, we characterize the contour lines of the winning sets with their gradient properties. Finally, we indicate the abrupt phase transitions between successful confinement and escaping, revealing the strong sensitivity and nonlinearities of the system under critical conditions.
关键词： Confinement-escape problem,phase transition,evader,pursuer-evader,defender,patrolling,pursuit-evasion
更新于2025-09-19 17:13:59
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Electro-absorption spectra of magnetic states of diamond shaped graphene quantum dots
摘要： In this work, employing restricted Hartree-Fock (RHF) as well as unrestricted Hartree-Fock (UHF) mean-field theory and incorporating long-range coulomb interactions within the Pariser-Parr-Pople (PPP) model based Hamiltonian, the effect of size and electric field on the optical properties of various magnetic states of diamond shaped graphene quantum dots (DQDs) has been elucidated. Our calculations have demonstrated that the energetic ordering of excited states and consequently the sequence of electric-field induced phase transition exhibited by the different magnetic phases changes with varying size of DQDs. The optical band-gap for the AF state decreases very gradually as compared to that of the FM and NM configurations, with increase in size of DQD. It is observed that the optical spectrum of the anti-ferromagnetic (AF) state exhibits a spin-sensitive splitting, while no such splitting is observed for the ferromagnetic (FM) configuration, under the application of electric field. In addition, our computations have established that the magnitude of optical band-gap splitting and the shifting trends (red-shift or blue-shift) of the optical spectrum of spin-up orbitals with respect to that of spin-down orbitals of the AF phase, with the application of electric field, can be tuned by changing the size of DQD.
关键词： Electro-absorption spectra,Phase transition,Pariser-Parr-Pople model,Graphene quantum dots,Magnetic properties
更新于2025-09-19 17:13:59
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The Scaling of Ligand Concentration and Soret Effect Induced Phase Transition in CsPbBr3 Perovskite Quantum Dots
摘要： The intelligent chemistry strategy based automated machine is applied for the study of the phase transition in the CsPbBr3 quantum dots (QDs). With the in-situ photoluminescence (PL) signal detector and analysis module, the oleyl amine (OLA) and oleyl acid (OA) ligands concentration dependent diffusion picture are well derived, a three-stage power-law scaling is disclosed on the ligands concentration dependent growth, and a phase transformation from CsPbBr3 to Cs4PbBr6 QDs are confirmed. Based on the experimental analysis associated with the G0W0-BSE calculation, we confirmed that there is no significant PL signal in the pure Cs4PbBr6 structure. With the steady temperature control module, we find the ligand concentration and the Soret effect are isomorphic for the mass flux in the QDs nucleation and phase transformation. We find the activity of the surface states can be essential for the size dependence of the Soret effect in a general way.
关键词： CsPbBr3,Soret effect,quantum dots,phase transition,ligand concentration
更新于2025-09-16 10:30:52
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From normal diffusion to superdiffusion: Photothermal heating of plasmonic core-shell microgels
摘要： The motion of core-shell colloids during laser heating is studied using angle-dependent pump-probe dynamic light scattering. The cores consist of a single spherical gold nanoparticle whose localized surface plasmon resonance has a strong spectral overlap with the wavelength of the pump laser. They are homogeneously encapsulated in thick hydrogel shells composed of either chemically cross-linked poly-N-isopropylacrylamide or poly[2-(2-methoxyethoxy)ethyl methacrylate], both of which exhibit a temperature-dependent volume phase transition. Thus, upon heating beyond the transition temperature, the hydrogel shells shrink. Intensity-time autocorrelation functions are recorded while illuminating the samples with the pump laser and hence heating the gold cores. With increasing laser intensity, the dynamics changes from normal Brownian motion to superdiffusion. Nevertheless, in the high-q limit, the relaxation times can be extracted and used to estimate the temperature increase, which can reach almost 10 K. This causes a significant deswelling of the hydrogel shells, which is also measured.
关键词： temperature-dependent volume phase transition,photothermal heating,dynamic light scattering,superdiffusion,plasmonic core-shell microgels
更新于2025-09-16 10:30:52
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Phase transition induced spectral tuning of dual luminescent crystalline zinc-phthalocyanine thin films and OLEDs
摘要： We analyze the impact of the first order structural phase transition between the a- and b-phases in crystalline zinc-phthalocyanine thin films on their luminescent behavior. Upon optical excitation, two intensity maxima governing the dual fluorescence can be attributed to thin film excimer emission of the a-phase at 930 nm and bulk Frenkel exciton emission of the corresponding b-phase at 780 nm. Comprehensive temperature and time dependent studies on the structural phase transition reveal a controllable shift of spectral weight between these two maxima. Applying this approach to thin film devices, we demonstrate the preparation of dual luminescent organic light emitting diodes with tunable emission characteristics in the near infrared, which are of interest as electro-optical units in future hybrid photonic devices.
关键词： phase transition,zinc-phthalocyanine,spectral tuning,OLEDs,thin films
更新于2025-09-16 10:30:52
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Facile Preparation of Molybdenum Disulfide Quantum Dots Using a Femtosecond Laser
摘要： Molybdenum disulfide (MoS2) is rapidly emerging in a wide range of applications owing to its superior optical, electrical, and catalytic properties. In particular, aside from the current great interest in monolayer MoS2, MoS2 quantum dots (QDs) have received much attention in the electronics and optoelectronics fields owing to their inherent electrical and optical properties arising from the quantum confinement effect. Thus, various methods for producing MoS2 QDs, such as exfoliation, substrate growth, and colloidal synthesis, have been attempted. In this study, the method for manufacturing MoS2 QD with a size of 10 nm which is simpler than the conventional method was devised. On the basis of characterization of the prepared MoS2 QD samples, resistive switching devices was fabricated. These devices demonstrated stable unipolar resistive switching behavior without an electroforming process. This study provides a new approach for the mass production of MoS2 QD and one of their potential applications.
关键词： exfoliation,memristor,MoS2,quantum confinement effect,phase transition
更新于2025-09-16 10:30:52