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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57
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Field Squeezing in a Quantum-Dot Molecule Jaynes-Cummings Model
摘要： We investigate the field squeezing in a system composed of an initial coherent field interacting with two quantum dots coupled by electron tunneling. An approximate quantum-dot molecule Jaynes-Cummings model describing the system is given, and the effects of physical quantities, such as the temperature, phonon-electron interaction, mean photon number, field detuning, and tunneling-level detuning, are discussed in detail.
关键词： Jaynes-Cummings model,phonon-electron interaction,electron tunneling,quantum-dot molecule,field squeezing
更新于2025-09-23 15:19:57
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Determination of size dependent carrier capture in InGaN/GaN quantum nanowires by femto-second transient absorption spectroscopy: effect of optical phonon, electron-electron scattering and diffusion
摘要： Understanding the ultrafast processes corresponding to carrier capture, thermalization and relaxation is essential to design high-speed optoelectronic devices. Here, we have investigated size dependent carrier capture process in InGaN/GaN 20 nm, 50 nm nanowires and quantum well systems. Femto-second transient absorption spectroscopy reveals that the carrier capture is a two-step process. The carriers are captured in the barrier by polar optical phonon scattering. They further scatter into the active region by electron-electron and polar optical phonon scatterings. The capture is found to slow down for quantum confined structures. A significant number of carriers are found to disappear from the barrier during the diffusion process. All the experimental observations are explained in a simulation framework depicting various scattering mechanisms.
关键词： nanowire,polar optical phonon scattering,electron-electron scattering,transient absorption spectroscopy,carrier capture,electron and phonon dynamics
更新于2025-09-19 17:15:36
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Thermoelectric Properties of (100) Oriented Silicon and Nickel Silicide Nanocomposite Films Grown on Si on Insulator and Si on Quartz Glass Substrates
摘要： We have grown (100) oriented composite films of Si and Ni silicide nanocrystals (Ni–Si NC film) on substrates of Si on insulator (SOI) and Si on quartz glass (SOQ). Owing to improvement of carrier transport properties and reduction of the thermal conductivity in the oriented films, they have higher dimensionless figures of merit, ZT of 0.22–0.42 for p-type Ni–Si NC film and 0.08–0.13 for n-type Ni–Si NC film than that of bulk Si (ZT < 0.01) at 30°C. The ZT values of p-type and n-type Ni–Si NC films were increased to 0.65 and 0.40 at 500°C, respectively.
关键词： silicon based thermoelectric materials,nanocomposite films,nickel silicide nanocrystals,silicon nanostructures,phonon scattering
更新于2025-09-19 17:15:36
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Transient Dynamics of Super Bloch Oscillations of a 1D Holstein Polaron under the Influence of an External AC Electric Field
摘要： Theoretical formalism for DC-field polaron dynamics is extended to the dynamics of a 1D Holstein polaron in an external AC electric field using multiple Davydov trial states. Effects of carrier–phonon coupling on detuned and resonant scenarios are investigated for both zero and nonzero phase. For slightly off-resonant or detuned cases, a beat between the usual Bloch oscillations and an AC driving force results in super Bloch oscillations, that is, rescaled Bloch oscillations in both the spatial and the temporal dimension. Super Bloch oscillations are damped by carrier–phonon coupling. For resonant cases, if the carrier is created on two nearest-neighboring sites, the carrier wave packet spreads with small-amplitude oscillations. Adding carrier–phonon coupling localizes the carrier wave packet. If an initial broad Gaussian wave packet is adopted, the centroid of the carrier wave packet moves with a certain velocity and with its shape unchanged. Adding carrier–phonon coupling broadens the carrier wave packet and slows down the carrier movement. Our findings may help provide guiding principles on how to manipulate the dynamics of the super Bloch oscillations of carriers in semiconductor superlattice and optical lattices by modifying DC and AC field strengths, AC phases, and detuning parameters.
关键词： Davydov Ansatz,polaron dynamics,carrier–phonon coupling,super Bloch oscillations
更新于2025-09-19 17:15:36
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Tamm Polaritons and Cavity Modes in the FIR Range
摘要： Tamm polaritons (TPs) are formed at the interface between two semi-infinite periodic dielectric structures (Bragg mirrors) or other reflectors. Contrary to usual surface polaritons, TPs exist inside the "light cone", even though their amplitude also decreases exponentially with the distance from the interface as it is characteristic of evanescent waves. They couple to elementary excitations in the materials or structures that form the interface, such as metal plasmons or semiconductor excitons. Here we discuss the formation of TPs in the far-infrared (FIR) spectral range, in the optical-phonon reststrahlen band of a polar semiconductor such as GaAs, with a Bragg reflector (BR) as the second mirror. Their dispersion relation and the frequency window for the TP existence are discussed for a GaAs-BR interface and also structures containing a gap between the two reflectors.
关键词： phonon,Bragg reflector,semiconductor,optical Tamm state
更新于2025-09-19 17:15:36
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Phonon scattering by dislocations in GaN
摘要： Crystal imperfections such as dislocations strongly influence the performance and thermal transport behavior of GaN-based devices. We show that the experimental data used to parameterize the effect of dislocations on the thermal conductivity can be explained using only the reported film thickness and point defect concentrations. The analysis highlights the boundary-scattering-governed reduction of thermal conductivity in GaN, which had been underestimated in earlier models. To quantify the influence of dislocations on the thermal transport in GaN, we adopt a Green’s function approach based on accurate ab-initio interatomic force constants. While calculations at the level of density functional theory are necessary for 3-phonon and point defect scattering, we show that scattering due to dislocations can be satisfactorily approximated using semiempirical potentials. This makes the Green’s function approach to dislocation scattering a quantitatively predictive, yet computationally practical, method for obtaining detailed phonon scattering rates.
关键词： Dislocation,Phonon Scattering,Density Functional Theory,GaN,Thermal Conductivity
更新于2025-09-19 17:15:36
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Remote Phonon Scattering in Two-Dimensional InSe FETs with High-κ Gate Stack
摘要： This work focuses on the effect of remote phonon arising from the substrate and high-κ gate dielectric on electron mobility in two-dimensional (2D) InSe field-effect transistors (FETs). The electrostatic characteristic under quantum confinement is derived by self-consistently solving the Poisson and Schr?dinger equations using the effective mass approximation. Then mobility is calculated by the Kubo–Greenwood formula accounting for the remote phonon scattering (RPS) as well as the intrinsic phonon scatterings, including the acoustic phonon, homopolar phonon, optical phonon scatterings, and Fr?hlich interaction. Using the above method, the mobility degradation due to remote phonon is comprehensively explored in single- and dual-gate InSe FETs utilizing SiO2, Al2O3, and HfO2 as gate dielectric respectively. We unveil the origin of temperature, inversion density, and thickness dependence of carrier mobility. Simulations indicate that remote phonon and Fr?hlich interaction plays a comparatively major role in determining the electron transport in InSe. Mobility is more severely degraded by remote phonon of HfO2 dielectric than Al2O3 and SiO2 dielectric, which can be effectively insulated by introducing a SiO2 interfacial layer between the high-κ dielectric and InSe. Due to its smaller in-plane and quantization effective masses, mobility begins to increase at higher density as carriers become degenerate, and mobility degradation with a reduced layer number is much stronger in InSe compared with MoS2.
关键词： two-dimensional material,indium selenide,mobility,phonon scattering,high-κ dielectric,field effect transistor
更新于2025-09-19 17:15:36
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Thermostimulated THz Radiation Emission of GaAs at Surface Plasmon-Phonon Polariton Frequencies
摘要： The THz radiation reflection, absorption and emission spectra of conductive n-GaAs/air surface are considered. The influence of thermostimulated surface plasmon-phonon (SPP) polariton oscillations on THz radiation reflection, absorption and emission of high conductivity GaAs polished plates with electron density n = 7·1017 cm–3 and 4·1018 cm–3 and thickness of 350 μm is studied experimentally. The frequencies of thermostimulated transverse and longitudinal optical phonons and SPP oscillations, which characterize a heated lattice state, were determined. It is found that the heated highly doped interface layer (GaAs/air) emits the THz radiation at selected frequencies of SPP oscillations in the (7 – 8) THz and (10 – 15) THz ranges. It is shown that thermal heating of the GaAs/air interface enhances the absorption of the incident THz radiation. The huge decrease of the incident radiation reflectivity at the SPP frequencies with an increase of GaAs temperature is observed experimentally.
关键词： surface plasmon-phonon polaritons,black-body radiation,GaAs,thermostimulated THz radiation emission
更新于2025-09-19 17:15:36
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Hydrothermal Synthesis and Luminescent Properties of Spindle-Like NaGd(MoO <sub/>4</sub> ) <sub/>2</sub> :Eu <sup>3+</sup> Phosphors
摘要： Spindle-like NaGd(MoO4)2: Eu3 + phosphors with various Eu3 + concentrations were prepared via a hydrothermal process and characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The XRD results suggested that the prepared samples had a scheelite structure. The FE-SEM images indicated that the prepared NaGd(MoO4)2: Eu3 + phosphors were spindle-like. The influences of the ratio of sodium citrate and the rare earth cations on the product were studied. It was found that sodium citrate, as the chelating agent, could significantly influence the structure and morphology of the samples. The emission spectra, excitation spectra, fluorescence decay curves, and quantum yields of the samples were measured. The luminescent properties of the materials were studied. The results indicated that the electron–phonon coupling between the Eu3 + and the NaGd(MoO4)2 host was weak, and with the increase of the Eu3 + concentration, the Huang–Rhys factor increased. Additionally, the quantum efficiency of the Eu3 + 5D0 level was calculated, and it was found that the quantum efficiency decreased with the increase of the Eu3 + concentration.
关键词： Electron-phonon coupling,Rare earth,Hydrothermal,Molybdate,Luminescence
更新于2025-09-19 17:15:36