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关键词： Silicon quantum dots   Surface functionalization   Luminescence properties   Charge transfer  

摘要： Controlling the emission wavelength by the quantum confinement or the size effect of silicon quantum dots (Si QDs) has a limitation in that it can be only approximately 600 nm or above. To overcome this limitation, in the recent decade, numerous studies have been conducted for reproducing the entire visible range from blue to red from Si QDs by their surface functionalization. In this study, we fabricated alkyl- and amine-passivated Si QDs and investigated their emission mechanism following surface functionalization. We interpreted the emission mechanism of the surface-functionalized Si QDs by combined experimental analysis of the decay time dynamics and density functional theory-based model calculation of the highest occupied molecular orbital-lowest unoccupied molecular orbital electronic structures. Our comprehensive studies could provide insight into the debated problems of the luminescence mechanism of surface-functionalized Si QDs.

关键词： Modulated photoluminescence   Photocarrier radiometry   Lifetime metrology   Nonlinear dynamics   Physical lifetime resolution   Homodyne and heterodyne detection  

摘要： Semiconductor characterization techniques based on modulated photoluminescence (PL) combine the general advantages of PL metrology with the superior quality benefits of modulated signal generation and lock-in detection. The exciting field of camera-based PL imaging has recently emerged and is proving to be very promising for in-line spatially resolved and globally integrated monitoring of dynamic electronic properties of semiconductor materials and devices during various fabrication and manufacturing stages. Yet, the multiple nonlinearities involved in dynamic PL and their behavior under modulated excitation have neither been adequately addressed theoretically nor quantitatively analyzed, resulting in either misleading interpretations of experimental data or leading to the popular compromise of using the physically ambiguous concept - effective lifetime - as the target measurement parameter, which lumps all the excess carrier de-excitation events together and creates persistent confusion in the comparison among different lifetime measurement techniques. By taking three dominant nonlinearities into account that contribute to dynamic PL responses in Si, the present investigation provides a fully nonlinear frequency-domain model of carrier recombination dynamics under harmonically modulated excitation, based on which six intrinsic electronic parameters of a Si wafer can be resolved and measured simultaneously, i.e. the doping density, the two Shockley-Read-Hall time constants, the radiative recombination coefficient, and the two Auger recombination coefficients. The combined theoretical and experimental technique represents a time demultiplexing methodology which allows the deconvolution of temporally superposed excess carrier de-excitation processes which might otherwise remain unresolved - hidden in superposition - as is typically the case with conventional effective lifetime metrologies. This all-optical and noncontacting electronic quality control approach links su

关键词： Integral fractional Laplacian   Fractional generalized wave equation   Dissipation-preserving difference scheme   Krylov subspace solver   Preconditioner   Fast Fourier transform  

摘要： In this paper, we construct a dissipation-preserving difference scheme for two-dimensional nonlinear generalized wave equations with the integral fractional Laplacian. We discuss the discrete dissipation property of the scheme in detail, and we also analyze the existence, uniqueness and the unconditional convergence of the proposed scheme. Further, we reveal that the spatial discretization generates a block-Toeplitz coefficient matrix, and it will be ill-conditioned as the spatial grid mesh number M and the fractional order alpha increase. Thus, we exploit an efficient linearized iteration algorithm for the nonlinear system, such that it can be efficiently solved by the Krylov subspace solver with a suitable preconditioner, where the two-dimensional fast Fourier transform is used in the solver to accelerate the matrix-vector product. Extensive numerical experiments are provided to verify the theoretical analysis and discrete dissipation law of the proposed scheme in long-time computations. (C) 2021 Published by Elsevier B.V.

关键词： Fractional p‐   Laplacian   bifurcation from infinity   Nehari Manifold   Fibering Maps  

摘要： In this paper, we discuss the bifurcation from infinity for nonlinear problem with a fractional p-Laplacian in.. -fractional space H..,..;.. p, whose bifurcation is directly linked to the signal T. 0 b(x)|..1|q+1dx with 1< q< p- 1.

关键词： critical point theorem   fractional differential equations   instantaneous and non‐   instantaneous impulses   p‐   Laplacian  

摘要： We discuss a class of p-Laplacian fractional differential equations with instantaneous and non-instantaneous impulsive boundary conditions. The existence of an unbounded sequence of weak solutions is given by a recent critical point theory proposed by Bonanno and Bisci. At the end, an example is presented to illustrate our main results.

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关键词： Tensors  

摘要： We describe an iterative formalism to compute influence functionals that describe the general quantum dynamics of a subsystem beyond the assumption of linear coupling to a quadratic bath. We use a space-time tensor network representation of the influence functional and investigate its approximability in terms of its bond dimension and time-like entanglement in the tensor network description. We study two numerical models, the spin-boson model and a model of interacting hard-core bosons in a 1D harmonic trap. We find that the influence functional and the intermediates involved in its construction can be efficiently approximated by low bond dimension tensor networks in certain dynamical regimes, which allows the quantum dynamics to be accurately computed for longer times than with direct time evolution methods. However, as one iteratively integrates out the bath, the correlations in the influence functional can first increase before decreasing, indicating that the final compressibility of the influence functional is achieved via non-trivial cancellation. Published under an exclusive license by AIP Publishing.

关键词： Copolymerization   Monomers   Copolymers   Solvents   Reactivity  

摘要： The thermodynamic formulation of transition state theory is applied to compute the effect of the medium (solvent type and concentration) on the copolymer composition obtained in radical copolymerization. The magnitude of the medium effect on the deviation of the reactivity ratios (of the terminal model) with respect to the value observed in a reference state is shown to be linked to the degree of the thermodynamic nonideality of the system and, more specifically, to the activity coefficients of the two monomers and transition states involved in each reactivity ratio. To illustrate and validate this thermodynamic approach, the quantum chemistry-based solvation model COSMO-RS (Conductor-like Screening MOdel for Real Solvents) was used to estimate the relevant activity coefficients for a variety of comonomer-solvent combinations for which copolymer composition curves are reported in the literature. The evaluation was based on a limited (by necessity) but broad selection of systems for which different qualitative explanations for the medium effect are proposed in the literature. Overall, the comparison between measurements and predictions shows that the qualitative trends are well captured, and in many cases, the quantitative agreement is also quite remarkable, demonstrating the potential of our unified approach. There is one exception: for reasons not yet understood, our method considerably fails for copolymer systems involving amide monomers.

关键词： Degrees of freedom (mechanics)  

摘要： Ultrafast chemical reactions are difficult to simulate because they involve entangled, many-body wavefunctions whose computational complexity grows rapidly with molecular size. In photochemistry, the breakdown of the Born-Oppenheimer approximation further complicates the problem by entangling nuclear and electronic degrees of freedom. Here, we show that analog quantum simulators can efficiently simulate molecular dynamics using commonly available bosonic modes to represent molecular vibrations. Our approach can be implemented in any device with a qudit controllably coupled to bosonic oscillators and with quantum hardware resources that scale linearly with molecular size, and offers significant resource savings compared to digital quantum simulation algorithms. Advantages of our approach include a time resolution orders of magnitude better than ultrafast spectroscopy, the ability to simulate large molecules with limited hardware using a Suzuki-Trotter expansion, and the ability to implement realistic system-bath interactions with only one additional interaction per mode. Our approach can be implemented with current technology;e.g., the conical intersection in pyrazine can be simulated using a single trapped ion. Therefore, we expect our method will enable classically intractable chemical dynamics simulations in the near term.

关键词： Parabolic partial differential equation   Blowing up   Parabolic   Blowup  

摘要： In this article, we are concerned with a problem for the p-Laplacian parabolic equation with logarithmic nonlinearity;the blow-up result of the solution is proven. This work is completed Boulaaras' work in Math. Methods Appl. Sci., (2020), where the author did not study the blowup of the solution.