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Hafnia (HfO2) is a potential candidate for the high-k gate dielectrics in next-generation high-power electronics. Its thermal transport properties, which determine the performance of these related high-power electronics, are critical while rarely investigated. Here, the thermal transport properties of HfO2 in a wide temperature range of 300–2000 K with a phase transition between monoclinic and tetragonal phases at ∼1765 K, are systematically studied based on the temperature-dependent effective potential landscapes with both propagating and coherence thermal transport considered. It is found that the cage-like structure of monoclinic HfO2 results in the avoid crossing in the phonon band structures, which increases the three-phonon scattering largely. Some phonon modes with significant scattering matrix can have relatively larger 3ph and 4ph scattering rates in tetragonal HfO2. Consequently, the thermal conductivity of HfO2 is only 11.95–1.72 W/mK at 300–2000 K. Our results further show that propagating phonon channels dominate the thermal transport in HfO2 and contribute at least 70% to the total thermal conductivity. The rest of the thermal conductivity of HfO2 results from the coherence thermal transport channels, which is caused by the overlap of phonons. Four-phonon scatterings are found to be significant for the thermal transport in tetragonal HfO2, which can result in a thermal conductivity reduction of ∼50%. Our results here advance the understanding of the thermal transport in HfO2, which may benefit the performance optimization of HfO2-related electronics. [ABSTRACT FROM AUTHOR]

In this work, we have studied the spin-dependent ballistic transport and anomalous quantum tunneling in bilayer graphene horizontally placed in between two Rashba–Zeeman (RZ) leads under external electric biasing. We investigated the transmission and conductance for the proposed system using scattering matrix formalism and the Landauer–Büttiker formula considering a double delta-like barrier under a set of experimentally viable parameters. We found that the transmission characteristics are notably different for up- and down-spin incoming electrons depending upon the strength of magnetization. Moreover, the transmission of up- and down-spin electrons is found to be magnetization orientation dependent. The maximum tunneling conductance can be achieved by tuning biasing energy and magnetization strength and choosing a material with suitable Rashba spin–orbit coupling (RSOC). This astonishing property of our system can be utilized in fabricating devices, such as spin filters. We found that the Fano factor of our system is 0.4 under strong magnetization conditions, while it reduces to 0.3 under low magnetization conditions. Moreover, we also noticed that the transmission and conductance significantly depend on the Rashba–Zeeman effect. Therefore, considering a suitable RZ material, the tunneling of the electrons can be tuned and controlled. Our result suggests that considering suitable strength and orientation of magnetization with moderate RSOC, one can obtain a different transmission probability for spin species under suitable biasing energy. These results indicate the suitability of the proposed system in fabrication of spintronic devices, such as spin filter, spin transistor, etc. [ABSTRACT FROM AUTHOR]

Within aerosol-rich environments, efficient simulation of frequency-modulated continuous wave (FMCW) laser detector echo characteristics is crucial. Conventional methods often need more efficiency. To address this, we propose a photon matrix-based approach for simulating intricate photon scattering processes, enhancing simulation accuracy. This study focuses on short-range FMCW laser detection under aerosol interference, assessing performance via signal-to-noise ratio (SNR). We analyze the impact of amplitude modulation coefficient and photon count on SNR. Surprisingly, the photon count minimally affects SNR, while the amplitude modulation coefficient significantly influences it. These findings shed light on optimizing FMCW laser detection in aerosol-laden environments. Attention to the amplitude modulation coefficient can notably enhance SNR and overall detection efficiency. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) metasurfaces comprising artificially designed subwavelength unit cells have drawn considerable attention due to the EM properties beyond the limits of natural materials. As one of the representative structures, active polarization conversion metasurface (APCM) is switchable by loading active components. It provides great freedom to manipulate the polarization state of EM waves. However, the current research mainly focused on the application of communication and paid less attention to the radar effect of APCM. APCM redistributes electromagnetic wave energy in multi-polarization channels, so it will have great application potential in polarimetric radar. Herein, based on the fully polarimetric radar one-dimensional high resolution range profile, the radar effect of time-modulated metasurface is studied. For this purpose, a method of target scattering mechanisms manipulation and a polarization-insensitive structure of APCM are proposed. The amplitude-phase joint modulation method is specifically analyzed in detail. The distance transformation and virtual multi-target phenomena are further discovered. Virtual targets along the distance dimension are generated in multi-polarization channels, while the scattering mechanisms of k-order targets are effectively manipulated. The relationship between the target scattering matrix and the modulation parameters is obtained. It may provide an effective method for the application of active metasurface in fully polarimetric radars. [ABSTRACT FROM AUTHOR]

Transfer matrix formalism is widely used in modeling periodic heat diffusion in layered structures. Due to an intrinsic numerical instability issue, this formalism fails at high heating frequencies and/or in thick structures. Inspired by its success in modeling wave propagation, we develop a numerically stable scattering matrix framework to model periodic heat diffusion in stratified solid media. As a concrete example, we apply this scattering matrix methodology to the 3ω method. We first validate our framework using various well-known solutions. Next, we demonstrate the numerical stability of the framework using a configuration that resembles the three-dimensional stacked architecture for chip packing. Last, we propose synthetic "experiments" to exhibit, under certain circumstances, the merits of the scattering matrix formalism in extracting thermal properties. [ABSTRACT FROM AUTHOR]

In this work, we propose a simple scheme to realize an acoustic coherent perfect absorber (CPA) and laser modes by embedding a non-Hermitian dopant in a zero index metamaterial. When the dopant is filled with a loss medium at a specific level, the sample can absorb the incident waves completely. On the other hand, when the dopant is filled with a gain medium, the sample can act as a laser oscillator to boost the incident waves. The theoretical derivation based on the scattering matrix and the numerical simulation based on the finite element method are performed and both show good agreement with each other. We also discover that the CPA and laser modes are very sensitive and can be controlled by adjusting the structure parameters or the relative phase of the incident waves. Moreover, the case that asymmetric incidences have different beam widths is considered. We envision that our work may have potential applications in designing acoustic devices, such as absorbers, transducers, and receivers. [ABSTRACT FROM AUTHOR]

Non-Hermitian scattering systems respecting parity-time symmetry exhibit unidirectional invisibility or reflectionlessness at an exceptional point of the scattering matrix. In this study, we investigate the scattering properties of a one-dimensional acoustic parity-time-symmetric multilayered medium. Parity-time symmetry is defined by a spatial small-amplitude square-wave modulation of the medium parameters in the complex plane. Such a multilayered medium has been demonstrated to reach an exceptional point and support unidirectional invisibility for balanced real and imaginary part modulations of the refractive index. Through the analysis of interference within the medium, we show that the complex modulation of acoustic impedance instead of the refractive index governs the exceptional point of the scattering matrix and determines the occurrence of the unidirectional invisibility. This unidirectional invisibility is further investigated for more general cases of complex parameter distribution including unequal modulation amplitudes and rectangular wave modulation. Our study provides an intuitive physical picture of the occurrence of unidirectional invisibility induced by an exceptional point in acoustic wave systems. Moreover, this study could facilitate the design and practical realization of acoustic parity-time-symmetric structures. [ABSTRACT FROM AUTHOR]

The polarization- and angle-resolved optical responses of the anapole mode in silicon nano-disks array have been experimentally and theoretically investigated. The good agreement between measured data and simulations yields to a consistent description of the anapole mode behavior that exhibits different features for TE or TM polarization excitation. Scattering matrix calculation allows us to disentangle scattered and diffused light contributions and to provide a quantitative estimation of the absorbance enhancement associated with 2D excitation of the anapole mode. We performed the multipolar decomposition of the far-field scattered radiation for both TE and TM polarizations and unambiguously identified the anapole resonant condition in excellent agreement with the experimental results over a large range of incident angles. Our findings demonstrate the controlled excitation of electromagnetic anapole modes in engineered arrays of silicon nano-disks for the development of optical nanostructures with enhanced light–matter interaction. [ABSTRACT FROM AUTHOR]

A three dimensional (3D) dual-band phase gradient metamaterial (PGM) is proposed based on the Pancharatnam-Berry phase approach in this work. First, a 3D dual-band co-polarization reflection metamaterial under circularly polarized (CP) wave incidence was achieved by a vertical metallic Split-Ring Resonator (SRR). The co-polarization reflection efficiency is more than 90% over the spectra 4.78 GHz–4.92 GHz and 11.2 GHz–12.8 GHz. The underlying physical mechanism for copolarization reflection is analyzed by using the scattering matrix approach. Then, the dual-band PGM is constructed by utilizing the vertical metallic SRR with different rotation angles. The PGM can achieve surface wave coupling and efficiently anomalous reflection, respectively, in the two spectra under CP wave incidence. Due to the opposite phase gradients for left-handed circularly polarized and right-handed circularly polarized wave incidence, the incidence linearly polarized wave was divided into two beams of CP waves and coupled into surface waves or anomalously reflected along opposite directions. Both the simulated and measured results demonstrated the great performances of dual-band PGMs. [ABSTRACT FROM AUTHOR]

In this work, we generalize the cascading scattering matrix algorithm for calculating the optical response of concentric multilayered structures comprised of either plasmonic metal or dielectric, within the framework of hydrodynamic convection-diffusion model of electrodynamics. Two additional boundary conditions, namely, the continuity of first order pressure of free electron density and the continuity of normal components of free charge velocity, respectively, are adopted in order to handle the behaviour at interfaces involving metals. Scattering matrices at interfaces can be readily obtained and cascaded to obtain the modal coefficients in each layer by expanding electromagnetic waves in harmonic modes with cylindrical vector wave functions. We have validated the proposed method by analyzing the optical responses of several configurations of nanostructures, including a bi-metallic nanocylinder and a hyperlens. We found that nonlocal effects can be important for small structures, when the characteristic size is comparable to the Fermi wavelength. The proposed method shows its capability and flexibility to solve hybrid metal-dielectric multilayer structures even when the number of layers is large. Although we have discussed our method in the context of the retarded radiation regime, it can be applied in quasi-static scenarios without any difficulties. Furthermore, it may be extended to solve similar problems in other areas of physics, such as acoustics. [ABSTRACT FROM AUTHOR]

A highly efficient nano-periodical grating is theoretically investigated for spectral beam combining (SBC) and is experimentally implemented for attaining high-brightness laser from a diode laser array. The rigorous coupled-wave analysis with the S matrix method is employed to optimize the parameters of the grating. According the optimized parameters, the grating is fabricated and plays a key role in SBC cavity. The diffraction efficiency of this grating is optimized to 95% for the output laser which is emitted from the diode laser array. The beam parameter product of 3.8mmmrad of the diode laser array after SBC is achieved at the output power of 46.3 W. The optical-to-optical efficiency of SBC cavity is measured to be 93.5% at the maximum operating current in the experiment. [ABSTRACT FROM AUTHOR]

This paper presents a new model for the surface roughness (SR) limited mobility in MOS transistors. The model is suitable for bulk and thin body devices and explicitly takes into account the non linear relation between the displacement Δ of the interface position and the SR scattering matrix elements, which is found to significantly influence the r.m.s value (Δrms) of the interface roughness that is necessary to reproduce SR-limited mobility measurements. In particular, comparison with experimental mobility for bulk Si MOSFETs shows that with the new SR scattering model a good agreement with measured mobility can be obtained with Δrms values of about 0.2 nm, which is in good agreement with several AFM and TEM measurements. For thin body III-V MOSFETs, the proposed model predicts a weaker mobility degradation at small well thicknesses (Tw), compared to the Tw6 behavior observed in Si extremely thin body devices. [ABSTRACT FROM AUTHOR]

Using the scattering-matrix method, we studied ballistic phonon transmission and thermal conductance at low temperatures in a cylindrical quantum wire with bridge contacts. The transmission coefficient exhibited a stepped profile, which became more evident as the bridge radius increased. When the dimensions of the bridge are identical to those of main wires, we observed a quantum platform of the thermal conductance, even in the presence of interface scattering. When the dimensions of the bridge are smaller than those of main wires, however, we could not observe the quantum platform. We also revealed other interesting physical properties, such as universal quantum thermal conductance and resonant transmission. A brief analysis of these results is given. [ABSTRACT FROM AUTHOR]

Ballistic thermal conductances (BTCs) by phonons through superlattice quantum-waveguides are investigated by using the scattering-matrix method and the elastic continuum theory. A comparison for the cylindrical model (CM) and the rectangular model (RM) is addressed. We find that for these two models, the quantum thermal conductance can be observed even when the superlattices exist in quantum-waveguides. At low temperature, BTCs for the CM and the RM present almost the same behaviors regardless of the periodic length of superlattices. However, at higher temperature, BTCs for the RM are larger than those for the CM stemming from lower cutoff frequencies of high order modes for the RM. We also find that BTCs undergo a noticeable transformation from the monotonic decrease to constant with increasing the periodic number of superlattices. A brief analysis of these results is given. [ABSTRACT FROM AUTHOR]

We study spin-dependent electron transport in a quantum ring with three leads in the presence of Rashba spin-orbit interaction using the S-matrix method. The effects of coupling between the leads and the ring on spin transport properties are taken into account. The conditions needed for perfect spin polarization, including the value of electron energy, the angles between the leads, the coupling constant of the leads and the Rashba constant are calculated, using contour maps. It is shown that total spin filtering with zero reflection is possible for low coupling constant as well as high coupling constant. In addition, we obtain the maximum value of the lead coupling constant at which perfect spin polarization can take place. [ABSTRACT FROM AUTHOR]

Interest in carbon-based electronics has been stimulated in recent years, initially through the discovery of carbon nanotubes, but recently with the formation of graphene layers. In this paper metal-oxide-semiconductor (MOS) systems based on these carbon structures are used to model and compare charge transport within them. Schrödinger’s equation is solved self-consistently with Poisson’s equation, using the scattering matrix method. A tight-binding model is used to determine the energy band structure in graphene. The current-voltage characteristics of MOS devices based on graphene and those based on carbon nanotubes demonstrate significant differences associated with their respective transmission probabilities. [ABSTRACT FROM AUTHOR]

Tuning the resonant frequency of a 1 uc defect across the bandgap of a three-dimensional woodpile photonic crystal (PC) was achieved by altering the defect¿s permittivity. Experiments were performed at microwave frequencies and calculations were made using the transfer-scattering matrix method. Defect permittivity was varied by using solid materials of different permittivities or by constructing structures smaller than a lattice constant from the the PC lattice materials. These small structures, which will be referred to as ¿sublattice defects,¿ produce an effective permittivity between their two materials¿ permittivities. Changes in mode shape with resonant frequency and permittivity were also examined. [ABSTRACT FROM AUTHOR]

We report a theoretical study of the equilibrium spin current (ESC) flowing in a ferromagnet/ferromagnet (FM/FM) graphene junction with noncollinear magnetizations, in which the FM correlation in graphene is induced by depositing an FM insulator on it. Using the scattering matrix method, we derived an analytical expression of the ESC which is formally the same as that of a normal FM/FM junction. The ESC comes from the exchange coupling between the two FM magnetizations. Owing to the linear dispersion of graphene, the ESC disappears in the one-dimensional case, while it exists in the two-dimensional case. It exhibits damped oscillations with change in the Fermi energy, the layer length between the two FM regions, and the FM exchange splitting. It is also found that ESC in FM/FM graphene junctions has electron-hole inversion symmetry whereas it has electron-hole inversion antisymmetry in normal FM/FM junctions. [ABSTRACT FROM AUTHOR]

The acoustic phonon transport in a four-channel quantum structure is investigated by use of the scattering matrix method. It is found that different acoustic phonon modes transport selectively into different channels, standing waves can be formed owning to acoustic phonons interfering with each other in the quantum structure, the transmission coefficients of acoustic phonon through different channels depend sensitively on the parameters of the structure, and the channels all exhibit the noninteger quantized thermal conductance at very low temperatures due to the splitting of the quantum structure. The structure may be used as a split device for acoustic phonon modes and controlling the acoustic phonon transport. [ABSTRACT FROM AUTHOR]

We derive semianalytic models of two types of photonic crystal resonators by simplifying the Bloch mode scattering matrix method. Essential to the models are two parameters, which are interpreted to be the phase change upon reflection and the measure of orthogonality between modes of adjacent waveguides. The models can predict the resonance position to better than 0.02% and the full width at half maximum to within 10%. [ABSTRACT FROM AUTHOR]

Ultrathin double-gate silicon-on-insulator transistors are studied in the quantum coherent limit. By treating electron-electron interaction on the level of a mean field approach, the density matrix of the device becomes diagonal when expressed in a basis that results from imposing scattering boundary conditions at the terminals. The self-consistent scattering wave functions are computed using a multisubband scattering matrix formalism. This allows us to retain the full dimensionality of the wave functions and eliminates the need for the adiabatic decomposition of the Schrödinger equation. Subband mixing is fully taken into account and a piecewise analytical representation of the wave functions can significantly reduce the number of sampling positions along transport direction. By self-consistent simulations the size of source-to-drain tunneling as a function of gate length is demonstrated for different body thicknesses. A strong forward bias is shown to increase the tunnel current due to the thinning of the source-drain potential barrier. The effect of channel orientation on the tunnel current is also discussed. [ABSTRACT FROM AUTHOR]

We present a compact gate-current model based on the scattering matrix method for metal-oxide-semiconductor devices. The analytical integration of the tunneling current over the incident energy is simplified by making use of the single tunneling energy approximation, and the model error is further reduced by introducing different effective conduction band edges for the supply function and for the transmission coefficient function. Results calculated by the proposed model agree with the experimental data with satisfactory accuracy. [ABSTRACT FROM AUTHOR]

Focuses on the scattering matrix method which was used in the theoretical investigation of magnetotransport in a window-coupled quantum-wire system. Consistency of the system; Information on two magnetic-field configurations; When the electron waveguide couplers were proposed.

Presents information on a study using the scattering-matrix method to present a numerical analysis of an electron waveguide coupler based on two quantum wires coupled by a magnetically defined barrier. How the scattering approach to the magnetically coupled quantum wires was employed; Further details and conclusions of the study.

Electron transport in quantum coherent networks (interacting quantum waveguide arrays) is investigated theoretically with use of the scattering-matrix method. The scattering matrix for the basic unit of networks, the cross junction with square or rounded corners, is derived using the mode-matching technique. The overall scattering matrix for the network is obtained by the composition of the scattering matrices associated with each unit of the network. For a uniform network, the transmission spectra are calculated in the single-mode regime and are found notably dependent on the junction geometry. Small reflection for the input terminal and uniform output for some output ports are obtained, which means that the quantum coherent network can be used as a distributing net for the electron waves. Cross junctions with rounded corners of large radii are found to play a negative role in the device application of quantum coherent networks. [ABSTRACT FROM AUTHOR]

Focuses on a study on the numerical simulation of a coupled-quantum-well resonant tunneling transistor. Improvements made on the quantum distributed model of the resonant tunneling transistor based on a generalized S-matrix method; Reduction of the collector current resonance and the mechanism of the base current; Calculation for the resonant tunneling transistor.

Reports on the calculation of the time-varying charge buildup in the quantum well region of a resonant tunneling diode (RTD) and related capacitive effects using the scattering matrix method. Band structure of a resonant tunneling diode under bias; Scattering matrix between regions with different modulation phases; Discussion on the capacitive effect in a RTD.

Reports on realistic structures for electron interferometers constituted by the control of the wavefunctions in double quantum wire structures. Calculation of electron wave functions and propagation by scattering matrix formalism; Features of semiconductor devices based on quantum interference phenomena; Schematic structure of the electron interferometer.

Presents a spectral method for solving the Boltzmann equation by the scattering matrix approach. Information on the rationale behind the choice of the basis function; Discussion of the orthogonal transformation; Application in the simulation of both the bulk and device properties with arbitrary field profiles.

Presents a study that calculated the far-infrared optical response of a structure consisting of a perfectly conducting grating gate on a modulation-doped gallium arsenide/aluminum gallium arsenide heterojunction using the scattering matrix technique. Discussion of the scattering matrix model for heterojunction systems; Details of an effective dielectric constant; Field distributions.

Presents a study that used a practical numerical method for obtaining the scattering matrix for an electron at a junction between regions having different confining potentials in the transverse direction. Theoretical formulation; Information on coupling from a channel to a reservoir; Summary and conclusions.

The practical design of composite material suggests that there is a need for an improved quantitative understanding of the interaction between acoustic waves and microspheres. The multiple scattering method is used to investigate the sound attenuation of the viscoelastic polymer containing hollow glass microspheres. Then the dynamics of the hollow glass microspheres is investigated by reference to the elements of the scattering matrices. It shows that the dilatational vibration of the microsphere plays a key role in the sound attenuation within the viscoelastic polymer composite at the quasistatic region. The thinner glass shell undergoes more severe dilatational vibration and induces more attenuation in the polymer composite. [ABSTRACT FROM AUTHOR]

A simple photonic device consisting of two dangling side resonators grafted at two sites on a waveguide is designed in order to obtain sharp resonant states inside the transmission gaps without introducing any defects in the structure. This results from an internal resonance of the structure when such a resonance is situated in the vicinity of a zero of transmission or placed between two zeros of transmission, the so-called Fano resonances. A general analytical expression for the transmission coefficient is given for various systems of this kind. The amplitude of the transmission is obtained following the Fano form. The full width at half maximum of the resonances as well as the asymmetric Fano parameter are discussed explicitly as function of the geometrical parameters of the system. In addition to the usual asymmetric Fano resonance, we show that this system may exhibit an electromagnetic induced transparency resonance as well as well as a particular case where such resonances collapse in the transmission coefficient. Also, we give a comparison between the phase of the determinant of the scattering matrix, the so-called Friedel phase, and the phase of the transmission amplitude. The analytical results are obtained by means of the Green's function method, whereas the experiments are carried out using coaxial cables in the radio-frequency regime. These results should have important consequences for designing integrated devices such as narrow-frequency optical or microwave filters and high-speed switches. This system is proposed as a simpler alternative to coupled-micoresonators. [ABSTRACT FROM AUTHOR]