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Journal articles on the topic 'Two-dimensional materials; quantum-mechanical modeling; electron transport simulations'
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Lovarelli, Giuseppe, Gaetano Calogero, Gianluca Fiori, and Giuseppe Iannaccone. "Multiscale Pseudoatomistic Quantum Transport Modeling for van der Waals Heterostructures." Physical Review Applied 18 (September 19, 2022): 034045. https://doi.org/10.1103/PhysRevApplied.18.034045.
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Several electronic and optoelectronic devices have been proposed in recent years based on vertical heterostructures of two-dimensional (2D) materials. The large number of combinations of available 2D materials and the even larger number of possible heterostructures require effective and predictive device-simulation methods, to inform and accelerate experimental research and to support the interpretation of experiments. Here, we propose a computationally effective and physically sound method to model electron transport in 2D van der Waals heterostructures, based on a multiscale approach and quasiatomistic Hamiltonians. The method uses <em>ab initio</em> simulations to extract the parameters of a simplified tight-binding Hamiltonian based on a uniform three-dimensional lattice geometry that enables device simulations using the nonequilibrium Green’s function approach in a computationally effective way. We describe the application and limitations of the method and discuss the examples of two use cases of practical electronic devices based on 2D materials, such as a field-effect transistor and a floating-gate memory, composed of molybdenum disulphide, hexagonal boron nitride and graphene.
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Lee, Youseung, Demetrio Logoteta, Nicolas Cavassilas, Michel Lannoo, Mathieu Luisier, and Marc Bescond. "Quantum Treatment of Inelastic Interactions for the Modeling of Nanowire Field-Effect Transistors." Materials 13, no. 1 (2019): 60. http://dx.doi.org/10.3390/ma13010060.
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During the last decades, the Nonequilibrium Green’s function (NEGF) formalism has been proposed to develop nano-scaled device-simulation tools since it is especially convenient to deal with open device systems on a quantum-mechanical base and allows the treatment of inelastic scattering. In particular, it is able to account for inelastic effects on the electronic and thermal current, originating from the interactions of electron–phonon and phonon–phonon, respectively. However, the treatment of inelastic mechanisms within the NEGF framework usually relies on a numerically expensive scheme, implementing the self-consistent Born approximation (SCBA). In this article, we review an alternative approach, the so-called Lowest Order Approximation (LOA), which is realized by a rescaling technique and coupled with Padé approximants, to efficiently model inelastic scattering in nanostructures. Its main advantage is to provide a numerically efficient and physically meaningful quantum treatment of scattering processes. This approach is successfully applied to the three-dimensional (3D) atomistic quantum transport OMEN code to study the impact of electron–phonon and anharmonic phonon–phonon scattering in nanowire field-effect transistors. A reduction of the computational time by about ×6 for the electronic current and ×2 for the thermal current calculation is obtained. We also review the possibility to apply the first-order Richardson extrapolation to the Padé N/N − 1 sequence in order to accelerate the convergence of divergent LOA series. More in general, the reviewed approach shows the potentiality to significantly and systematically lighten the computational burden associated to the atomistic quantum simulations of dissipative transport in realistic 3D systems.
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Golsanamlou, Zahra, Luca Sementa, Teresa Cusati, Giuseppe Iannaccone, and Alessandro Fortunelli. "Theoretical Analysis of a 2D Metallic/Semiconducting Transition-Metal Dichalcogenide NbS2//WSe2 Hybrid Interface." Advanced Theory and Simulations 3 (October 27, 2020): 2000164. https://doi.org/10.1002/adts.202000164.
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A first-principles theoretical study of a monolayer-thick lateral heterostructure (LH) joining two different transition metal dichalcogenides, NbS<sub>2</sub> and WSe<sub>2</sub>, is reported. The NbS<sub>2</sub>//WSe<sub>2</sub> LH can be considered a prototypical example of a metal (NbS<sub>2</sub>)/semiconductor (WSe<sub>2</sub>) 2D hybrid heterojunction. First, realistic atomistic models of the NbS<sub>2</sub>//WSe<sub>2</sub> LH are generated and validated, its band structure is derived, and it is subjected to a fragment decomposition and electrostatic potential analysis to extract a simple but quantitative model of this interfacial system. Stoichiometric fluctuations models are also investigated and found not to alter the qualitative picture. Then, electron transport simulations are conducted and they are analyzed via band alignment analysis. It is concluded that the NbS<sub>2</sub>//WSe<sub>2</sub> LH appears as a robust seamless in-plane 2D modular junction for potential use in optoelectronic devices going beyond the present miniaturization technology.
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Luisier, Mathieu, Jan Aeschlimann, Jonathan Backman, et al. "(Invited) Advanced Modeling of Nanoscale Devices." ECS Meeting Abstracts MA2023-01, no. 33 (2023): 1849. http://dx.doi.org/10.1149/ma2023-01331849mtgabs.
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Moore’s scaling law has survived during more than 50 years because the transistor fabrication recipes have been continuously adapted and technology boosters have been gradually introduced, e.g. strain, high- dielectrics, or 3-D FinFETs. The driving force behind these innovations has always been the intuition of clever researchers who benefited from classical technology computer aided design (TCAD) tools. The latter have been used in the semiconductor industry since the end of the 1970’s, when the first 2-D simulations of CMOS devices became feasible on a supercomputer [1]. Over the last 40 years, transistors have undergone tremendous evolutions, their dimensions being reduced by several orders of magnitude, while the physical models at the core of commercially available device simulators have remained the same: electron transport is still described by classical drift-diffusion (DD) equations, which have been modified to capture parts of the quantum mechanical effects affecting nano-transistors, e.g. geometrical confinement tunnelling leakages, or energy quantization [2]. A new generation of advanced TCAD tools that go beyond the DD equations and rely on atomistic quantum mechanical concepts is needed to reproduce the characteristics of today’s nanostructures and to predict the performance of not-yet-fabricated components. Such tools should combine different modelling approaches to be able to treat various device types, from state-of-the-art nano-transistors to photo-detectors based on two-dimensional materials or resistive switching random access memories. For example, to shed light on the behaviour of valence change memory (VCM) cells, which consist of metal-insulator-metal stacks, molecular dynamics (MD), kinetic Monte Carlo (KMC), density functional theory (DFT), and quantum transport (QT) should be allied, as illustrated in the accompanying figure. By doing so, the growth of nano-filaments through realistic oxides embedded between two metallic electrodes can be accurately simulated and the electrical current flowing through computed with, e.g., the Non-equilibrium Green’s Function (NEGF) formalism [3]. In this presentation the multi-method simulation environment shown the accompanying Figure will be briefly reviewed. The main focus will be set on the discussion of few applications, among them transistors and memory cells. References: [1] S. Selberherr, W. Fichtner, and H.W. Potzl, “Minimos - A program package to facilitate MOS device design and analysis”, Proceedings of NASECODE I, 275 (1979). [2] A. Wettstein, A. Schenk, and W. Fichtner, “Quantum device-simulation with the density-gradient model on unstructured grids”, IEEE Trans. On Elec. Dev. 48, 279 (2001). [3] M. Kaniselvan, M. Luisier, and M. Mladenovic, “An Atomistic Modelling Framework for Valence Change Memory Cells”, Solid-State Electronics 199, 108506 (2023). Figure Caption: Multi-method simulation framework dedicated to the investigation of resistive switching devices, here valence change memory (VCM) cells. First, oxide samples with a low defect concentration are constructed withclassical molecular dynamics (MD) using a melt-and-quench procedure. They arethentransferredto akinetic Monte Carlo (KMC) solver that determines the distribution of oxygen vacancies (VO,green spheres) within the oxide layer. All input parameters to KMC (diffusioncoefficients and generation/recombination rates) are computed with density functional theory(DFT), which is also used to calculate the Hamiltonian (H) and Overlap (S) matrices of the created VCM structure. Finally, these quantities are passed to aquantum transport (QT) tool to perform ab initiodevice simulations. Figure 1
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Ghadban, Mohamad, Mayank Sabharwal, Xiaolin Li, et al. "(Digital Presentation) Three-Dimensional Pore-Scale Modelling of NMC Cathodes Using Multi-Resolution FIB-SEM Images." ECS Meeting Abstracts MA2022-02, no. 2 (2022): 126. http://dx.doi.org/10.1149/ma2022-022126mtgabs.
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Lithium-ion battery (LIB) cathodes are porous electrodes made of active material (AM) that stores lithium, a composite of carbon additives and polymeric binder (CBD) that facilitates electron transport and ensures the mechanical integrity of the electrode, and electrolyte-filled pore space that facilitates lithium-ion transport [1]. The volume fraction and morphology of the different constituents at the microscale necessarily determine transport properties and influence the measurable performance [2]. In this work, the impact of NMC electrode microstructure on the effective transport properties is studied using FIB-SEM-based three-dimensional (3D) particle-resolved microscale simulations. The effect of AM and CBD bulk electronic conductivity on the effective electronic conductivity is first studied and used to highlight that the impact of the AM bulk conductivity is negligible compared to that of the CBD. Next, the impact of CBD volume fraction, in isolation from its morphology, is studied using morphological operations by eroding and dilating the CBD phase in the FIB-SEM images and analyzing its impact on the effective conductivity using multiple 3D reconstructions. Increasing the CBD volume fraction results in a nonlinear increase in the effective electronic conductivity. To study the effect of CBD morphology, two stochastic CBD reconstruction techniques are proposed. The first method places new CBD voxels preferentially next to existing CBD voxels, and the second method deposits the CBD randomly in the pore space. The effective electronic conductivity for microstructures containing stochastic CBD morphologies is calculated and compared to that evaluated for microstructures with eroded and dilated CBD. The CBD generated stochastically results in a predicted higher effective electronic conductivity primarily due to a lower CBD tortuosity when compared to the CBD generated with morphological operations. Finally, the impact of CBD porosity on electrode tortuosity is studied by estimating the pore-phase tortuosity considering a solid and a porous CBD. The diffusivity of the porous CBD is estimated using multi-resolution FIB-SEM images. Results show that not accounting for the CBD porosity increases the electrode tortuosity by a factor of up to three at low electrode porosities. References [1] B. L. Trembacki, A. N. Mistry, D. R. Noble, M. E. Ferraro, P. P. Mukherjee, S. A. Roberts, Mesoscale analysis of conductive binder domain morphology in lithium-ion battery electrodes, Journal of The Electrochemical Society 165 (13) (2018) E725–E736 [2] Xu, Hongyi, et al. ‘Guiding the Design of Heterogeneous Electrode Microstructures for Li‐Ion Batteries: Microscopic Imaging, Predictive Modeling, and Machine Learning’. Advanced Energy Materials, vol. 11, no. 19, May 2021, p. 2003908. DOI.org (Crossref), https://doi.org/10.1002/aenm.202003908. Figure 1
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Benam, Majid, Mauro Ballicchia, Josef Weinbub, Siegfried Selberherr, and Mihail Nedjalkov. "A computational approach for investigating Coulomb interaction using Wigner–Poisson coupling." Journal of Computational Electronics 20, no. 2 (2021): 775–84. http://dx.doi.org/10.1007/s10825-020-01643-x.
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AbstractEntangled quantum particles, in which operating on one particle instantaneously influences the state of the entangled particle, are attractive options for carrying quantum information at the nanoscale. However, fully-describing entanglement in traditional time-dependent quantum transport simulation approaches requires significant computational effort, bordering on being prohibitive. Considering electrons, one approach to analyzing their entanglement is through modeling the Coulomb interaction via the Wigner formalism. In this work, we reduce the computational complexity of the time evolution of two interacting electrons by resorting to reasonable approximations. In particular, we replace the Wigner potential of the electron–electron interaction by a local electrostatic field, which is introduced through the spectral decomposition of the potential. It is demonstrated that for some particular configurations of an electron–electron system, the introduced approximations are feasible. Purity, identified as the maximal coherence for a quantum state, is also analyzed and its corresponding analysis demonstrates that the entanglement due to the Coulomb interaction is well accounted for by the introduced local approximation.
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Takeda, H., and N. Mori. "Three-Dimensional Quantum Transport Simulation of Ultra-Small FinFETs." Journal of Computational Electronics 4, no. 1-2 (2005): 31–34. http://dx.doi.org/10.1007/s10825-005-7102-0.
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Kalsh, Aditi, and V. K. Lamba. "Modelling and simulation of charge transport phenomena in graphene on SiO2 / Si substrate and graphene on complex oxide substrates." Independent Journal of Management & Production 13, no. 4 (2022): s569—s583. http://dx.doi.org/10.14807/ijmp.v13i4.1995.
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Graphene and silicon are two prominent lithium-ion battery anode materials that have recently received a lot of attention. In this paper we have modelled and simulated the charge transport phenomena in Graphene on Si / SiO2 and SrTiO3 substrates. The Graphene monolayer's interface with the SrTiO3 (111) surface is analyzed using ab initio density-functional measurements. Both charge and heat flows are produced in solids, at the same time when an electrochemical potential is available, bringing about novel properties. The band structure and the electron dissolution process decide the Seebeck coefficient and electrical conductivity. It has been discovered that the interaction of Graphene with SiTiO3 accommodates electronic properties, Seebeck coefficient, and electronic conductivity. For the Graphene / SrTiO3 interface, the best values for the Seebeck coefficient were calculated. All the findings of this work suggest that the Graphene-SrTiO3 (111) and Graphene-Si structure could exhibit interesting quantum transport behavior.
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Pañeda, Emilio Martínez. "Progress and opportunities in modelling environmentally assisted cracking." RILEM Technical Letters 6 (July 19, 2021): 70–77. http://dx.doi.org/10.21809/rilemtechlett.2021.145.
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Environmentally assisted cracking phenomena are widespread across the transport, defence, energy and construction sectors. However, predicting environmentally assisted fractures is a highly cross-disciplinary endeavour that requires resolving the multiple material-environment interactions taking place. In this manuscript, an overview is given of recent breakthroughs in the modelling of environmentally assisted cracking. The focus is on the opportunities created by two recent developments: phase field and multi-physics modelling. The possibilities enabled by the confluence of phase field methods and electro-chemo-mechanics modelling are discussed in the context of three environmental assisted cracking phenomena of particular engineering interest: hydrogen embrittlement, localised corrosion and corrosion fatigue. Mechanical processes such as deformation and fracture can be coupled with chemical phenomena like local reactions, ionic transport and hydrogen uptake and diffusion. Moreover, these can be combined with the prediction of an evolving interface, such as a growing pit or a crack, as dictated by a phase field variable that evolves based on thermodynamics and local kinetics. Suitable for both microstructural and continuum length scales, this new generation of simulation-based, multi-physics phase field models can open new modelling horizons and enable Virtual Testing in harmful environments.
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Strnad, David, Gabriel Fedorko, and Patrik Ščavnický. "Modeling of the two shuttle box system within the internal logistics system using simulation software." Open Engineering 11, no. 1 (2021): 887–95. http://dx.doi.org/10.1515/eng-2021-0090.
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Abstract The efficiency and effectiveness of the production system are influenced by the logistical arrangement of material flows. The smooth production, especially for assembly lines in the required quantity and at the required time (JIT or JIS systems), is currently ensured by automatically controlled towing sets (logistics trains), which consist of a tractor and several trucks. Another factor that affects the smooth production of assembly lines is the system of controlling the circulation of transport units. The number of transport units used in combination with the transport system significantly affects the efficiency of assembly workplaces. This article presents an analysis of the supply of assembly workplaces using a system of two shuttle boxes. The aim of this article is to investigate the influence of transport speed and capacity on the smoothness of the assembly process. Within the described analysis, the transport of 50,000 components is analyzed using a simulation model, while the length of the transport route is 32 km and 65 transport units per shift are used.
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Köbbing, Lukas, Arnulf Latz, and Birger Horstmann. "Modeling of the Solid-Electrolyte Interphase: Transport Mechanisms and Mechanics." ECS Meeting Abstracts MA2023-01, no. 45 (2023): 2480. http://dx.doi.org/10.1149/ma2023-01452480mtgabs.
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The solid-electrolyte interphase (SEI) considerably affects the performance and lifetime of lithium-ion batteries. Although the SEI has been investigated for many years, various central aspects of this thin passivation layer are still ambiguous due to its generic complexity. Therefore, we thoroughly investigate the growth mechanisms and the mechanical behavior of the SEI. The long-term growth of the SEI is the main reason which determines the shelf-life of state-of-the-art lithium-ion batteries. Nonetheless, the relevant transport mechanism responsible for the continued growth of the SEI is still highly debated in the literature. Thus, we carefully compare the two mostly considered mechanisms, namely electron diffusion and solvent diffusion [1]. We investigate whether the two mechanisms can describe the observed state-of-charge (SOC) dependence and the typical square-root behavior in time for capacity loss during open-circuit battery storage. We demonstrate that the electron diffusion mechanism reproduces both the SOC dependence as well as the time dependence. Contrarily, we show that solvent diffusion can describe either the SOC dependence or the typical behavior in time. We demonstrate that there is no intermediate regime between the reaction-limited and the transport-limited regimes, which reproduces both dependencies at the same time. In addition, we examine the interdependence of the SOC and square-root time behavior of SEI growth. Due to self-discharge, the combination of both aspects leads to deviations from the typical square-root behavior in time. Our simulations of capacity fade account for this effect and reasonably match capacity fade experiments. Another substantial aspect of lithium-ion battery research is the transition to next-generation anode materials. As a promising candidate with a high theoretical capacity, silicon receives a lot of research interest. Two major drawbacks of this material are the massive volume expansion and the observed open-circuit voltage hysteresis. Similar to graphite, the SEI covers silicon anodes and has to withstand the expansion and shrinkage of the anode during lithiation and delithiation [2]. We check whether the plasticity of the silicon particle will contribute substantially to the voltage hysteresis. Further, we examine the impact of stress and plastic deformations of the SEI on the volume expansion and the voltage hysteresis. We demonstrate that the mechanics of both silicon anode and SEI will determine the observed voltage hysteresis. Köbbing, L.; Latz, A.; Horstmann, B. Preprint arXiv 2022, DOI: 10.48550/arXiv.2209.10854 Kolzenberg, L.; Latz, A.; Horstmann, B. Batter. Supercaps 2022, 5. DOI: 10.1002/batt.202100216 Figure 1
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Kim, Moonbon, and Jiwan Kim. "A Study on the Stability of TiO2 Nanoparticles as an Electron Transport Layer in Quantum Dot Light-Emitting Diodes." Korean Journal of Metals and Materials 59, no. 7 (2021): 476–80. http://dx.doi.org/10.3365/kjmm.2021.59.7.476.
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We report highly efficient and robust quantum dot light-emitting diodes (QLEDs) with Li-doped TiO2 nanoparticles (NPs) as an electron transport layer (ETL). As core materials, ZnO-based inorganic NPs can enhance the performance of QLEDs due to their suitable energy level and solution processability. However, their fast electron mobility and instability in organic solvents are two main obstacles to practical display applications. The colloidal stability of TiO2 NPs in ethanol was confirmed after three day-storage, while ZnO NPs showed severe agglomeration. Inverted structure QLEDs using 3% Li-doped TiO2 NP were successfully fabricated and their optical/electrical properties were investigated. With 3% Li-doped TiO2 NPs, the charge balance in the emitting layer of the QLEDs was improved, which resulted in a maximum luminance of 159,840 cd/m<sup>2</sup> and external quantum efficiency (EQE) of 9.12%. These results were comparable to the performance of QLEDs with commonly used ZnO NPs. Moreover, the QLEDs with the Li-doped TiO2 NPs showed more stable characteristics than those with ZnO NPs after 7 days in ambient conditions. The EQE of the QLEDs with Li-doped TiO2 NPs was reduced by only 4.9%. These results indicate that Li-doped TiO2 NPs show great promise for use as a solution based inorganic ETL for QLEDs.
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Achar, Siddarth K., Leonardo Bernasconi, and J. Karl Johnson. "Machine Learning Electron Density Prediction Using Weighted Smooth Overlap of Atomic Positions." Nanomaterials 13, no. 12 (2023): 1853. http://dx.doi.org/10.3390/nano13121853.
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Having access to accurate electron densities in chemical systems, especially for dynamical systems involving chemical reactions, ion transport, and other charge transfer processes, is crucial for numerous applications in materials chemistry. Traditional methods for computationally predicting electron density data for such systems include quantum mechanical (QM) techniques, such as density functional theory. However, poor scaling of these QM methods restricts their use to relatively small system sizes and short dynamic time scales. To overcome this limitation, we have developed a deep neural network machine learning formalism, which we call deep charge density prediction (DeepCDP), for predicting charge densities by only using atomic positions for molecules and condensed phase (periodic) systems. Our method uses the weighted smooth overlap of atomic positions to fingerprint environments on a grid-point basis and map it to electron density data generated from QM simulations. We trained models for bulk systems of copper, LiF, and silicon; for a molecular system, water; and for two-dimensional charged and uncharged systems, hydroxyl-functionalized graphane, with and without an added proton. We showed that DeepCDP achieves prediction R2 values greater than 0.99 and mean squared error values on the order of 10−5e2 Å−6 for most systems. DeepCDP scales linearly with system size, is highly parallelizable, and is capable of accurately predicting the excess charge in protonated hydroxyl-functionalized graphane. We demonstrate how DeepCDP can be used to accurately track the location of charges (protons) by computing electron densities at a few selected grid points in the materials, thus significantly reducing the computational cost. We also show that our models can be transferable, allowing prediction of electron densities for systems on which it has not been trained but that contain a subset of atomic species on which it has been trained. Our approach can be used to develop models that span different chemical systems and train them for the study of large-scale charge transport and chemical reactions.
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Rau, Hans, and Friederike Picht. "Modeling of diamond growth from a microwave plasma: C2H as growth species." Journal of Materials Research 8, no. 9 (1993): 2250–64. http://dx.doi.org/10.1557/jmr.1993.2250.
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Diamond growth experiments were performed in a microwave plasma ball reactor on silicon wafers or on a molybdenum sheet provided with cones (stamped into the sheet with a punch). All substrates had been treated by scratching with diamond powder in advance. The gas mixture used was CH4/H2, sometimes with the addition of CO. Substrate temperatures ranged from 953 to 1428 K, pressures from 100 to 400 mbar, and microwave powers from 250 to 700 W. A strong preference of diamond growth was observed on the cones in the molybdenum substrates. This is interpreted as being caused by gas transport hindrance. The resulting deposition coefficient of the “active” species is about 0.1 under all conditions investigated. The deposition experiments on silicon substrates are numerically modeled in two steps. In the first step, temperature fields and electron density and energy distributions in pure hydrogen are calculated following the method described previously. The output of this first simulation step is taken as input data for the second step. The condition is applied that chemical reaction rates due to thermal or electronic activation and diffusional flows compensate each other at every point of the reactor. In this way stationary concentrations of the 13 species in 29 elementary reactions are computed and, from these, the expected deposition profile of diamond on the silicon substrate, assuming one of the carbon-containing species to be the “active” one. When the experimental deposition profiles are compared with the calculated ones, C2H as the “active” species gives the best match to all the experimental results. CH3 and C2H2 (and perhaps others) might contribute to the diamond growth to a limited extent only.
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Saeedi, Sevan, and Edris Faizabadi. "Lead position and lead-ring coupling effects on the spin-dependent transport properties in a two-dimensional network of quantum nanorings in the presence of Rashba spin–orbit interaction." Journal of Computational Electronics 19, no. 3 (2020): 1014–30. http://dx.doi.org/10.1007/s10825-020-01506-5.
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Kang, Myoungsuk, and Jiwan Kim. "A Study on the ZnO Thin Film Deposited by RF Sputtering Method as an Electron Transport Layer in Quantum Dot Light-Emitting Diodes." Korean Journal of Metals and Materials 59, no. 10 (2021): 718–23. http://dx.doi.org/10.3365/kjmm.2021.59.10.730.
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We report a highly efficient quantum dot light emitting diode (QLEDs) with a radio frequency (RF) sputtered ZnO thin film as an electron transport layer (ETL) instead of the conventional ZnO nanoparticles (NPs) by solution process. ZnO NPs have been used as a key material to improve the performance of QLEDs, but the charge imbalance in ZnO NPs resulting from fast electron injection, and their limited uniformity are significant disadvantages. In this study, ZnO layers were deposited by RF sputtering with various O2 partial pressures. All of the ZnO films showed preferential growth along the (002) direction, smooth morphology, and good optical transmittance. To test their feasibility for QLEDs, we fabricated devices with RF sputtered ZnO layers as an ETL, which has the inverted structure of ITO/RF sputtered ZnO/QDs/CBP/MoO3/Al. The optical/electrical characteristics of two devices, comprised of RF sputtered ZnO and ZnO NPs, were compared with each other. QLEDs with the sputtered ZnO ETL achieved a current efficiency of 11.32 cd/A, which was higher than the 8.23 cd/A of the QLEDs with ZnO NPs ETL. Next, to find the optimum ZnO thin film for highly efficient QLEDs, deposition conditions with various O2 partial pressures were tested, and device performance was investigated. The maximum current efficiency was 13.33 cd/A when the ratio of Ar/O2 was 4:3. Additional oxygen gas reduced the O vacancies in the ZnO thin film, which resulted in a decrease in electrical conductivity, thereby improving charge balance in the emission layer of the QLEDs. As a result, we provide a way to control the ZnO ETL properties and to improve device performance by controlling O2 partial pressure.
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Kang, Myoungsuk, and Jiwan Kim. "A Study on the ZnO Thin Film Deposited by RF Sputtering Method as an Electron Transport Layer in Quantum Dot Light-Emitting Diodes." Korean Journal of Metals and Materials 59, no. 10 (2021): 718–23. http://dx.doi.org/10.3365/kjmm.2021.59.10.718.
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We report a highly efficient quantum dot light emitting diode (QLEDs) with a radio frequency (RF) sputtered ZnO thin film as an electron transport layer (ETL) instead of the conventional ZnO nanoparticles (NPs) by solution process. ZnO NPs have been used as a key material to improve the performance of QLEDs, but the charge imbalance in ZnO NPs resulting from fast electron injection, and their limited uniformity are significant disadvantages. In this study, ZnO layers were deposited by RF sputtering with various O2 partial pressures. All of the ZnO films showed preferential growth along the (002) direction, smooth morphology, and good optical transmittance. To test their feasibility for QLEDs, we fabricated devices with RF sputtered ZnO layers as an ETL, which has the inverted structure of ITO/RF sputtered ZnO/QDs/CBP/MoO3/Al. The optical/electrical characteristics of two devices, comprised of RF sputtered ZnO and ZnO NPs, were compared with each other. QLEDs with the sputtered ZnO ETL achieved a current efficiency of 11.32 cd/A, which was higher than the 8.23 cd/A of the QLEDs with ZnO NPs ETL. Next, to find the optimum ZnO thin film for highly efficient QLEDs, deposition conditions with various O2 partial pressures were tested, and device performance was investigated. The maximum current efficiency was 13.33 cd/A when the ratio of Ar/O2 was 4:3. Additional oxygen gas reduced the O vacancies in the ZnO thin film, which resulted in a decrease in electrical conductivity, thereby improving charge balance in the emission layer of the QLEDs. As a result, we provide a way to control the ZnO ETL properties and to improve device performance by controlling O2 partial pressure.
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Ma, Shao-Qiang, and Guo-Feng Zhang. "The transport character of quantum state in one-dimensional coupled-cavity arrays: effect of the number of photons and entanglement degree." Quantum Information Processing 15, no. 4 (2015): 1499–512. http://dx.doi.org/10.1007/s11128-015-1214-7.
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Jin, Xinfang, Puvikkarasan Jayapragasam, Yasser Shoukry, Yeting Wen, and Kevin Huang. "Evolution of 2PB/3PB Transport Pathways in Oxygen Electrodes during Degradation Test: A Perspective from Electro-Chemo-Mechanical Coupling on Microstructures." ECS Meeting Abstracts MA2024-01, no. 38 (2024): 2266. http://dx.doi.org/10.1149/ma2024-01382266mtgabs.
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The solid oxide electrolysis cell (SOEC) has garnered significant attention over the past decades for hydrogen generation integrated with intermittent renewable energy [1]. However, a major hurdle in the commercialization of SOEC is cell degradation when operated beyond 1000 hours [2]. SOEC degrades two times more quickly than the same cell operated in fuel cell mode [3]. Perovskite oxygen electrodes (OEs), such as La1-xSrxCo1-yFeyO3-δ (LSCF), exhibit flexible oxygen stoichiometry [4-6] depending on the operating conditions. The delamination failure in perovskite OEs arises from a mismatch between the slower O2 evolution rate at the surface and the rapid O2 current in the bulk from the electrolyte (EL), which causes variations in oxygen stoichiometry. This variation in oxygen stoichiometry enhances bonding, contracts lattice volume, and leads to chemical stress at the OE/EL interface [7]. In this research, we aim to construct an electro-chemo-mechanically coupled model with synthetic microstructures (Fig.1a) to explore the intricate interactions between delamination at the OE/EL interface and oxygen ion transport pathway evolution. The Dream 3D software will be utilized for microstructure generation, Matlab for mesh preparation, and Comsol for Multiphysics simulation. We will examine two OE configurations known for achieving high electrocatalytic activity [8]: single layer and bilayer OEs . For the single layer configuration, La0.6Sr0.4Co0.4Fe0.6O3 (LSCF) [9, 10] serves as the sole electrode material. For bilayer OEs, we incorporate SrTa0.1Co0.9O3 (SCT) [11, 12] as the capping layer for electrocatalytic activity, with LSCF acting as the supporting backbone. The evolution of two transport pathways (Fig.1b&c), double phase boundary (2PB) and tripe phase boundary (3PB), in different configurations during long-term degradation tests will be evaluated by coupling the models with experimental polarization curves and electrochemical impedance spectra. The investigations will focus on the effects of delamination resulting from lattice volume variations on shifting of transport pathways (Fig.1d) in different OE configurations. References Nechache, A. and S. Hody, Alternative and innovative solid oxide electrolysis cell materials: A short review. Renewable and Sustainable Energy Reviews, 2021. 149. Rashkeev, S.N. and M.V. Glazoff, Atomic-scale mechanisms of oxygen electrode delamination in solid oxide electrolyzer cells. International Journal of Hydrogen Energy, 2012. 37(2): p. 1280-1291. Moçoteguy, P. and A. Brisse, A review and comprehensive analysis of degradation mechanisms of solid oxide electrolysis cells. International Journal of Hydrogen Energy, 2013. 38(36): p. 15887-15902. Adler, S.B., Chemical Expansivity of Electrochemical Ceramics. Journal of the American Ceramic Society, 2001. 84(9): p. 2117-2119. Atkinson, A. and T.M.G.M. Ramos, Chemically-induced stresses in ceramic oxygen ion-conducting membranes. Solid State Ionics, 2000. 129(1): p. 259-269. Bishop, S.R., K.L. Duncan, and E.D. Wachsman, Defect equilibria and chemical expansion in non-stoichiometric undoped and gadolinium-doped cerium oxide. Electrochimica Acta, 2009. 54(5): p. 1436-1443. Cook, K., J. Wrubel, Z. Ma, K. Huang, and X. Jin, Modeling Electrokinetics of Oxygen Electrodes in Solid Oxide Electrolyzer Cells. Journal of The Electrochemical Society, 2021. 168(11): p. 114510. Laguna-Bercero, M.A., H. Monzón, A. Larrea, and V.M. Orera, Improved stability of reversible solid oxide cells with a nickelate-based oxygen electrode. Journal of Materials Chemistry A, 2016. 4(4): p. 1446-1453. Mogensen, M.B., M. Chen, H.L. Frandsen, C. Graves, J.B. Hansen, K.V. Hansen, A. Hauch, T. Jacobsen, S.H. Jensen, T.L. Skafte, and X. Sun, Reversible solid-oxide cells for clean and sustainable energy. Clean Energy, 2019. 3(3): p. 175-201. Jiang, S.P., Challenges in the development of reversible solid oxide cell technologies: a mini review. Asia-Pacific Journal of Chemical Engineering, 2016. 11(3): p. 386-391. Huang, K. and Y. Wen, Electrochemical Performance of New Bilayer Oxygen Electrode for Reversible Solid Oxide Cells. ECS Meeting Abstracts, 2021. MA2021-03(1): p. 138-138. Huang, K., Method to Make Isostructural Bilayer Oxygen Electrode. 2020, University of South Carolina: US. Figure 1
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Gorospe, Alloyssius E. G., Dongwoo Kang, and Dongwook Lee. "Electrochemical Characteristics of Elastic, Non-Polar Polyurethane-Based Polymer Gel Electrolyte for Separator-Less Lithium-Ion Batteries." Korean Journal of Metals and Materials 61, no. 8 (2023): 616–24. http://dx.doi.org/10.3365/kjmm.2023.61.8.616.
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Lithium-ion batteries (LIBs) have undergone countless enhancements in the past decade, mainly improvements in the basic components: electrodes, electrolyte, and separator. The separator, which acts as a physical barrier between the two electrodes, does not directly participate in the charge and energy storage.However, it is involved in the safety, form factor, and packaging density of the LIBs. While it occupies relatively less internal space than other components, the separator can be replaced with active materials such as gel polymer electrolytes (GPEs) which can serve as both the electrolyte and physical barrier between the electrodes. GPEs can potentially minimize the risks of liquid electrolytes, including flammability, electrolyte leakage, and explosion. Here we report the characteristics of polyurethane (PU)-based gel swollen in concentrated electrolyte solutions in separator-less cells. The poreless PU-based gel electrolyte conducts lithium ions, while preventing internal short-circuits. This is attributed to the presence of soft segments, which allow ion transport, and hard segments, which ensure mechanical integrity. Electrochemical measurements carried out in LFP half cells and symmetric Li cells revealed that the separator-less cells were operable between 0.2 C to 1 C rates, and that during long term cycling, the cells achieved stable Li electroplating overpotential, as the number of cycles increased.
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Gelmont, B. L., M. S. Shur, and M. Stroscio. "Analytical Theory of Electron Mobility and Drift Velocity in GaN." MRS Proceedings 449 (1996). http://dx.doi.org/10.1557/proc-449-609.
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ABSTRACTWe derive balance transport equations for the electron mobility and drift velocity, which are applicable at any degeneracy of the electron gas. These equations account for the polar optical phonon scattering and ionized impurity scattering and include the effects of screening. These equations are valid only for very high concentrations (above 1019 cm-3 for GaN). However, the comparison with the results of Monte Carlo simulations shows that they fairly accurately reproduce the field-velocity curves in GaN in moderate electric fields (up to 100 kV/cm). The comparison with the electron mobility calculated using the two-step model [1] shows a much larger difference but allows us to illustrate the trends in mobility dependencies caused by electron-electron collisions. We also derive the balance transport equations accounting for the polar optical phonon scattering in a two-dimensional electron gas. The calculations based on these equations, show that the unscreened polar optical scattering mobility is smaller in the two-dimensional gas than in the bulk intrinsic semiconductor and that the mobility decreases with the decrease of the quantum well thickness.
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Lee, Hyungjun, Samuel Poncé, Kyle Bushick, et al. "Electron–phonon physics from first principles using the EPW code." npj Computational Materials 9, no. 1 (2023). http://dx.doi.org/10.1038/s41524-023-01107-3.
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AbstractEPW is an open-source software for ab initio calculations of electron–phonon interactions and related materials properties. The code combines density functional perturbation theory and maximally localized Wannier functions to efficiently compute electron–phonon coupling matrix elements, and to perform predictive calculations of temperature-dependent properties and phonon-assisted quantum processes in bulk solids and low-dimensional materials. Here, we report on significant developments in the code since 2016, namely: a transport module for the calculation of charge carrier mobility under electric and magnetic fields using the Boltzmann transport equation; a superconductivity module for calculations of phonon-mediated superconductors using the anisotropic multi-band Eliashberg theory; an optics module for calculations of phonon-assisted indirect transitions; a module for the calculation of small and large polarons without supercells; and a module for calculating band structure renormalization and temperature-dependent optical spectra using the special displacement method. For each capability, we outline the methodology and implementation and provide example calculations.
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Mil’nikov, Gennady, Jun-ichi Iwata, Nobuya Mori, and Atsushi Oshiyama. "RSDFT-NEGF transport simulations in realistic nanoscale transistors." Journal of Computational Electronics, June 20, 2023. http://dx.doi.org/10.1007/s10825-023-02046-4.
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AbstractThe paper presents a device simulator for computing transport characteristics from first principles. The developed computer program effectively performs large-scale parallel calculation of quasi-one-dimensional quantum transport in realistic nanoscale devices with thousands of atoms in the cross section area of the device channel. Our simulator is based on the real-space Kohn–Sham Hamiltonian in the density functional theory and improved numerical algorithms for reducing computational burden in non-equilibrium Green’s function (NEGF) method. Several computational improvements have been introduced in constructing a reduced quantum transport model from the original Kohn-Sham Hamiltonian and implementing the R-matrix computational scheme in the NEGF simulations.
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Aldegunde, Manuel, Steven P. Hepplestone, Peter V. Sushko, and Karol Kalna. "Multi-Scale Simulation of Transport via a Mo/n+-GaAs Schottky Contact." MRS Proceedings 1553 (2013). http://dx.doi.org/10.1557/opl.2013.1057.
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ABSTRACTA multi-scale modeling of electron transport via a metal-semiconductor interface is carried out by coupling ab initio calculations with three-dimensional finite element ensemble Monte Carlo simulations. The results for the Mo/GaAs (001) interface show that variations of the electronic properties with the distance from the interface have a strong impact on the transport characteristics. In particular, the calculated tunneling barrier differs dramatically from that of the ideal Schottky model of an abrupt metal-semiconductor interface. The band gap narrowing near the interface lowers resistivity by more than one order of magnitude: from 2.1×10-8 Ωcm² to 4.7×10-10 Ωcm². The dependence of the electron effective mass from the distance to the interface also plays an important role bringing resistivity to 7.9×10-10 Ωcm².
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Dong, Zirui, Yubo Zhang, Jun Luo, et al. "High-performance non-Fermi-liquid metallic thermoelectric materials." npj Computational Materials 9, no. 1 (2023). http://dx.doi.org/10.1038/s41524-023-01001-y.
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AbstractSearching for high-performance thermoelectric (TE) materials in the paradigm of narrow-bandgap semiconductors is hampered by a bottleneck. Here we report on the discovery of metallic compounds, TiFexCu2x−1Sb and TiFe1.33Sb, showing the thermopower exceeding many TE semiconductors and the dimensionless figure of merits zTs comparable with the state-of-the-art TE materials. A quasi-linear temperature (T) dependent electrical resistivity in 2–700 K and the logarithmic T-dependent electronic specific heat at low temperature coexist with the high thermopower, highlighting the strong intercoupling of the non-Fermi-liquid (NFL) quantum critical behavior of electrons with TE transports. Electronic structure analysis reveals a competition between the antiferromagnetic (AFM) ordering and Kondo-like spin compensation as well as a parallel two-channel Kondo effect. The T-dependent magnetic susceptibility agrees with the quantum critical scenario of strong local correlation. Our work demonstrates the correlation among high TE performance, NFL quantum criticality, and magnetic fluctuation, which opens up directions for future research.
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Yesilyurt, Serhat. "Modeling and Simulations of Polymer Electrolyte Membrane Fuel Cells With Poroelastic Approach for Coupled Liquid Water Transport and Deformation in the Membrane." Journal of Fuel Cell Science and Technology 7, no. 3 (2010). http://dx.doi.org/10.1115/1.3207869.
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Performance degradation and durability of polymer electrolyte membrane (PEM) fuel cells depend strongly on transport and deformation characteristics of their components especially the polymer membrane. Physical properties of membranes, such as ionic conductivity and Young’s modulus, depend on the water content that varies significantly with operating conditions and during transients. Recent studies indicate that cyclic transients may induce hygrothermal fatigue that leads to the ultimate failure of the membrane shortening its lifetime and, thus, hindering the reliable use of PEM fuel cells for automotive applications. In this work, we present two-dimensional simulations and analysis of coupled deformation and transport in PEM fuel cells to improve the understanding of membrane deformation under steady-state and transient conditions. A two-dimensional cross section of anode and cathode gas diffusion layers, and the membrane sandwiched between them is modeled using Maxwell–Stefan equations for species transport in gas diffusion layers, Biot’s poroelasticity, Darcy’s law for deformation and water transport in the membrane, and Ohm’s law for ionic currents in the membrane and electric currents in the gas diffusion layers. Steady-state deformation and transport of water in the membrane, transient responses to step changes in load, and relative humidity of the anode and cathode are obtained from simulation experiments, which are conducted by means of a commercial finite-element package, COMSOL MULTIPHYSICS.
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Song, Biyu, Guoxiang Zhi, Chenqiang Hua, et al. "One-dimensional topological phase and tunable soliton states in atomic nanolines on Si(001) surface." npj Quantum Materials 9, no. 1 (2024). http://dx.doi.org/10.1038/s41535-024-00637-3.
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AbstractFormation of exotic topological states on technologically important semiconductor substrate is significant from the aspects of both fundamental research and practical implementation. Here, we demonstrate one-dimensional (1D) topological phase and tunable soliton states in atomic nanolines self-assembled on Si(001) surface. By first-principles calculations and tight-binding modeling, we reveal that Bi nanolines provide an ideal system to realize a multi-orbital Su–Schrieffer–Heeger (SSH) model, and the electronic properties can be modulated by substrate-orbital-filtering effect. The topological features are confirmed by nontrivial end states for a finite-length nanoline and (anti-)soliton states at the boundary of two topologically distinct phases. We demonstrate that solitons are highly mobile on the surface, and their formation could be controlled by surface B/N doping. As these nanolines can extend several micrometers long without kinks, and quantum transport simulations suggest clear signatures of topological states characterized by transmission resonance peaks, our work paves an avenue to achieve 1D topological phase compatible with semiconductor technology and to engineer the properties with high tunability and fidelity for quantum information processing.
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Hu, Pei-Jia, Si-Xian Wang, Xiao-Feng Chen, et al. "Resonant tunneling in disordered borophene nanoribbons with line defects." npj Computational Materials 8, no. 1 (2022). http://dx.doi.org/10.1038/s41524-022-00816-5.
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AbstractRecently, borophene has attracted extensive interest as the wonder material, showing that line defects (LDs) occur widely at the interface between $$\nu _{1/5}$$ ν 1 / 5 and $$\nu _{1/6}$$ ν 1 / 6 boron sheets. Here, we study theoretically the electron transport through two-terminal disordered borophene nanoribbons (BNRs) with random distribution of LDs. Our results indicate that LDs strongly affect the electron transport properties of BNRs. Both $$\nu _{1/5}$$ ν 1 / 5 and $$\nu _{1/6}$$ ν 1 / 6 BNRs exhibit metallic behavior without any LD, in agreement with experiments. While in the presence of LDs, the overall electron transport ability is dramatically decreased, but some resonant peaks of conductance quantum are found in the transmission spectrum of any disordered BNR with arbitrary arrangement of LDs. These disordered BNRs exhibit metal-insulator transition with tunable transmission gap in the insulating regime. Furthermore, two evolution phenomena of resonant peaks are revealed for disordered BNRs with different widths. These results may help for understanding structure-property relationships and designing LD-based nanodevices.
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Shaw, John G., and Mike G. Hack. "Simulation and Modeling of Amorphous Silicon Thin-Film Devices." MRS Proceedings 278 (1992). http://dx.doi.org/10.1557/proc-278-127.
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AbstractWe describe a computer program which solves the complete set Of transport equations for device-quality amorphous silicon in two spatial dimensions and time. When modeling amorphous silicon devices, it is extremely important to account for the high concentration of time-dependent trapped charge present due to the continuous distribution of localized states in the semiconductor's bandgap. Our model is based on a realistic density-of-states distribution and includes a detailed description of the trap occupation functions for electrons and holes. These occupation functions are calculated self-consistently with respect to the electrostatic potential and free-carrier concentrations within the semiconductor.
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Popp, Johannes, Michael Haider, Martin Franckié, Jérôme Faist, and Christian Jirauschek. "Bayesian optimization of quantum cascade detectors." Optical and Quantum Electronics 53, no. 6 (2021). http://dx.doi.org/10.1007/s11082-021-02885-0.
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AbstractA Bayesian optimization algorithm in combination with a scattering based simulation approach is used for the optimization of quantum cascade detectors (QCDs). QCDs operate in the mid-infrared and terahertz regime and are, together with quantum cascade lasers, appropriate for the integration into on-chip applications such as gas sensors. Our modeling approach is based on a rate equation model and a Kirchhoff resistance network for noise modeling, using scattering rates calculated with Fermi’s golden rule, or alternatively extracted from an ensemble Monte Carlo transport approach. The appropriate surrogate model of Bayesian optimization is based on Gaussian process regression, which can handle noisy offsets on the objective function evaluations inherent in ensemble Monte Carlo simulations. Here, we focus on the optimization of a matured mid-infrared QCD design detecting at 4.7 $$\upmu {\mathrm{m}}$$ μ m . For optimization we choose as figure of merit the specific detectivity, which is a measure for the signal-to-noise ratio. As the trade-off between high extraction efficiency and low detector conductance is important for good detection performance, we search for the perfect layer composition and vary the thicknesses of different cascade layers. Due to the high-temperature requirements interesting for cost-effective and mobile on-chip sensing applications, a simulation temperature of 300 K is selected. Our optimization strategy yields an improvement of specific detectivity by a factor of $${\sim 2-3}$$ ∼ 2 - 3 at room temperature using two different parameter sets. Furthermore, we investigate the sensitivity of our approach to fabrication tolerances, showing robustness of the optimized designs against growth fluctuations under fabrication conditions.
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Luo, Pengfei, Peichao Li, Dezheng Ma, Keyong Wang, and Hengyun Zhang. "Coupled Electrochemical-Thermal-Mechanical Modeling and Simulation of Lithium-Ion Batteries." Journal of The Electrochemical Society, October 13, 2022. http://dx.doi.org/10.1149/1945-7111/ac9a04.
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Abstract A generalized pseudo three-dimensional (P3D) electrochemical-thermal-mechanical coupling (ETM) model is proposed to describe the multiphysics coupling behavior during the discharge of lithium-ion battery (LIB). The proposed model is established and simulated by using COMSOL Multiphysics. In particular, the influence of external loads on the LIB is investigated via the stress field where the particle scale is coupled with the representative volume element scale. Moreover, dynamic parameters dependent on the temperature and the lithium concentration are introduced to enable the proposed model more physically realistic. We validate the model by comparing the numerical results with experimental data available in the literature. In addition, we find that the lithium concentration gradient is reduced by the stress effect inside the active particles. Then, we show the distributions of stress and lithium concentration in the electrodes during the discharge process. Finally, the effect of external loads on the electrochemical process is investigated. It indicates that the electrochemical reaction is promoted. The results are of benefit to obtain an in-depth understanding of the stress mechanism, the lithium transport mechanism, and the synergistic mechanism among the multiphysics fields during the operation of LIBs.
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Hu, Huamin, Zhaoyong Chen, Junfei Duan, Guang Zeng, and Gang Ouyang. "Quantum-confined ultramicropores in nodal-line semimetal C32 for high-efficiency lithium/sodium-ion battery anodes." Applied Physics Letters 126, no. 25 (2025). https://doi.org/10.1063/5.0278988.
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Carbon-based materials integrating ultramicroporous architectures with topological quantum characteristics have recently gained prominence as next-generation ion battery anodes due to their exceptional electron/ion transport synergies. Through first-principles calculations, we propose a kind of two-dimensional (2D) tetragonal carbon allotrope (C32) possessing robust structural stability across mechanical, dynamical, and thermal domains. This material's unique sp2/sp3-hybridized bonding network simultaneously establishes uniformly distributed ultramicroporous channels (5.43 Å pore diameter, effectively preventing solvent co-intercalation) and manifests highly conductive nodal-line semimetallic properties. Theoretical simulations reveal exceptional Li/Na storage characteristics in bulk C32, including high theoretical capacities (837 mAh/g for Li, 558 mAh/g for Na), low diffusion barriers (0.22 eV for Li, 0.60 eV for Na), and moderate open-circuit voltages (0.26 V for Li, 0.33 V for Na). Notably, it has significantly lower volumetric expansion compared to conventional graphite during Li+/Na+ intercalation. Our work proposes a kind of optimization strategy combining topological electronic state modulation with precise pore structure design, suggesting an effective method for developing high-energy-density and long-cycle-life Li/Na-ion battery anodes.
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Fuhrmann, Jürgen, Hong Zhao, Ekkehard Holzbecher, and Hartmut Langmach. "Flow, Transport, and Reactions in a Thin Layer Flow Cell." Journal of Fuel Cell Science and Technology 5, no. 2 (2008). http://dx.doi.org/10.1115/1.2821598.
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The performance of fuel cells depends on the rate parameters of the kinetic reactions between the involved species, among other conditions. The determination of these parameters is crucial for the understanding of the functionality of fuel cells. Differential electrochemical mass spectroscopy in thin layer flow cells is used as a tool to gain improved understanding of the heterogeneous catalytic reactions taking place in fuel cell catalytic layers. In this paper, we focus on the description of thin layer cells by numerical models based on partial differential equations and the extraction of kinetics parameters by inverse modeling. For the model setup, various software tools are used. The simulation of laminar free flow is performed by the commercial code COMSOL. A finite volume code is used for the simulation of the reactive transport. The latter is coupled with a Levenberg–Marquardt algorithm for the determination of kinetic constants. Two designs of thin layer flow cells are considered: a cylindrical and a rectangular design. A drawback of the cylindrical cell design is the highly inhomogeneous velocity field leading to spatial variations of the conditions for electrode reactions. In contrast, the rectangular cell design shows a homogeneous flow field in the vicinity of the catalyst. The rectangular cell design has the additional advantage that flow is essentially two dimensional and can be computed analytically, which simplifies the numerical approach. The inverse modeling procedure is demonstrated for a hydrogen-carbon monoxide system.
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Annoni, Emilio, Massimo Frigerio, and Matteo G. A. Paris. "Enhanced quantum transport in chiral quantum walks." Quantum Information Processing 23, no. 4 (2024). http://dx.doi.org/10.1007/s11128-024-04331-y.
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AbstractQuantum transport across discrete structures is a relevant topic that can be suitably studied in the context of continuous-time quantum walks. The addition of phase degrees of freedom, leading to chiral quantum walks, can also account for directional transport on graphs with loops. We discuss criteria for quantum transport and study the enhancement that can be achieved with chiral quantum walks on chain-like graphs, exploring different topologies for the chain units and optimizing over the phases. We select three candidate structures with optimal performances and we investigate their transport behaviour with Krylov reduction. While one of them can be reduced to a weighted line with minor couplings modulation, the other two are truly chiral quantum walks, with enhanced transport probability over long chain structures.
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Paramasivam, Pattunnarajam, Naveenbalaji Gowthaman, and Viranjay M. Srivastava. "Analysis of Lanthanum Oxide Based Double-Gate SOI MOSFET using Monte-Carlo Process." Recent Patents on Nanotechnology 18 (January 10, 2024). http://dx.doi.org/10.2174/0118722105273476231201073651.
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Introduction: This work proposes a Double-Gate (DG) MOSFET with a Single Material made of Silicon On-Insulator (SOI). The Lanthanum Oxide material with a high k-dielectric constant has been used as an interface between two gates and the channel. The Monte Carlo analysis has been used to determine the Conduction Band Energy (Ec) profiles and electron sheet carrier densities (ns) for a Silicon channel thickness (tsi) of 10 nm at 0.5 V gate drain-source voltages. The transverse electric fields are weak at the midchannel of DG SOI MOSFETs, where quantum effects are encountered. The Monte Carlo simulation has been confirmed to be effective for high-energy transport. A particle description reproduces the granularity property of the transport for nanoscale modeling. background: Basics of Quantum effects and effects of inversional layer were discussed Methods: This work utilizes a Monte Carlo (MC) Simulation for the proposed Double Gate Single Material Silicon On Insulator MOSFET with (La2O3=2 nm) as dielectric oxide on upper and lower gate material. The electrical properties of the DG SOI MOSFETs with Lanthanum Oxide were analyzed using Monte Carlo simulation, including the conduction band energy, electric field, potential distribution, particle movement, and average velocity. objective: The Monte Carlo analysis has been used to determine the Conduction Band Energy (Ec) profiles and electron sheet carrier densities (ns) for a Silicon channel thickness (tsi) of 10 nm at 0.5 V gate drain-source voltages. The transverse electric fields are weak at the midchannel of DG SOI MOSFETs, where quantum effects are encountered. The Monte Carlo simulation has been confirmed to be effective for high-energy transport. A particle description reproduces the granularity property of the transport for nanoscale modeling. Results: The peak electric field (E) simulation results and an average drift velocity (υavg) of 6Í105 V/cm and 1.6Í107 cm/s were obtained, respectively. The conduction band energy for the operating region of the source has been observed to be 4 % to the drain side, which obtained a value of -0.04 eV at the terminal end. Conclusion: This proposed patent design, such as double-gate SOI-based devices, is the best suggestion for significant scalability challenges. Emerging technologies reach the typical DG SOI MOSFET's threshold performance when their geometrical dimensions are in the nanometer region. This device based on nanomaterial compounds has been more submissive than conventional devices. The nanomaterials usage in the design is more suitable for downscaling and reducing packaging density. result: The peak electric field (E) simulation results and an average drift velocity (υavg) of 6105 V/cm and 1.6107 cm/s were obtained, respectively. The conduction band energy for the operating region of the source has been observed to be 4 % to the drain side, which obtained a value of -0.04 eV at the terminal end. conclusion: This proposed design, such as double-gate SOI-based devices, is the best suggestion for significant scalability challenges. Emerging technologies reach the typical DG SOI MOSFET&amp;amp;#039;s threshold performance when their geometrical dimensions are in the nanometer region. This device based on nanomaterials compound has been more submissive than conventional devices. The nanomaterials usage in the design makes it more suitable for downscaling and reducing packaging density.
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Zhong, Linlin, Bingyu Wu, and Yifan Wang. "Low-temperature plasma simulation based on physics-informed neural networks: frameworks and preliminary applications." Physics of Fluids, July 26, 2022. http://dx.doi.org/10.1063/5.0106506.
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Plasma simulation is an important and sometimes only approach to investigating plasma behavior. In this work, we propose two general AI-driven frameworks for low-temperature plasma simulation: Coefficient-Subnet Physics-Informed Neural Network (CS-PINN) and Runge-Kutta Physics-Informed Neural Network (RK-PINN). CS-PINN uses either a neural network or an interpolation function (e.g. spline function) as the subnet to approximate solution-dependent coefficients (e.g. electron-impact cross sections, thermodynamic properties, transport coefficients, et al.) in plasma equations. On the basis of this, RK-PINN incorporates the implicit Runge-Kutta formalism in neural networks to achieve a large-time-step prediction of transient plasmas. Both CS-PINN and RK-PINN learn the complex non-linear relationship mapping from spatio-temporal space to equation's solution. Based on these two frameworks, we demonstrate preliminary applications by four cases covering plasma kinetic and fluid modeling. The results verify that both CS-PINN and RK-PINN have good performance in solving plasma equations. Moreover, RK-PINN has ability of yielding a good solution for transient plasma simulation with not only large time step but also limited noisy sensing data.
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Rama, Pratap, Yu Liu, Rui Chen, et al. "An X-Ray Tomography Based Lattice Boltzmann Simulation Study on Gas Diffusion Layers of Polymer Electrolyte Fuel Cells." Journal of Fuel Cell Science and Technology 7, no. 3 (2010). http://dx.doi.org/10.1115/1.3211096.
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This work reports a feasibility study into the combined full morphological reconstruction of fuel cell structures using X-ray computed micro- and nanotomography and lattice Boltzmann modeling to simulate fluid flow at pore scale in porous materials. This work provides a description of how the two techniques have been adapted to simulate gas movement through a carbon paper gas diffusion layer (GDL). The validation work demonstrates that the difference between the simulated and measured absolute permeability of air is 3%. The current study elucidates the potential to enable improvements in GDL design, material composition, and cell design to be realized through a greater understanding of the nano- and microscale transport processes occurring within the polymer electrolyte fuel cell.
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Herman, Rudi, Arody Tanga, I. Gede Tunas, Muh Galib Ishak, and Ardee Madman. "Characteristics of Sediment Transport After Morphological Changes at Palu Estuary, Sulawesi, Indonesia as The Impact of 2018 Tsunami." International Journal of Integrated Engineering 14, no. 9 (2022). http://dx.doi.org/10.30880/ijie.2022.14.09.002.
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The tsunami triggered by the 2018 Palu Earthquake has not only caused the collapse of public infrastructure, but also damaged beaches along Palu Bay. Based on direct investigation along the beaches, the coastlines have shifted inland up to 30 meters. This shoreline change was caused by the attack of the tsunami waves at high speed followed by massive abrasion. Another impact of the wave attackis a change in the morphology of the beach bed, including in the Palu Estuary. This study aims to investigate the impact of changes in bed morphology around the Palu Estuary as a result of the tsunami attack on transport sediment characteristics, as one of the determinants of bed morphology. Quantitative analysis was carried out by numerical simulation based on 2D hydrodynamic modeling using the Surface-water Modeling System (SMS). The geometry of the model is formed from the mesh generated from the bed elevation based on the after-tsunami bathymetry survey. Two boundary conditions and one main input data are applied to this model: discharge data, tidal data and bed load data. Discharge data as an upstream boundary condition consists of minimum discharge, average discharge and maximum discharge. The downstream boundary is defined by a tidal curve predicted from 15 daily data. The bed load data is presented in the form of a gradation curve that describes the distribution of sediment grains. The simulation output indicates that sediment settles intensively downstream of the river mouth at high discharge and low tide. At low discharge and high tide, sediment tends to settle before the flow reaches the river mouth. Referring to the results of previous studies, the direction and velocity of sediment motion changed slightly after the tsunami. Changes in the direction and speed of movement are related to changes in bed morphology at the river mouth due to the 2018 Palu Tsunami.
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Baruah, Smriti, Janmoni Borah, Perugu Yaswanth Reddy, Chamarthi Sindhupriya, Nara Sathvika, and Subramaniam Rajasekaran. "Device engineering of lead‐free FaCsSnI3/Cs2AgBiI6‐based dual‐absorber perovskite solar cell architecture for powering next‐generation wireless networks." International Journal of Communication Systems, July 11, 2024. http://dx.doi.org/10.1002/dac.5903.
Full textAbstract:
SummarySolar‐powered devices, such as wireless networks, are a crucial component of the Internet of Things (IoT). Designing and creating a solar cell architecture with an extended light absorption regime at a reasonable cost is therefore exceedingly important. All inorganic bismuth‐based Cs2AgBiI6 planar perovskite solar cells (PSCs) have garnered enormous significance due to their exceptional stability against oxygen, heat, and moisture. However, the power conversion efficiencies of Cs2AgBiI6‐based planar PSCs remain relatively low, primarily due to their limited light absorption range and interfacial charge recombination losses. This issue can be effectively addressed using a novel multi‐absorber architecture that incorporates dual absorbers with both lower band gap and wider band gap materials. This approach extends the light absorption range, enabling maximal utilization of the solar spectrum. Therefore, this article incorporates numerical modeling and guided optimization of ITO/ETL/Cs2AgBiI6/Fa0.75Cs0.25SnI3/HTL/Ag dual absorber‐based heterojunction structure to improvise the power conversion efficiency of Cs2AgBiI6‐based single‐absorber PSCs. The proposed configuration employs dual perovskite absorber layers (PALs) consisting of wide band gap Cs2AgBiI6 (1.6 eV) as the top absorber layer along with narrow bandgap Fa0.75Cs0.25SnI3 (1.27 eV) to act as the bottom absorber layer. Before evaluating the bilayer configuration, two standalone PSC architectures, namely, ITO/ETL/Fa0.75Cs0.25SnI3/HTL/Ag (D1)‐ and ITO/ETL/Cs2AgBiI6/HTL/Ag (D2)‐based PSC have been simulated and computed to perfectly fit the earlier anticipated state of art results. After effective validation of the photovoltaic parameters of the standalone architectures, both the absorber layers are appraised to constitute a dual active layer configuration ITO/ETL/Cs2AgBiI6/Fa0.75Cs0.25SnI3/HTL/Ag (D3) maintaining the overall absorber layer width constant to elevate the overall solar cell efficiency. Herein, a combination of various competent hole transport layers (HTLs) such as CBTS, CFTS, Cu2O, CuI, CuO, CuSCN, P3HT, PEDOT:PSS, and Spiro‐OMeTAD, as well as electron transport layers (ETLs) like C60, CeO2, IgZo, PCBM, TiO2, WS2, and ZnO, are adopted and compared to attain highly efficient bilayer PSC configuration. The crucial variables of all ETL‐ and HTL‐based proposed bilayer solar cell configurations including the thickness of PALs, the width of the carrier transport layers, defect densities of transport layers, the effect of operating temperature, series, and shunt resistances have been extensively optimized and tuned to attain preeminent photovoltaic power conversion efficiencies (PCEs) and quantum efficiencies (QEs). It has been well evinced that the proposed configuration with dual‐absorber layers could effectively widen the light absorption regime to the near‐infrared range and thus significantly contribute toward enhanced photovoltaic performance. The simulation results attained with SCAPS showcase the outstanding performance of the proposed dual active layer solar structure obtained with the combination of CuSCN HTL and TiO2 ETL pair. The work concludes a 35.01% optimized efficient ITO/TiO2/Cs2AgBiI6(PAL‐2)/Fa0.75Cs0.25SnI3(PAL‐1)/CuSCN/Ag bilayer solar cell configuration with enhanced short circuit current density (Jsc) of 32.24 mA/cm2, open circuit voltage (Voc) of 1.273 V, and 85.31% fill factor (FF) with 0.6‐ and 0.8‐μm PAL‐1 and PAL‐2 width respectively and 1014‐cm−3 defect density under AM1.G solar spectrum illumination with 1000‐W/m2 light power density. The proposed eco‐friendly solar structure will also help in providing power backup to the next‐generation communication units and devices. Notably the dual‐absorber structure integrating Cs2AgBiI6 and Fa0.75Cs0.25SnI3 materials demonstrates significant advantages in quantum efficiency and spectral coverage compared to using either material independently as single absorbers. The proposed model achieves a peak efficiency of approximately 93% across a spectral range of 300–975 nm, surpassing the 90% efficiency obtained with a single Cs2AgBiI6 absorber covering 300–700 nm. Moreover, it exceeds the 89% efficiency achieved by the single Fa0.75Cs0.25SnI3 absorber within the 300‐ to 974.5‐nm spectral range. Solar cells play a pivotal role in ensuring the sustainability, reliability, and cost efficiency of powering wireless nodes, especially in remote or environmentally sensitive areas where traditional power sources may be inadequate or unavailable. The proposed PSC, with a PCE of 35.01%, can generate 350.1 watts under standard test conditions. This provides sufficient power to support approximately 70 wireless nodes, including wireless sensor nodes, IoT devices, and others, each consuming approximately 5 watts of power.