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2. BiFeO3 Electronic Band Structure Calculations.
- Author
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STOCH, A., ZACHARIASZ, P., KRAKOWIAK, I., and STOCH, P.
- Subjects
- *
ELECTRONIC band structure , *ELECTRONIC paper , *MAGNETIC properties , *TRANSITION temperature , *DENSITY of states - Abstract
Bismuth ferrite belongs to magnetoelectric compounds which join, in the same crystal phase, two mutually excluding order parameters like magnetic and ferroelectric. In case of BiFeO3 both of these transition temperatures are considerably above room temperature what is important form the point of view of applications. In this paper electronic band structure calculations are presented. In the calculations, hybrid exchange interaction potential is applied, which gives the possibility to obtain correct insulating character of the compound without application of arbitrary Hubbard U parameter. The calculated densities of electronic states and magnetic properties are described. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
3. First-Principles Calculations of the Mechanical Properties of Doped Cu 3 P Alloys.
- Author
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Ma, Xiao, Cheng, Fang, Huang, Weiqing, He, Lian, Ye, Zixin, Yu, Shimeng, Hu, Ling, Yu, Dingkun, and Shen, Hangyan
- Subjects
COPPER ,MECHANICAL behavior of materials ,LATTICE constants - Abstract
In the quest to enhance the mechanical properties of CuP alloys, particularly focusing on the Cu
3 P phase, this study introduces a comprehensive investigation into the effects of various alloying elements on the alloy's performance. In this paper, the first principle of density universal function theory and the projection-enhanced wave method under VASP 5.4.4 software are used to recalculate the lattice constants, evaluate the lattice stability, and explore the mechanical properties of selected doped elements such as In, Si, V, Al, Bi, Nb, Sc, Ta, Ti, Y and Zr, including shear, stiffness, compression, and plasticity. The investigation reveals that strategic doping with In and Si significantly enhances shear resistance and stiffness, while V addition notably augments compressive resistance. Furthermore, incorporating Al, Bi, Nb, Sc, Ta, Ti, V, Y, and Zr has substantially improved plasticity, indicating a broad spectrum of mechanical enhancement through precise alloying. Crucially, the validation of our computational models is demonstrated through hardness experiments on Si and Sn-doped specimens, corroborating the theoretical predictions. Additionally, a meticulous analysis of the states' density further confirms our computational approach's accuracy and reliability. This study highlights the potential of targeted alloying to tailor the mechanical properties of Cu3 P alloys and establishes a robust theoretical framework for predicting the effects of doping in metallic alloys. The findings presented herein offer valuable insights and a novel perspective on material design and optimization, marking a significant stride toward developing advanced materials with customized mechanical properties. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
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4. Predicting the thermal decomposition temperature of energetic materials from a simple model.
- Author
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Zhang, Xuan, Liu, Qi-Jun, Liu, Fu-Sheng, and Liu, Zheng-Tang
- Subjects
- *
YOUNG'S modulus , *BAND gaps , *DENSITY of states , *FUNCTIONALS - Abstract
Context: The key factor in designing heat-resistant energetic materials is their thermal sensitivity. Further research and prediction of thermal sensitivity remains a great challenge for us. This study is based on first-principles calculations and establishes a theoretical model, which comprehensively considers band gap, density of states, and Young's modulus to obtain a empirical parameter Ψ. A quantitative relationship was established between the new parameter and the thermal decomposition temperature. The value of Ψ is calculated for 10 energetic materials and is found to have a strong correlation with the experimental thermal decomposition temperature. This further proves the reliability of our model. Specifically, the larger the value of Ψ, the higher the thermal decomposition temperature, and the more stable the energetic material will be. Therefore, to some extent, we can use the new parameter Ψ calculated by the model to predict thermal sensitivity. Methods: Based on first-principles, this paper used the Cambridge Serial Total Energy Package (CASTEP) module of Materials Studio (MS) for calculations. The Perdew-Burke-Ernzerhof (PBE) functionals in Generalized Gradient Approximation (GGA) method as well as the Grimme dispersion correction was used in this paper. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
5. Dependence of the incorporated boron concentration near SiO2/4H–SiC interface on trap passivation reduction.
- Author
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Wang, Runze, Noguchi, Munetaka, Watanabe, Hiroshi, and Kita, Koji
- Subjects
INTERFACE stability ,SPIN coating ,TEMPERATURE control ,HIGH temperatures ,DENSITY of states - Abstract
By systematically varying the boron concentration near the oxide/4H–SiC interface within a specifically designed boron-diffusion layer oxide structure, this paper explores the influence of boron concentration on interface state density and near-interface trap density in 4H–SiC MOS capacitors. Additionally, the effect of boron near the oxide/4H–SiC interface on device stability under elevated temperature conditions was examined. The boron species were introduced into the SiO
2 /4H–SiC interface by spin coating followed by annealing, whose temperature controls the amount of boron present in the near interface region. It is suggested that a higher concentration of boron leads to a better trap passivation effect while preserving the stability of flat band voltage. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
6. Impact of Temperature on Seebeck Coefficient of Nodal Line Semimetal in Molecular Conductor.
- Author
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Suzumura, Yoshikazu
- Subjects
SEEBECK coefficient ,ORGANIC conductors ,ELECTRIC conductivity ,CHEMICAL potential ,HIGH temperatures - Abstract
We examine the impact of temperature (T) on the Seebeck coefficient S, i.e., the T dependence of S for a single-component molecular conductor [Pd(dddt)
2 ] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) with a half-filled band, where the coefficient is obtained from a ratio of the thermal conductivity to the electrical conductivity. The present paper demonstrates theoretically the novel result of large anisotropy in the Seebeck coefficient components of three-dimensional Dirac electrons in a molecular conductor. The conductor exhibits a nodal line with the energy variation around the chemical potential and provides the density of states (DOS) with a minimum. Using a threedimensional tight-binding (TB) model in the presence of both impurity and electron–phonon (e–p) scatterings, we study the Seebeck coefficient Sy for the molecular stacking and the most conducting direction. The impact of T on Sy exhibits a sign change, where Sy > 0 with a maximum at high temperatures and Sy < 0 with a minimum at low temperatures. The T dependence of Sy suggests that the contribution from the conduction (valence) band is dominant at low (high) temperatures. Further, it is shown that the the Seebeck coefficient components for perpendicular directions Sx and Sz are much smaller than Sy and present no sign change, in contrast to Sy . These results are analyzed in terms of the spectral conductivity as a function of the energy ϵ close to the chemical potential μ. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
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7. Ab Initio Modelling of g -ZnO Deposition on the Si (111) Surface.
- Author
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Alzhanova, Aliya, Mastrikov, Yuri, and Yerezhep, Darkhan
- Subjects
ELECTRON density ,ZINC oxide ,SUBSTRATES (Materials science) ,DENSITY of states ,COMPUTER simulation - Abstract
Recent studies show that zinc oxide (ZnO) nanostructures have promising potential as an absorbing material. In order to improve the optoelectronic properties of the initial system, this paper considers the process of adsorbing multilayer graphene-like ZnO onto a Si (111) surface. The density of electron states for two- and three-layer graphene-like zinc oxide on the Si (111) surface was obtained using the Vienna ab-initio simulation package by the DFT method. A computer model of graphene-like Zinc oxide on a Si (111)-surface was created using the DFT+U approach. One-, two- and three-plane-thick graphene-zinc oxide were deposited on the substrate. An isolated cluster of Zn
3 O3 was also considered. The compatibility of g-ZnO with the S (100) substrate was tested, and the energetics of deposition were calculated. This study demonstrates that, regardless of the possible configuration of the adsorbing layers, the Si/ZnO structure remains stable at the interface. Calculations indicate that, in combination with lower formation energies, wurtzite-type structures turn out to be more stable and, compared to sphalerite-type structures, wurtzite-type structures form longer interlayers and shorter interplanar distances. It has been shown that during the deposition of the third layer, the growth of a wurtzite-type structure becomes exothermic. Thus, these findings suggest a predictable relationship between the application method and the number of layers, implying that the synthesis process can be modified. Consequently, we believe that such interfaces can be obtained through experimental synthesis. [ABSTRACT FROM AUTHOR]- Published
- 2024
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8. Understanding the Competition Mechanism between Na 2 O and CaO for the Formation of the Initial Layer of Zhundong Coal Ash.
- Author
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Abudoureheman, Maierhaba, He, Lanzhen, Liu, Kunpeng, Wei, Bo, Lv, Jia, Wang, Jianjiang, and Zhu, Quan
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COAL ash ,COMBUSTION kinetics ,COAL combustion ,ORBITAL hybridization ,ALKALINE earth metals ,BINDING energy ,DENSITY functional theory - Abstract
The contents of alkali and alkaline earth metals are higher in Zhundong coal, and there are serious problems of slagging and fouling during the combustion process. Therefore, it is of great significance to reveal the mechanism of slagging and fouling in the boiler of Zhundong coal. In this paper, first-principle calculations based on density functional theory are used to study the competition mechanism of alkaline metal oxides during the combustion process in Zhundong coal by establishing the Na
2 O(110)/CaO(100)-SiO2 (100) double-layer interface model. The results show that the bond lengths of the surface of Na2 O(110) and CaO(100) with SiO2 (100) after adsorption were generally lengthened and the value of bond population became smaller, which formed a stable binding energy during the reaction. The electron loss of Na is 0.05 e, the electron loss of Ca is 0.03 e, and the electron loss of Na2 O is greater than that of CaO. The charge transfer on the surface of Na2 O with SiO2 is obviously higher than that of CaO and the orbital hybridization on the surface of CaO with SiO2 is weaker than that on the surfaces of Na2 O with SiO2 . Na2 O is easier to react with SiO2 than CaO. The adsorption energies on the surface of Na2 O and CaO with SiO2 are −5.56 eV and −0.72 eV, respectively. The adsorption energy of Na2 O is higher than that of CaO, indicating that Na2 O is more prone to adsorption reactions and formation of Na-containing minerals and other minerals, resulting in more serious slagging. In addition, the XRD analyses at different temperatures showed that Na-containing compounds appeared before Ca-containing ones, and the reaction activity of Na2 O is stronger than that of CaO in the reaction process. The experimental results have good agreement with the calculation results. This provides strong evidence to reveal the slagging and fouling of Zhundong coal. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
9. Derivation of Bose's Entropy Spectral Density from the Multiplicity of Energy Eigenvalues.
- Author
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Spalvieri, Arnaldo
- Subjects
SPECTRAL energy distribution ,EIGENVALUES ,ENTROPY ,QUANTUM numbers ,MULTIPLICITY (Mathematics) ,THERMAL analysis - Abstract
The modern textbook analysis of the thermal state of photons inside a three-dimensional reflective cavity is based on the three quantum numbers that characterize photon's energy eigenvalues coming out when the boundary conditions are imposed. The crucial passage from the quantum numbers to the continuous frequency is operated by introducing a three-dimensional continuous version of the three discrete quantum numbers, which leads to the energy spectral density and to the entropy spectral density. This standard analysis obscures the role of the multiplicity of energy eigenvalues associated to the same eigenfrequency. In this paper we review the past derivations of Bose's entropy spectral density and present a new analysis of energy spectral density and entropy spectral density based on the multiplicity of energy eigenvalues. Our analysis explicitly defines the eigenfrequency distribution of energy and entropy and uses it as a starting point for the passage from the discrete eigenfrequencies to the continuous frequency. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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10. Triple‐Vertex Linkage of (BO4)‐Tetrahedra in a Borosulfate: Synthesis, Crystal Structure, and Quantum‐Chemical Investigation of Sr[B3O(SO4)4(SO4H)]
- Author
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Pasqualini, Leonard C., Huppertz, Hubert, Je, Minyeong, Choi, Heechae, and Bruns, Jörn
- Subjects
charge-density calculations ,borosulfates ,Communication ,Borosulfates | Hot Paper ,density of states ,solvothermal synthesis ,Communications ,density functional theory - Abstract
Borosulfates are classified as silicate analogue materials. The number of crystallographically characterized compounds is still limited, whereas the structural diversity is already impressive. The anionic substructures of borosulfates exhibit vertex‐connected (BO4)‐ and (SO4)‐tetrahedra, whereas bridging between two (SO4)‐ or even between two (BO4)‐tetrahedra is scarce. The herein presented compound Sr[B3O(SO4)4(SO4H)] is the first borosulfate with a triple‐vertex linkage of three (BO4) tetrahedra via one common oxygen atom. DFT calculations complement the experimental studies. Bader charges (calculated for all atoms) as well as charge‐density calculations give hint to the electron distribution within the anionic substructure and density‐of‐states calculations support the interpretation of the bonding situation., Sr[B3O(SO4)4(SO4H)] was obtained under harsh conditions in a specially designed setup. In contrast to silicates and its substitution variants like alumosilicates, the anionic substructure of Sr[B3O(SO4)4(SO4H)] reveals vertex linkage of three (BO4) tetrahedra via a common oxygen atom. DFT calculations help to elucidate the nature of this special bonding situation.
- Published
- 2021
11. New Insights into the Catalytic Activity of Cobalt Orthophosphate Co3(PO4)2 from Charge Density Analysis
- Author
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Regine Herbst-Irmer, Helena Keil, Claudia Stückl, Matti Hellström, Dietmar Stalke, and Jörg Behler
- Subjects
Population ,chemistry.chemical_element ,010402 general chemistry ,solid-state catalysis ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,charge density investigation ,education ,cobalt phosphate ,Lone pair ,education.field_of_study ,Full Paper ,010405 organic chemistry ,Organic Chemistry ,Atoms in molecules ,Charge density ,General Chemistry ,Full Papers ,computational chemistry ,0104 chemical sciences ,density of states ,chemistry ,Chemical physics ,Chemisorption ,Density functional theory ,Catalysis from Charge Density ,Cobalt ,Cobalt phosphate - Abstract
An extensive characterization of Co3(PO4)2 was performed by topological analysis according to Bader‘s Quantum Theory of Atoms in Molecules from the experimentally and theoretically determined electron density. This study sheds light on the reactivity of cobalt orthophosphate as a solid‐state heterogeneous oxidative‐dehydration and ‐dehydrogenation catalyst. Various faces of the bulk catalyst were identified as possible reactive sites given their topological properties. The charge accumulations and depletions around the two independent five‐ and sixfold‐coordinated cobalt atoms, found in the topological analysis, are correlated to the orientation and population of the d‐orbitals. It is shown that the (011) face has the best structural features for catalysis. Fivefold‐coordinated ions in close proximity to advantageously oriented vacant coordination sites and electron depletions suit the oxygen lone pairs of the reactant, mainly for chemisorption. This is confirmed both from the multipole refinement as well as from density functional theory calculations. Nearby basic phosphate ions are readily available for C−H activation., How to Cat: The experimental and theoretical topological analysis of the electron density distribution in Co3(PO4)2 identified the (011) face to be best suited for catalysis. Fivefold‐coordinated Co ions in close proximity to advantageously oriented electron‐depletion sites suit the reactant's oxygen lone pairs most for chemisorption and heterogeneous C−H activation.
- Published
- 2019
12. Study on transient photocurrent induced by energy level defect of schottky diode irradiated by high power pulsed laser.
- Author
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Wang, Y. H., Su, J. H., Wang, T. W., Lei, Z. Y., Chen, Z. J., Shangguan, S. P., Han, J. W., and Ma, Y. Q.
- Subjects
HIGH power lasers ,PHOTOELECTRIC devices ,SCHOTTKY barrier diodes ,PULSED lasers ,PHOTOELECTRIC effect ,DENSITY of states ,VALENCE bands ,SEMICONDUCTOR lasers - Abstract
The transient photocurrent is one of the key parameters of the spatial radiation effect of photoelectric devices, and the energy level defect affects the transient photocurrent. In this paper, by studying the deep level transient spectrum of a self-designed Schottky diode, the defect properties of the interface region of the anode metal AlCu and Si caused by high-temperature annealing at 150 ℃, 200 ℃ and 300 ℃ for 1200 h have been quantitatively analyzed. The study shows that the defect is located at the position of + 0.41 eV on the valence band, the concentration is 2.8 × 10
13 /cm2 , and the capture cross section is σ = 8.5 × 1017 . The impurity energy level mainly comes from the diffusion of Al atom in anode metal. We found that the defect did not cause the electrical performance degradation and obvious morphology change of the device, but the transient photocurrent increased significantly. The reason is that the high temperature treatment results in a growth in the density of states at the interface between AlCu–Si. The more mismatched dislocations and recombination center increased the reverse current of the heterojunction. The above view is proved by the TCAD simulation test. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
13. Suppressed-gap millimetre wave kinetic inductance detectors using DC-bias current
- Author
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Songyuan Zhao, Stafford Withington, Christopher N. Thomas, David J. Goldie, Zhao, Songyuan [0000-0002-5712-6937], Apollo - University of Cambridge Repository, Goldie, David [0000-0001-8472-5110], and Thomas, Christopher [0000-0002-4039-6551]
- Subjects
Paper ,Materials science ,Acoustics and Ultrasonics ,Condensed matter ,FOS: Physical sciences ,Applied Physics (physics.app-ph) ,02 engineering and technology ,01 natural sciences ,GeneralLiterature_MISCELLANEOUS ,Resonator ,Quality (physics) ,Transmission line ,0103 physical sciences ,ComputingMilieux_COMPUTERSANDEDUCATION ,010306 general physics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,ComputingMilieux_MISCELLANEOUS ,Superconductivity ,Range (particle radiation) ,ComputingMilieux_THECOMPUTINGPROFESSION ,DC-bias ,superconducting resonators ,Physics - Applied Physics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Computational physics ,kinetic inductance detectors ,Density of states ,Quasiparticle ,ComputingMilieux_COMPUTERSANDSOCIETY ,0210 nano-technology ,Astrophysics - Instrumentation and Methods for Astrophysics ,DC bias - Abstract
Funder: CSC Cambridge Scholarship, In this study, we evaluate the suitability of using DC-biased aluminium resonators as low-frequency kinetic inductance detectors capable of operating in the frequency range of 50–120 GHz. Our analysis routine for supercurrent-biased resonators is based on the Usadel equations and gives outputs including density of states, complex conductivities, transmission line properties, and quasiparticle lifetimes. Results from our analysis confirm previous experimental observations on resonant frequency tuneability and retention of high quality factor. Crucially, our analysis suggests that DC-biased resonators demonstrate significantly suppressed superconducting density of states gap. Consequently these resonators have lower frequency detection threshold and are suitable materials for low-frequency kinetic inductance detectors.
- Published
- 2022
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14. Split Happens! Imprecise and Negative Information in Gaussian Mixture Random Finite Set Filtering.
- Author
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LEGRAND, KEITH A. and FERRARI, SILVIA
- Subjects
RANDOM sets ,NATURAL languages ,DENSITY of states ,NONLINEAR equations ,MIXTURES - Abstract
In object-tracking and state-estimation problems, ambiguous evidence such as imprecise measurements and the absence of detections can contain valuable information and thus be leveraged to further refine the probabilistic belief state. In particular, knowledge of a sensor's bounded field of view (FoV) can be exploited to incorporate evidence of where an object was not observed. This paper presents a systematic approach for incorporating knowledge of the FoV geometry, position, and object inclusion/exclusion evidence into object state densities and random finite set multiobject cardinality distributions. The resulting state estimation problem is nonlinear and solved using a new Gaussian mixture approximation based on recursive component splitting. Based on this approximation, a novel Gaussian mixture Bernoulli filter for imprecise measurements is derived and demonstrated in a tracking problem using only natural language statements as inputs. This paper also considers the relationship between bounded FoVs and cardinality distributions for a representative selection of multiobject distributions, which can be used for sensor planning, as is demonstrated through a problem involving a multi-Bernoulli process with up to 100 potential objects. [ABSTRACT FROM AUTHOR]
- Published
- 2022
15. A carrier velocity model for electrical detection of gas molecules
- Author
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Niayesh Gharaei, Razali Ismail, Mohammad Taghi Ahmadi, Sharifah H. S. Ariffin, and Ali Hosseingholi Pourasl
- Subjects
carrier velocity ,Materials science ,General Physics and Astronomy ,armchair graphene nanoribbons ,02 engineering and technology ,molecular adsorption ,lcsh:Chemical technology ,01 natural sciences ,lcsh:Technology ,Full Research Paper ,law.invention ,gas sensor ,Adsorption ,Tight binding ,law ,Molecule ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,Electronic band structure ,lcsh:Science ,Graphene ,lcsh:T ,010401 analytical chemistry ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,0104 chemical sciences ,I–V characteristics ,Nanoscience ,Chemical physics ,Density of states ,First principle ,lcsh:Q ,0210 nano-technology ,Graphene nanoribbons ,lcsh:Physics - Abstract
Nanomaterial-based sensors with high sensitivity, fast response and recovery time, large detection range, and high chemical stability are in immense demand for the detection of hazardous gas molecules. Graphene nanoribbons (GNRs) which have exceptional electrical, physical, and chemical properties can fulfil all of these requirements. The detection of gas molecules using gas sensors, particularly in medical diagnostics and safety applications, is receiving particularly high demand. GNRs exhibit remarkable changes in their electrical characteristics when exposed to different gases through molecular adsorption. In this paper, the adsorption effects of the target gas molecules (CO and NO) on the electrical properties of the armchair graphene nanoribbon (AGNR)-based sensor are analytically modelled. Thus, the energy dispersion relation of AGNR is developed considering the molecular adsorption effect using a tight binding (TB) method. The carrier velocity is calculated based on the density of states (DOS) and carrier concentration (n) to obtain I–V characteristics and to monitor its variation in the presence of the gas molecules. Furthermore, the I–V characteristics and energy band structure of the AGNR sensor are simulated using first principle calculations to investigate the gas adsorption effects on these properties. To ensure the accuracy of the proposed model, the I–V characteristics of the AGNR sensor that are simulated based both on the proposed model and first principles calculations are compared, and an acceptable agreement is achieved.
- Published
- 2019
16. Nonequilibrium Kondo effect in a graphene-coupled quantum dot in the presence of a magnetic field
- Author
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Ioan Grosu and Levente Máthé
- Subjects
Kondo effect ,General Physics and Astronomy ,FOS: Physical sciences ,magnetic field ,02 engineering and technology ,Electron ,lcsh:Chemical technology ,01 natural sciences ,lcsh:Technology ,Full Research Paper ,law.invention ,pseudogap Anderson model ,symbols.namesake ,law ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,010306 general physics ,lcsh:Science ,Physics ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Graphene ,lcsh:T ,graphene ,Coulomb blockade ,quantum dot ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,lcsh:QC1-999 ,Nanoscience ,Quantum dot ,symbols ,Density of states ,lcsh:Q ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,Pseudogap ,Hamiltonian (quantum mechanics) ,lcsh:Physics - Abstract
Quantum dots connected to larger systems containing a continuum of states like charge reservoirs allow the theoretical study of many-body effects such as the Coulomb blockade and the Kondo effect. Here, we analyze the nonequilibrium Kondo effect and transport phenomena in a quantum dot coupled to pure monolayer graphene electrodes under external magnetic fields for finite on-site Coulomb interaction. The system is described by the pseudogap Anderson Hamiltonian. We use the equation of motion technique to determine the retarded Green's function of the quantum dot. An analytical formula for the Kondo temperature is derived for electron and hole doping of the graphene leads. The Kondo temperature vanishes in the vicinity of the particle-hole symmetry point and at the Dirac point. In the case of particle-hole asymmetry, the Kondo temperature has a finite value even at the Dirac point. The influence of the on-site Coulomb interaction and the magnetic field on the transport properties of the system shows a tendency similar to the previous results obtained for quantum dots connected to metallic electrodes. Most remarkably, we find that the Kondo resonance does not show up in the density of states and in the differential conductance for zero chemical potential due to the linear energy dispersion of graphene. An analytical method to calculate self-energies is also developed which can be useful in the study of graphene-based systems. Our graphene-based quantum dot system provides a platform for potential applications of nanoelectronics. Furthermore, we also propose an experimental setup for performing measurements in order to verify our model., 13 pages
- Published
- 2020
17. Anomalous current–voltage characteristics of SFIFS Josephson junctions with weak ferromagnetic interlayers
- Author
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Aleksei Yu. Kuzin, Elena A. Kazakova, Boris G. Lvov, Shiro Kawabata, Andrey S. Vasenko, Tairzhan Karabassov, and Anastasia V. Guravova
- Subjects
Josephson effect ,Materials science ,Josephson junctions ,Field (physics) ,current–voltage characteristics ,FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,lcsh:Chemical technology ,01 natural sciences ,lcsh:Technology ,Full Research Paper ,Superconductivity (cond-mat.supr-con) ,Condensed Matter::Superconductivity ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,superconductor/ferromagnet hybrid nanostructures ,Proximity effect (superconductivity) ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,010306 general physics ,lcsh:Science ,Superconductivity ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Scattering ,lcsh:T ,Condensed Matter - Superconductivity ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,lcsh:QC1-999 ,Nonlinear system ,Nanoscience ,Ferromagnetism ,proximity effect, superconductivity ,Density of states ,lcsh:Q ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,lcsh:Physics - Abstract
We present a quantitative study of the current-voltage characteristics (CVC) of SFIFS Josephson junctions (S denotes bulk superconductor, F - metallic ferromagnet, I - insulating barrier) with weak ferromagnetic interlayers in the diffusive limit. The problem is solved in the framework of the nonlinear Usadel equations. We consider the case of a strong tunnel barrier such that the left SF and the right FS bilayers are decoupled. We calculate the density of states (DOS) in SF bilayers using a self-consistent numerical method. Then we obtain the CVC of corresponding SFIFS junctions, and discuss their properties for different set of parameters including the thicknesses of ferromagnetic layers, the exchange field, and the magnetic scattering time. We observe the anomalous nonmonotonic CVC behavior in case of weak ferromagnetic interlayers, which we ascribe by DOS energy dependencies in case of small exchange fields in F layers.
- Published
- 2020
18. Improvement of the thermoelectric properties of a MoO3 monolayer through oxygen vacancies
- Author
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Jing Shi, Huixiong Deng, Ziyu Wang, Wei Cao, Rui Xiong, and Wenwen Zheng
- Subjects
Materials science ,molybdenum trioxides ,General Physics and Astronomy ,02 engineering and technology ,lcsh:Chemical technology ,010402 general chemistry ,lcsh:Technology ,01 natural sciences ,Full Research Paper ,oxygen vacancies ,symbols.namesake ,Thermal conductivity ,Thermoelectric effect ,Monolayer ,Figure of merit ,Nanotechnology ,lcsh:TP1-1185 ,General Materials Science ,MoO3 monolayer ,Electrical and Electronic Engineering ,lcsh:Science ,Anisotropy ,Condensed matter physics ,lcsh:T ,Boltzmann transport theory ,Fermi level ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,thermoelectric properties ,lcsh:QC1-999 ,0104 chemical sciences ,Nanoscience ,first-principles calculations ,symbols ,Density of states ,lcsh:Q ,0210 nano-technology ,lcsh:Physics - Abstract
We have investigated the thermoelectric properties of a pristine MoO3 monolayer and its defective structures with different oxygen vacancies using first-principles methods combined with Boltzmann transport theory. Our results show that the thermoelectric properties of the MoO3 monolayer exhibit an evident anisotropic behavior which is caused by the similar anisotropy of the electrical and thermal conductivity. The thermoelectric materials figure of merit (ZT) value along the x- and the y-axis is 0.72 and 0.08 at 300 K, respectively. Moreover, the creation of oxygen vacancies leads to a sharp peak near the Fermi level in the density of states. This proves to be an effective way to enhance the ZT values of the MoO3 monolayer. The increased ZT values can reach 0.84 (x-axis) and 0.12 (y-axis) at 300 K.
- Published
- 2019
19. Engineering surface state density of monolayer CVD grown 2D MoS2 for enhanced photodetector performance.
- Author
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Polumati, Gowtham, Kolli, Chandra Sekhar Reddy, de Luna Bugallo, Andres, and Sahatiya, Parikshit
- Subjects
SURFACE states ,DENSITY of states ,PHOTODETECTORS ,DOPING agents (Chemistry) ,MONOMOLECULAR films ,ENGINEERING - Abstract
This study demonstrates the effect of nitrogen doping on the surface state densities (Nss) of monolayer MoS
2 and its effect on the responsivity and the response time of the photodetector. Our experimental results shows that by doping monolayer MoS2 by nitrogen, the surface state (Nss) increases thereby increasing responsivity. The mathematical model included in the paper supports the relation of photocurrent gain and its dependency on trap level which states that the increasing the trap density increases the photocurrent gain and the same is observed experimentally. The experimental results at room temperature revealed that nitrogen doped MoS2 have a high NSS of 1.63 X 1013 states/m2 /eV compared to undoped MoS2 of 4.2 x 1012 states/m2 /eV. The increase in Nss in turn is the cause for rise in trap states which eventually increases the value of photo responsivity from 65.12 A/W (undoped MoS2 ) to 606.3 A/W (nitrogen doped MoS2 ). The response time calculated for undoped MoS2 was 0.85 sec and for doped MoS2 was 0.35 sec. Finally, to verify the dependence of surface states on the responsivity, the surface states were varied by varying temperature and it was observed that upon increment in temperature, the surface states decreases which causes the responsivity values also to decrease. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
20. LaZn 1− x Bi 2 as a Candidate for Dirac Nodal-Line Intermetallic Systems.
- Author
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Ruszała, Piotr, Winiarski, Maciej J., and Samsel-Czekała, Małgorzata
- Subjects
FERMI surfaces ,ELECTRONIC band structure ,DENSITY functionals ,DENSITY functional theory ,UNIT cell ,DENSITY of states ,PETRI nets - Abstract
The complex theoretical analysis of the density of states, band structures, and Fermi surfaces, based on predictions of the density functional theory methods, unveils the unique electronic properties of the LaZn
1−x Bi2 system. In this paper, the Zn vacancies (for x = 0.5 ) were modeled using a modified unit cell of lower symmetry than that for a fully stoichiometric one (for x = 0 ). The existence of several Dirac-like features in the electronic band structures was found. Some of them were found to be intimately associated with the nonsymmorphic symmetry of the system, and these were investigated in detail. The calculated Fermi surface shapes, as well as the Fermi velocity values (up to ∼1.2 × 10 6 m/s), are in good agreement with other analogous square-net Dirac semimetals. The combination of charge-carrier uncompensation, relatively small band splitting, and the tolerance factor for square-net semimetals t ≤ 0.95 for LaZn0.5 Bi2 , constitutes a very promising indicator of the topological features of this system, warranting further experimental studies. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
21. CO and HCHO Sensing by Single Au Atom-Decorated WS 2 Monolayer for Diagnosis of Thermal Aging Faults in the Dry-Type Reactor: A First-Principles Study.
- Author
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Zhao, Qi, Man, Yuyan, He, Jin, Li, Songyuan, and Li, Lin
- Subjects
CARBON monoxide detectors ,GAS detectors ,GAS absorption & adsorption ,THERMAL insulation ,DENSITY of states ,MONOMOLECULAR films ,RECOVERY rooms - Abstract
CO and HCHO are the main pyrolysis gases in long-term running dry-type reactors, and thus the diagnosis of thermal insulation faults inside such devices can be realized by sensing these gases. In this paper, a single Au atom-decorated WS
2 (Au-WS2 ) monolayer is proposed as an original sensing material for CO or HCHO detection to evaluate the operation status of dry-type reactors. It was found that the Au atom prefers to be adsorbed at the top of the S atom of the pristine WS2 monolayer, wherein the binding force is calculated as −3.12 eV. The Au-WS2 monolayer behaves by chemisorption upon the introduction of CO and HCHO molecules, with the adsorption energies of −0.82 and −1.01 eV, respectively. The charge density difference was used to analyze the charge-transfer and bonding behaviors in the gas adsorptions, and the analysis of density of state as well as band structure indicate gas-sensing mechanisms. As calculated, the sensing responses of the Au-WS2 monolayer upon CO and HCHO molecule introduction were 58.7% and −74.4%, with recovery times of 0.01 s and 11.86 s, respectively. These findings reveal the favorable potential of the Au-WS2 monolayer to be a reusable and room-temperature sensing candidate for CO and HCHO detections. Moreover, the work function of the Au-WS2 monolayer was decreased by 13.0% after the adsorption of CO molecules, while it increased by 1.2% after the adsorption of HCHO molecules, which implies its possibility to be a work-function-based gas sensor for CO detection. This theoretical report paves the way for further investigations into WS2 -based gas sensors in some other fields, and it is our hope that our findings can stimulate more reports on novel gas-sensing materials for application in evaluating the operation conditions of dry-type reactors. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
22. Real-time label-free detection of DNA hybridization using a functionalized graphene field effect transistor: a theoretical study
- Author
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Sheida Bagherzadeh-Nobari and Reza Kalantarinejad
- Subjects
Field effect transistor ,Materials science ,DNA hybridization ,Bioengineering ,PBASE ,law.invention ,law ,General Materials Science ,Graphene nanoribbon ,Graphene ,business.industry ,Detector ,Conductance ,Fermi energy ,General Chemistry ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Quantum transport ,Modeling and Simulation ,Electrode ,Density of states ,Optoelectronics ,Density functional theory ,Field-effect transistor ,business ,Research Paper - Abstract
Graphical abstract Detection of DNA hybridization with high sensitivity and accuracy plays a major role in clinical diagnosis and treatment. Despite intense experimental studies of graphene field effect transistor as DNA hybridization detector, the mechanism of detection and changes in the electrical properties of the device is not investigated in detail. To this end, we have investigated an armchair graphene nanoribbon (AGNR) interconnected between gold electrodes as a detector of DNA hybridization. Using non-equilibrium Green’s function method and density functional theory, the effect of 1-pyrenebutanoic acid succinimidyl ester (PBASE) linker, probe, and target DNA on the electrical properties of the device has been investigated at zero bias voltage. The results show that, after functionalization of AGNR with PBASE, the conductance of the device increases while functionalization with probe and target DNA leads to a decrease in conductance. The changes in the projected density of states on the AGNR and transmission around Fermi energy are the reason for the change in conductance of the system. In all cases, both charge transfer and electrostatic gating are responsible for the change in the electrical properties of the system. The results show that our device detects DNA hybridization with a sensitivity of 10% at zero bias voltage, and by applying a suitable gate voltage, it can show higher sensitivity.
- Published
- 2021
23. Structural parameters and electronic properties of 2D carbon allotrope: Graphene with a kagome lattice structure
- Author
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Sefer Bora Lisesivdin, Fedor Jelezko, B. Sarikavak-Lisesivdin, Esra Kizildag Ozbay, and Özbay, Ekmel
- Subjects
Materials science ,General Physics and Astronomy ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,01 natural sciences ,law.invention ,law ,Physical and Theoretical Chemistry ,Electronic band structure ,ComputingMethodologies_COMPUTERGRAPHICS ,Superconductivity ,Condensed matter physics ,Graphene ,Kagome lattice ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Two-dimensional material ,Bond length ,Carbon allotrope ,Density of states ,Density functional theory ,0210 nano-technology ,Dispersion (chemistry) ,Research Paper - Abstract
Graphical abstract, Highlights • Structure parameters and electronic properties of graphene with kagome lattice structure is calculated. • Various XC and dispersion correction methods are used and similar results are obtained. • Pristine graphene with kagome lattice structure shows very small magnetic properties. • A kagome flat-band structure is observed near the EF. • High DOS at flat-band is mostly consisting of pz orbital and also dxz and dyz orbital contributions., In this paper, the electronic properties of a carbon allotrope, graphene with a kagome lattice structure, are investigated. Spin-polarized density functional theory (DFT) calculations with Grimme dispersion corrections were done. Bond lengths, electronic band structure, and projected density of states were calculated. Electronic band structure calculations show kagome flat-band formation with higher d-orbital contributed bonding behavior than the pristine graphene structure. The structural parameters and electronic band results of this 2D carbon allotrope show wider possible usage in many applications from desalination membranes to possible high-temperature superconductors.
- Published
- 2020
24. Novel Gas-Sensitive Material for Monitoring the Status of SF 6 Gas-Insulated Switches: Gese Monolayer.
- Author
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Qian, Guochao, Hu, Xiqian, Chen, Weigen, and Zhou, Qu
- Subjects
DENSITY of states ,ENERGY bands ,GAS detectors ,DESORPTION ,THERMAL desorption - Abstract
Detecting the decomposition components of SF
6 insulating gas is recognized as an effective means to monitor the operating status of the SF6 insulating switch. In this paper, the adsorption characteristics of a new two-dimensional material GeSe for five SF6 decomposition gases (SO2 , SOF2 , SO2 F2 , H2 S and HF) are reported by first-principles simulation. Through the analysis of the change of energy band structure, density of states distribution, and gas desorption time, it is found that GeSe has the potential as a gas-sensitive material for the selective detection of SO2 F2 , and the computational work in this paper provides theoretical guidance for the development of new gas-sensitive sensors applied in monitoring SF6 insulated switches. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
25. Effect of swap disorder on the physical properties of the quaternary Heusler alloy PdMnTiAl: a first-principles study
- Author
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Shunbo Hu, Guanhua Qin, Hui Gu, Xiaoyan Yan, Wei Ren, Shixun Cao, Xi Li, Yongxue Tao, Wei Wu, and Chao Jing
- Subjects
Materials science ,Composite number ,Alloy ,quaternary Heusler alloy ,02 engineering and technology ,engineering.material ,01 natural sciences ,Biochemistry ,Condensed Matter::Materials Science ,Gapless playback ,Lattice (order) ,0103 physical sciences ,General Materials Science ,010306 general physics ,Electronic band structure ,Crystallography ,Spintronics ,Condensed matter physics ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Research Papers ,QD901-999 ,Density of states ,engineering ,electronic properties ,magnetic properties ,0210 nano-technology ,swap disorder ,Swap (computer programming) - Abstract
The effect of swap disorder on the physical properties of the quaternary Heusler alloy PdMnTiAl is described from first principles., Heusler alloys crystallize in a close-packed cubic structure, having a four-atom basis forming a face-centred cubic lattice. By selecting different composite elements, Heusler alloys provide a large family of members for frontier research of spintronics and magnetic materials and devices. In this paper, the structural, electronic and magnetic properties of a novel quaternary Heusler alloy, PdMnTiAl, have been investigated using a first-principles computational materials calculation. It was found that the stable ordered structure is a non-magnetic Y-type1, in good agreement with the Slater–Pauling rule. From the band structure and the density of states, it is predicted that this Y-type1 configuration is a new gapless semi-metal material. Furthermore, it was discovered that the Pd–Mn swap-disordered structure is more stable than the Y-type1 structure. The present work provides a guide for experiments to synthesize and characterize this Heusler alloy.
- Published
- 2017
26. A First-Principle Study of Two-Dimensional Boron Nitride Polymorph with Tunable Magnetism.
- Author
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Qiao, Liping, Ma, Zhongqi, Yan, Fulong, Wang, Sake, and Fan, Qingyang
- Subjects
BORON nitride ,POISSON'S ratio ,BAND gaps ,MAGNETISM ,YOUNG'S modulus ,MAGNETIC properties - Abstract
Using the first-principles calculation, two doping two-dimensional (2D) BN (boron nitride) polymorphs are constructed in this work. The two doping 2D BN polymorphs B
5 N6 Al and B5 N6 C sheets are thermally stable under 500 K. All the B6 N6 , B5 N6 Al, and B5 N6 C sheets are semiconductor materials with indirect band gaps on the basis of a hybrid functional. The anisotropic calculation results indicate that Young's modulus (E) and Poisson's ratio (v) of the B6 N6 , B5 N6 Al, and B5 N6 C sheets are anisotropic in the xy plane. In addition, the magnetic properties of the B6 N6 , B5 N6 Al, and B5 N6 C sheets have also been investigated. According to the calculation of the magnetic properties, B6 N6 sheet does not exhibit magnetism, while it shows weak magnetism after doping carbon atom to the BN sheet. This paper explores the influence mechanism of doping different atoms on the basic physical properties of two-dimensional BN sheets. It not only constructs a relationship between structure and performance but also provides theoretical support for the performance regulation of BN materials. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
27. Optimal investment of DC pension plan under a joint VaR-ES constraint.
- Author
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Yinghui Dong, Chengjin Tang, and Chunrong Hua
- Subjects
DEFINED contribution pension plans ,PENSIONS ,MARTINGALES (Mathematics) ,DENSITY of states ,VALUE at risk - Abstract
In this paper, we investigated an optimal investment problem of a defined contribution (DC) pension plan under a joint Value-at-Risk (VaR) and an expected shortfall (ES) constraint. By using a martingale method, we transformed a dynamic optimization problem to a static pointwise optimization problem and derived the closed-form representations of the optimal wealth and portfolio processes in terms of the state price density. Numerical results showed that in comparison to only an ES constraint or a VaR constraint, the joint VaR-ES constraint can not only improve risk management for the bad economic states but also lower the volatility of the optimal terminal wealth. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
28. Ultrahigh-energy density state in nanowire arrays irradiated with picosecond kilojoule-class ultra-intense laser.
- Author
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Tanaka, D., Maeda, Y., Hironaka, Y., Kawasaki, K., Higashi, N., Iwata, N., Sentoku, Y., Kodama, R., Ozaki, N., Somekawa, T., Shinguubara, S., Shimizu, T., Sawada, H., and Shigemori, K.
- Subjects
NANOWIRES ,ULTRASHORT laser pulses ,DENSITY of states ,INERTIAL confinement fusion ,HOT carriers ,FEMTOSECOND lasers ,LASERS - Abstract
Ultrahigh-energy density (UHED) states greater than 1 Gbar pressure are typically observed under extreme conditions, such as in the core of an inertial confinement fusion implosion. A novel alternative approach for generating volumetric UHED states is to use nanowire arrays irradiated with a femtosecond ultrahigh-intensity laser. In this paper, we present an experimental investigation on laser absorption and energy transport in nanowire arrays irradiated with a picosecond kilojoule petawatt laser. The laser–target interactions were studied by measuring the x-ray emission and escaping hot electrons from a bare Cu foil and a foil with a nanowire array grown on its surface. The measured Cu-Kα and He-α emissions from the nanowire array were higher than those from the flat foil. In addition, hot electrons observed from the front surface of the nanowire array were enhanced. On the other hand, despite the stronger Kα emission from the nanowire array and the enhancement of hot electrons escaping from the front surface of the nanowire array, the number of hot electrons observed from the rear side of the flat foil target was slightly lower than that of the flat foil. A comparison of the experimental results with the results of a two-dimensional particle-in-cell simulation code suggested that the magnetic fields generated around the periodic nanowire array trap hot electrons, improving the electron-to-target energy coupling and efficiently producing UHED states. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
29. High-throughput ab initio design of atomic interfaces using InterMatch.
- Author
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Gerber, Eli, Torrisi, Steven B., Shabani, Sara, Seewald, Eric, Pack, Jordan, Hoffman, Jennifer E., Dean, Cory R., Pasupathy, Abhay N., and Kim, Eun-Ah
- Subjects
PHASE space ,CHARGE transfer ,RIESZ spaces ,INTERFACE structures ,DENSITY of states ,TRANSITION metals - Abstract
Forming a hetero-interface is a materials-design strategy that can access an astronomically large phase space. However, the immense phase space necessitates a high-throughput approach for an optimal interface design. Here we introduce a high-throughput computational framework, InterMatch, for efficiently predicting charge transfer, strain, and superlattice structure of an interface by leveraging the databases of individual bulk materials. Specifically, the algorithm reads in the lattice vectors, density of states, and the stiffness tensors for each material in their isolated form from the Materials Project. From these bulk properties, InterMatch estimates the interfacial properties. We benchmark InterMatch predictions for the charge transfer against experimental measurements and supercell density-functional theory calculations. We then use InterMatch to predict promising interface candidates for doping transition metal dichalcogenide MoSe
2 . Finally, we explain experimental observation of factor of 10 variation in the supercell periodicity within a few microns in graphene/α-RuCl3 by exploring low energy superlattice structures as a function of twist angle using InterMatch. We anticipate our open-source InterMatch algorithm accelerating and guiding ever-growing interfacial design efforts. Moreover, the interface database resulting from the InterMatch searches presented in this paper can be readily accessed online. Predicting properties at the interface of materials is crucial for advanced materials design. Here, the authors introduce a high-throughput computational framework, InterMatch, for predicting several properties of an interface by using the databases of individual bulk materials. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
30. Electron Compton scattering and the measurement of electron momentum distributions in solids
- Author
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A. Talmantaite, Michael R. C. Hunt, and Budhika G. Mendis
- Subjects
Physics ,Histology ,density distribution ,Electron energy loss spectroscopy ,electron momentum ,Compton scattering ,electron energy‐loss spectroscopy ,Electron ,Impulse (physics) ,Pathology and Forensic Medicine ,Computational physics ,Themed Issue Paper ,impulse approximation ,Density of states ,Valence electron ,Ground state ,Themed Issue Papers ,Plasmon - Abstract
Summary Electron Compton scattering is a technique that gives information on the electron momentum density of states and is used to characterize the ground state electronic structure in solids. Extracting the momentum density of states requires us to assume the so‐called ‘impulse approximation’, which is valid for large energy losses. Here, the robustness of the impulse approximation in the low energy transfer regime is tested and confirmed on amorphous carbon films. Compared to traditional Compton measurements, this provides additional benefits of more efficient data collection and a simplified way to probe valence electrons, which govern solid state bonding. However, a potential complication is the increased background from the plasmon signal. To overcome this, a novel plasmon background subtraction routine is proposed for samples that are resistant to beam damage. Lay Description Properties of solids depend on their electronic structure which can be studied using electron Compton scattering technique. Here, an electron beam is used to penetrate a very thin sample. During the interaction between the electrons in the beam and electrons in the sample, the former transfer a part of their energy to the latter, resulting in a measurable energy loss of the transmitted beam. The amount of the energy transfer depends on the angle of incidence between the beam and the sample. Typically, the experiments are carried out using high tilt angles and high energy transfer; however, in this work, we show that even smaller angles of incidence are suitable, which improve the signal quality and ease data processing procedures.
- Published
- 2019
31. Revealing the interference effect of Majorana fermions in a topological Josephson junction
- Author
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Tiantian Yu, Juntao Song, and Jie Liu
- Subjects
Josephson effect ,fractional Josephson effect ,General Physics and Astronomy ,02 engineering and technology ,Topology ,lcsh:Chemical technology ,01 natural sciences ,lcsh:Technology ,Full Research Paper ,Andreev reflection ,Condensed Matter::Superconductivity ,0103 physical sciences ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,010306 general physics ,lcsh:Science ,Quantum tunnelling ,Physics ,Majorana fermion ,Local density of states ,lcsh:T ,Fermion ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,Nanoscience ,MAJORANA ,density of states ,Density of states ,lcsh:Q ,0210 nano-technology ,lcsh:Physics - Abstract
We study theoretically the local density of states (DOS) in a topological Josephson junction. We show that the well-known 4π Josephson effect originates from the interference effect between two Majorana fermions (MFs) that are localized at the Josephson junction. In addition, the DOS for electrons (holes) shows the 4π interference information along each parity conserved energy spectrum. The DOS displays a 2π period oscillation when two trivial states interfere with each other. This means that the DOS information may be used to distinguish the MFs from trivial localized states. We suggest that the interference effect and the DOS can be detected by using two STM leads or two normal leads. A single side lead can only detect the Andreev reflection tunneling process in the junction, which cannot reveal information about the interference effect in general. However, using two side leads, we can reveal information about the interference effect of the MFs as well as the DOS by combining Andreev reflection with the electron transmission process.
- Published
- 2018
32. The Structural, Electronic and Optical Properties of the AlAs/InP/CdS Heterotrilayer: A First-Principles Study.
- Author
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Lichuan, Deng, Zhou, Xiaolong, Jie, Yu, and Wang, Lihui
- Subjects
HETEROJUNCTIONS ,ORBITAL hybridization ,OPTICAL properties ,VAN der Waals forces ,BAND gaps ,DENSITY of states - Abstract
The structural stability, electrical properties (energy band structure, density of states) and optical properties of AlAs/InP/CdS multilayer heterojunctions have been systematically investigated using first-principles calculations based on density functional theory. The A-type structure in this paper is the most stable, with a direct band gap of 0.477 eV. The heterojunction is strongly bonded due to the aggregation of electrons among all three layers of atoms, the formation of van der Waals forces between the atoms and the formation of orbital hybridization among some of the atoms. The optoelectronic properties of multilayer heterojunctions are superior to those of single layers. AlAs/InP/CdS multilayer heterojunctions have high absorption peaks in the UV and visible regions and also have good absorption capability in the infrared. The AlAs/InP/CdS multilayer heterojunction has a stable structure and excellent optoelectronic properties, and has great potential and broad application prospects in the fields of visible light absorption, photocatalysis, infrared light and ultraviolet light detection. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
33. Manipulated Optical Absorption and Accompanied Photocurrent Using Magnetic Field in Charger Transfer Engineered C/ZnO Nanowires
- Author
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Yen-Fa Liao, Tzu‐Chun Hsu, Kuo‐Yi Hung, Ting‐Yi Huang, Hua-Shu Hsu, Wei-Jhong Chen, Zdenek Remes, Jun Xiao Lin, Jiann-Shing Lee, and Guan‐Xun Chen
- Subjects
magneto‐optical absorption ,Photocurrent ,Technology ,Range (particle radiation) ,Materials science ,Full Paper ,business.industry ,charge transfer ,Zno nanowires ,Full Papers ,Magnetic field ,Environmental sciences ,Condensed Matter::Materials Science ,Amorphous carbon ,magneto‐photocurrent ,Low magnetic field ,Density of states ,Optoelectronics ,GE1-350 ,spin‐polarized band engineering ,business ,Absorption (electromagnetic radiation) - Abstract
The rarely explored, spin‐polarized band engineering, enables direct dynamic control of the magneto‐optical absorption (MOA) and associated magneto‐photocurrent (MPC) by a magnetic field, greatly enhancing the range of applicability of photosensitive semiconductor materials. It is demonstrated that large negative and positive MOA and MPC effects can be tuned alternately in amorphous carbon (a‐C)/ZnO nanowires by controlling the sp2/sp3 ratio of a‐C. A sizeable enhancement of the MPC ratio (≈15%) appears at a relatively low magnetic field (≈0.2 T). Simulated two peaks spin‐polarized density of states is applied to explain that the alternate sign switching of the MOA is mainly related to the charge transfer between ZnO and C. The results indicate that the enhanced magnetic field performance of (a‐C)/ZnO nanowires may have applications in renewable energy‐related fields and tunable magneto‐photonics., The alternate magnetic‐field‐manipulated optical absorption (MOA) and associated photocurrent can be engineered by spin‐polarized band at room temperature. Simulated two peaks spin‐polarized density of states is applied to explain that the alternate sign switching of the MOA is mainly related to the charge transfer between ZnO and C.
- Published
- 2020
34. Effect of Defects and Oxidation on CNT–Copper Interface: First-Principles Calculation and Experiment.
- Author
-
Ju, Boyu, Zhu, Yubo, Yang, Wenshu, Sun, Jinpeng, Li, Haozhe, Yuan, Feng, and Xiu, Ziyang
- Subjects
CARBON nanotubes ,COPPER surfaces ,COPPER ,ELECTRIC conductivity ,SURFACE defects ,DENSITY of states ,DOUBLE walled carbon nanotubes - Abstract
In this paper, the effects of carbon nanotube defects and a copper surface oxide layer on a carbon nanotube–copper interface were studied via first-principles. A defect-free CNT-Cu interface, Stone–Wales defect CNT-Cu interface, single-hole and double-hole defect CNT-Cu interface, and Cu
2 O-Cu interface were simulated and calculated. By simulating the differential charge density, atomic population, bond population and density of states of the interface model, the effects of various defects on the interface bonding and electrical conductivity of the composites during the preparation of the CNT-reinforced copper matrix composites were analyzed, which provided theoretical guidance for the preparation of CNT/Cu composites. After that, copper matrix composites with different CNT defect contents were prepared via different rolling deformation processes. Their hardness and electrical conductivity were tested, and the results were consistent with the results obtained via the first-principles calculations. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
35. Regularity of the integrated density of states in the continuous spectrum
- Author
-
Krishna, M.
- Published
- 2024
- Full Text
- View/download PDF
36. Auxiliary two-filter particle smoothing for one generalized hidden Markov model.
- Author
-
Chen, Yunqi, Yan, Zhibin, and Zhang, Xing
- Subjects
HIDDEN Markov models ,COMPUTATIONAL complexity ,DENSITY of states ,SAMPLING (Process) ,MONTE Carlo method - Abstract
This paper develops two-filter particle smoothing (TFPS) algorithms for the nonlinear fixed-interval smoothing problem of one generalized hidden Markov model (GHMM), where the current observation depends not only on the current state, but also on one-step previous state. Firstly, by Bayesian approach, the two-filter smoothing (TFS) formula for GHMM is established to calculate smoothing densities. In this TFS formula, the backward information prediction density is generally not a density of the state. This results in a difficulty that the normal sequential Monte Carlo (SMC) sampling technique cannot be directly applied to design corresponding TFPS algorithms based on the TFS formula. To solve this difficulty, a generalized TFS formula for GHMM is then proposed by introducing a sequence of artificial densities. By combining this generalized TFS formula, SMC, and the auxiliary variable sampling technique, a basic auxiliary TFPS (ATFPS) algorithm with quadratic computational complexity is proposed, and a simplified ATFPS algorithm with linear computational complexity is further developed. Finally, the effectiveness and superiority of the two proposed ATFPS algorithms for GHMM are verified via simulation examples and real experimental data. • It studies a generalized HMM where observation depends on two-step states. • Two-filter smoothing formula and its generalization are established. • Auxiliary variable sampling technique is applied to draw samples. • It proposes two particle smoothing algorithms by using sequential Monte Carlo. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
37. Influence of interface structures on the properties of molybdenum disulfide/graphene composites: A density functional theory study
- Author
-
Huanxiang Liu, Wenyan Zan, Xiaojun Yao, and Wei Geng
- Subjects
Materials science ,Graphene ,Mechanical Engineering ,Doping ,Binding energy ,Metals and Alloys ,law.invention ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,law ,Materials Chemistry ,Density of states ,Density functional theory ,Composite material ,Molybdenum disulfide ,Graphene nanoribbons ,Graphene oxide paper - Abstract
Density functional theory calculations were performed to study the photocatalytic properties of molybdenum disulfide/graphene composites by analyzing the structure, electronic properties and optical properties of molybdenum disulfide/graphene composites. Three typical structures of molybdenum disulfide considered in our work include pristine molybdenum disulfide and molybdenum disulfide with mononiobium doping. They were then composited with graphene, N-doped graphene and graphene with epoxy, respectively. The characteristics of these composites (MoS 2 /graphene, MoS 2 /N-G, MoS 2 /O-G and Nb–MoS 2 /N-G) including binding energies, charge transfer, projected density of states, electron density and optical properties were calculated and analyzed. The binding energies of between MoS 2 and graphene were related to the extent of charge transfer. The data of projected density of states, band structures and optical properties gave an explanation of the mechanism for significant photocatalytic activity of MoS 2 /N-doped graphene and Nb-doped MoS 2 /N-doped graphene composites.
- Published
- 2015
38. High-temperature superconductivity as viewed from the maximum hardness principle
- Author
-
Wojciech Grochala and Mariana Derzsi
- Subjects
Materials science ,High-temperature superconductivity ,Band gap ,Electron ,010402 general chemistry ,01 natural sciences ,Catalysis ,law.invention ,Inorganic Chemistry ,Critical superconducting temperature ,law ,Polarizability ,Hardness ,Metastability ,Condensed Matter::Superconductivity ,0103 physical sciences ,Physical and Theoretical Chemistry ,010306 general physics ,Superconductivity ,Original Paper ,Condensed matter physics ,Metal ,Organic Chemistry ,Density of states ,0104 chemical sciences ,Computer Science Applications ,Computational Theory and Mathematics ,Density functional theory ,Superconductor - Abstract
The Maximum Hardness Principle – and its reformulation by Chattaraj as the Minimum Polarizability Principle – is an immensely useful concept which works in support of a chemical intuition. As we show here, it may also be used to rationalize the scarcity of high-temperature superconductors, which stems – inter alia – from rarity of high-density of state metals in Nature. It is suggested that the high-temperature oxocuprate superconductors as well as their iron analogues – are energetically metastable at T ➔ 0 K and p ➔ 0 atm conditions, and their tendency for disproportionation is hindered only by the substantial rigidity of the crystal lattice, while the phase separation and/or superstructure formation is frequently observed in these systems. This hypothesis is corroborated by hybrid density functional theory theoretical calculations for Na- (thus: hole) or La- (thus: electron) doped CaCu(II)O2 precursor. Non-equilibrium synthetic methods are suggested to be necessary for fabrication of high-temperature superconductors of any sort. Graphical abstractDoped oxocuprate superconductors are shown to be unstable with respect to phase separation (disproportionation) in accordance with the Maximum Hardness Principle; their metastability is mostly due to rigidity of [CuO2] sheets and preparation using high-temperature conditions
- Published
- 2018
39. Generation of thermal scattering laws with the CINEL code.
- Author
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Noguere, G., Xu, S., Desgrange, L., Boucher, J., Bourasseau, E., Carlot, G., Filhol, A., Ollivier, J., Hansen, T., Nassif, V., Ouente Orench, I., Colin, C., Laversenne, L., Zanotti, J.-M., and Berrod, Q.
- Subjects
SCATTERING (Physics) ,CRYSTAL structure ,RADIOISOTOPES ,DENSITY of states ,PHONONS - Abstract
The thermal scattering laws (TSL) take into account the crystalline structure and atomic motions of isotopes bound in materials. This paper presents the CINEL code, which was developed to generate temperature-dependent TSL for solid, liquid and free gas materials of interest for nuclear reactors. CINEL is able to calculate TSL from the phonon density of states (PDOS) of materials under the Gaussian-Incoherent approximations. The PDOS can be obtained by using theoretical approaches (e.g., ab initio density functional theory and molecular dynamics) or experimental results. In this work, the PDOS presented in the ENDF/BVIII.0 and NJOY-NCrystal libraries were used for numerical validation purposes. The CINEL results are in good agreement with those reported in these databases, even in the specific cases of TSL with the newly mixed elastic format. The coding flexibility offered by Python using the JupyterLab interface allowed to investigate limits of physical models reported in the literature, such as a four-site model for UO2, anharmonic behaviors of oxygen atoms bound in a Fm3m structure, texture in Zry4 samples and jump corrections in a roto-translational diffusion model for liquid water. The use of graphic processing units (GPU) is a necessity to perform calculations in a few minutes. The performances of the CINEL code is illustrated with the results obtained on actinide oxides having a Fm3m structure (UO
2 , ThO2 , NpO2 and PuO2 ), low enriched fuel (UMo), cladding (Zry4) and moderators (H2 O with a specific emphasis on ice). [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
40. Mechanisms of Na adsorption on graphene and graphene oxide: density functional theory approach
- Author
-
Hye Sook Moon, Seung Geol Lee, Il Tae Kim, Ji Hye Lee, and Soonchul Kwon
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Graphene ,Process Chemistry and Technology ,Organic Chemistry ,Inorganic chemistry ,Graphene foam ,Energy Engineering and Power Technology ,Sodium-ion battery ,law.invention ,Inorganic Chemistry ,Adsorption ,law ,Materials Chemistry ,Ceramics and Composites ,Density of states ,Bilayer graphene ,Graphene nanoribbons ,Graphene oxide paper - Abstract
We investigated the adsorption of Na on graphene and graphene oxide, which are used as anode materials in sodium ion batteries, using density functional theory. The adsorption energy for Na on graphene was -0.507 eV at the hollow sites, implying that adsorption was favorable. In the case of graphene oxide, Na atoms were separately adsorbed on the epoxide and hydroxyl functional groups. The adsorption of Na on graphene oxide-epoxide (adsorption energy of -1.024 eV) was found to be stronger than the adsorption of Na on pristine graphene. However, the adsorption of Na on graphene oxide-hydroxyl resulted in the generation of NaOH as a by-product. Using density of states (DOS) calculations, we found that the DOS of the Na-adsorbed graphene was shifted down more than that of the Na-adsorbed graphene oxide-epoxide. In addition, the intensity of the DOS around the Fermi level for the Na-adsorbed graphene was higher than that for the Na-adsorbed graphene oxide-epoxide.
- Published
- 2015
41. Analysis of Option Butterfly Portfolio Models Based on Nonparametric Estimation Deep Learning Method.
- Author
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Ge, Xiangyu, Zhu, Xia, Bi, Gang, Zheng, Hao, and Li, Qing
- Subjects
DEEP learning ,BUTTERFLIES ,NONPARAMETRIC estimation ,INVESTORS ,PRICES ,DENSITY of states - Abstract
The option butterfly portfolio is the commonly option arbitrage strategy. In reality, because the distribution of the option state price density (SPD) function is not normal and unknown, so the nonparametric deep learning methods to estimate option butterfly portfolio returns are proposed. This paper constructs the single-index nonparametric option pricing model which contains multiple influencing factors and presents the nonparametric estimation form for option butterfly portfolio returns. The empirical analysis shows that the SPD function estimated by using single-index nonparametric option model can effectively calculate the option butterfly portfolio returns with the minimum option strike price interval and provide an effective reference tool for risk-averse investors with limited risk preferences. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
42. Analyzing Acceptor-like State Distribution of Solution-Processed Indium-Zinc-Oxide Semiconductor Depending on the In Concentration.
- Author
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Kim, Dongwook, Lee, Hyeonju, Yun, Youngjun, Park, Jaehoon, Zhang, Xue, Bae, Jin-Hyuk, and Baang, Sungkeun
- Subjects
SEMICONDUCTORS ,DENSITY of states ,MOLARITY ,THERMAL analysis ,ACTIVATION energy ,SURFACE potential - Abstract
Understanding the density of state (DOS) distribution in solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs) is crucial for addressing electrical instability. This paper presents quantitative calculations of the acceptor-like state distribution of solution-processed IZO TFTs using thermal energy analysis. To extract the acceptor-like state distribution, the electrical characteristics of IZO TFTs with various In molarity ratios were analyzed with respect to temperature. An Arrhenius plot was used to determine electrical parameters such as the activation energy, flat band energy, and flat band voltage. Two calculation methods, the simplified charge approximation and the Meyer–Neldel (MN) rule-based carrier–surface potential field-effect analysis, were proposed to estimate the acceptor-like state distribution. The simplified charge approximation established the modeling of acceptor-like states using the charge–voltage relationship. The MN rule-based field-effect analysis validated the DOS distribution through the carrier–surface potential relationship. In addition, this study introduces practical and effective approaches for determining the DOS distribution of solution-processed IZO semiconductors based on the In molarity ratio. The profiles of the acceptor-like state distribution provide insights into the electrical behavior depending on the doping concentration of the solution-processed IZO semiconductors. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
43. Critical JT gravity.
- Author
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Castro, Alicia
- Subjects
GRAVITY ,PHASE transitions ,GENERATING functions ,DENSITY of states ,SURFACE defects ,BRANES ,QUANTUM gravity - Abstract
In this paper, we investigate a critical behavior of JT gravity, a model of two-dimensional quantum gravity on constant negatively curved spacetimes. Our approach involves using techniques from random maps to investigate the generating function of Weil-Petersson volumes, which count random hyperbolic surfaces with defects. The defects are weighted geodesic boundaries, and criticality is reached by tuning the weights to the regime where macroscopic holes emerge in the hyperbolic surface, namely non-generic criticality. We analyze the impact of this critical regime on some universal features, such as its density of states. We present a family of models that interpolates between systems with ρ
0 (E) ~ E − E 0 and ρ0 (E) ~ (E − E0 )3/2 , which are commonly found in models of JT gravity coupled to dynamical end-of-the-world and FZZT branes, and give a precise definition of what this phase transition means from the random geometry point of view. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
44. A Novel Density of States (DOS) for Disordered Organic Semiconductors.
- Author
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Qin, Dong, Chen, Jiezhi, and Lu, Nianduan
- Subjects
ORGANIC semiconductors ,TRANSPORT theory ,FRONTIER orbitals ,PROBABILITY theory ,ORGANIC bases ,DENSITY of states - Abstract
In this work, we proposed a novel theory of DOS for disordered organic semiconductors based on the frontier orbital theory and probability statistics. The proposed DOS has been verified by comparing with other DOS alternatives and experimental data, and the mobility calculated by the proposed DOS is closer to experimental data than traditional DOS. Moreover, we also provide a detailed method to choose the DOS parameter for better use of the proposed DOS. This paper also contains a prediction for the DOS parameters, and it has been verified by the experimental data. More importantly, the physical meaning of the proposed DOS parameter has been explained by equilibrium energy theory and transport energy theory to make this proposed model more rational. Compared with the improved DOS based on Gaussian and exponential DOS, this work is a new attempt to combine probabilistic theory with physical theory related to DOS in disordered organic semiconductors, showing great significance for the further investigation of the properties of DOS. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
45. Increasing the conductivity of V2O5-TeO2 glass by crystallization: structure and charge transfer studies.
- Author
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Okoczuk, Piotr, Wójcik, Natalia Anna, Murawski, Leon, Wicikowski, Leszek, Łapiński, Marcin Stanisław, Winiarz, Piotr, and Kościelska, Barbara
- Subjects
GLASS structure ,GLASS-ceramics ,ELECTRIC conductivity ,ACTIVATION energy ,FERMI level ,DENSITY of states - Abstract
In the present paper, V
2 O5 -TeO2 glass was prepared by the melt-quenching technique. Crystallization of glass with a vanadium content higher than 35%mol results in an increase in electrical conductivity by a few orders of magnitude and a decrease in activation energy from ~0.40 to ~0.12 eV. In this work, a critical review of existing charge transfer models was presented on the example of V2 O5 -TeO2 glass and glass–ceramics. Schnakenberg's and Friedman-Triberis' charge transfer models were found to be applicable to both glass and glass–ceramics. Optical phonon frequencies obtained from Schnakenberg's model are in agreement with FTIR studies. Values of activation energies obtained from the Schnakenberg model decrease after crystallization. Friedman-Triberis' model shows an increase in the density of states near the Fermi level from 1019 eV−1 cm−3 in glass, to 1021 eV−1 cm−3 in glass ceramics. Structural studies show that the main crystallizing phase is Te2 V2 O9 which occurs with the V2 O5 shell in glasses with compositions 50–50%mol and 45–55%mol. It is concluded that crystallization results in the reduction of vanadium ions in the remaining glass matrix which leads to an increase in the V4+ /V5+ ratio and therefore, an increase in electrical conductivity. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
46. Features of Light-Matter Coupling in Non-Ideal Lattice of Coupled Microcavities Containing Quantum Dots.
- Author
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Rumyantsev, Vladimir V., Fedorov, Stanislav A., Gumennyk, Konstantin V., and Rybalka, Alexey Ye.
- Subjects
PHOTONIC crystals ,DENSITY of states ,EXCITATION spectrum ,QUANTUM dots - Abstract
In this paper, within the framework of virtual crystal approximation, the mathematical modeling of the dependence of the density of states of polariton excitations in a 1D photonic crystal—a system of pores (tunnel-coupled microresonators) containing quantum dots—on the concentration of structural defects is performed. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
47. Identification of Nonlinear State-Space Systems With Skewed Measurement Noises.
- Author
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Liu, Xinpeng and Yang, Xianqiang
- Subjects
NOISE measurement ,NONLINEAR systems ,MONTE Carlo method ,NONLINEAR equations ,DENSITY of states - Abstract
In this paper, we consider the identification problem for nonlinear state-space models with skewed measurement noises. The generalized hyperbolic skew Student’s t (GHSkewt) distribution is employed to describe the skewed noises and formulate the hierarchical model of the considered system. A unified framework for estimating unknown states and model parameters is presented based on expectation-maximization (EM) algorithm, in which the forward filtering backward simulation with rejection sampling (RS-FFBSi) is employed to efficiently estimate the smoothing densities of the hidden states, and optimization method is adopted to update model parameters. One numerical study and the electro-mechanical positioning system (EMPS) are employed to verify the effectiveness of the developed approach. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
48. Solid-like heat transfer in confined liquids
- Author
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Michael Frank and Dimitris Drikakis
- Subjects
Phonon ,Mean free path ,02 engineering and technology ,01 natural sciences ,Physics::Fluid Dynamics ,Molecular dynamics ,Thermal conductivity ,Normal mode ,0103 physical sciences ,Heat transfer ,Materials Chemistry ,Confined liquid ,010306 general physics ,Condensed matter physics ,Chemistry ,Relaxation (NMR) ,Relaxation time ,Density of states ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Phonons ,TJ ,0210 nano-technology ,Research Paper - Abstract
The aim of this research is to identify possible mechanisms that govern heat transport at a solid–liquid interface using molecular dynamics. The study reveals that, unlike its bulk analogue, a liquid in a nanochannel sustains long-lived collective vibrations, phonons, which propagate over longer timescales and distances. The larger phonon mean free path in nanochannels is attributed to the greater structural order of the liquid atoms and to the larger liquid relaxation time—the time in which the liquid structure remains unchanged and solid-like. For channels of height less than \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10\sigma$$\end{document}10σ, long-range phonons are the dominant means of heat transfer in the directions parallel to the channel walls. The present findings are in agreement with experiments, which have observed significantly increased liquid relaxation times for the same range of channel heights. Finally, it is argued that confinement introduces additional transverse modes of vibration that also contribute to the thermal conductivity enhancement.
- Published
- 2017
49. Sensitivity Properties of Graphene with Metal Nanoparticles.
- Author
-
Konobeeva, N. N., Kulbina, A. S., Zaporotskova, I. V., and Belonenko, M. B.
- Subjects
METAL nanoparticles ,GRAPHENE ,COPPER surfaces ,CURRENT-voltage characteristics ,DENSITY of states ,RESONANT tunneling ,QUANTUM dots - Abstract
In this paper, we investigate the influence of metal nanoparticles on the sensitivity properties of graphene with respect to gas molecules adsorbed on its surface on the example of copper nanoparticles. The influence of the metal atom is taken into account by changing the hopping integral for the regions adjacent to it. Such features are due to the presence of a metal nanoparticle on the surface of a graphene nanoribbon which changes the hybridization of pi electrons in the immediate vicinity of the adsorption site of a metal atom. First of all we use the transition from a two-dimensional array corresponding to the sites of the graphene plane to a one-dimensional array for the determination of the density of states of the system under consideration. Secondly, we are based on the numerical diagonalization of the Hamiltonian for rectangular graphene nanoribbon in the tight-binding approximation. It allows us to estimate the response of the system based on the current-voltage characteristic for the tunneling contact of the graphene nanoribbon with different materials. In this paper we choose metal and quantum dots. The best results have been demonstrated in terms of sensitivity to adsorbed gas molecules for contacts with these materials. In this case, the tunnel current density is calculated from the density of states of the system. Decorating the graphene plane with copper nanoparticles significantly changes the resistance in the tunneling contact of the nanoribbon with the quantum dots or with the metal. Also we observe an increase in the sensitivity of graphene nanoribbons to impurities with an increase in the concentration of metal nanoparticles. Thus, we propose an approach based on the study of tunneling current, which has several advantages, since it allows optimizing the choice of the second sample to achieve the highest sensitivity. Equally important is the fact that various types of contacts may be more optimal for determining various types of impurities. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
50. Theoretical Insights into Band Gap Tuning Through Cu Doping and Ga Vacancy in GaSe Monolayer: A First-Principles Perspective.
- Author
-
Behjatmanesh-Ardakani, Reza
- Subjects
COPPER ,BAND gaps ,DENSITY functional theory ,MONOMOLECULAR films ,GALLIUM selenide ,DENSITY of states - Abstract
Gallium selenide (GaSe) has become increasingly popular in the field of optoelectronics due to its suitable band gap. The layered structure of bulk crystal GaSe makes it easy to create a monolayer of GaSe. However, this also results in an increase in the band gap. In this paper, we used the full-potential periodic density functional theory (DFT) method to examine the electronic structure of both pure and Cu-doped GaSe. We modeled Ga
1-x Cux Se with x = 0.02, 0.03, 0.056, and 0.125 with and without Ga vacancy. We compared the structure, electronic properties, and magnetic properties of the pure bulk and monolayer with those of the Cu-doped samples. The density of state graphs clearly demonstrate that Ga-defected and Cu-doped GaSe have p-type characteristics. The presence of a Ga vacancy causes the GaSe monolayer to become half-metallic, which has potential applications in spintronics. When the Cu concentration reaches approximately 3%, there is a 20% reduction in the band gap. Both the Ga vacancy and Cu doping create deep defect levels that lead to carrier recombination. The position of these levels is highly dependent on the concentration of Cu. Increasing the Cu concentration from% 1 to 2.78% results in a decrease in recombination. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
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