scholarly journals Цепочечная модель декорирования зигзагообразной кромки графена

2019 ◽  
Vol 53 (1) ◽  
pp. 83
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Energy Band ◽  
Structural Model ◽  
Metal Substrate ◽  
Band Spectrum ◽  
Brick Wall ◽  
Zigzag Edge ◽  
Occupation Numbers ◽  
Graphene Lattice ◽  
Densities Of States ◽  
Analytical Expressions

AbstractFor a brick-wall-like lattice topologically equivalent to the graphene lattice, a simple structural model of a zigzag edge decorated with particles is constructed. Analytical expressions for the energy band spectrum, densities of states, and occupation numbers of the graphene–particles system are derived for a system in the free state and for a system formed on a metal substrate.

scholarly journals Точно решаемая модель графеновой наноленты с зигзагообразными краями

2020 ◽  
Vol 54 (2) ◽  
pp. 170
Author(s):  
С.Ю. Давыдов ◽  
А.В. Зубов
Keyword(s):  
Structural Model ◽  
Graphene Nanoribbon ◽  
Zigzag Edge ◽  
Occupation Numbers ◽  
Densities Of States ◽  
Local Densities ◽  
Analytical Expressions

Abstract Exact analytical expressions for the local densities of states and the occupation numbers of atoms at the zigzag edge of a graphene nanoribbon are derived in the context of a simple structural model. As an example of application of the results, the problem of a Koster–Slater defect is considered.

scholarly journals О магнитных состояниях зигзагообразной кромки графеновой наноленты

2020 ◽  
Vol 62 (1) ◽  
pp. 180
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Electronic Structure ◽  
Density Of States ◽  
Structural Model ◽  
Magnetic Moments ◽  
Nearest Neighbors ◽  
Metal Substrate ◽  
Band Spectrum ◽  
Zigzag Edge ◽  
Anderson Hamiltonian ◽  
Occupation Numbers

Abstract Using a simple structural model and the multicenter Anderson Hamiltonian, Green’s functions are obtained for the atoms of the zigzag edge of an epitaxial graphene nanoribbon. The electronic structure of the free nanoribbon is discussed in detail. Specifically, expressions for the band spectrum and density of states are found and estimates of the occupation numbers and magnetic moments are given. For a nanoribbon strongly bonded to a metal substrate, the criteria for the appearance of magnetic moments are determined. As it is shown for both free and epitaxial nanoribbons, the probability of the appearance of magnetic moments and their magnitude for zigzag edge atoms that have two nearest neighbors is higher than for atoms with three nearest neighbors.

scholarly journals О декорировании зигзагообразной кромки эпитаксиального графена

2019 ◽  
Vol 61 (1) ◽  
pp. 186
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Electronic Structure ◽  
Graphene Sheet ◽  
Cluster Model ◽  
Dipole Interaction ◽  
Metal Substrate ◽  
Zigzag Edge ◽  
Occupation Numbers ◽  
Local Densities ◽  
Analytical Expressions

AbstractTwo approaches are proposed to the problem of the coupling of adsorbed particles with atoms of a zigzag edge of graphene formed on a metal substrate. The first approach is based on the Kalkstein and Soven scheme, which makes it possible to determine the electronic structure of a semi-infinite graphene sheet. The second approach is based on a cluster model of a zigzag edge. Analytical expressions are obtained for the local densities of the system’s states and the occupation numbers of a carbon adatom and an adparticle. The case of an isolated adparticle is considered in detail, and a method of taking into account the dipole–dipole interaction of particles aligned along the edge is proposed.

scholarly journals Цепочечная модель зигзагообразного контакта латеральных графеноподобных гетероструктур

2018 ◽  
Vol 44 (21) ◽  
pp. 55
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Boron Nitride ◽  
Density Of States ◽  
Structural Model ◽  
Hexagonal Boron Nitride ◽  
Two Dimensional ◽  
Occupation Numbers ◽  
Densities Of States ◽  
Spectrum Density ◽  
Analytical Expressions ◽  
Good Agreement

AbstractA simple structural model is proposed for the zigzag interface formed by contacting two-dimensional graphene-like compounds AB and CD (both free and formed on a metal). For the graphene–hexagonal boron nitride system, analytical expressions for the electron spectrum, density of states, and atom occupation numbers at the interface are obtained. The results of calculating the densities of states and occupation numbers within two alternative approximations are in good agreement.

scholarly journals Кластерная модель латеральной графеноподобной гетероструктуры: оценки перехода заряда

2018 ◽  
Vol 60 (9) ◽  
pp. 1815
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Charge Transfer ◽  
Boron Nitride ◽  
Cluster Model ◽  
Binary Compound ◽  
Metal Substrate ◽  
Two Dimensional ◽  
Occupation Numbers ◽  
Densities Of States ◽  
Local Densities ◽  
Analytical Expressions

AbstractA simple cluster model is proposed to describe zigzag and armchair contacts of graphene to a hexagonal two-dimensional binary compound adsorbed on a metal substrate. A graphene–boron nitride heterostructure (HS) is studied in detail. Analytical expressions are obtained for the local densities of states and the occupation numbers of contact atoms. The charge transfer for quasi-free HSs is analyzed. The energy of binding of a HS to a metal substrate is estimated.

scholarly journals О декорировании зигзагообразных краев наноленты эпитаксиального графена

2019 ◽  
Vol 61 (3) ◽  
pp. 610
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Density Of States ◽  
Tight Binding ◽  
Free State ◽  
Band Spectrum ◽  
Adsorption Complex ◽  
Chain Model ◽  
Double Chain ◽  
Occupation Numbers ◽  
A Chain ◽  
Analytical Expressions

AbstractA double-chain model of an epitaxial graphene nanoribbon, the zigzag edges of which are decorated with foreign adparticles, has been proposed. The substrate is assumed to be a metal. Analytical expressions for the Green’s functions of carbon adatoms and adparticles are obtained. The band spectrum for the free state is determined, and the approximation of the density of states is proposed. Analytical expressions for the occupation numbers in the mode of tight binding between the adsorption complex and the substrate are presented. A chain of carbon adatoms decorated with adparticles (epicarbyne) is considered.

scholarly journals APPLICATIONS OF DENSITY MATRICES IN A TRAPPED BOSE GAS

2006 ◽  
Vol 20 (15) ◽  
pp. 2189-2221 ◽  
Author(s):  
K. CH. CHATZISAVVAS ◽  
S. E. MASSEN ◽  
CH. C. MOUSTAKIDIS ◽  
C. P. PANOS
Keyword(s):  
Quantum Information ◽  
Bose Gas ◽  
Einstein Condensation ◽  
Density Distributions ◽  
Occupation Numbers ◽  
The One ◽  
Bose Einstein ◽  
Jensen Shannon Divergence ◽  
Analytical Expressions ◽  
Short Range Correlations

An overview of the Bose–Einstein condensation of correlated atoms in a trap is presented by examining the effect of interparticle correlations to one- and two-body properties of the above systems at zero temperature in the framework of the lowest order cluster expansion. Analytical expressions for the one- and two-body properties of the Bose gas are derived using Jastrow-type correlation function. In addition numerical calculations of the natural orbitals and natural occupation numbers are also carried out. Special effort is devoted for the calculation of various quantum information properties including Shannon entropy, Onicescu informational energy, Kullback–Leibler relative entropy and the recently proposed Jensen–Shannon divergence entropy. The above quantities are calculated for the trapped Bose gases by comparing the correlated and uncorrelated cases as a function of the strength of the short-range correlations. The Gross–Piatevskii equation is solved, giving the density distributions in position and momentum space, which are employed to calculate quantum information properties of the Bose gas.

Electronic Structure of Epitaxial SiO2/Si(100) Interfaces

1989 ◽  
Vol 159 ◽  
Author(s):  
T. Motooka
Keyword(s):  
Tight Binding ◽  
Interface States ◽  
Photoelectron Spectra ◽  
Band Spectrum ◽  
Binding Model ◽  
Initial Oxidation ◽  
Recursion Method ◽  
Densities Of States ◽  
Local Densities ◽  
Gap States

ABSTRACTThe local densities of states (LDOS) of epitaxial SiO, layers on Si(100) surfaces have been calculated using the recursion method combined with the Harrison's universal tight-binding model. The interface states associated with strained epitaxial layers of β-cristobalite (√2×√2)R45° and tridymite (1010)<0001> || Si(100)<011> were examined. In the β-cristobalite layer, gap states due to the surface Si dangling bonds appeared while they were eliminated by H termination. In the tridymite layer, the interface states primarily composed of the surface Si back bonds appeared near the Si conduction band minimum. Comparing the calculated DOS with photoelectron spectra for initial oxidation processes of clean Si(100), it was found that the valence band spectrum from the initial oxide formed at ∼300°C resembled that of the β-cristobalite layer.

scholarly journals Porous Si Partially Filled with Water Molecules—Crystal Structure, Energy Bands and Optical Properties from First Principles

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 396
Author(s):  
Ya. Shchur ◽  
O. Pavlyuk ◽  
A.S. Andrushchak ◽  
S. Vitusevich ◽  
A.V. Kityk
Keyword(s):  
Optical Properties ◽  
Hydrogen Bonds ◽  
First Principles ◽  
Energy Band ◽  
Visible Range ◽  
Band Spectrum ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Porous Si ◽  
Oh Groups

The paper reports the results on first-principles investigation of energy band spectrum and optical properties of bulk and nanoporous silicon. We present the evolution of energy band-gap, refractive indices and extinction coefficients going from the bulk Si of cubic symmetry to porous Si with periodically ordered square-shaped pores of 7.34, 11.26 and 15.40 Å width. We consider two natural processes observed in practice, the hydroxylation of Si pores (introduction of OH groups into pores) and the penetration of water molecules into Si pores, as well as their impact on the electronic spectrum and optical properties of Si superstructures. The penetration of OH groups into the pores of the smallest 7.34 Å width causes a disintegration of hydroxyl groups and forms non-bonded protons which might be a reason for proton conductivity of porous Si. The porosity of silicon increases the extinction coefficient, k, in the visible range of the spectrum. The water structuring in pores of various diameters is analysed in detail. By using the bond valence sum approach we demonstrate that the types and geometry of most of hydrogen bonds created within the pores manifest a structural evolution from distorted hydrogen bonds inherent to small pores (∼7 Å) to typical hydrogen bonds observed by us in larger pores (∼15 Å) which are consistent with those observed in a wide database of inorganic crystals.

scholarly journals Simulation Study on the Effect of Doping Concentrations on the Photodetection Properties of Mg2Si/Si Heterojunction Photodetector

Photonics ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 509
Author(s):  
Hong Yu ◽  
Chenggui Gao ◽  
Jiang Zou ◽  
Wensheng Yang ◽  
Quan Xie
Keyword(s):  
Energy Band ◽  
Dark Current ◽  
High Performance ◽  
Structural Model ◽  
Low Cost ◽  
Simulation And Optimization ◽  
Photoelectric Properties ◽  
Silvaco Atlas ◽  
Shortwave Infrared ◽  
Ratio Response

To develop and design an environmentally friendly, low-cost shortwave infrared (SWIR) photodetector (PD) material and extend the optical response cutoff wavelengths of existing silicon photodetectors beyond 1100 nm, high-performance silicon-compatible Mg2Si/Si PDs are required. First, the structural model of the Mg2Si/Si heterojunction was established using the Silvaco Atlas module. Second, the effects of the doping concentrations of Mg2Si and Si on the photoelectric properties of the Mg2Si/Si heterojunction PD, including the energy band, breakdown voltage, dark current, forward conduction voltage, external quantum efficiency (EQE), responsivity, noise equivalent power (NEP), detectivity, on/off ratio, response time, and recovery time, were simulated. At different doping concentrations, the heterojunction energy band shifted, and a peak barrier appeared at the conduction band of the Mg2Si/Si heterojunction interface. When the doping concentrations of Si and Mg2Si layer were 1017, and 1016 cm−3, respectively, the Mg2Si/Si heterojunction PD could obtain optimal photoelectric properties. Under these conditions, the maximum EQE was 70.68% at 800 nm, the maximum responsivity was 0.51 A/W at 1000 nm, the minimum NEP was 7.07 × 10−11 WHz–1/2 at 1000 nm, the maximum detectivity was 1.4 × 1010 Jones at 1000 nm, and the maximum on/off ratio was 141.45 at 1000 nm. The simulation and optimization result also showed that the Mg2Si/Si heterojunction PD could be used for visible and SWIR photodetection in the wavelength range from 400 to 1500 nm. The results also provide technical support for the future preparation of eco-friendly heterojunction photodetectors.

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