Influence of temperature on the displacement threshold energy in graphene

Abstract The atomic structure of nanomaterials is often studied using transmission electron microscopy. In addition to image formation, the energetic electrons impinging on the sample may also cause damage. In a good conductor such as graphene, the damage is limited to the knock-on process caused by elastic electron-nucleus scattering. This process is determined by the kinetic energy an atom needs to be sputtered, i.e. its displacement threshold energy Ed. This is typically assumed to have a fixed value for all electron impacts on equivalent atoms within a crystal. Here we show using density functional tight-binding simulations that the displacement threshold energy is affected by thermal perturbations of atoms from their equilibrium positions. This effect can be accounted for in the estimation of the displacement cross section by replacing the constant threshold energy value with a distribution. Our refined model better describes previous precision measurements of graphene knock-on damage, and should be considered also for other low-dimensional materials.

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Atomic origin of spin-valve magnetoresistance at the SrRuO3 grain boundary

National Science Review ◽

10.1093/nsr/nwaa004 ◽

2020 ◽

Vol 7 (4) ◽

pp. 755-762 ◽

Cited By ~ 2

Author(s):

Xujing Li ◽

Li Yin ◽

Zhengxun Lai ◽

Mei Wu ◽

Yu Sheng ◽

...

Keyword(s):

Grain Boundary ◽

Density Functional ◽

Magnetic Moments ◽

Spin Valve ◽

Density Functional Theory Calculations ◽

Precise Knowledge ◽

Transmission Electron ◽

Defect Control ◽

Scanning Transmission ◽

Low Dimensional

Abstract Defects exist ubiquitously in crystal materials, and usually exhibit a very different nature from the bulk matrix. Hence, their presence can have significant impacts on the properties of devices. Although it is well accepted that the properties of defects are determined by their unique atomic environments, the precise knowledge of such relationships is far from clear for most oxides because of the complexity of defects and difficulties in characterization. Here, we fabricate a 36.8° SrRuO3 grain boundary of which the transport measurements show a spin-valve magnetoresistance. We identify its atomic arrangement, including oxygen, using scanning transmission electron microscopy and spectroscopy. Based on the as-obtained atomic structure, the density functional theory calculations suggest that the spin-valve magnetoresistance occurs because of dramatically reduced magnetic moments at the boundary. The ability to manipulate magnetic properties at the nanometer scale via defect control allows new strategies to design magnetic/electronic devices with low-dimensional magnetic order.

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Density-Functional Based MD Studies of Low-Energy Atom Collisions onto Diamond and Graphite

MRS Proceedings ◽

10.1557/proc-389-15 ◽

1995 ◽

Vol 389 ◽

Cited By ~ 2

Author(s):

S. Uhlmann ◽

U. Stephan ◽

Th. Frauenheim ◽

G. Seifert

Keyword(s):

Density Functional ◽

Noble Gas ◽

Tight Binding ◽

Initial Energy ◽

Graphite Substrate ◽

Structural Topology ◽

Near Surface ◽

Displacement Threshold ◽

Induced Defects ◽

The Impact

ABSTRACTThe near-surface implantation of hyperthermal neutral atoms with (15 - 75) eV onto diamond (111) and graphite substrates is studied by molecular-dynamics (MD) using a density-functional (DF) based non-orthogonal tight-binding (TB) scheme. Depending on the initial energy and the impact point the atoms penetrate beneath the surface forming regions of local disorder and stress. The energy partition during the collision is analyzed yielding results about penetration and displacement threshold. After a final relaxation of the structures the penetration depths of the colliding particles are determined. The structural topology and the electronic properties of the induced defects and surface modifications are discussed. The penetration thresholds for noble gas atoms, hydrogen and carbon and the atomic-size dependent bulge arising after the subplantation process into a graphite substrate have been determined.

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Point defects in turbostratic stacked bilayer graphene

Nanoscale ◽

10.1039/c7nr03879h ◽

2017 ◽

Vol 9 (36) ◽

pp. 13725-13730 ◽

Cited By ~ 3

Author(s):

Chuncheng Gong ◽

Sungwoo Lee ◽

Suklyun Hong ◽

Euijoon Yoon ◽

Gun-Do Lee ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Point Defects ◽

Density Functional ◽

Tight Binding ◽

Bilayer Graphene ◽

Dynamics Simulation ◽

Functional Theory ◽

Transmission Electron ◽

Aberration Corrected

The point defects in turbostratic bilayer graphene are characterized using aberration-corrected transmission electron microscopy, density functional theory, and tight-binding molecular dynamics simulation.

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Structural, Electronic and Mechanical Properties of Few-layer Porous Nanosheet from Spheroidal Cage-like ZnO Polymorph

VNU Journal of Science Mathematics - Physics ◽

10.25073/2588-1124/vnumap.4517 ◽

2020 ◽

Vol 36 (4) ◽

Author(s):

Le Thi Hong Lien ◽

Nguyen Thi Thao ◽

Vu Ngoc Tuoc

Keyword(s):

Mechanical Properties ◽

Density Functional ◽

Mechanical Stability ◽

Electronic Band Structure ◽

Tight Binding ◽

Sheet Thickness ◽

High Symmetry ◽

Electronic Band ◽

Interesting Candidate ◽

Low Dimensional

The low-dimensional II-VI group semiconductors have recently emerged as interesting candidate materials for the tailoring of two dimensional (2D) layered structures. Herein, a series of the cage-like nanoporous composed of spheroidal hollow cages (ZnO)12, cutting from the high symmetrical cubic SOD cage-like polymorph as building block, is proposed. We have performed the density-functional tight binding (DFTB+) calculations on the structural, electronic and mechanical properties of this few-layer SOD-cage-block nanosheet series, to investigate the effects of structural modification and sheet thickness on their structural, electronic, and mechanical properties. Optimized geometries, formation energy, phonon spectra, electronic band structure, and elastic tensor calculation has ensured the energetically, dynamical and mechanical stability for the sheets. Furthermore, the theoretically found nanosheet series possess an intrinsic wide direct band gap preserving from wurtzite tetragonal-based bonding. This high symmetry wide bandgap semiconductor nanosheet series and their derivatives are expected to have broad applications in photocatalysis, and biomedicine.

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Parametrization of Density Functional Tight-Binding Method for Thermal Transport in Bulk and Low-Dimensional Si Systems

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.7b04182 ◽

2017 ◽

Vol 121 (28) ◽

pp. 15472-15480 ◽

Cited By ~ 3

Author(s):

Qi Wang ◽

Xinjiang Wang ◽

Ruiqiang Guo ◽

Baoling Huang

Keyword(s):

Thermal Transport ◽

Density Functional ◽

Tight Binding ◽

Tight Binding Method ◽

Low Dimensional

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Amorphization of Graphite Under ion or Electron Irradiation

MRS Proceedings ◽

10.1557/proc-373-383 ◽

1994 ◽

Vol 373 ◽

Cited By ~ 9

Author(s):

Hiroaki Abe ◽

Hiroshi Naramoto ◽

Chiken Kinoshita

Keyword(s):

Electron Microscope ◽

Energy Density ◽

Experimental Error ◽

Room Temperature ◽

Pyrolytic Graphite ◽

Threshold Energy ◽

Accelerator Facility ◽

Lattice Disorder ◽

Displacement Threshold ◽

Transmission Electron

AbstractA transmission electron microscope interfaced with ion accelerators (TEM-Accelerator Facility) in JAERI-Takasaki has been used to get insights into the irradiation-induced amorphization of highlyoriented pyrolytic graphite. Amorphization is induced through lattice disorder under irradiation with electrons or ions at room temperature. The displacement threshold energy is determined as 27 eV and 28 eV from the electron-energy dependence of the amorphization fluence at room temperature and 373 K, respectively. The amorphization fluences in dpa are almost identical for irradiation with various kinds of ions within the experimental error. It indicates the thermal spikes do not have an important role for the amorphization over the energy density between 10-4 to 10-2 eV/atom.

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Isotope analysis in the transmission electron microscope

Nature Communications ◽

10.1038/ncomms13040 ◽

2016 ◽

Vol 7 (1) ◽

Cited By ~ 36

Author(s):

Toma Susi ◽

Christoph Hofer ◽

Giacomo Argentero ◽

Gregor T. Leuthner ◽

Timothy J. Pennycook ◽

...

Keyword(s):

Electron Microscope ◽

Transmission Electron Microscope ◽

Density Functional ◽

Isotope Analysis ◽

Scanning Transmission Electron Microscope ◽

Transmission Electron ◽

Isotope Concentration ◽

Scanning Transmission ◽

Low Dimensional ◽

Low Dimensional Materials

Abstract The Ångström-sized probe of the scanning transmission electron microscope can visualize and collect spectra from single atoms. This can unambiguously resolve the chemical structure of materials, but not their isotopic composition. Here we differentiate between two isotopes of the same element by quantifying how likely the energetic imaging electrons are to eject atoms. First, we measure the displacement probability in graphene grown from either 12C or 13C and describe the process using a quantum mechanical model of lattice vibrations coupled with density functional theory simulations. We then test our spatial resolution in a mixed sample by ejecting individual atoms from nanoscale areas spanning an interface region that is far from atomically sharp, mapping the isotope concentration with a precision better than 20%. Although we use a scanning instrument, our method may be applicable to any atomic resolution transmission electron microscope and to other low-dimensional materials.

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First-Principles Study of Point-Defect Production in Si and SiC

MRS Proceedings ◽

10.1557/proc-490-41 ◽

1997 ◽

Vol 490 ◽

Cited By ~ 1

Author(s):

W. Windl ◽

T. J. Lenosky ◽

J. D. Kress ◽

A. F. Voter

Keyword(s):

Point Defect ◽

First Principles ◽

Tight Binding ◽

Threshold Energy ◽

Finite Size ◽

Finite Size Effect ◽

Defect Production ◽

Empirical Potentials ◽

Displacement Threshold ◽

Experimental Values

ABSTRACTWe have calculated the displacement-threshold energy Ed for point-defect production in Si and SiC using empirical potentials, tight-binding, and first-principles methods. We show that—depending on the knock-on direction—64-atom simulation cells can be sufficient to allow a nearly finite-size-effect-free calculation, thus making the use of first-principles methods possible. We use molecular dynamics (MD) techniques and propose the use of a sudden approximation which agrees reasonably well with the MD results for selected directions and which allows estimates of Ed without employing an MD simulation and the use of computationally more demanding first-principles methods. We compare our results for Ed with the available experimental values. Furthermore, we have examined the temperature dependence of Ed for C in SiC and found it to be negligible.

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Anisotropy of damage productions in electron irradiated molybdenum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010891x ◽

1978 ◽

Vol 36 (1) ◽

pp. 354-355

Author(s):

K. Izui ◽

S. Furuno ◽

H. Otsu ◽

T. Nishida ◽

H. Maeta

Keyword(s):

Electron Flux ◽

Threshold Energy ◽

High Energy ◽

Voltage Electron ◽

High Voltage Electron Microscope ◽

Displacement Threshold ◽

The Mean ◽

Channeling Effect ◽

Different Origins ◽

Threshold Energies

Anisotropy of damage productions in crystals due to high energy electron bombardment are caused from two different origins. One is an anisotropic displacement threshold energy, and the other is an anisotropic distribution of electron flux near the atomic rows in crystals due to the electron channeling effect. By the n-beam dynamical calculations for germanium and molybdenum we have shown that electron flux at the atomic positions are from ∽4 to ∽7 times larger than the mean incident flux for the principal zone axis directions of incident 1 MeV electron beams, and concluded that such a locally increased electron flux results in an enhanced damage production. The present paper reports the experimental evidence for the enhanced damage production due to the locally increased electron flux and also the results of measurements of the displacement threshold energies for the <100>,<110> and <111> directions in molybdenum crystals by using a high voltage electron microscope.

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Vapour Pressure Isotope Eﬀect on Evaporation from Pure Organic Phases - a PIMD Approach

10.26434/chemrxiv.12003186.v1 ◽

2020 ◽

Author(s):

Luis Vasquez ◽

Agnieszka Dybala-Defratyka

Keyword(s):

Path Integral ◽

Vapour Pressure ◽

Density Functional ◽

Isotope Effects ◽

Tight Binding ◽

Decomposition Analysis ◽

Energy Decomposition Analysis ◽

Special Importance ◽

Non Covalent Interactions ◽

Covalent Interactions

Very often in order to understand physical and chemical processes taking place among several phases fractionation of naturally abundant isotopes is monitored. Its measurement can be accompanied by theoretical determination to provide a more insightful interpretation of observed phenomena. Predictions are challenging due to the complexity of the effects involved in fractionation such as solvent effects and non-covalent interactions governing the behavior of the system which results in the necessity of using large models of those systems. This is sometimes a bottleneck and limits the theoretical description to only a few methods. In this work vapour pressure isotope effects on evaporation from various organic solvents (ethanol, bromobenzene, dibromomethane, and trichloromethane) in the pure phase are estimated by combining force field or self-consistent charge density-functional tight-binding (SCC-DFTB) atomistic simulations with path integral principle. Furthermore, the recently developed Suzuki-Chin path integral is tested. In general, isotope effects are predicted qualitatively for most of the cases, however, the distinction between position-specific isotope effects observed for ethanol was only reproduced by SCC-DFTB, which indicates the importance of using non-harmonic bond approximations. Energy decomposition analysis performed using the symmetry-adapted perturbation theory (SAPT) revealed sometimes quite substantial differences in interaction energy depending on whether the studied system was treated classically or quantum mechanically. Those observed differences might be the source of different magnitudes of isotope effects predicted using these two different levels of theory which is of special importance for the systems governed by non-covalent interactions.

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