Effects of Stone-Wales and vacancy defects in atomic-scale friction on defective graphite

2014 ◽  
Vol 104 (18) ◽  
pp. 183109 ◽  
Author(s):  
Xiao-Yu Sun ◽  
RunNi Wu ◽  
Re Xia ◽  
Xi-Hua Chu ◽  
Yuan-Jie Xu
Keyword(s):  
Atomic Scale ◽  
Vacancy Defects

scholarly journals Dynamic behavior of reversible oxygen migration in irradiated-annealed high temperature superconducting wires

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yi Zhang ◽  
M. W. Rupich ◽  
Vyacheslav Solovyov ◽  
Qiang Li ◽  
Amit Goyal
Keyword(s):  
High Temperature ◽  
Annealing Treatment ◽  
Atomic Scale ◽  
Vacancy Defects ◽  
Superconducting Wires ◽  
High Temperature Superconducting ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Effect Of Oxygen ◽  
Electron Energy Loss

Abstract We use atomically resolved scanning transmission electron microscopy and electron energy loss spectroscopy to determine the atomic-scale structural, chemical and electronic properties of artificial engineered defects in irradiated-annealed high temperature superconducting wires based on epitaxial Y(Dy)BCO film. We directly probe the oxygen vacancy defects in both plane and chain sites after irradiation with 18-meV Au ions. The plane site vacancies are reoccupied during post-annealing treatment. Our results demonstrate the dynamic reversible behavior of oxygen point defects, which explains the depression and recovery of self-field critical current and critical temperature in irradiation-annealing process. These findings reveal the strong effect of oxygen vacancies in different sites on the superconductivity properties of irradiated Y(Dy)BCO film, and provide important insights into defects engineering of 2G HTS coil wires.

MANIPULATING ATOMS ONE BY ONE WITH A SCANNING TUNNELING MICROSCOPE

1996 ◽  
Vol 03 (03) ◽  
pp. 1463-1472 ◽  
Author(s):  
DEHUAN HUANG ◽  
YOSHIHISA YAMAMOTO
Keyword(s):  
Electronic Devices ◽  
Hydrogen Desorption ◽  
Atomic Scale ◽  
Single Atom ◽  
Scanning Tunneling ◽  
Crystallographic Position ◽  
Hydrogen Atoms ◽  
Vacancy Defects ◽  
Scale Structures ◽  
A Chain

By using an STM operated in ultrahigh vacuum, we can extract single Si atoms from any predetermined positions of the Si(111)-(7×7) surface through field evaporation. This technique enables us to create novel atomic-scale structures, and even to fabricate a single atom groove and chain on the surface. The extracted Si atoms can be redeposited onto the surface, although the crystallographic position of these deposited Si atoms changes as their density increases. We have demonstrated that natural Si vacancy defects existing on the surface can be repaired by this technique. The deposited Si atoms can be reremoved by picking them up again with the tip, the substrate atomic arrangement remaining unperturbed. We can also remove individual hydrogen atoms from hydrogen-passivated Si(100)-(2×1) surfaces. A chain with equal separation of Si dimers produced by hydrogen desorption has been created. These results demonstrate the potential of STM for the construction of electronic devices with atomic dimensions.

Atomic-scale study of vacancy defects in SiC affecting on removal mechanisms during nano-abrasion process

2020 ◽  
Vol 145 ◽  
pp. 106136 ◽  
Author(s):  
Piao Zhou ◽  
Tao Sun ◽  
Xunda Shi ◽  
Jun Li ◽  
Yongwei Zhu ◽  
...  
Keyword(s):  
Atomic Scale ◽  
Vacancy Defects ◽  
Removal Mechanisms

Ab Initio Theory of Si-Vacancy Quantum Bits in 4H and 6H-SiC

2018 ◽  
Vol 924 ◽  
pp. 895-900 ◽  
Author(s):  
Viktor Ivády ◽  
Joel Davidsson ◽  
Nguyen Tien Son ◽  
Takeshi Ohshima ◽  
Igor A. Abrikosov ◽  
...  
Keyword(s):  
Ab Initio ◽  
Single Photon ◽  
Wide Band ◽  
Atomic Scale ◽  
Optical Data ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Vacancy Defects ◽  
Quantum Bits ◽  
Silicon Vacancy

Point defects in wide band gap semiconductors have recently shown outstanding potential for implementing room temperature quantum bits and single photon emitters. These atomic scale tools can be used in various quantum information processing, sensing, and imaging applications. Silicon vacancy related photoluminescence centers in 4H, 6H, and 15R-SiC are among the most studied quantum bits that possess a particular spin-3/2 ground and excited state. The microscopic structures of these defects have been recently identified as isolated negatively charged silicon vacancy defects at the symmetrically non-equivalent silicon sites in SiC. Relying on this identification, here we carry out high precision ab initio simulations on negatively charged silicon vacancies in 4H and 6H-SiC and calculate the most important magneto-optical data, such as the zero-phonon photoluminescence energies, the zero-field-splitting, and the hyperfine tensors for the nearest and farther nuclear spins.

Role of edge geometry and chemistry in the electronic properties of graphene nanostructures

2014 ◽  
Vol 173 ◽  
pp. 173-199 ◽  
Author(s):  
Shintaro Fujii ◽  
Maxim Ziatdinov ◽  
Misako Ohtsuka ◽  
Koichi Kusakabe ◽  
Manabu Kiguchi ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Atomic Scale ◽  
Strong Impact ◽  
Geometrical Shape ◽  
Vacancy Defects ◽  
Theoretical Simulation ◽  
Edge Geometry ◽  
Modified Graphene ◽  
Graphene Nanostructures

The geometry and chemistry of graphene nanostructures significantly affects their electronic properties. Despite a large number of experimental and theoretical studies dealing with the geometrical shape-dependent electronic properties of graphene nanostructures, experimental characterisation of their chemistry is clearly lacking. This is mostly due to the difficulties in preparing chemically-modified graphene nanostructures in a controlled manner and in identifying the exact chemistry of the graphene nanostructure on the atomic scale. Herein, we present scanning probe microscopic and first-principles characterisation of graphene nanostructures with different edge geometries and chemistry. Using the results of atomic scale electronic characterisation and theoretical simulation, we discuss the role of the edge geometry and chemistry on the electronic properties of graphene nanostructures with hydrogenated and oxidised linear edges at graphene boundaries and the internal edges of graphene vacancy defects. Atomic-scale details of the chemical composition have a strong impact on the electronic properties of graphene nanostructures,i.e., the presence or absence of non-bonding π states and the degree of resonance stability.

Structure and migration of planar defects in crystals observed in atomic scale

1978 ◽  
Vol 36 (1) ◽  
pp. 284-285 ◽  
Author(s):  
H. Hashimoto ◽  
Y. Sugimoto ◽  
Y. Takai ◽  
H. Endoh
Keyword(s):  
Electron Microscope ◽  
Rotation Angle ◽  
Crystal Surface ◽  
Electron Gun ◽  
Atomic Scale ◽  
Present Observation ◽  
Twist Boundary ◽  
Optical Magnification ◽  
Zinc Crystal ◽  
And Migration

As was demonstrated by the present authors that atomic structure of simple crystal can be photographed by the conventional 100 kV electron microscope adjusted at “aberration free focus (AFF)” condition. In order to operate the microscope at AFF condition effectively, highly stabilized electron beams with small energy spread and small beam divergence are necessary. In the present observation, a 120 kV electron microscope with LaB6 electron gun was used. The most of the images were taken with the direct electron optical magnification of 1.3 million times and then magnified photographically.1. Twist boundary of ZnSFig. 1 is the image of wurtzite single crystal with twist boundary grown on the surface of zinc crystal by the reaction of sulphur vapour of 1540 Torr at 500°C. Crystal surface is parallel to (00.1) plane and electron beam is incident along the axis normal to the crystal surface. In the twist boundary there is a dislocation net work between two perfect crystals with a certain rotation angle.

Resolution in the scanning tunneling microscope

1991 ◽  
Vol 49 ◽  
pp. 488-489
Author(s):  
R. J. Wilson ◽  
D. D. Chambliss ◽  
S. Chiang ◽  
V. M. Hallmark
Keyword(s):  
Scanning Tunneling Microscope ◽  
Fundamental Principle ◽  
Atomic Scale ◽  
Lateral Resolution ◽  
Scanning Tunneling ◽  
Electronic Noise ◽  
Vertical Resolution ◽  
Tunneling Microscopy ◽  
Spatial Profile ◽  
Theoretical Analyses

Scanning tunneling microscopy (STM) has been used for many atomic scale observations of metal and semiconductor surfaces. The fundamental principle of the microscope involves the tunneling of evanescent electrons through a 10Å gap between a sharp tip and a reasonably conductive sample at energies in the eV range. Lateral and vertical resolution are used to define the minimum detectable width and height of observed features. Theoretical analyses first discussed lateral resolution in idealized cases, and recent work includes more general considerations. In all cases it is concluded that lateral resolution in STM depends upon the spatial profile of electronic states of both the sample and tip at energies near the Fermi level. Vertical resolution is typically limited by mechanical and electronic noise.

What catalysis needs from the electron microscopist

1988 ◽  
Vol 46 ◽  
pp. 694-695
Author(s):  
Alexis T. Bell
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Surface Composition ◽  
Internal Surface ◽  
Active Phase ◽  
Atomic Scale ◽  
Metal Catalyst ◽  
Internal Surface Area ◽  
Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

Electron holography of catalysts

1995 ◽  
Vol 53 ◽  
pp. 416-417
Author(s):  
A. K. Datye ◽  
D. S. Kalakkad ◽  
L. F. Allard ◽  
E. Völkl
Keyword(s):  
Heterogeneous Catalysts ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Scale ◽  
Nano Particles ◽  
Phase Image ◽  
Electron Holography ◽  
Specimen Thickness ◽  
Phase Information ◽  
Particle Structure

The active phase in heterogeneous catalysts consists of nanometer-sized metal or oxide particles dispersed within the tortuous pore structure of a high surface area matrix. Such catalysts are extensively used for controlling emissions from automobile exhausts or in industrial processes such as the refining of crude oil to produce gasoline. The morphology of these nano-particles is of great interest to catalytic chemists since it affects the activity and selectivity for a class of reactions known as structure-sensitive reactions. In this paper, we describe some of the challenges in the study of heterogeneous catalysts, and provide examples of how electron holography can help in extracting details of particle structure and morphology on an atomic scale.Conventional high-resolution TEM imaging methods permit the image intensity to be recorded, but the phase information in the complex image wave is lost. However, it is the phase information which is sensitive at the atomic scale to changes in specimen thickness and composition, and thus analysis of the phase image can yield important information on morphological details at the nanometer level.

Limits for high-resolution electron microscopy of inorganic materials?

1987 ◽  
Vol 45 ◽  
pp. 4-5
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Spherical Aberration ◽  
High Resolution Electron Microscopy ◽  
Inorganic Materials ◽  
Atomic Scale ◽  
Resolution Limit ◽  
Contrast Transfer Function ◽  
Existing Problems ◽  
Resolution Electron ◽  
Electron Microscopes

The era of atomic-resolution electron microscopy has finally arrived. In virtually all inorganic materials, including oxides, metals, semiconductors and ceramics, it is possible to image individual atomic columns in low-index zone-axis projections. A whole host of important materials’ problems involving defects and departures from nonstoichiometry on the atomic scale are waiting to be tackled by the new generation of intermediate voltage (300-400keV) electron microscopes. In this review, some existing problems and limitations associated with imaging inorganic materials are briefly discussed. The more immediate problems encountered with organic and biological materials are considered elsewhere.Microscope resolution. It is less than a decade since the state-of-the-art, commercially available TEM was a 200kV instrument with a spherical aberration coefficient of 1.2mm, and an interpretable resolution limit (ie. first zero crossover of the contrast transfer function) of 2.5A.

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