Study on the formation mechanism of isoniazid crystal defects and defect elimination strategy based on ultrasound

A formation mechanism of crystal defects was proposed by investigations about the factors affecting the formation of macroscopic defects in dicumyl peroxide solution. The effects of crystallization parameters such as...

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Study of Carbonization Process on Surface of Si Substrate in High Vacuum Region with Hydrocarbon Gas

Materials Science Forum ◽

10.4028/www.scientific.net/msf.740-742.161 ◽

2013 ◽

Vol 740-742 ◽

pp. 161-164 ◽

Cited By ~ 1

Author(s):

Yukimune Watanabe ◽

Keisuke Shinoda ◽

Masahiro Tsukahara ◽

Hiroyuki Shimada ◽

Masahiro Furusawa ◽

...

Keyword(s):

Formation Mechanism ◽

High Vacuum ◽

Crystal Defects ◽

Process Time ◽

Process Conditions ◽

Si Substrate ◽

Pit Formation ◽

Gas Source ◽

Hydrocarbon Gas ◽

Low Temperature Process

The formation mechanism of a carbonized layer was investigated under low-pressure and low-temperature process conditions. The initial carbonized layer under those conditions was formed epitaxially using the silicon atoms sublimated from substrate and the carbon atoms of the gas source. This result is suggested from the consideration of pit formation mechanism at the Si/SiC interface. After the initial layer was formed, the carbonized layer grew by the diffusion process of the carbon atoms through the crystal defects in the initially formed layer. This is suggested from that the thickness of the carbonized layer increases linearly with the square root of the process time. The growth rate seemed to be determined by the concentration of carbon atoms taken into the SiC.

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The Imaging of Crystal Structures and Crystal Defects

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069995 ◽

1978 ◽

Vol 36 (3) ◽

pp. 207-217

Author(s):

J.M. Cowley

Keyword(s):

Electron Microscope ◽

Crystal Structures ◽

Phase Contrast ◽

Crystal Defects ◽

Atom Density ◽

Lack Of Information ◽

Spatial Frequencies

The problem of "understandinq" electron microscope imaqes becomes more acute as the resolution is improved. The naive interpretation of an imaqe as representinq the projection of an atom density becomes less and less appropriate. We are increasinqly forced to face the complexities of coherent imaqinq of what are essentially phase objects. Most electron microscopists are now aware that, for very thin weakly scatterinq objects such as thin unstained bioloqical specimens, hiqh resolution imaqes are best obtained near the optimum defocus, as prescribed by Scherzer, where the phase contrast imaqe qives a qood representation of the projected potential, apart from a lack of information on the lower spatial frequencies. But phase contrast imaqinq is never simple except in idealized limitinq cases.

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Studies of Oxide Formation on Copper Thin Films by Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100079103 ◽

1977 ◽

Vol 35 ◽

pp. 316-317

Author(s):

G. G. Hembree ◽

M. A. Otooni ◽

J. M. Cowley

Keyword(s):

Electron Microscopy ◽

Electron Diffraction ◽

Single Crystal ◽

Crystal Surface ◽

Crystal Defects ◽

Diffraction Reflection ◽

Reaction Products ◽

Intermediate Energies ◽

Crystal Films ◽

Reflection Electron Microscopy

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.

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Alternative approaches to ultra-high resolution imaging

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087562 ◽

1991 ◽

Vol 49 ◽

pp. 650-651

Author(s):

J.M. Cowley

Keyword(s):

High Resolution ◽

High Voltage ◽

High Resolution Electron Microscopy ◽

Crystal Defects ◽

High Resolution Imaging ◽

General Applicability ◽

Resolution Electron ◽

Radiation Resistant ◽

Resolution Imaging ◽

Alternative Approaches

By extrapolation of past experience, it would seem that the future of ultra-high resolution electron microscopy rests with the advances of electron optical engineering that are improving the instrumental stability of high voltage microscopes to achieve the theoretical resolutions of 1Å or better at 1MeV or higher energies. While these high voltage instruments will undoubtedly produce valuable results on chosen specimens, their general applicability has been questioned on the basis of the excessive radiation damage effects which may significantly modify the detailed structures of crystal defects within even the most radiation resistant materials in a period of a few seconds. Other considerations such as those of cost and convenience of use add to the inducement to consider seriously the possibilities for alternative approaches to the achievement of comparable resolutions.

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Defects in Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100962 ◽

1968 ◽

Vol 26 ◽

pp. 244-245

Author(s):

Kenneth R. Lawless

Keyword(s):

Electron Microscope ◽

Point Defects ◽

Surface Defects ◽

Chemical Properties ◽

Material Point ◽

Crystal Defects ◽

Defects In Crystals ◽

Irradiation Effects ◽

Normal Lattice ◽

Line Defects

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.

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Large-angle convergent-beam electron-diffraction study of coherent precipitates and decorated dislocations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100167470 ◽

1996 ◽

Vol 54 ◽

pp. 1002-1004

Author(s):

J.M.K. Wiezorek ◽

H.L. Fraser

Keyword(s):

Electron Diffraction ◽

Angular Resolution ◽

Large Angle ◽

Electron Diffraction Study ◽

Convergent Beam Electron Diffraction ◽

Crystal Defects ◽

High Angular Resolution ◽

Beam Electron ◽

Diffraction Plane ◽

Convergent Beam

Conventional methods of convergent beam electron diffraction (CBED) use a fully converged probe focused on the specimen in the object plane resulting in the formation of a CBED pattern in the diffraction plane. Large angle CBED (LACBED) uses a converged but defocused probe resulting in the formation of ‘shadow images’ of the illuminated sample area in the diffraction plane. Hence, low-spatial resolution image information and high-angular resolution diffraction information are superimposed in LACBED patterns which enables the simultaneous observation of crystal defects and their effect on the diffraction pattern. In recent years LACBED has been used successfully for the investigation of a variety of crystal defects, such as stacking faults, interfaces and dislocations. In this paper the contrast from coherent precipitates and decorated dislocations in LACBED patterns has been investigated. Computer simulated LACBED contrast from decorated dislocations and coherent precipitates is compared with experimental observations.

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Charging microscopy and cathodoluminescence imaging of semi-insulating gallium arsenide

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010014542x ◽

1986 ◽

Vol 44 ◽

pp. 816-817

Author(s):

T.C. Sheu ◽

S. Myhajlenko ◽

D. Davito ◽

J.L. Edwards ◽

R. Roedel ◽

...

Keyword(s):

Integrated Circuits ◽

Secondary Electron ◽

Crystal Defects ◽

Device Performance ◽

Gaas Wafer ◽

Surface Charging ◽

Gaas Substrates ◽

Voltage Contrast ◽

Cathodoluminescence Imaging ◽

Scanning Electron

Liquid encapsulated Czochralski (LEC) semi-insulating (SI) GaAs has applications in integrated optics and integrated circuits. Yield and device performance is dependent on the homogeniety of the wafers. Therefore, it is important to characterise the uniformity of the GaAs substrates. In this respect, cathodoluminescence (CL) has been used to detect the presence of crystal defects and growth striations. However, when SI GaAs is examined in a scanning electron microscope (SEM), there will be a tendency for the surface to charge up. The surface charging affects the backscattered and secondary electron (SE) yield. Local variations in the surface charge will give rise to contrast (effectively voltage contrast) in the SE image. This may be associated with non-uniformities in the spatial distribution of resistivity. Wakefield et al have made use of “charging microscopy” to reveal resistivity variations across a SI GaAs wafer. In this work we report on CL imaging, the conditions used to obtain “charged” SE images and some aspects of the contrast behaviour.

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Shot-noise simulations of HREM images of polymer crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153683 ◽

1989 ◽

Vol 47 ◽

pp. 342-343

Author(s):

Philippe Pradère ◽

Edwin L. Thomas

Keyword(s):

Low Dose ◽

Molecular Level ◽

High Resolution Electron Microscopy ◽

Crystal Defects ◽

Inorganic Materials ◽

Photographic Emulsion ◽

Polymer Crystals ◽

Resolution Electron ◽

Recent Developments ◽

Lattice Images

High Resolution Electron Microscopy (HREM) is a very powerful technique for the study of crystal defects at the molecular level. Unfortunately polymer crystals are beam sensitive and are destroyed almost instantly under the typical HREM imaging conditions used for inorganic materials. Recent developments of low dose imaging at low magnification have nevertheless permitted the attainment of lattice images of very radiation sensitive polymers such as poly-4-methylpentene-1 and enabled molecular level studies of crystal defects in somewhat more resistant ones such as polyparaxylylene (PPX) [2].With low dose conditions the images obtained are very noisy. Noise arises from the support film, photographic emulsion granularity and in particular, the statistical distribution of electrons at the typical doses of only few electrons per unit resolution area. Figure 1 shows the shapes of electron distribution, according to the Poisson formula :

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