Real-Time X-Ray Topographic Observation of Melting and Growth of Silicon Crystals

1980 ◽  
Vol 2 ◽  
Author(s):  
Jun-Ichi Chikawa ◽  
Fumio Sato
Keyword(s):  
Thermal Stresses ◽  
Melting Behavior ◽  
Interfacial Free Energy ◽  
Oxygen Effect ◽  
Oxygen Impurity ◽  
Television System ◽  
Growth Interface ◽  
X Ray ◽  
Silicon Crystals ◽  
Free Region

ABSTRACTA technique for the direct viewing of topographic images was developed based on a television system using an x-ray sensing PbO-vidicon camera tube (resolution 25 μm). Melting and growth processes of plate-shaped crystals were observed in an argon flow by this technique. The observation showed that dislocations have very high mobilities by superheating and the equilibrium dislocation density of zero is achieved just before melting. In melting of dislocation-free crystals, liquid drops (locally molten regions) were observed inside the crystals. While, crystallites appeared in the supercooled melt near the growth interface. It was found that both the drops and crystallites are not formed in 5% hydrogen/95% argon environment. Melting behavior of crystals covered with oxide films indicates that the solid-liquid interfacial free energy is greatly lowered by oxygen impurity. This oxygen effect may be responsible for both the drop and crystallite formation. Origin of swirl defects in dislocation-free crystals is discussed in the basis of these observations. Both composite and common a/2<110> dislocations were observed near the growth interface: The former are composed of three a/2<110> dislocations and are present at the interface so that, as the crystal grows, they propagate into the new crystal. They influence the interface morphology, when their Burgers vectors have the component perpendicular to the interface. The common dislocations cannot exist stably at the interface and are driven into the newly grown dislocation-free region by thermal stresses.

Microdefects and Impurities in Dislocation-Free Silicon Crystals

1982 ◽  
Vol 14 ◽  
Author(s):  
Takao Abe ◽  
Hirofumi Harada ◽  
Jun-Ichi Chikawa
Keyword(s):  
Temperature Gradient ◽  
Defect Formation ◽  
Mutual Interaction ◽  
Oxygen Impurity ◽  
Formation Processes ◽  
Impurity Effects ◽  
X Ray ◽  
Silicon Crystals ◽  
Residual Oxygen ◽  
New Type

ABSTRACTMicrodefects in striated (swirl defects) and nonstriated distribution (D-defects) have been observed in float-zoned crystals doped with various impurities by x-ray topography following copper decoration. A new type of defects were found to be present in swirl-free and D-defect-free regions and to become invisible by doping gallium. This gallium effect led to the conclusion that they are microprecipitates produced from residual oxygen impurity in FZ crystals. Effects of various impurities on defect formation indicate that D-defects are of vacancy agglomerates. It was observed that swirl defects are formed when the temperature gradient near the interface is high, and that their formation is suppressed by doping nitrogen. Formation processes of microprecipitates, swirls, and D-defects are discussed on the basis of observation of their mutual interaction and the impurity effects.

Characterization of defects in tabular silver halide grains

1990 ◽  
Vol 48 (4) ◽  
pp. 1046-1047
Author(s):  
C. Goessens ◽  
D. Schryvers ◽  
J. Van Landuyt ◽  
A. Verbeeck ◽  
R. De Keyzer
Keyword(s):  
Radiation Damage ◽  
Silver Halide ◽  
Chemical Characteristics ◽  
X Ray ◽  
Free Region ◽  
Central Defect ◽  
Crystallographic Defects ◽  
Physical And Chemical ◽  
Two Sides

Silver halide grains (AgX, X=Cl,Br,I) are commonly recognized as important entities in photographic applications. Depending on the preparation specifications one can grow cubic, octahedral, tabular a.o. morphologies, each with its own physical and chemical characteristics. In the present study crystallographic defects introduced by the mixing of 5-20% iodide in a growing AgBr tabular grain are investigated. X-ray diffractometry reveals the existence of a homogeneous Ag(Br1-xIx) region, expected to be formed around the AgBr kernel. In fig. 1 a two-beam BF image, taken at T≈100 K to diminish radiation damage, of a triangular tabular grain is presented, clearly showing defect contrast fringes along four of the six directions; the remaining two sides show similar contrast under relevant diffraction conditions. The width of the central defect free region corresponds with the pure AgBr kernel grown before the mixing with I. The thickness of a given grain lies between 0.15 and 0.3 μm: as indicated in fig. 2 triangular (resp. hexagonal) grains exhibit an uneven (resp. even) number of twin interfaces (i.e., between + and - twin variants) parallel with the (111) surfaces. The thickness of the grains and the existence of the twin variants was confirmed from CTEM images of perpendicular cuts.

In Situ X-Ray Diffraction Investigations during Diffusion Anneals of Ni-Cu Thin Film Diffusion Couples

2010 ◽  
Vol 89-91 ◽  
pp. 503-508 ◽  
Author(s):  
J. Sheng ◽  
U. Welzel ◽  
Eric J. Mittemeijer
Keyword(s):  
Thermal Stresses ◽  
Stress Generation ◽  
Ex Situ ◽  
Diffusion Annealing ◽  
X Ray Diffraction ◽  
Individual Layer ◽  
X Ray ◽  
Bilayer System ◽  
Stress Changes

The stress evolution during diffusion annealing of Ni-Cu bilayers (individual layer thicknesses of 50 nm) was investigated employing ex-situ and in-situ X-ray diffraction measurements. Annealing at relatively low homologous temperatures (about 0.3 - 0.4 Tm) for durations up to about 100 hours results in considerable diffusional intermixing, as demonstrated by Auger-electron spectroscopy investigations (in combination with sputter-depth profiling). In addition to thermal stresses due to differences of the coefficients of thermal expansion of layers and substrate, tensile stress con-tributions in the sublayers arise during the diffusion anneals. The obtained stress data have been discussed in terms of possible mechanisms of stress generation. The influence of diffusion on stress development in the sublayers of the diffusion couple during heating and isothermal annealing was investigated by comparing stress changes in the bilayer system with corresponding results obtained under identical conditions for single layers of the components in the bilayer system. The specific residual stresses that emerge due to diffusion between the (sub)layers in the bilayer could thereby be identified.

How Accurate is Qcbed ? -- the Case of Rutile (TiO2)

2001 ◽  
Vol 7 (S2) ◽  
pp. 368-369
Author(s):  
B. Jiang ◽  
J. Friis ◽  
J.C.H. Spence
Keyword(s):  
Systematic Errors ◽  
Mean Value ◽  
Order Structure ◽  
Data Sets ◽  
X Ray ◽  
Silicon Crystals ◽  
Structure Factors ◽  
The Mean ◽  
Mott Formula ◽  
Better Than

An accuracy of better than 1% is needed to measure the changes in charge density due to bonding. Here we report an accuracy up to 0.025% (random error) obtained in rutile crystal structure factors measurement by QCBED. This error is the standard deviation in the mean value obtained from ten data sets. Systematic errors may be present. Figure 1 gives an example of the (200) refinement results. Table 1 lists several low order structure factor refinement results. The accuracy of the measured electron structure factors was 0.1-0.2% but after conversion to x-ray structure factors, the accuracy for low orders improved due to the Mott formula [1] For (110) and (101) reflections, the accuracy in x-ray structure factors became 0.025% and 0.048% respectively. This accuracy is equivalent to that of the X-ray single crystal Pendellosung method on silicon crystals [2].The experiments were done on a Leo 912 Omega TEM.

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