• Proceedings of the Korean Vacuum Society Conference
• /
• 1996.06a
• /
• pp.173-173
• /
• 1996

• Applied Microscopy
• /
• v.16 no.2
• /
• pp.14-24
• /
• 1986

The interrelation of secondary defects, intermediate S' phase and aging condition in Al-2.0 wt% Cu-1.1 wt% Mg alloy is studied by transmission electron microscope. The results obtained in this study are as follows. 1. High density of dislocation loops, helices and stacking faults are observed in this specimen with aging treatment. 2. The number of dislocation loops and the width of loop free zone (LFZ) are increased with aging time. 3. The intermediate S' phase precipitates and grows on the dislocations and secondary defects. 4. The misfit dislocations are formed around intermediate S' phase. 5. It is thought that the helices appear to be produced by the climb of screw dislocations, while the dislocation loops appear to be formed both by condensation of vacancies into collapsed discs and by interaction of helices with screw of opposite sign.

• Journal of the Microelectronics and Packaging Society
• /
• v.9 no.3
• /
• pp.49-56
• /
• 2002

In this study, the InGaP epilayers were grown on the exact and the $2^{\circ}$, $6^{\circ}$, $10^{\circ}$ of cut GaAs substrates by metal-organic vapor phase epitaxy, and the effects of interfacial elastic strains determined by the substrate offcut angle upon the resulting dislocation density of epilayer were investigated for the first time. The elastic strains were obtained from lattice mismatch and lattice misfit by TXRD, and the dislocation densities from epilayer x-ray FWHM. For the offcut angle range used in this study, the elastic strain was maximum and x-ray FWHM minimum at offcut angle $6^{\circ}$. From 11K PL measurements, PL wavelength was found to decrease with an increase of offcut angle. PL intensity was maximum at offcut angle $6^{\circ}$. TEM results showed that the electron diffraction pattern was of typical zincblende structure, and that the dislocation density was minimum for substrate offcut angle $6^{\circ}$. The results obtained in this study, along with the device fabrication process and beam characteristics, clearly demonstrated that the optimum substrate offcut angle for the InGaP/GaAs heterostructures is $6^{\circ}$.

• Analytical Science and Technology
• /
• v.6 no.5
• /
• pp.515-520
• /
• 1993

By the real use of Rene 80 cast blades at high temperature ${\gamma}^{\prime}$ precipitates in the matrix(${\gamma}$) mainly due to the operating temperature. These precipitates play main role for strenthening of the blades. Generally known that dislocation density increases due to ${\gamma}-{\gamma}^{\prime}$ mismatch by the generation and growth of the precipitates, because the lattice parameter of ${\gamma}^{\prime}$ is higher than that of ${\gamma}$. These lattice parameters of ${\gamma}$ and ${\gamma}^{\prime}$ are determined through the CBED(Convergent Beam Electron Diffraction) method by STEM(Scanning Transmission Electron Microscope) in this work. And also studied, whether and how much the dislocation density increases by the generation and growth of the precipitates.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.9 no.2
• /
• pp.207-211
• /
• 1999

$Si/Si_{1-x}Ge_x$ MODFET structures, incorporating linearly-graded buffer layers have been grown by GaS Source Molecular Beam Epitaxy. The growth temperature of the graded layers has not significantly changed the distribution of misfit dislocation. However, the surface undulation and surface defects were increased with increasing growth temperature. In $Si/Si_{1-x}Ge_x$ MODFET structures, the densities of misfit dislocations near the Si-active layers were considerably reduced in comparison with the region of graded layers. The electron mobility of $Si/Si_{1-x}Ge_x$ MODFET structure has increased with lowering the growth temperature.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2007.02a
• /
• pp.116-116
• /
• 2007

• Journal of Korea Foundry Society
• /
• v.37 no.5
• /
• pp.139-147
• /
• 2017

Microstructural evolution of cast Hastelloy X during thermal exposure has been investigated. OM, SEM, and TEM microscopy were carried out on the as-cast, the standard heat treated, and the thermally exposed conditions. Tensile tests were also conducted to understand the effect of microstructural evolution on the degradation of tensile properties. Coarse $M_6C$ and fine $M_{23}C_6$ carbides were found in as-cast Hastelloy X with fine carbides on sub-boundary. Some of $M_{23}C_6$ carbide dissolved into the matrix during solution heat treatment and dislocation network formed at the interface between the carbide and the matrix due to the misfit strain. There was no significant microstructural difference between the exposed specimens at $400^{\circ}C$ and the solution heat treated specimen. A large amount of $M_{23}C_6$ carbides precipitated along and near grain boundaries and sub-boundaries after exposure at $650^{\circ}C$. Exposure at $870^{\circ}C$ of the alloy caused precipitation of $M_6C$ and ${\mu}$. The strength increased and the elongation decreased by thermal exposure at $650^{\circ}C$ and $870^{\circ}C$ because carbides interfere with the movement of the dislocation. It was found that the precipitation of carbide gave significant effects on the tensile properties of Hastelloy X.

• Journal of the Korean Vacuum Society
• /
• v.6 no.4
• /
• pp.354-358
• /
• 1997

Crystal properties of wurtzite GaN films grown on $Al_2O_3$(0001) substrates under various nitrogen pressure and plasma power by electron cyclotron resonance molecular beam epitaxy were investigated by full width at half maximum of X-ray diffraction peak and scanning electron microscope. It was found that the nitrogen pressure has a large effect on the FWHM value of XRD, and the GaN film grown under the optimum nitrogen pressure contains high density of dislocations. These results suggest that the crystal quality is sensitive to the plasma source conditions and that the relaxation of stress depends of V/III ratio. However, substrate-surface nitridation has little effect on the relaxation of misfit stress.

• Journal of the Korean Magnetics Society
• /
• v.10 no.6
• /
• pp.274-279
• /
• 2000

The microstructure and thermal properties of the Mn-IriNi-Fe exchange biased multi-layers with various buffer layers and stacking structures have been investigated. The H$_{e{\chi}}$ and the T$_{b}$ depend on the Mn-Ir grain size at the interface between the Mn-Ir layer and the Ni-Fe layer, The (111) preferred orientation of Mn-Ir/Ni-Fe on the Ta buffer layer may promote the values of J$_{k}$ and H$_{e{\chi}}$. The samples which produce the Hex have the epitaxial relationship at the interface between the Mn-Ir layer and the Ni-Fe layer due to the generation of misfit dislocation.

• Journal of Sensor Science and Technology
• /
• v.5 no.2
• /
• pp.61-67
• /
• 1996

The growth and characterization of heteroepitaxial $Si_{1-x}Ge_{x}$ films grown by the RTCVD (Rapid Thermal Chemical Vapor Deposition) method were described. For the growth of $Si_{1-x}Ge_{x}$ heteroepitaxial layers, $SiH_{4}$ / $GeH_{4}$ / $H_{2}$ gas mixtures were used. The growth conditions were varied to investigate their effects on the Si / Ge composition ratios, the interface abruptness and crystalline properties. The experimental data shows that the misfit threading dislocation in $Si_{1-x}Ge_{x}$ / Si heteroepitaxial film of about $400\;{\AA}$ thickness was not observed at the growth temperature of as low as $650^{\circ}C$, and the composition ratios of Si / Ge changed linearly with $SiH_{4}$ / $GeH_{4}$ gas mixing ratios in our experimental ranges. In the in-situ boron doping experiments, the doping abruptness would be controlled within several hundreds ${\AA}$/decade.