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전자회절 Kikuchi Pattern의 전산모사와 그 응용
이원범,박찬로,박찬경,천창환,Lee, Won-Beom,Park, Chan-Rho,Park, Chan-Gyung,Chun, Chang-Hwan 한국현미경학회 1994 Applied microscopy Vol.24 No.4
A computer program has been developed to analyze easily the Kikuchi pattern which is useful in obtaining the crystallographic data of materials. This program can simulate the Kikuchi patterns for 14 Bravais lattice by using the matrix algebra. Convenient menu system was also added to enhance the applications of the program. That is, by varying the tilting angle, camera length (RADIUS) and $S_{max}$ in the menu, various Kikuchi patterns can be obtained. The simulated patterns, then, can be compared with the experimentally-obtained Kikuchi pattern to examine validity of simulation.
신동원,박찬로,박찬경,김종철,Sin, Dong-Won,Park, Chan-Ro,Park, Chan-Gyeong,Kim, Jong-Cheol 한국재료학회 1994 한국재료학회지 Vol.4 No.7
본 연구에서는 반구형(HSG) 다결성 실리콘 박막을 제조하여 박막에 존재하는 결정립들의 특성과 각 결정립들의 형성기구를 예측하고자 하였다. LPCVD법으로 실리콘 박막을 증착하여 미세구조를 관찰, 분석한 결과 $575^{\circ}C$ 증착온도에서 HSG 다결정 실리콘 박막이 형성되었음을 관찰하였다. 이 HSG 박막은 비정질 및 결정질 상으로 구성되어 있었으며 결정립은 박막의 표면에 존재하는 upper grain들과 $SiO_{2}$와의계면에 존재하는 lower grain들로 구분되었다. Upper grain은 실리콘 원자의 표면확산에 의하여 형성되었으며, lower grain은 고상성장에 의하여 형성되었다. 성장한 결정립들의 성장방위를 분석한 결과 주로 upper grain은 <110>, lower grain은 <311>과 <111>방위를 나타내었다. 이러한 방위관계는 각 결정립들의 형성기구(formation mechanism)의 차이에 기인한다고 사료된다. 또한 HSG박막의 미세구조와 진공열처리한 시편을 관찰한 결과 HSG 박막의 형성은 실리콘 원자의 표면확산에 의해 지배됨을 알았다. The purpose of present study is to find out the formation mechanism of hemi-spherical grained(HSG) polysilicon film. Silicon film was deposited using LPCVD. Polycrystalline silicon film was deposited at $575^{\circ}C$ contained crystalline HSG in the amorphous matrix phase. The crystalline HSG can be categorized into two grains : lower grains and upper grains. Lower grains are located at interface between silicon dioxide and silicon film, and upper grains are located at surface. The growth orientations of HSG were identified as (311) or (111) directions for lower grains and perferentially (110) direction for upper grains. This difference of growth orientations seems to be caused by the difference of formation mechanisms. That is, lower grain is formed by soild phase crystallization, on the other hand, upper grain is formed by surface diffusion of silicon atoms. It was thus, proposed that the formation of practical HSG polysilicon film is mainly controlled by surface diffusion of silicon atoms.
금속의 소성변형중 입계를 통한 Slip Transfer 의 미시적기구 고찰
장영원,박찬경,박찬로 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.11
The interaction phenomena between dislocations and a grain boundary have been examined by conducting in-situ straining experiments with 316 stainless steel in a TEM. An emphasis was put on especially for the identification of the critical factors affecting slip transfer across a grain boundary. Various types of dislocation interactions with grain boundary were observed during in-situ deformation experiments, such as dislocation absorption into grain boundary, reflection from grain boundary, transmission across grain boundary, and microcrack initiation at grain boundary. Each phenomenon is considered as an effective relaxation mechanism for the accumulated internal strain energy induced by piled-up dislocations against grain boundary. The slip transfer across grain boundray was found to be affected by the geometric relationship between the two adjacent grains and also by the internal stress generated by a dislocation pile-up. The activated slip system could, therefore, be predicted by such factors as 1) the minimum intersection angle between the two slip planes in the two adjacent grains, 2) the largest resolved shear stress acting on the neighboring grain under the stress field caused by a dislocation pile-up, and 3) the smallest Burgers vector of residual dislocations remaining in the grain boundary after a slip transfer. These results appear to be in good agreement with the present direct observations of slip transfer behavior.
장영원,박찬경,박찬로 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.8
In-situ tensile deformation tests of molybdenum were carried out in a transmission electron microscope at temperatures ranging from 120K to room temperature. At all test temperatures, brittle crack propagation was observed to precede plastic deformation. The characteristics of cracks, either ductile or brittle, was found to vary depending on crack geometry and loading condition. In some cases the coexistence of brittle and ductile crack was observed and in other instances crack propagation changed from brittle to ductile mode. Such phenomena could be successfully explained by the concept of local stress intensity factor for dislocation emission and brittle crack propagation. Dislocations generated at a crack tip are thought to shield the crack. The shielding of a crack by emitted dislocations would then increase the fracture toughness of materials. On the other hand, the anti-shielding of a crack by externally generated dislocations could occur, just like the shielding due to dislocations generated at the crack tip to reduce the toughness of materials.