1992 Fiscal Year Final Research Report Summary
The analysis of small point defect clusters by diffraction contrast image using high resolution electron microscopy
| Project/Area Number |
03805057
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Physical properties of metals
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| Research Institution | KYOTO UNIVERSITY (1992)
Hokkaido University (1991) |
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Principal Investigator |
YOSHIIE Toshimasa Kyoto University, Research Reactor Institute, Professor, 原子炉実験所, 教授 (20124844)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Diffraction contrast image / High resolution electron microscopy / Radiation damage defect structure / Small point defect clusters / Weak beam method / Malti slice method |
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| Research Abstract |
For the study of radiation damage, statistical evaluation of radiation induced defect structures are essential. High resolution transmission electron microscopy has been one of the most powerful technique to investigate the type, the density and the size of point defect clusters. The diffraction contrast image, especially a dark-field image is commonly used for these studies. The relationship between observed image size and real defect size is, however not clear in the case of small clusters, especially in the order of 1nm size. The aim of this study was to develop the observation technique and the method of analysis for the diffraction contrast image of small defect clusters.
Point defect clusters were introduced in metals and semiconductors by various method such as high energy particle irradiation and quenching from high temperatures. Experimental dark-field diffraction contrast image of stacking fault tetrahedra, dislocation loops and voids was examined under various conditions. Image of dislocation loops below 1nm was observed. They are distinguished from stacking fault tetrahedra using a 220 reflection if the size is above 2nm. For the image of stacking fault tetrahedra, 0.6nm for gold and 0.5nm for nickel were observed. Image of stacking fault and stair-rod dislocations were simulated based on the dynamical theory. Image of very small stacking fault tetrahedra was calculated by multi-slice method. Stacking fault instead of stair-rod dislocations have large contribution to the total stacking fault image. It is clarified that image size is smaller than the stacking fault size. The size difference depends on many parameters, but is always smaller than the fringe spacing of stacking fault tetrahedra. The contrast of stacking fault tetrahedra smaller than the fringe spacing sometimes goes out. Visible ratio is smaller for smaller deviation from the Bragg condition.
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