電子顯微鏡學 指導教授：王聖璋 班級：碩研機械一甲 姓名：李文妤 學號：ＭＡ１１０１１３ Paper Survey J. Phys. Chem. B 2000, 104, Transmission Electron Microscopy of Shape-Controlled Nanocrystals and Their Assemblies Z. L. Wang* School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia ReceiVed: October 7, 1999; In Final Form: NoVember 18, 1999

3.2 Twinned and Multiply Twinned Nanocrystals  Twinned nanocrystals One of the most popular planar defects in nanocrystals. Frequently observed for FCC structured metallic nanocrystals. The result of two subgrains sharing a common crystallographic plane. The structure of one subgrain is the mirror reflection of the other by the twin plane.

Figure 5. (c) Geometrical shapes of multiply twinned decahedraland icosahedral particles. 3.2 Twinned and Multiply Twinned Nanocrystals  The two most typical examples of multiply twinned particles ( MTPs ) Assembled form 5 tetrahedrals sharing an edge.Assembled form 20 tetrahedrals sharing an edge.

Figure 9. TEM images of decahedral Au nanocrystals when the incident electron beam is parallel or nearly parallel to the 5-fold symmetry axis (The Au nanocrystals were supplied by S. Link). 3.2 Twinned and Multiply Twinned Nanocrystals  MTP Au particles Single decahedral particle Two decahedra particle

Figure 10. (a) A high-resolution TEM image showing the presence of twinning in Au nanoparticles. (b) A dark-field image recorded using a small section of the {111} and {200} reflection rings displaying the distribution of twinned particles in the specimen. 3.2 Twinned and Multiply Twinned Nanocrystals  Strongly optical properties ： stacking faults and twins in the nanocrystals.  Dark-field ： The fraction of twinned particles.  Identifying the presence of twins and their distribution among the particles. Twinned structure & strain induced by the twin structure Distribution of twins

Thanks for your attention!