| AVS 54th International Symposium | |
| In-situ Electron Microscopy Topical Conference | Monday Sessions |
| Session IE-MoM |
| Session: | Structure-Property Characterization |
| Presenter: | J.M. Zuo, University of Illinois, Urbana-Champaign |
| Authors: | K. Sato, University of Illinois, Urbana-Champaign W.J. Huang, University of Illinois, Urbana-Champaign J.M. Zuo, University of Illinois, Urbana-Champaign |
| Correspondent: | Click to Email |
Understanding different structures of nanoparticles and their transition can have a large impact on our ability to self-assemble controlled nanostructures and understanding properties of nanoparticles. Small nanoparticles of a few nanometers in diameter are difficult to characterize by traditional surface characterization techniques. Here we report two recent developments in nanoparticle characterization. The first is an in-situ RHEED characterization of the size dependence of structural transition from multiply-twinned particle (MTP) to epitaxial face centered cubic (FCC) nanocrystal for Ag nanoparticle formed on Si(001) surfaces. The transition from MTP to nanocrystals was promoted by post-deposition annealing. Clear particle size dependence is found in the epitaxial formation temperatures (TE), which is about 2/3 of the calculated, size-dependent, melting temperature (TM) for particles larger than 2 nm in diameter. For smaller nanoparticles, TE is about the same as TM. Once nanocrystals are formed, they decay and disappear in a narrow temperature range between 794 and 849 K. No evidence of nanocrystal melting was detected from the RHEED observation. In the second study, we show that coherent electron diffraction patterns recorded from individual nanocrystals are very sensitive to, and can be used to study, the structures of nanocrystal surfaces. We use this to study the bond-length dependent atomic contractions in Au nanocrystals 3 to 5 nm. Evidences of inhomogeneous surface relaxation will be presented.