Structure and shape transformation from multiply twinned particles to epitaxial nanocrystals: Importance of interface on the structure of Ag nanoparticles

The effect of a substrate on the structure of nanometer-sized metal particles was investigated for Ag on silicon surfaces by using high-resolution transmission electron microscope and electron diffraction. The nanometer-sized Ag particles, formed by the vapor deposition of Ag on (001) hydrogen-terminated Si (H-Si) surfaces at room temperature, adopt multiply twinned structures. Upon annealing, the multiply twinned Ag nanoparticles on H-Si (001) transform into fcc nanocrystals. The fcc Ag takes up the cube-on-cube epitaxy, with the orientation relationship of Ag(001)∕∕Si(001) and Ag0.3em0ex[110]∕∕Si0.3em0ex[110]. An energetic model is developed to account for the structure and shape transition of supported multiply twinned particles to fcc epitaxial nanocrystals. Possible transition mechanisms are discussed.