Behavior of metal nanoparticles in the electron beam

Fabrication and structural observation of In, Pd and Mo nanoparticles deposited on Si(110) substrates were performed in an ultrahigh vacuum field emission transmission electron microscope. In situ and/or dynamic observation of In nanoparticles showed fluctuation of their structures. The smaller particles of size of 3-5 nm showed frequent fluctuation, while the nanoparticles of more than 10 nm in size showed relatively slower fluctuation. The bigger nanoparticles showed coalescence with a weaker beam. Pd nanoparticles of size of 3-5 nm showed structural fluctuation after 10-30 s of electron beam irradiation. Stronger beam irradiation resulted in the dissipation of the nanoparticles probably due to diffusion. Mo nanoparticles of size of 3-5 nm never showed structural fluctuation. Intensive electron beam irradiation resulted in the dissipation of the particles. The difference in structural fluctuation depending on the metal and the beam intensity, and the peculiar coalescence of In nanoparticles are discussed qualitatively.