  Ru nanoparticles (NPs) can precipitate in Ru doped SiO2 amorphous thin films,
triggered by electron irradiation in (scanning) transmission electron
microscope ((S)TEM). A new mechanism was introduced to interpret the formation
of metal NPs in (S)TEM. The induced electric field by electron irradiation,
which originates from charging due to ionizations and excitations of atom
electrons, can reduce the Gibbs free energy barrier for nucleation of metal
particles. Furthermore, the directional ion drifting driven by the electric
forces may accelerate the kinetic process of metal particle precipitation.
