Quantitative experimental studies of spontaneous rotations of bismuth nanoparticles

A phenomenon of spontaneous rotations of Bi nanoparticles is reported. Fourier transform (FT) analysis of the high resolution electron microscopy (HREM) images indicates that the rotations occur by plane after plane gliding rather than a collective movement of the entire particle as a rigid body. The phenomenon rate was studied quantitatively by time resolved transmission electron microscopy (TEM). The origin of the phenomenon as a radiation effect of the high voltage electron beam was excluded by finding the same rates at 200 kV and 1250 kV electron beams, below and above the threshold for the knock-on process. The dependence of phenomenon rate on the particles' size was found to be inversely proportional to the particle volume, with a threshold at particle radius of 5 nm. The temperature was found to activate both the probability for a particle to be in the rotating state, and the rotation rate.