In situ high-resolution transmission electron microscopy was used to study grain boundary structure and kinetics in bicrystalline films at high temperatures. The first direct evidence for the existence of cooperative atomic motion in grain boundary migration was reported. Certain nano-regions of grain boundaries, which typically involved up to several hundred atoms, were found to switch back and forth between neighboring grains. Reversible structural fluctuations, at homologous temperatures near to 0.5 and above, were discovered in [110] and [001] tilt, as well as in general grain boundaries.

Collective Effects in Grain Boundary Migration. K.L.Merkle, L.J.Thompson, F.Phillipp: Physical Review Letters, 2002, 88[22], 225501 (4pp)