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Yang, Ding-Shyue; Baum, Peter; Zewail, Ahmed H. (2016): Ultrafast electron crystallography of the cooperative reaction path in vanadium dioxide. In: Structural Dynamics, Vol. 3, No. 3, 034304


Time-resolved electron diffraction with atomic-scale spatial and temporal resolution was used to unravel the transformation pathway in the photoinduced structural phase transition of vanadium dioxide. Results from bulk crystals and single-crystalline thin-films reveal a common, stepwise mechanism: First, there is a femtosecond V-V bond dilation within 300 fs, second, an intracell adjustment in picoseconds and, third, a nanoscale shear motion within tens of picoseconds. Experiments at different ambient temperatures and pump laser fluences reveal a temperature-dependent excitation threshold required to trigger the transitional reaction path of the atomic motions. (C) 2016 Author(s).