title: 4D electron diffraction reveals correlated unidirectional behavior in zinc oxide nanowires.
abstract: The confined electronic structure of nanoscale materials has increasingly been shown to induce behavior quite distinct from that of bulk analogs. Direct atomic-scale visualization of nanowires of zinc oxide was achieved through their unique pancake-type diffraction by using four-dimensional (4D) ultrafast electron crystallography. After electronic excitation of this wide-gap photonic material, the wires were found to exhibit colossal expansions, two orders of magnitude higher than that expected at thermal equilibrium; the expansion is highly anisotropic, a quasi-one-dimensional behavior, and is facilitated by the induced antibonding character. By reducing the density of nanowires, the expansions reach even larger values and occur at shorter times, suggesting a decrease of the structural constraint in transient atomic motions. This unanticipated ultrafast carrier-driven expansion highlights the optoelectronic consequences of nanoscale morphologies.
authors.affiliation: Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Ding-Shyue
authors.initials: DS
authors.lastname: Yang
authors.forename: Changshi
authors.initials: C
authors.lastname: Lao
authors.forename: Ahmed H
authors.initials: AH
authors.lastname: Zewail
mesh_terms: D016880:Anisotropy; D003461:Crystallography; D004583:Electrons; D008855:Microscopy, Electron, Scanning; D053770:Nanowires / Q000648:ultrastructure*; D015034:Zinc Oxide
chemical_list: D015034:Zinc Oxide