AVS 66th International Symposium & Exhibition
    Nanometer-scale Science and Technology Division Friday Sessions
       Session NS+AS-FrM

Paper NS+AS-FrM9
Atomic-Scale Mechanism of Unidirectional Oxide Growth

Friday, October 25, 2019, 11:00 am, Room A222

Session: Electron-Beam Promoted Nanoscience
Presenter: Xianhu Sun, SUNY Binghamton University
Authors: X. Sun, SUNY Binghamton University
W. Zhu, SUNY Binghamton University
D. Wu, SUNY Binghamton University
Z. Liu, University of Pittsburgh
X. Chen, SUNY Binghamton University
L. Yuan, SUNY Binghamton University
G. Wang, University of Pittsburgh
R. Sharma, National Institute of Standards and Technology (NIST)
G. Zhou, SUNY Binghamton University
Correspondent: Click to Email
A fundamental knowledge of the unidirectional growth mechanisms is required for precise control on size, shape, and thereby functionalities of nanostructures. Using transmission electron microscopy that spatially and temporally resolves CuO nanowire growth during the oxidation of copper, here we provide direct evidence of the correlation between unidirectional crystal growth and bicrystal boundary diffusion. Based on atomic scale observations of the upward growth at the nanowire tip and oscillatory downward growth of atomic layers on the nanowire sidewall, we clearly show that bicrystal boundary diffusion is the mechanism by which Cu atoms are delivered from the nanowire root to the tip. Together with density-functional theory calculations, we further show that the asymmetry in the corner-crossing barriers promotes the unidirectional oxide growth by hindering the transport of Cu atoms from the nanowire tip to the sidewall facets. We expect broader applicability of our results in manipulating the growth of nanostructured oxides by controlling the bicrystal boundary structure that favors anisotropic diffusion for unidirectional, one-dimensional crystal growth for nanowires or isotropic diffusion for two-dimensional platelet growth.