Molecular Origin of Valence Band Anisotropy in Single 尾-Ga2O3 Nanowires Investigated by Polarized X-ray Absorption Imaging

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• 作者：Manu Hegde ; Ian D. Hosein ; Pavle V. Radovanovic
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：July 30, 2015
• 年：2015
• 卷：119
• 期：30
• 页码：17450-17457
• 全文大小：494K
• ISSN：1932-7455

文摘

The origin of anisotropy at the molecular and electronic structure levels in individual 尾-Ga₂O₃ nanowires grown along the crystallographic b direction was studied using linearly polarized X-ray absorption imaging at both gallium L₃ and oxygen K edges. The O K-edge spectrum shows significant linear dichroism for the electric field vector of the X-rays oriented parallel and perpendicular to the nanowire long axis. The contributions from the three nonequivalent oxygen sites to the observed spectral anisotropy were elucidated by using FDMNES calculations in the framework of the multiple scattering theory. The role of relevant O and Ga orbitals in the linearly polarized O K-edge absorption was determined based on the point group symmetry arguments. The results of this work suggest mixed covalent and ionic character of the Ga鈥揙 bond in individual nanowires, with the dominant contribution of O 2p_z orbitals to the absorption spectrum for the electric field vector oriented perpendicular, and O 2p_x,y orbitals for the electric field vector oriented parallel to the nanowire long axis. Gallium 4p and d orbitals were found to contribute mostly to the antibonding states. These results improve the understanding of the origin of anisotropy in complex transparent metal oxide nanostructures, and could lead to the prediction of physical properties for different nanowire growth directions.