The interfacial complexions, with distinct structures, are considered as quasi-two-dimensional phases, which undergo the structural and chemical changes associated with thermodynamic parameters [1-2]. We recently discovered the formation of gold-spinel interfacial complexions, with well-defined atomic structures, and the related growth of nominally stable spinel lattice underneath the gold nanoparticles after annealing [3-5]. As shown in Figure 1, the necking structure, which is tens of nanometers high, is detected under dewetted gold nanoparticles. Such necking structure has the same contrast with spinel substrate, maintains the spinel composition confirmed by the energy dispersive X-ray spectroscopy, and keeps an ideal epitaxial relationship with the substrate. In associated with the substrate growth, an interfacial bilayer with distinct crystalline structure forms between gold nanoparticles and the substrate. Further studies reveal that the formation and migration of the interfacial complexions are related to the defects at the interfaces, such as, the intersections of gold twinned planes and the interface (see details in Figure 2). In spite of their importance in synthesizing nanostructures, the atomic structures of interfacial complexions have not been fully elucidated yet.
Herein, in this paper, we investigated the detailed atomic models of such interfacial complexions in combination of atomic-resolution experimental images and first-principle computations. Experimentally, we synthesized a series of Au-MgAl2O4 samples within different annealing profiles and proposed the initial atomic models based on atomic-resolution scanning transmission electron microscopy (STEM) – high-angle annular dark-field (HAADF) images in Figure 3. Experimental images with two orthogonal crystallographic directions were selected to provide the three-dimensional structural information. A few possible atomic models, with different oxygen vacancies, were built through our MATLAB codes, and inputted into the density functional theory (DFT) computation. The relaxed atomic models, carried out with generalized gradient approximation (GGA) and Perdew-Burker-Ernzerhof (PBE) exchange-correlation density functional , were applied to simulate the HAADF images  in order to further verify the validity of the structures. Our results provide a new clue to the field of interfacial complexions, particularly to the structural origins of the abnormal phenomenon of self-assembled growth of oxide substrates underneath dewetted gold nanoparticles.
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We acknowledge the financial support from the National Science Foundation of China (No. 51401124).
To cite this abstract:Fang Liu, Dong Yue Xie, Yong-sheng Fu, Guo-zhen Zhu; Atomic structures of interfacial complexions between gold nanoparticles and nominally stable spinel-substrate. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/atomic-structures-of-interfacial-complexions-between-gold-nanoparticles-and-nominally-stable-spinel-substrate/. Accessed: December 4, 2023
EMC Abstracts - https://emc-proceedings.com/abstract/atomic-structures-of-interfacial-complexions-between-gold-nanoparticles-and-nominally-stable-spinel-substrate/