Temperature‐Induced Atomic Reconstruction At Au/MgAl₂O₄ Interfaces

Abstract

e.g., Co/Al 2 O 3 or Co/SrTiO 3 ) [4] and the switching polarity (e.g., Pt/TiO 2 [5] ) for memory and other electronic applications. Despite a variety of excellent properties associated with metal-oxide interfaces, the microscopic nature of metal-oxide interfaces is still a matter of debate.The structural mismatch across nonreactive metal-oxide interfaces often results in the formation of steps, [7] misfit dislocations, [8] and periodic structural units [9] in the interface. For example, misfit dislocation networks are observed in the Nb/Al 2 O 3 interface [8] and the termination Ni layer is periodically buckled in the Ni/Al 2 O 3 interface. [9] Besides, atomic reconstruction of interfacial structure has been experimentally observed in a lattice-matched system of Au/ MgAl 2 O 4 . [10,11] The thermally stable interface consists of sparsely arranged gold atoms with a well-defined periodicity. Such interface reconstruction could be ascribed to phase-like behaviors, referring to structure transitioning as a function of temperature and composition, because Au/MgAl 2 O 4 interface displays distinctive atomic arrangement under particular thermodynamic conditions. Such phase-like characters have been intensively studied in the case of segregated grain boundaries in doped metals [12] and oxides [13] for their broad applications in comprehending microstructure evolution and materials properties.Here, we studied the structural characters of heat-treated Au-MgAl 2 O 4 interfaces. Gold nanoparticles supported on MgAl 2 O 4 single crystals were prepared by a thermal dewetting method. 10 nm thick gold films were deposited on (111) MgAl2O4 surfaces, heated to 600-1100 °C for 10-90 min with a heating rate of 10 °C min −1 , and then rapidly cooled to freeze their high-temperature states in 5 min or slowly cooled down to room temperatures within 5 h. During the heat treatment, continuous gold films break into gold nanoparticles (see details in the Supporting Information). These distributed gold nanoparticles [14] have a 〈111〉 fiber texture, i.e., {111} Au parallel to the substrate surfaces. X-ray diffraction analysis shows that the in-plane orientation of gold nanoparticles is random [11] for a thin film heated up to a temperature lower than 900 °C. When the thin film is heated up to >900 °C, the in-plane orientation of gold nanoparticles shows a preferred orientation [10] {111} Au ||{111} MgAl2O4 and 〈 〉 110 Au ||〈 〉 110 MgAl2O4 and its twins. In this work, we aim to understand interface structures associated with the formation of the in-plane orientation {111} Au ||{111} MgAl2O4 and 〈 〉 110 Au ||〈 〉 110 MgAl2O4 . We observed three different Au/MgAl 2 O 4 interfacesThe metal-oxide interaction, associated with intermingling delocalization of bonding electrons in metals and ionic bonds in oxides, may cause reconstruction of interface structure and accordingly affect physical properties of heterogeneous materials. This Communication reports reconstructions of (111) interface between gold and magnesium aluminate spinel according to ...

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