Abstract
Important properties of materials are strongly influenced or controlled by the presence of solid interfaces, i.e. from the atomic arrangement in a region which is a few atomic spacing wide. Using the quantitative analysis of atom column positions enabled by CS-corrected transmission electron microscopy and theoretical calculations, atom behaviors at and adjacent to the interface was carefully explored. A regular variation of Cu interplanar spacing at a representative metal-ceramic interface was experimentally revealed, i.e. Cu-MgO (001). We also found the periodic fluctuations of the Cu and Mg atomic positions triggered by the interfacial geometrical misfit dislocations, which are partially verified by theoretical calculations using empirical potential approach. Direct measurements of the bond length of Cu-O at the coherent regions of the interface showed close correspondence with theoretical results. By successively imaging of geometrical misfit dislocations at different crystallographic directions, the strain fields around the interfacial geometrical misfit dislocation are quantitatively demonstrated at a nearly three-dimensional view. A quantitative evaluation between the measured and calculated strain fields using simplified model around the geometrical misfit dislocation is shown.
Highlights
This largely prompts a new view on interface controlled materials, such as metal-ceramic composites and their interface structures
To discriminate between subtle differences in the interfacial structure it would be beneficial to observe the interfaces edge-on along two different directions at the atomic scale, which is hardly possible in normal transmission electron microscopy (TEM)
For epitaxial Cu films grown on (001) MgO substrate, the dislocation network was found to lie along 〈100〉 directions with a Burgers vector of 1⁄2aCu 〈100〉 deduced from HRTEM images in an earlier study15, which is in agreement with other report4
Summary
Massive investigations of dislocation core structure of interfacial misfit dislocations have been performed using high–resolution transmission electron microscopy (HRTEM), the accurate and quantitative description on the local atomic structure is so far less advanced due to the limitations of lens aberration of the microscopes This is especially true for semi-coherent interfaces, i.e. metal-oxide interfaces. The intrinsic physics of materials is possible to be directly read out of the HRTEM images12,13 This largely prompts a new view on interface controlled materials, such as metal-ceramic composites and their interface structures. In this work, combining quantitative atom position measurements with theoretical calculations, and successively imaging of the same interface position along two different crystallographic orientations, we present a picometer-scale understanding of atom behaviors at and adjacent to the Cu-MgO interface
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