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September 2020

The sample is a phase-separated Copper-Tungsten nanocomposite prepared via physical vapor co-deposition. As opposed to well-studied multilayers where the elements are deposited sequentially, we explored nanocomposites where elements are deposited simultaneously. Along with a unique hill-shaped morphology, we observed novel crystallographic character in these nanocomposites. This novel persistent crystallographic orientations in successive Cu-W nanolayers gives rise to the formation of regions which we term as “supergrains”.

We used the NanoMegas ASTAR® system in conjunction with FEI Tecnai G2 F20 TEM to perform precession electron diffraction (PED). The minimization of dynamical effects in PED improves the orientation mapping capabilities.

The Virtual bright-field map is acquired by mapping direct beam intensity. This highlights the phase-separated Copper (Cu)-Tungsten (W) nanolayered morphology. The mass thickness contrast results in Cu appearing bright and W appearing dark.

The Crystal structure map is acquired by analyzing the diffraction patterns at each pixel. The face-centered cubic Cu and body-centered cubic W appear in good agreement with the virtual bright-field image.

The Index map is acquired by analyzing the diffraction patterns at each pixel. The low angle grain boundaries in a each W nanolayer marked by white boxes.

The Orientation map (out-of-plane): highlights the novel persistence of crystallographic orientations in successive W and Cu nanolayers is highlighted white dashed lines. We term these regions as “super grains”.

Image taken on FEI Tecnai G2 F20 TEM-Materials. Image courtesy of Digvijay R. Yadav (Dr. Kelvin Xie, Materials Science & Engineering) and sample courtesy of Dr. Kelvin Xie (MSEN) and Dr. Michael Demkowicz (MSEN).