Abstract
Multilayers composed of aluminum (Al) and platinum (Pt) exhibit a nonmonotonic trend in thermal resistance with bilayer thickness as measured by time domain thermoreflectance. The thermal resistance initially increases with reduced bilayer thickness only to reach a maximum and then decrease with further shrinking of the multilayer period. These observations are attributed to the evolving impact of an intermixed amorphous complexion approximately 10 nm in thickness, which forms at each boundary between Al- and Pt-rich layers. Scanning transmission electron microscopy combined with energy dispersive x-ray spectroscopy find that the elemental composition of the complexion varies based on bilayer periodicity as does the fraction of the multilayer composed of this interlayer. These variations in complexion mitigate boundary scattering within the multilayers as shown by electronic transport calculations employing density-functional theory and nonequilibrium Green's functions on amorphous structures obtained via finite temperature molecular dynamics. The lessening of boundary scattering reduces the total resistance to thermal transport leading to the observed nonmonotonic trend thereby highlighting the central role of complexion on thermal transport within reactive metal multilayers.
| Original language | English |
|---|---|
| Article number | 245422 |
| Journal | Physical Review B |
| Volume | 101 |
| Issue number | 24 |
| DOIs | |
| State | Published - Jun 15 2020 |
| Externally published | Yes |
Funding
The authors acknowledge the assistance of C. Sobczak and M. Rodriguez. A.S. and Z.D.M. acknowledge computational resources from Purdue University and nanoHUB. This work was performed under the Laboratory Directed Research and Development program at Sandia National Laboratories and undertaken, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the US DOE's National Nuclear Security Administration under Contract No. DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the US DOE or the United States Government.
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