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Title: Maximization of thermal conductance at interfaces via exponentially mass-graded interlayers

Here, we propose a strategy to potentially best enhance interfacial thermal transport through solid–solid interfaces by adding nano-engineered, exponentially mass-graded intermediate layers. This exponential design rule results in a greater enhancement than a linearly mass-graded interface. By combining calculations using non-equilibrium Green's functions (NEGF) and non-equilibrium molecular dynamics (NEMD), we investigated the role of impedance matching and anharmonicity in the enhancement in addition to geometric parameters such as the number of layers and the junction thickness. Our analysis shows that the effect on thermal conductance is dominated by the phonon thermalization through anharmonic effects, while elastic phonon transmission and impedance matching play a secondary role. In the harmonic limit, increasing the number of layers results in greater elastic phonon transmission at each individual boundary, countered by the decrease of available conducting channels. Consequently, conductance initially increases with number of layers due to improved bridging, but quickly saturates. The presence of slight anharmonic effects (at very low temperature, T = 2 K) turns the saturation into a monotonically increasing trend. Anharmonic effects can further facilitate interfacial thermal transport through the thermalization of phonons at moderate temperatures. At high temperature, however, the role of anharmonicity as a facilitator of interfacial thermal transportmore » reverses. Strong anharmonicity introduces significant intrinsic resistance, overruling the enhancement in thermal conduction at the boundaries. It follows that at a particular temperature, there exists a corresponding junction thickness at which thermal conductance is maximized.« less
Authors:
 [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ;  [1] ; ORCiD logo [1]
  1. Univ. of Virginia, Charlottesville, VA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. U.S. Naval Research Lab. (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; Graduate opportunity (GO!) program
Type:
Accepted Manuscript
Journal Name:
Nanoscale
Additional Journal Information:
Journal Name: Nanoscale; Journal ID: ISSN 2040-3364
Publisher:
Royal Society of Chemistry
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1502588
Alternate Identifier(s):
OSTI ID: 1501687

Rastgarkafshgarkolaei, Rouzbeh, Zhang, Jingjie, Polanco, Carlos A., Le, Nam Q., Ghosh, Avik W., and Norris, Pamela M.. Maximization of thermal conductance at interfaces via exponentially mass-graded interlayers. United States: N. p., Web. doi:10.1039/C8NR09188A.
Rastgarkafshgarkolaei, Rouzbeh, Zhang, Jingjie, Polanco, Carlos A., Le, Nam Q., Ghosh, Avik W., & Norris, Pamela M.. Maximization of thermal conductance at interfaces via exponentially mass-graded interlayers. United States. doi:10.1039/C8NR09188A.
Rastgarkafshgarkolaei, Rouzbeh, Zhang, Jingjie, Polanco, Carlos A., Le, Nam Q., Ghosh, Avik W., and Norris, Pamela M.. 2019. "Maximization of thermal conductance at interfaces via exponentially mass-graded interlayers". United States. doi:10.1039/C8NR09188A.
@article{osti_1502588,
title = {Maximization of thermal conductance at interfaces via exponentially mass-graded interlayers},
author = {Rastgarkafshgarkolaei, Rouzbeh and Zhang, Jingjie and Polanco, Carlos A. and Le, Nam Q. and Ghosh, Avik W. and Norris, Pamela M.},
abstractNote = {Here, we propose a strategy to potentially best enhance interfacial thermal transport through solid–solid interfaces by adding nano-engineered, exponentially mass-graded intermediate layers. This exponential design rule results in a greater enhancement than a linearly mass-graded interface. By combining calculations using non-equilibrium Green's functions (NEGF) and non-equilibrium molecular dynamics (NEMD), we investigated the role of impedance matching and anharmonicity in the enhancement in addition to geometric parameters such as the number of layers and the junction thickness. Our analysis shows that the effect on thermal conductance is dominated by the phonon thermalization through anharmonic effects, while elastic phonon transmission and impedance matching play a secondary role. In the harmonic limit, increasing the number of layers results in greater elastic phonon transmission at each individual boundary, countered by the decrease of available conducting channels. Consequently, conductance initially increases with number of layers due to improved bridging, but quickly saturates. The presence of slight anharmonic effects (at very low temperature, T = 2 K) turns the saturation into a monotonically increasing trend. Anharmonic effects can further facilitate interfacial thermal transport through the thermalization of phonons at moderate temperatures. At high temperature, however, the role of anharmonicity as a facilitator of interfacial thermal transport reverses. Strong anharmonicity introduces significant intrinsic resistance, overruling the enhancement in thermal conduction at the boundaries. It follows that at a particular temperature, there exists a corresponding junction thickness at which thermal conductance is maximized.},
doi = {10.1039/C8NR09188A},
journal = {Nanoscale},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {2}
}

Works referenced in this record:

Nanoscale thermal transport
journal, January 2003
  • Cahill, David G.; Ford, Wayne K.; Goodson, Kenneth E.
  • Journal of Applied Physics, Vol. 93, Issue 2, p. 793-818
  • DOI: 10.1063/1.1524305