Research Papers: Micro/Nanoscale Heat Transfer

Influence of Prestress Fields on the Phonon Thermal Conductivity of GaN Nanostructures

[+] Author and Article Information
Linli Zhu

Department of Engineering Mechanics,
School of Aeronautics and Astronautics,
Zhejiang University,
Hangzhou 310027,
Zhejiang, China
e-mail: llzhu@zju.edu.cn

Haihui Ruan

Department of Mechanical Engineering,
The Hong Kong Polytechnic University,
Kowloon, Hong Kong, China
e-mail: haihui.ruan@polyu.edu.hk

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received February 4, 2014; final manuscript received July 6, 2014; published online August 5, 2014. Assoc. Editor: Robert D. Tzou.

J. Heat Transfer 136(10), 102402 (Aug 05, 2014) (7 pages) Paper No: HT-14-1060; doi: 10.1115/1.4028023 History: Received February 04, 2014; Revised July 06, 2014

The phonon thermal conductivity of Gallium nitride (GaN) nanofilms and nanowires under prestress fields are investigated theoretically. In the framework of elasticity theory, the phonon dispersion relations of spatially confined GaN nanostructures are achieved for different phonon modes. The acoustoelastic effects stemmed from the preexisting stresses are taken into account in simulating the phonon properties and thermal conductivity. Our theoretical results show that the prestress fields can alter the phonon properties such as the phonon dispersion relation and phonon group velocity dramatically, leading to the change of thermal conductivity in GaN nanostructures. The phonon thermal conductivity is able to be enhanced or reduced through controlling the directions of prestress fields operated on the GaN nanofilms and nanowires. In addition, the temperature and size-dependence of thermal conductivity of GaN nanostructures will be sensitive to the direction and strength of those prestress fields. This work will be helpful in controlling the phonon thermal conductivity based on the strain/stress engineering in GaN nanostructures-based electronic devices and systems.

Copyright © 2014 by ASME
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Fig. 1

Schematic drawings of a stressed GaN nanofilm (a) and a stressed rectangular GaN nanowire with the prestress σ0 in x1 and x2 directions

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Fig. 2

Phonon energy of SH modes (a) and phonon group velocity (b) as the function of the wave vector with the positive and negative stresses; and the phonon density of states as a function of phonon energy with different stress fields (c)

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Fig. 3

Phonon scattering rates of GaN bulk and nanofilm as functions of the phonon frequency for different scattering mechanisms. The prestress is 20 GPa in the stressed nanofilm.

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Fig. 4

The phonon thermal conductivity of confined GaN nanofilms varied with the prestress from −20 GPa to 20 GPa for different geometrical size of the films (a), and the geometrical size of the nanofilms for different prestresses (b)

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Fig. 5

Acoustic phonon dispersion relation of thickness mode for GaN nanowire with various prestress fields. The size of nanowire is 3.19 nm × 6.38 nm. Suppose that the nanowire is subjected to the prestresses of ±20 GPa.

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Fig. 6

The phonon thermal conductivity of confined GaN nanowires varied with the prestress from −20 GPa to 20 GPa with different temperatures (a), and the geometrical size of the wires with different prestresses (b)

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Fig. 7

Comparisons between the predicted phonon thermal conductivity and the ones from MD simulations [33] for free standing GaN nanowires (a) and stressed/strained GaN nanowires (b)




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