Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/132111
Title: ANISOTROPIC PHONON TRANSPORT IN MATERIALS WITH LAYERED STRUCTURES AND THREADING DISLOCATIONS
Authors: SUN BO
Keywords: heat conduction, phonon transport, 2D materials, Anisotropy, Dislocations, thermal conductivity
Issue Date: 3-Aug-2016
Source: SUN BO (2016-08-03). ANISOTROPIC PHONON TRANSPORT IN MATERIALS WITH LAYERED STRUCTURES AND THREADING DISLOCATIONS. ScholarBank@NUS Repository.
Abstract: In semiconductors, phonons are the dominate heat carriers. The transport property of phonons is of great interest since it represents the ability of heat conduction, which would be crucial for applications such as semiconductor devices. Except for bulk isotropic materials, phonons are commonly transported anisotropically, especially in nanostructured materials. Understanding such anisotropic phonon transport is the key for nanoscale heat transfer. However, our knowledge of anisotropic phonon transport is still limited due to technical challenge as phonons are collective excitations and thus much harder to manipulate than other heat carriers such as electrons. In this thesis, I explored the anisotropic phonon transport in materials with layered structures and threading dislocations using a newly developed beam-offset time-domain thermoreflectance (TDTR) technique which enables the measurement of three-dimensional thermal conductivity. For materials with layered structure, I use black phosphorus as the example. At room temperature, I get a thermal conductivity ratio of ~13:4.3:1 for zigzag, armchair and through-plane directions. I find that the anisotropy in the thermal conductivity tensor is due to anisotropy in phonon dispersion, as well as phonon relaxation times. For materials with threading dislocations, theories predict that scattering of phonons by threading dislocations is anisotropic; phonons are unscattered along the dislocations but strongly scattered in the direction perpendicular to the dislocations. The theoretical predictions are still yet to be demonstrated experimentally. Here I present the first experimental evidence of the anisotropic scattering of phonons by threading dislocations. My result is particular valuable for understanding heat transport in materials with high density threading dislocations such as GaN, InN, GaAs, which are all important materials in semiconductor industry.
URI: http://scholarbank.nus.edu.sg/handle/10635/132111
Appears in Collections:Ph.D Theses (Open)

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