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Title: Probing Heat Transport in Nanowires Using a Focused Electron Beam Heating Technique
Authors: LIU DAN
Keywords: nanoscale thermal transport, phonon transport, electron beam heating technique, nanowires, nanostructures, spatial resolution
Issue Date: 27-Mar-2014
Citation: LIU DAN (2014-03-27). Probing Heat Transport in Nanowires Using a Focused Electron Beam Heating Technique. ScholarBank@NUS Repository.
Abstract: The understanding of nanoscale thermal transport plays an important role in the thermal management of modern integrated circuits and in the development of thermoelectric materials. Numerous experimental and theoretical works have emerged during the past decade, deepening the understanding of how heat flows in nanostructures. However the tools available to the experimentalist to probe thermal transport at the nanoscale are still quite limited. In this thesis, a new thermal measurement technique that is capable of profiling nanowire thermal resistance with a spatial resolution of nanometers is developed. The technique uses a focused electron beam as a localized heat source to establish a temperature gradient along the nanowire. The heat fluxes from the two ends of the nanowire are measured using platinum resistance thermometers on two suspended thermally-isolated islands from which the local thermal conductivity can be derived. This electron beam heating technique was then used to study three material systems, namely helium-ion irradiated Si nanowires, Si1-xGex/NiSi1-xGex bamboo-structured nanowires and Si/NixSiy nanowire heterointerfaces. We show that by a single scan of the electron beam along the nanowire, the local thermal conductance altered by non-uniformities in the nanowire, such as local defects, change of surface roughness and variations in diameter, can be discriminated. Moreover, the long-standing problem of ill-defined thermal contact resistance between the nanowire and the two temperature sensors, which is a serious drawback in the conventional thermal bridge method, is avoided. This technique is also capable of measuring the thermal boundary resistance across epitaxial material `interfaces in the nanowire. This technique thus provides a powerful tool for studying the underlying physics of thermal transport in nanostructures, which will in turn improve the thermal models adopted in the design of nano-devices, and inform the fabrication of nanostructured thermoelectric materials with enhanced performance.
Appears in Collections:Ph.D Theses (Open)

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