Nanoscale Thermal Management and Advanced Thermal Characterization

Overview

nanomaterials and nano devices exhibit exceptional thermal properties at the nanoscale. Heat which can be viewed as destructive in electronics, it can be an enrich source of energy. We study the thermal properties and thermoelectric behavior of emerging materials at the nanoscale and the characterize their properties

Thermal Effects and Phonon Dynamics of Laser Heated Nanomaterials

Laser heating and laser irradiation can be a promising method to obtain selective number of layers in a specific location, giving us an extra degree of freedom to engineer different structures with different number of layers at the atomic level. However, this method exhibit high thermal energy due to the relatively high laser power density. This high thermal energy can affect the structure and the morphology of the nanomaterial which affects the phonon behavior of the material.

In this work, we examine the effect of thermal energy on different nanomaterials and test the optical properties along with lattice structure. For example, in the case of MoS2, single layer MoS2 phonons exhibit different behavior than multilayer MoS2. This non-equilibrium effect is found to be caused by the formation of anomalous particles in the laser irradiated region, where these amorphous particles opens a phonon decay path for cross plane phonon mode, causing a "cooling" effect.

Advanced Raman Thermometry and Phonon Transport

Raman microscopy is an important technique to characterize the thermal properties of nanomaterials. At the nanoscale, phonons can exhibit different behavior and sometimes cause non-equilibrium thermal effects, which prompts the investigation of phonon transport and phonon dynamics at the nanoscale. In this work, we study the thermal properties such as thermal conductivity, thermal boundary conductance, etc. of emerging materials using advanced Raman spectroscopy. We also investigate the phonon transport of these materials when thermally excited either optically or by joule heating. Our work shed light on the fundamental properties of thermal materials at the nanoscale for energy conservation and energy harvesting.

Low Dimensional Thermoelectric Generator

Another source of energy that solar power provide is heat. Some geographic areas exhibit high temperatures, especially during the summer. This wasted heat can be a good source of energy if invested wisely. Thermoelectric devices are one way to use this wasted heat. The seebeck phenomenon, which is the sole mechanism of thermoelectric devices, arises when the surface of a material is thermally excited. This leads to a temperature gradient across the material. During the process, carriers tend to move from the hot side to the cold side. For a n-type (p-type) material, electrons (holes) will move from the top to the bottom, creating an electric current. For a thermoelectric generator to work, three main features are required, a heat source, a heat sink, and a thermoelectric material. In this work, we investigate the thermoelectric properties of low dimensional materials and test the thermoelectric generator efficiency based on these low dimensional materials. These thermoelectric generators will be a promising route for clean energy generation and harvesting.

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