Applications of thermophysical characterization using the 3-omega technique

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Kommandur, Sampath
Yee, Shannon
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The 3-omega technique is a commonly used electrothermal technique to characterize thermal conductivity. While most commonly used to characterize isotropic thin films on substrates, the high accuracy and versatility of the technique can be extended to a broader application space, which are explored in this dissertation. Using experiments on gas mixtures, a gas sensing technique is developed that can determine gas concentrations in binary mixtures based on their thermophysical properties. This is demonstrated using two sensor geometries with sensitivities comparable to other electrothermal techniques, but with a lower power consumption. Using temperature dependent thermal conductivity of polymers, an empirical model is proposed to aid in predicting temperature-dependent thermal conductivity of amorphous polymers. The model depends on only the density, monomer molecular weight, and speed of sound, and its predictions are validated using the 3-omega technique across a range of temperatures. As a parallel effort, two variants of 3-omega technique to characterize anisotropic thermal conductivity in polymer films and nanostructures, respectively, are developed. A suspended film configuration to measure anisotropic thermal conductivity of polymers, along with a simplified 1-D model for data analysis is developed. This is followed by measurements of semiconducting polymers, including n-type thermoelectric polymers. Finally, a suspended microbridge platform to measure temperature-dependent thermal conductivity in nanowires is explored using a modification of 3ω technique. Data analysis using the modified technique is performed using an equivalent thermal impedance circuit and is validated using measurements on axially modulated Silicon nanowires.
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