| Recent years have witnessed the emergence of the field of microscale heat transfer. The origin of this field lies in understanding the energy interaction in miniaturized systems. Microstructures with extremely small spatial dimensions are routinely fabricated using moderndeposition and patterning techniques, and serve as the basis for integrated electronic circuits, photovoltaic cells, infrared detectors, sensors, actuators and laser diodes. As the characteristic device size decreases, however, the material no longer behaves as a bulk material. Investigations reported in the heat transfer literature over the past decade have focused on the reduction in the thermal conductivity of very small structures, such as thin films used in electronic devices. However, very little work has been done on the size effect on other thermophysical properties at small dimensions, such as internal energy and heat capacity.; This thesis addresses itself to the calculation of the size effects on the thermodynamic properties of thin films and microstructures. A nondimensional parameter is introduced in this thesis, which captures all the essence of the size effects on the thermodynamic properties. The onset of the microscopic regime for different microstructures is also defined. The Debye temperature remains independent of the size effects.; Solid-solid thermal boundary resistance plays an important role in determining heat flow, both in cryogenic and room temperature applications, such as very large scale integrated circuitry, superlattices, and superconducting applications. The acoustic mismatch model (AMM) describes the thermal transport at a solid-solid interface below a few Kelvin quite accurately. Another model, known as the diffuse mismatch model (DMM), theoretically more suitable for interfacial transport above a few Kelvin, is no better than AMM for predicting the thermal boundary resistance at a solid-solid interface. One of the primary reasons that both these models fail to predict thermal boundary resistance at high temperatures is that both of them neglect the scattering near the interface. At moderate cryogenic temperatures and above, thermal boundary resistance is primarily dominated by near-interfacial scattering caused by various sources, such as damage in the dielectric substrates and formation of an imperfect boundary layer near the interface. A new model called the scattering-mediated acoustic mismatch model (SMAMM) is developed in this thesis, which accurately describes the behavior of thermal boundary resistance at high temperatures and reduces to the AMM at low temperatures, where the AMM is very successful in predicting thermal boundary resistance. |
