Synthetic diamond films are promising for a broad variety of engineering applications incuding wear-resistance coatings, semiconductor passivation, and high-temperature electronics. Diamond enjoys the highest thermal conductivity of any standard crystalline material at room temperature, and many of the basic physical phenomena governing conduction in other dielectrics and semiconductors are amplified in this unique limiting material.
This work develops measurement techniques for the thermal conductivities along diamond films based on both electrical heating and thermometry and nanosecond laser reflectance. In addition, fundamental modeling using the Boltzmann transport equation for phonons and scanning electron microscopy data serves to predict the effective conductivities both along and normal to polycrystalline diamond films. A major focus of this work is the effective thermal resistance between diamond films and the deposition substrate, which can strongly impact the ability of this material to conduct heat in many applications. One example is the development of novel composite substrates containing diamond films, in which heat spreading in diamond can help alleviate the problem of hotspots both within transistors and near computational hotspots.