Thermal Transport at Interfaces: Electron-Phonon Coupling, Chemical Reactions, Diffusion Barriers, and Annealing

Material interfaces are the dominant thermal resistance in modern electronic devices, promoting overheating issues. Improving the ability to transport heat across these interfaces (i.e., thermal boundary conductance) is thus a reliable avenue for enhancing device performance. Including nanometric layers of adhesive metals at an interface can assist adhesion and vibrational bridging between materials, improving the thermal boundary conductance. The extent of thermal boundary conductance improvement is dependent on the thickness of the added metal interlayers. Determining the optimal interlayer thickness for improved thermal transport is thus a reliable avenue for enhancing device performance.

In this dissertation, I explore the physical origins for interlayer-thickness dependent thermal transport at interfaces. The influence of electron-phonon coupling, chemical reactions, diffusion barriers and annealing on the thermal boundary conductance of these interfaces is investigated using various experimental, simulation, and analytical techniques. To investigate the influence of electron-phonon coupling on thermal boundary conductance, two-temperature model molecular dynamics simulations were used to qualitatively recreate thermal transport at a metal/metal/dielectric junction. An underlying correlation was discovered between the thermal boundary conductance of the interface and the amount of electron-phonon coupling occurring in the metal interlayer. Using this correlation, an analytical model was developed to predict the thermal boundary conductance of non-reactive interfaces as a function of interlayer thickness. The model was validated against more than one hundred  experimental measurements from literature, with 92% of the data lying within ±10% of the model. The model provides guidance for streamlining the design of thermally-efficient electrical contacts.