Heat flow and Kapitza resistance across a Si|SiO2 interface: A first principles study
Oxide layers are very common in semiconductor Si technology, but their impact on the flow of heat has only been calculated by three groups using empirical methods. The present study is the first fully ab-initio molecular-dynamics simulation of this problem at and below room temperature. The simulations involve no thermostat. The host material is a piece of hydrogen-saturated Si nanowire in a 1D-periodic box larger than the nanowire in all directions. This periodic cluster is isolated and strictly microcanonical (no heat flows between adjacent image nanowire). The oxide layer is constructed in a manner that mimics the exposure to an O2 gas. The oxide is shown to be a substantial barrier to heat flow, a fact that should be considered when designing device structures and cooling processes. A novel method to calculate the Kapitza resistance directly from the MD runs is developed. The results bridge the apparent disagreement between the Kapitza resistances calculated by other authors in two different temperature ranges.