Remarkable enhancement of thermal conductivity induced by coordination transition in SiO2 thin films

The heat transfer in SiO2 is mainly dominated by phonons, but the void defects and boundary effects in the films cause strong scattering of phonons, resulting in a low thermal conductivity. Herein, we report the SiO2 thin films with prominently enhanced thermal conductivity after high-temperature annealing. Through combined experiments and non-equilibrium molecular dynamics simulation, we reveal the improvement of thermal conductivity that is originally attributed to coordination transition during the high-temperature annealing. Analysis indicates that a more ordered atom structure and denser grain boundaries could derive from the coordination transition, resulting in the crystallization of grains and defect mending. These behaviors induce a reduction of phonons scattering and increase in mean free path, which lead to nearly twofold enhance in the thermal conductivity to 2.66 Wm(-1) K-1.