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.