Thermal conduction in nanocrystalline diamond films: Effects of the grain boundary scattering and nitrogen doping

The authors investigated thermal conductivity (K) in nanocrystalline diamond (NCD) films on silicon using the 3ω and laser flash techniques. The K temperature dependence has been studied for the undoped and nitrogen-doped NCD films for T=80–400K and compared with that in microcrystalline diamond (MCD) films. The effects of phonon scattering from the grain boundaries and film interfaces on thermal conduction have been studied using three different models. For NCD the room temperature K is 0.1–0.16W∕cmK and decreases with nitrogen doping. The K temperature dependence in NCD is different from that in MCD films and can be adequately described by the phonon-hopping model.