Thermal Conductivity—Films

The typical columnar microstructure of chemical-vapor-deposited (CVD) diamond has a strong influence on the thermal properties, causing a steep gradient in both the in-plane (κ || ) and normal (κ ⊥ ) conductivities as well as considerable anisotropy. Data for κ || from above room temperature down to liquid helium temperatures for high-quality thick samples has revealed several types of phonon scattering centers preferentially located along grain boundaries. This model of dirty grain boundaries provides a framework for understanding the conductivity of thinner, lower-quality material. Recent work on the interfacial resistance between thin-film CVD diamond and the Si substrate shows that the columnar microstructure can have a strong influence for high-quality films as thin as 2 μm.