Thermal conductivity of diamond films:: 0.5 μm to 0.5 μm

A review of the thermal properties of chemical-vapor-deposited (CVD) diamond ranging in thickness from 0.5 mu m to 0.5 mm is presented. The typical columnar microstructure of the material has a strong influence on the thermal properties, causing a steep gradient in both the in-plane (kappa(parallel to)) and normal (kappa(perpendicular to)) conductivities, as well as considerable anisotropy. Data for kappa(parallel to) 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. The general difficulty of identifying microscopic sources of thermal resistance in CVD diamond is discussed, especially in view of the tendency for the concentrations of many types of defects to be highly correlated with each other. Finally, recent work on interfacial resistance between CVD diamond and Si substrate shows that the columnar microstructure has a strong influence for high-quality films as thin as 2 mu m.