Thermal conductivity of diamond films deposited at low surface temperatures

Polycrystalline diamond films are deposited on p-type Si (100) and n-type SiC (6H) substrates at the low surface deposition temperatures of 370°C-530°C using a microwave plasma-enhanced chemical vapor deposition system in which the surface temperature during deposition is monitored and controlled. A very high growth rate up to 1.3 μm/h on SiC substrate at 530°C surface temperature is obtained. The room temperature in-plane thermal conductivity of the low-surface-temperature-deposited thin films is measured by a traveling wave method. The diamond films of grain sizes between 3 and 7 μm and deposited at 370°C showed a high thermal conductivity value of ∼6.5 W/cm-K, which is much higher than the single crystal SiC thermal conductivity value at room temperature. Diamond films deposited on Si and SiC single crystals at higher temperatures showed even higher thermal conductivities of 11-17 W/cm-K. The structure and microstructure of these films are characterized by x-ray diffraction, scanning electron microscopy, and Raman spectroscopy, and are related to measured thermal conductivities.