Thermal conductivity in molten-metal-etched diamond films

Abstract

Substantial thinning of chemical vapor deposited diamond films has been accomplished by a diffusional transfer of carbon atoms from diamond to molten rare-earth metals. Cerium and lanthanum are particularly useful because of their large liquid solubility of carbon. The perpendicular thermal conductivity of the processed diamond film (after removal of about 40 μm from the bottom surface) is remarkably improved from ∼14–15 to about 20–22 W/cm °C, a value approaching that of high-quality Type IIa single crystal diamond. The in-plane conductivity, on the other hand, is improved only slightly because of the anisotropic microstructure. The improvement in conductivity implies that few phonon scattering centers are introduced by the thinning process, for example, through grain boundary contamination by metal atoms.