THERMAL-CONDUCTIVITY IN MOLTEN-METAL-ETCHED DIAMOND FILMS

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