THERMAL-PROPERTIES OF C H-GROWN, C/H/O-GROWN, C/H/N-GROWN AND C/H/X-GROWN POLYCRYSTALLINE CVD DIAMOND/

Over 60 CVD diamond films with thicknesses in the range 2-600 mu m, gr own from C/H, C/H/O, C/H/Cl and C/H/N gas mixtures by microwave plasma CVD, combustion flame synthesis and r.f. plasma torch CVD, were compa red in terms of their thermal, morphological, Raman and luminescence d ata. Correlation diagrams reveal that the content of sp(2)-hybridized carbon is the main factor determining the thermal properties of the fi lms. Other parameters, e.g. thickness, crystallinity and defects, only influence the thermal performance by changing the phase purity. The p resence of oxygen and nitrogen in the CVD gas phase restricts the ther mal conductivity of the films to values well. below the 2200 +/- 200 W m(-1) K-1 achieved for polycrystalline films, 250 mu m thick, grown f rom methane and hydrogen. Diamond films with thicknesses of less than 4 mu m and thermal conductivities of more than 700 W m(-1) K-1 were gr own from C/H and C/H/O mixtures.