DEPOSITION OF DIAMOND FILMS ON SAPPHIRE - STUDIES OF INTERFACIAL PROPERTIES AND PATTERNING TECHNIQUES

Polycrystalline diamond films were grown on single crystal sapphire su bstrates using hot filament chemical vapour deposition (CVD). Problems with poor adhesion, stress and film cracking became severe for deposi ted areas greater than about (100 mum)2. Scanning electron microscopy analysis showed the films to be failing both at the interface and in t he diamond layer itself. Transmission electron microscopy cross-sectio ns of the interface showed that the interface was clean and free from non-diamond carbon impurities. Spallation problems in the diamond film could be reduced by introducing a barrier layer of epitaxial silicon grown on the sapphire prior to the diamond CVD step. Patterned silicon -on-sapphire wafers were then used as substrates for CVD of diamond in order to define features of linewidth more than 10 mum in the diamond films. Two methods were used: selective nucleation and lift off.