CHEMICALLY VAPOR-DEPOSITED DIAMOND FILMS GROWN ON TITANIUM NITRIDE COATED AND UNCOATED IRON SUBSTRATES

The nature of the interfaces of chemically vapor deposited diamond films on Fe substrates with and without a protective TiN coating is investigated. For unprotected Fe substrates a thick graphitic soot containing 6.5% Fe grows upon the Fe in the first few minutes of exposure to the plasma and, once this soot completely covers the substrate, diamond can nucleate and grow upon it into an average quality unfaceted continuous diamond film. However, adhesion is poor, the weak link being the lack of structural integrity of the soot layer itself. A TiN coating is found to prevent soot formation, C diffusion into the Fe bulk, and Fe diffusion into the diamond films. In the initial stages of growth the TiN is covered with a thin layer of amorphous carbon (a-C), and it is on this layer that diamond nucleates and grows. Here, again, adhesion is not strong, with delamination occurring at the TiN/a-C interface.