GROWTH METHODOLOGIES AND CHARACTERIZATION OF DIFFERENT POLYCRYSTALLINE DIAMOND FILMS ON TA SUBSTRATES

The results of research undertaken with the aim of setting up a procedure for coating tantalum plates with good quality diamond films are presented. The deposition was carried out using a hot filament chemical vapour deposition technique from mixtures of methane and hydrogen. The morphology of the deposits was characterized by scanning electron microscopy and replica transmission electron microscopy, while the structural properties were analysed by reflection high energy electron diffraction. The effects of modification of the substrate surface on both the nucleation density and growth rates of diamond crystallites were investigated. Deposition experiments were carried out using ''as received'' and variously treated Ta substrates. A suitable choice of experimental conditions allowed us to obtain fine grained and oriented polycrystalline diamond coatings. Good adhesion to the substrate can be achieved by employing a particular procedure at the end of the deposition process.