Bias enhanced nucleation and growth of diamond films on titanium substrates

Diamond films have been deposited on titanium substrates by microwave plasma chemical vapour deposition using the bias enhanced nucleation procedure. In the first minutes of exposure to the plasma there is a strong roughening of the titanium surface and a reduction of the oxide layer. Interaction with the gas phase as well as dissolution of the oxygen in the bulk contribute to this reduction. After 30 min plasma treatment the oxygen concentration in the bulk is reduced down to 0.2-0.3% and an accelerated hydrogen dissolution, hydride formation and carburization follow. Analogously to silicon the nucleation density increases with biasing time accompanied by a rise in the biasing current. Surpassing an optimum duration of the biasing process deposition of graphitic carbon is enhanced. The nucleation layer determines the bonding at the interface even after a long diamond growth process resulting in a bad adhesion of the films for long biasing procedures.