Cathode poisoning during reactive arc evaporation of titanium in nitrogen atmosphere

Titanium nitride thin films have been deposited by reactive arc evaporation of Ti in N 2 atmosphere. The evaporated cathode is 65 mm in diameter produced of Ti with 99.90% purity. The N 2 pressure, arc current and arc voltage have been maintained as constant during each evaporation in the ranges 2 × 10 −2 − 1 Pa, 90–160 A and 16–21 V respectively. The increase of N 2 pressure leads to a decrease of the deposition rate in two steps from the cathode poisoning, which was attributed to formation of Ti 2N and TiN on the cathode surface. A simple model of the poisoning process has been proposed. On the basis of this model the relationship between the degree of poisoning and the nitrogen pressure and the relationship at constant current between the arc voltage and the degree of poisoning have been obtained. The experimental results fit well to the theoretically obtained relations. The influence of the cathode poisoning on the droplet formation on the film surface has also been studied.