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Electrical and optical characterization of a pulsed discharge in an inverted cylindrical magnetron

An inverted cylindrical magnetron operating in pulsed mode was developed, with a rotating unbalanced system of magnets. The magnetic field was calculated using the finite integration technique in order to determine the optimal anode-to-cathode distance inside the reactor. A cylindrical titanium target was used for our experiments. The average power input was varied between 500 and 1300 W leading to low power densities varying between 0.9 and 2.4 W cm−2. The frequency was fixed at a low value of 250 Hz, suitable for depositing Ti and TiO2 at low temperatures on polymer substrates. Long on-time pulses (400 µs) were used in order to reach interesting deposition rates (>1 µm h−1). A transition from metallic to oxide mode was observed for all power inputs. Time-resolved optical emission spectroscopy was used for the investigation of plasma dynamics during the on-time pulse in both metallic and reactive regimes. Three phases of discharge evolution were identified in the metallic mode: the Ar-dominated phase, followed by a transition zone and a Ti-dominated phase. The emission of Ti species completely disappeared in the reactive mode, associated with the fact that titanium atoms left the target surface as TiOx molecular fragments. In conclusion, the deposition system and conditions used resulted in a new mode of TiO2 deposition.