High-current Magnetron Discharge Research Articles

On the role of helium metastable (23S1) measured by time resolved tunable diode laser spectroscopy in high current magnetron discharge

Tunable diode laser absorption spectroscopy is applied to measure the density and gas temperature of helium metastable (23S1) in the ionization region of magnetron discharge operated at very high current density (), which is achievable in helium at 10 Pa with molybdenum target. Those measurements were combined to electrical characterization of the current and the voltage at the magnetron cathode. The discharge current waveform is anti-correlated with the time-evolution of helium metastable () density showing that the main depletion process of is its ionization. Counterintuitively, the higher the gas temperature the lower the discharge peak current. Gas rarefaction and gas recycling are discussed as major contributors for this phenomenon in very high current glow discharge.

Formation of low-frequency periodic structures in a pulsed magnetron discharge

Periodic plasma structures are observed in non-sputtering magnetron discharge (NSMD) that is the transient quasi-stationary low-voltage regime between the high-current magnetron discharge (HCIMD) and an arc. The fast camera imaging synchronized with the magnetic probe diagnostics reveals the correlation between the observed rotation of the plasma inhomogeneities and the magnetic field perturbation behaviour. The frequencies of the periodic processes fall into kHz-range. A simple analytical model of the ionization instability in crossed electric and magnetic fields is suggested for the low-pressure discharge case. Using the model, the possible ranges of wavelengths and frequencies for the plasma inhomogeneities are evaluated. The results show good agreement between the experimental data and theory.

Controlled glow to arc transition in sputtering for high rate deposition of carbon films

We achieve control over the transition from a magnetically confined (magnetron) glow discharge to an arc discharge operating on a carbon cathode by applying constant voltage square wave pulses. A power supply with rapid turn off at a chosen current set point is used to produce a mode with a high current magnetron discharge and no arc (the high power impulse magnetron sputtering or HIPIMS mode) or a high current magnetron discharge that includes a short lived cathodic arc with very high but controlled current density (mixed HIPIMS arc mode). The deposition rate in the mixed HIPIMS arc mode at a duty factor of less than 1% was found to be greater than for conventional r.f. sputtering. We have studied the properties of carbon films deposited using both modes. In the mixed mode, the films contain graphitic nanoclusters with a number density and a morphology that depends on the bias applied to the substrate. The nanoclusters in the films prepared with bias have a flattened shape with graphitic layers approximately parallel to the surface, consistent with energetic impact of a spherical cluster of graphitic material. The matrix of the films has a sp 3 content of approximately 50%, significantly greater than that for a conventionally sputtered film, but with a much higher instantaneous deposition rate. For negative substrate bias values of greater than 80 V, the surface is smooth enough to make films of interest as wear resistant coatings.