Spatial and temporal evolution of plasma potential in hipims discharge

Summary form only given. Time-resolved plasma potential measurements, in HIPIMS discharge with a titanium target and argon sputtering gas, have been carried out using emissive probe with time resolution of 20 ns. Measurements were performed parallel to discharge centre line, above the racetrack, normal to target, at a fixed frequency of 100 Hz, pulse width of 100 I????s, two operating pressures of 0.54 and 1.08 Pa and average power 660W. Peak current and current density were 440 Amps and 2.5 A/cm2. It was found that plasma potential V_p follows the cathode voltage pulse with additional humps during the on phase of discharge pulse. At the beginning of reverse phase V_p showed a overshoot of few voltage depending on the power and pressure and then settled at 4 V. In the on phase of the pulse, a significant electric field with plasma potential dropping from - 220V to - 46 V, has been observed over the distance of 30 cm from the cathode. Plasma potential changed from -18 to -14 V over the distance from 50 mm to 100mm resulting weak electric field in this region. During the reverse phase of the discharge, plasma potential is almost constant at 4 V along the axial distance. The spatial and temporal measurements of plasma potential presented in this work show a picture of evolution of plasma potential in HIPIMS discharge. This paper also describes the development of emissive probe for very high temporal resolution in HIPIMS discharge.