Time- and Species-Resolved Plasma Imaging as a New Diagnostic Approach for HiPIMS Discharge Characterization

We present a novel approach in fast imaging of high-power impulse magnetron sputtering (HiPIMS) discharges in which bandpass optical interference filters are used to isolate the optical emission signal originating from different species populating the plasma. In this paper, we describe the methodology of the proposed diagnostics and discuss its application. In particular, we demonstrate the use of this technique for the time-resolved analysis of HiPIMS discharges operated with a chromium cathode in argon at 4 Pa. Two optical filters were designed and fabricated: (i) one for neutral chromium emission lines (400-540 nm); and (ii) the other one for neutral working gas emission lines and bands (above 750 nm). The introduction of such filters is used to distinguish different phases of the discharge and to reveal numerous plasma effects including background gas excitations during the discharge ignition, gas shock waves, and expansion of metal-rich plasmas.