Measurement of the Parameters of Atmospheric-Pressure Barrier-Torch Discharge

Summary: The atmospheric plasma jet system was investigated for deposition of oxide layers on polymer (kapton) substrates. The plasma in the system was excited by an RF power source working in pulse modulated mode. This modulation allowed exciting high density plasma in the active part of the duty cycle and simultaneously keeping the neutral gas in the plasma jets at the substrate sufficiently cold, thus protecting the kapton substrate from thermal damage. The atmospheric plasma jet system was tested in two configurations: as single jet system and as linear multi-jet system with four equivalent jets. The plasma in the system was investigated by means of impedance measurements. A calibrated capacitive voltage probe and a Rogowski current coil were used for direct measurement of voltage and current RF waveforms, respectively. From these data the power deposited in the discharge and the plasma column impedance were estimated. The real part of plasma impedance was used for electron concentration n_e estimation. It was found that the electron concentration in the plasma jet was about 2 × 10¹³ cm⁻³. The atmospheric plasma jet source was used for low temperature deposition of conductive oxide (ZnO) thin films on kapton, silicon and quartz glass substrates. As growth precursors for ZnO films, Zn-acetylacetonate vapors were used. Deposited ZnO films on both kapton and quartz glass contained hexagonal crystalline phase. They were optically transparent and had an electrical conductivity σ ≈ 10⁻¹–10⁰ S · cm⁻¹.