Two-dimensional spatially resolved absolute atomic oxygen densities are measured within an atmospheric pressure micro plasma jet and in its effluent. The plasma is operated in helium with an admixture of 0.5% of oxygen at 13.56 MHz and with a power of 1 W. Absolute atomic oxygen densities are obtained using two photon absorption laser induced fluorescence spectroscopy. The results are interpreted based on measurements of the electron dynamics by phase resolved optical emission spectroscopy in combination with a simple model that balances the production of atomic oxygen with its losses due to chemical reactions and diffusion. Within the discharge, the atomic oxygen density builds up with a rise time of 600 µs along the gas flow and reaches a plateau of 8 × 1015 cm−3. In the effluent, the density decays exponentially with a decay time of 180 µs (corresponding to a decay length of 3 mm at a gas flow of 1.0 slm). It is found that both, the species formation behavior and the maximum distance between the jet nozzle and substrates for possible oxygen treatments of surfaces can be controlled by adjusting the gas flow.

In this work, the deposition of SiOx films from O2/hexamethyldisiloxan (HMDSO) or Ar/HMDSO mixtures in an inductively coupled plasma is investigated. Substrate temperature and electron density are measured during the deposition process. Furthermore, the deposited layers are analyzed with a profilometer (thickness), infrared absorption spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS). Processes with continuous and pulsed HMDSO flows are compared to characterize the effect of surface treatment of a grown layer. Pure O2 or Ar plasmas between the HMDSO gas flow pulses can offer a “post‐oxidation” or “post‐treatment” of the grown films. The discharge dynamics during the different phases are also investigated by time‐resolved electron density measurements. This approach has led to formation of carbon and Si‐OH group free SiOx films even without addition of O2 gas under atmospheric pressure conditions.

The effects of structured electrode topologies on He/O2 radio frequency (RF) micro-atmospheric pressure plasma jets (μAPPJs) driven at 13.56 MHz are investigated by a combination of 2D fluid simulations and experiments. Good qualitative agreement is found between the computational and experimental results for the 2D spatio-temporally resolved dynamics of energetic electrons measured by Phase Resolved Optical Emission Spectroscopy (PROES), 2D spatially resolved helium metastable densities measured by Tunable Diode Laser Absorption Spectroscopy (TDLAS) and 2D spatially resolved atomic oxygen densities measured by Two Photon Absorption Laser Induced Fluorescence (TALIF). The presence of rectangular trenches of specific dimensions inside the electrodes is found to cause a local increase of the electron power absorption inside and above/below these surface structures. This method of controlling the Electron Energy Distribution Function (EEDF) via tailored surface topologies leads to a local increase of the metastable and atomic oxygen densities. A linear combination of trenches along the direction of the gas flow is found to result in an increase of the atomic oxygen density in the effluent, depending linearly on the number of trenches. These findings are explained by an enhanced Ohmic electric field inside each trench, originating from (i) the low electron density, and, consequently, the low plasma conductivity inside the trenches, and (ii) the presence of a current focusing effect as a result of the electrode topology.