A low-voltage atmospheric pressure nonthermal argon plasma jet using a circular piezoelectric transducer is proposed. An Ar plasma flame is generated at an input voltage of 87 V. The consumed power is 2 W. The electrical and optical properties of the jet are analyzed. In particular, the transient Ar discharge ignition and evolution including the so-called plasma bullet phenomenon is examined temporally resolved with the aid of a fast camera. It is found that four discharge phases can be identified, designated as ignition, extension, self-propagation, and attenuation. The plasma bullet is launched while the electric field in the discharge space is decreasing. The average bullet velocity is 23 km/s.

W e developed ana tested a LangmJir aouble-probe system s. . taole for measJrement in industr'al environments. where quic6 and easy-to-nandle methods are requ'red. Data acquisition and calculation of plasma parameters are cantro led ay a personal computer. An evalLation agorithm 's presented and its properties are brielly dscussed. SJccessful operat'on of !ne system can ae proved :n a var:ery of different plasma configurations, namely 'n raaiolreqJency driven, pulsed direct current ana microwave plasmas. Typical measuements and the conclusions that have been arawn are presentea. Plasma aensit'es were in tne range 108-10'3cm-3. From the ena user's point of v:ew the main appl'cation areas are tro-be-snoot:ng, on-line process control and plasma source characterization auring the aevelopment stages of a plasma plant.

The absolute electron density in the downstream region of a 2.45 GHz microwave plasma source has been measured by the plasma oscillation method. In the plasma oscillation method a weak electron beam injected into the plasma excites electrostatic electron waves oscillating at the electron plasma frequency, which is proportional to the square root of the electron density. The plasma source is a slot antenna (SLAN) type, that is the microwave power is coupled from a ring resonator through equidistantly positioned resonant coupling slots into the plasma chamber which is made of quartz. The results of the plasma oscillation method are compared with the results of single and double Langmuir probe (LP) measurements. In Ar and Ar:O 2 mixtures reasonable agreement between the two diagnostic methods is found. However, in depositing plasmas traditional LPs cannot be used with confidence. We studied Ar:O 2 gas mixtures with hexamethyldisiloxane (HMDSO) added downstream for the deposition of quartz-like films. We found that even a small amount of HMDSO in the gas mixture leads to erroneous LP measurements due to probe surface coating, while the plasma oscillation method is still applicable here.

The density of atomic oxygen in pulsed microwave excited oxygen plasmas has been measured by means of time-resolved two-photon laser-induced fluorescence. The plasma source is a slot antenna type that is operated at 2.45 GHz. Calibration of the measurements has been performed by the use of a two-photon transition of xenon in order to obtain absolute densities of atomic oxygen in the downstream zone. Besides the influence of pulse frequency on the time-averaged density, we also studied pulsed plasmas at higher pressures, which show a significant delay between the onset of microwave power and the rise of the atomic oxygen density. By changing pulse frequency, an optimum frequency is obtained which leads to a gain in the measured time-averaged atomic oxygen density as compared to cw plasmas. This effect is compared to the properties of deposited films generated in a pulsed oxygen/hexamethyldisiloxane process plasma. The results are discussed in the framework of a volume-averaged model for oxygen plasmas, which takes into account molecular and atomic oxygen, metastable oxygen, and positive and negative oxygen ions.