DNA strand scission induced by a non-thermal atmospheric pressure plasma jet

The DNA molecule is observed to be very susceptible to short term exposures to an atmospheric pressure plasma jet. The DNA damage induced by plasma-generated species, i.e. excited atoms, charged particles, electrons and UV light is determined

Time-resolved ion flux, electron temperature and plasma density measurements in a pulsed Ar plasma using a capacitively coupled planar probe

The resurgence of industrial interest in pulsed radiofrequency plasmas for etching applications highlights the fact that these plasmas are much less well characterized than their continuous wave counterparts. A capacitively coupled planar probe is used to determine the time variations of the ion flux, electron temperature (of the high-energy tail of the electron energy distribution function) and plasma density. For a pulsing frequency of 1 kHz or higher, the plasma never reaches a steady state during the on-time and is not fully extinguished during the off-time. The drop of plasma density during the off-time leads to an overshoot in the electron temperature at the beginning of each pulse, particularly at low frequencies, in good agreement with modeling results from the literature

Density fluctuation measurements with laser scattering

-2 power law. The average phase velocities are around 4.5 km/sec and are slightly larger than the electron diamagnetic drift velocity. The waves are tentatively identified with the electron drift mode. Coherent signals due to long wavelength MHD modes are detected. Results from a Langmuir probe corroborate most of these data

The influence of amino acids on DNA damage induced by cold plasma radiation

Highly purified plasmid DNA both with and without amino acids (glycine and arginine) was irradiated using a cold plasma under ambient conditions. Damage to the plasmid DNA in the form of single- and double-strand breaks was determined by gel electrophoresis. Depending on either the molar ratio of the amino acid:nucleotide mixture or the type of amino acid used, some measure of protection of the DNA can be achieved

A numerical and experimental investigation of an axially symmetric RF plasma

The characteristics of an atmospheric pressure, RF discharge in air were determined and compared with a 2D numerical model adapted from that used for a dc glow discharge. For a 15 mm discharge, the RF plasma's electrical and optical characteristics show a close correlation to several equivalent dc plasmas and to the results calculated from the adapted model. For an rms conduction current range of 11–30 mA, the rotational temperature varies between 2800 and 3200 K; the vibrational temperature shows a change of 3500–4000 K with near equilibrium conditions to the rotational state occuring in the central region of the discharge. Spatial measurements and modelling of nitrogen emission spectra identify the changes in the temperatures and dimensions along the vertical z-axis as well as the spatial dependence on the atomic and molecular species generated in the discharge

Optical and electrical diagnostics in chlorine based pulsed plasmas of an industrial silicon etching reactor

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Physique des plasmas

Dynamique des espèces chargées dans un réacteur de gravure diélectrique à couplage capacitif excité par deux fréquences The dynamics of the charged particles in a dual frequency capacitively coupled dielectric etch reactor. Thèse soutenue le 30 avril 2008 Devant le jury composé de Messieurs

Optimization of plasma etch processes using evolutionary search methods with in-situ diagnostics

This paper presents several approaches that have been used to control, optimize and characterize a low pressure (10–300 mTorr) plasma processing system. Methods such as contour following and differential evolution have been used to find contours of DC bias, total ion flux, ion energy flux, quadrupole mass spectrum (QMS) intensity ratios and line intensity ratios of the optical emission spectrum (OES) in argon and nitrogen plasmas. A mapping for a 4 × 4 multi-dimensional parameter space is also presented, in which the relationship between four control parameters (power, pressure, mass flow rates of two supplied gases) and four measurement outputs (DC bias, ion flux, QMS ratios and OES line intensity ratios) is determined in a plasma etching process. The use of these methods significantly reduces the time needed to re-configure the processing system and will benefit transfer of processes between different systems. A similar approach has also been used to find quickly an optimum condition for directional etching of a silicon wafer