Surface recombination of hydrogen atoms studied by a pulsed plasma excitation technique

Abstract

The H atom lifetime in a low pressure hydrogen microwave plasma was measured using a pulse induced fluorescence technique. This technique is compared to results obtained by a laser spectroscopy technique. We first demonstrate the validity of the method and then deduce H atom lifetime pressure dependence. The H atom surface loss probability on fused silica was also deduced from our measurements. We show that this coefficient is not constant in the time afterglow but decreases almost by one order of magnitude (from 2.3×10−3 to 2.1×10−4) during the first milliseconds. These results are explained using recent experimental and theoretical works concerning atom-surface interaction in low temperature plasmas.

Effect of energetic ions on plasma damage of porous SiCOH low-k materials

“…It seems that ion irradiation can modify the SiO 2 surface and create such centers. [35][36][37][38][39] However, application of these phenomena to low-k dielectrics needs additional research.…”

“…37 The mechanism of the generation of active centers by a reactive plasma has been intensively discussed in literature. [37][38][39][40][41] Although the mechanism of the generation of such centers can be different, it was proposed that the active sites might be related to electron deficient or deformed siloxane bridges. 41 Surface contamination may also play an important role 42 but it is difficult to expect that the contamination level can drastically change in the conditions of our study.…”

Attenuation of hydrogen radicals traveling under flowing gas conditions through tubes of different materials

“…This recombination seriously depletes the atomic hydrogen concentration and can also significantly heat the corresponding surfaces. Although hydrogen recombination coefficients have been reported for various materials, [7][8][9][10][11][12] there are no measurements of hydrogen radical concentrations traveling under flowing gas conditions through tubes of different materials. Measurements of atomic hydrogen concentration as a function of distance from the source, gas flow velocity, and tube wall material are important for defining hydrogen radical transport.…”

Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H2-Ar low-pressure plasmas

“…At the wall H atoms recombine forming H 2 . Other loss processes such as three-body recombination in the plasma volume or pumping can be neglected for the present conditions [14][15][16][17]34 . The wall loss time t wH , which is the inverse of the wall loss rate coefficient, is the mean time for a hydrogen atom to reach the plasma surrounding wall.…”

“…This process is predominantly affected by the electron density and electron temperature of the respective plasma. In these plasmas the loss of atomic hydrogen is determined by the flux to the wall [14][15][16][17] . In our case, as in most other cases, the wall loss is determined by recombination of atomic hydrogen to form molecular hydrogen which desorbs from the surface.…”