Low-pressure RF plasma

The SNMS instrumentation that has been most extensively applied and evaluated has been of the electron-gas type, combining ion bombardment by a separate ion beam and by direct plasma-ion bombardment, coupled with postionization by a low-pressure RF plasma. The direct bombardment electron-gas SNMS (or SNMSd) adds a distinctly different capability to the arsenal of thin-film analytical techniques, providing not only matrbe-independent quantitation, but also the excellent depth resolution available from low-energy sputterii. It is from the application of SNMSd that most of the illustrations below are selected. Little is lost in this restriction, since applications of SNMS using the separate bombardment option have been very limited to date. 

Stokes et al. 47) reported similar conversions of oxygen in air to nitrogen oxides in a low-pressure RF plasma. After a run time of 2.5 hr, 0.4 ml of material was collected in liquid nitrogen traps, which on analysis showed a 2% conversion to nitric oxide. LaRoche 36) had previously demonstrated the beneficial effect of quenching the reaction products. In experiments with a low-pressure RF discharge, he obtained an increase in conversion to nitric oxide from 2 to 4% by a rapid quenching technique. 

The experimental approach was outlined in Sec. 2.3. HyperthermaJ beams of energy selected Ar atoms or N2 molecules were directed at polymer surfaces that were continously bathed with the effluent of a low pressure RF plasma source of oxygen atoms (see Fig. 7). Interaction of the effusive 0-atom beam with polymer samples produced both CO and CO 2 continuously, and data were collected under conditions of steady-state oxidation, as verified by the unchanging signals from CO and CO2 in the mass spectrometer. Product TOF distributions were collected at m/z = 28(CO+) and 44(002 ), following impingement of hyperthermaJ beam pulses on polymer surfaces that had reached a steady state of oxidation. 

D.P. Subedi, L. Zajickova, V. Bursikova, and J. Janca, Surface modification of polycarbonate (bisphenol A) by low pressure rf plasma, Himalayan Journal of Sciences, 1 (2), 115-118, 2003. 

Hot RF and - DC plasma, are discharge, plasma jets Oxy-acetylene flames Low pressure microwave plasma, holt filament. Low pressure DC or RF glow discharge Thermal decomposition... 

Several environment-friendly surface preparation for the treatment of mbber soles with radiations have been recently studied. These treatments are clean (no chemicals or reactions by-products are produced) and fast, and furthermore online bonding at shoe factory can be produced, so the future trend in surface modification of substrates in shoe industry will be likely directed to the industrial application of those treatments. Corona discharge, low-pressure RF gas plasma, and ultraviolet (UV) treatments have been successfully used at laboratory scale to improve the adhesion of several sole materials in shoe industry. Recently, surface modification of SBR and TR by UV radiation has been industrially demonstrated in shoe industry... 

Low-pressure RF gas plasma is effective to enhance the adhesion of SBR and Oxygen,... 

In a silane-hydrogen discharge the feedstock gases SiHa and H2 take part in all the processes that occur. A large number of reactions have been proposed (see e.g. Kushner [190]). Nienhuis et al. [191] have performed a sensitivity analysis in their self-consistent fluid model, from which a minimum set of reactions have been extracted for a typical low-pressure RF discharge. Tables II and III list these reactions. They will be used in the plasma models described in subsequent sections. The review articles on silane chemistry by Perrin et al. [192] and on hydrogen by Phelps [193] and Tawara et al. [194] have been used. The electron collision data are compiled in Figure 13 [189]. 

The modification of cotton cellulose by treatment with low-temperature, low-pressure ammonia plasma created by passing ammonia gas through a radiofrequency (rf) electric field of 13.56 MHz has been reported (1). Earlier reports (2,3,4) were on the effects of rf plasma of argon, nitrogen or air on a group of polysaccharides that included cotton and purified cellulose. 

Figure 4-79. Low-pressure RF-CCP diseharge parameters as funetions of current density (a) plasma eoneentration, (b) mean energy of plasma eleetrons, (e) depth of sheath, (d) discharge power.

Cluster formation in low-pressure RF silane plasma starts from the formation of negative ions SiH3 and their derivatives. For the discharge parameters described earlier, the density of the negative ions can be found from the balance of dissociative attachment and ion-ion recombination ... 

Puac, N., Petrovic, Z.Lj., Radetic, M., Djordjevic, A., 2005. Low pressure RF capacitively coupled plasma reactor for modification of seeds, polymers and textile fabrics. Mater. Sci. Forum 494, 291-296. 

An alternative to water-based technology is the use of low-pressure RF gas plasmas that is effective to enhance the adhesion of SBR rubber sole (Pastor-Bias et al. 1998). The treatment in oxygen plasma for 1 min is enough to noticeably increase adhesion of SBR rubber sole to polyurethane adhesive. 

Low pressure vacuum plasmas are low temperature (non-thermal) plasmas and are generated by the application of a DC, low frequency RF (< 100 kHz), high frequency RF (typically 13.56 MHz), or microwave frequency (2.45 GHz) electric field to the gap between two metal electrodes, or where the electrode is wrapped by a coil whereby a plasma is excited by induction. 

In two other implementations of electron impact SNMS, a plasma is generated in the ionizer volume to provide an electron gas sufFiciendy dense and energetic for efficient postionization (Figure 2c). In one instrument, the electrons are a component of a low-pressure radiofrequency (RF) plasma in Ar, and in the second, the plasma is an electron beam excited plasma, also in Ar. The latter type of electron-gas SNMS is still in the developmental stages, while the former has been incorporated into commercial instmmentation. 

Amorphous Silicon. Amorphous silicon is generally deposited by Reaction (4) at a deposition temperature of 560°C and at low pressure (ca. 1 Torr).P l Helium RF plasma CVD is also commonly used, especially in the production of solar photovoltaic devices. 

Figure 1. Schematic description of the low-pressure inductively coupled rf plasma CVD system. Adapted with permission from [33], K. Okada et al., J. Mater. Res. 14, 578 (1999). 1999, Materials Research Society.

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