Dry plasma conditions

On line additions of aqueous standard solutions for the calibration of LA-ICP-MS including a comparison of wet and dry plasma conditions are discussed by O Connor et al.ls For solution calibration of standard solutions the authors used a 100 (xl PFA nebulizer together with a cyclonic spray chamber or a MCN-6000 sample introduction system with desolvator, to study the wet and dry plasma, respectively. A polypropylene Y piece was applied to mix the laser ablated material and the nebulized standard solutions. The authors found that the on line addition of water is the preferred mode of operation for quantification by LA-ICP-MS, i.e., wet plasma is more stable (improved standard deviation of sensitivity ratios). 

MeHg using isotopically enriched Me Hg and Bus Sn wet and dry plasma conditions used to facilitate mass bias correction and signal optimization CRM 710 analyzed to validate method... 

O Connor, C., Sharp, B.L., Evans, P. (2006) On-line additions of aqueous standards for cahbration of laser ablation inductively coupled plasma mass spectrometry theory and comparison of wet and dry plasma conditions./oMrnaZ of Analytical Atomic Spectrometry,21, 556-565. 

Operation under dry plasma conditions is the second option. The standard solution is introduced as a dry aerosol through a desolvating system (such as an Aridus, DSN-100 or Apex unit) [12, 23]. The use of this configuration significantly reduces oxide-based interferences. This is essential for some elements, such as sulfur [19]. 

ICP-MS (the signals of and Ar" show isobaric overlap), hence the corresponding isotope ratios can be used to study isotope fractionation during different processes and the isotopic composition in different sulfur species can be determined. Sulfur isotope ratio measurement is complicated as a result of interference from O2, which can be overcome either by using a higher mass resolution or by using dry plasma conditions. 

A drawback of all these solution-based techniques are the different excitation processes between wet and dry plasma conditions occurring in the ICP, resulting in different signal responses... 

Figure 13a shows the resist in a three-layer Al-RIE-PCM system by Havas et al. The dry etching conditions were similar to those of plasma etching. Therefore, an undercut was produced under the Al PCM to facilitate lift-off. Figure 13b shows the resist image in a three-layer siloxane RIE PCM system. The dry etching process was sufficiently anisotropic to eliminate the undercut. 

These apparent contradictions can be rationalized in terms of a model which incorporates plasma-induced polymerization along with depolymerization. PBS has long been known to exhibit a marked temperature-dependent etch rate in a variety of plasmas. This is clearly seen in the previously published Arrhenius plots (3,7) for two different plasma conditions (Figure 1). This dependence is characteristic of an etch rate that is dominated by an activated material loss as would occur with polymer depolymerization. The latter also greatly accelerates the rate of material loss from the film. Bowmer et al. (10-13) have shown in fact that poly(butene-l sulfone) is thermally unstable and degrades by a depolymerization pathway. A similar mechanism had been proposed by Bowden and Thompson (1) to explain dry-development (also called vapor-development) under electron-beam irradiation. 

Several polymethacrylates, primarily alkyl esters, were compared with a novolac resist in terms of etch rates in CF4 and Ar plasmas. The alkyl groups examined included methyl, terf-butyl, cyclohexyl, norbonyl, adamantyl, and benzyl [226]. The polymerization of alicyclic methacrylates was pioneered by Otsu, who has demonstrated facile polymerization of bulky methacrylates and reported high Tg of this class of polymethacrylates [230]. It has been found that alicyclic polymers exhibit better dry etch resistance than acyclic esters and that the dry etch durability is increased by an increase in the number of rings. Thus, poly(adamantyl methacrylate) is as stable as a novolac resist under dry etch conditions. A 30/70 copolymer of adamantyl methacrylate with ter/-butyl... 

Sample preparation Plasma. Condition a Toxiclean SPE cartridge (Alltech) with 3 mL MeOH, two 3 mL portions of water, and 2 mL buffer. 100 pL Plasma or serum -I- 100 pL MeOH + 200 pL MeCN + 100 pL buffer, vortex for 1 min, centrifuge at 4000 rpm for 15 min, add the supernatant to the SPE cartridge, wash with two 3 mL portions of water, dry under vacuum for 10 min, elute with 2 mL MeOH. Evaporate the eluate to (hyness under a stream of nitrogen at 45°, reconstitute the residue in 100 pL 2.5 pg/mL flufenamic acid in MeOH ( ), iiyect an aliquot. Urine. Condition a Bond Elut C8 SPE cartridge with 3 mL MeOH, two 3 mL portions of water, and 2 mL buffer. 100 pL Urine + 100 pL MeOH -I- 200 pL MeCN + 500 pL buffer, vortex for 1 min, centrifuge at 2000 rpm for 5 min. 

Comparison of dry-etching rates of aromatic and aliphatic copolymers for CF4 plasma (conditions 100 seem CF4,80 Pa, Pp = 500 n). ... 

M.B. Karamis, Tribological behavior of plasma nitrided 722M24 material under dry sliding condition. Wear, Vol. 147, 385-99 (1991). 

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