Plasmas gas pressure

Deposition of copper metal Since Cu(II) is the preferred oxidation state of copper, Cu2+ salts are more stable and more available, hence, in a technical application it would be favorable to use them as starting material. We tried to reduce Cu(CF3S03)2 dissolved in [EMIM][TfO], [BMP][TfO] and [BMIM][TfO] with an argon plasma (gas pressure 100 Pa) as well as with a nitrogen plasma (100 Pa), respectively. Additional experiments with Cu(CF3SC>3)2 dissolved in [EMIM][TfO] and Ar/H2 plasmas were carried out, with the distance between the hollow cathode in the gas phase and the surface of the ionic liquid metal salt solution being 3, 45 and 100 mm. Moreover, for the 3 mm distance several experiments with different gas pressures from 50 to 500 Pa were carried out. 

Figure 5-20. CO2 thermal dissociation energy efficiency as a function of heating temperature in plasma gas pressure p = 0.16 atm (1) ideal quenehing, (2) super-ideal quenehing, (3) upper limit of super-ideal quenehing related to energy balanee.

Speeifie textile treatment Discharge Power, current Plasma gas Pressure Flow rate Other... 

Figure 3. Main contributors to improved adhesion. Plasma etch time has the strongest effect while sample condition and plasma gas are also significant. Plasma gas pressure is an insignificant effect.

In the laboratory, it has been found that similar effects can be produced if a voltage is applied between two electrodes immersed in a gas. The nature of the laboratory or instrumental discharge depends critically on the type of gas used, the gas pressure, and the magnitude of the applied voltage. The actual electrical and gas pressure conditions determine whether or not the discharge is called a corona, a plasma, or an arc. 

Particularly in mass spectrometry, where discharges are used to enhance or produce ions from sample materials, mostly coronas, plasmas, and arcs are used. The gas pressure is normally atmospheric, and the electrodes are arranged to give nonuniform electric fields. Usually, coronas and plasmas are struck between electrodes that are not of similar shapes, complicating any description of the discharge because the resulting electric-field gradients are not uniform between the electrodes. 

The exact conditions of gas pressure, current flow, and applied voltage under which the discharge occurs determine if it is of the corona, plasma, or arc type. The color of the emitted light may also change, depending not only on the type of gas used but also on whether it is a corona, plasma, or arc discharge. 

Most Ar and Kr lasers are CW. A gas pressure of about 0.5 Torr is used in a plasma tube of 2-3 mm bore. Powers of up to 40 W distributed among various laser wavelengths can be obtained. 

Compared with GD-OES (and -MS, if used for depth profiling) SNMS provides somewhat better depth resolution (1 nm range) HE-plasma SNMS hardly suffers from molecule formation in the plasma gas (Ar), as do the CD techniques, in which ar-gides are formed because of the comparatively high pressure. 

Fig. 3.32. Basic principles of HF-plasma SNMS. Vhf, PHrarethe HF generator frequency and power, respectively, PArthe plasma gas (Ar) pressure 7e and the electron and plasma gas temperatures, respectively. Hpi = n is the plasma e, Ar" ) density. Bo the...

Type of plasma Discharge power Gas pressure Treatment time... 

Modulation of the RF excitation has been used in an attempt to increase the deposition rate. Increasing the gas pressure or raising the power generally leads to dust formation and deterioration of material properties. To overcome this problem, one can pulse the plasma by modulating the RF signal in amplitude with a square wave (SQWM). Depending on the regime (a or y ), different effects are observed. 

The afterglow data for Ne, 60 ArJ,61 Kr, 62 and Xe2 63 showed that the total recombination coefficients, as determined from the decay of the electron density, were sensibly independent of the gas pressure. Typically, the pressure was varied by at least a factor of 3 and no systematic variation of the total recombination coefficient was found. The observed plasma decay was compatible with the assumption that the total recombination coefficients are independent of the electron density (in the range from approximately 109 to 1010 cm-3). 

Figure 3. Variation of ion and electron temperatures with gas pressure in a plasma.

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