Ar, DC discharge

Figure 3.3 Change of the intensity and location of luminous gas phase depending on the discharge power and the system pressure of Ar DC discharge. Left column 25mtorr, right column lOOmtorr. Top row 3 W, middle row 10 W, bottom row 15W.

Figure 3.10 Ar DC discharge a cathode (steel plate) and two magnetron anodes, 1 seem, SOmtorr, 5W the intensity of Ar glow is more than five times greater than that of TMS.

Figure 1 Schematic of DC glow-discharge atomization and ionization processes. The sample is the cathode for a DC discharge in 1 Torr Ar. Ions accelerated across the cathode dark space onto the sample sputter surface atoms into the plasma (a). Atoms are ionized in collisions with metastable plasma atoms and with energetic plasma electrons. Atoms sputtered from the sample (cathode) diffuse through the plasma (b). Atoms ionized in the region of the cell exit aperture and passing through are taken into the mass spectrometer for analysis. The largest fraction condenses on the discharge cell (anode) wall.

Figure 3.7 Distribution of electron temperature, electron density and Debye length in DC discharge of Ar in an LCVD reactor A Debye length, cm x 10 B electron temperature, eV C electron density, cm x 10. ...

In DC discharge for LCVD, the main core is the DG adhering to the cathode surface, and the anode is out of the onion structure in most cases. In DC discharge of Ar for glow discharge treatment or sputter deposition of the cathode material, the core is the IG, which does not touch the cathode surface. 

The luminous gas phase created by a special mode of DC discharge recognized as the low-pressure cascade arc torch (LPCAT) provides an especially important case for understanding the fundamental aspects of the luminous gas phase. The luminous gas phase in form of luminous gas jet stream or torch are created by blowing out DC discharge into an expansion chamber in vacuum. The luminous gas jet of Ar mainly consists of photon-emitting excited neutral species of Ar, which is certainly not the plasma of classical definition. The core of LPCAT is the tip of injection nozzle however, it is not the core of electrical discharge. 

Figure 15.4 Electron temperature (eV) and electron density ( /cm ) versus axial distance (from cathode to anode) for two radial positions (R) in Ar DC glow discharge lOW, 2 seem, SOmtorr, and 76 mm electrode distance.

Radial distributions of electron temperature and electron density are compared at axial distance 2.5 mm and 7.5 mm, respectively, in Figures 15.16 and 15.17. In DC discharge of Ar without magnetron, the distributions of electron temperature and electron density near the electrode surface (2.5 mm from the cathode) are uniform, but both show the edge effect, more pronounced in electron temperature. At this position (in cathode dark region), there are small numbers of electrons that have low electron energy. 

How effectively a DC discharge of argon could clean the cathode surface can be seen by observing the disappearance of color of the cathode, which is created by the deposition of TMS on a cold-rolled steel, by Ar discharge treatment [2]. The cathodic... 

Figure 15.29 Effect of anode magnetron on the breakdown voltage of DC discharge of Ar in low-pressure regime.

In the LPCAT process, only an inert gas such as Ar exists in the cascade arc generator, and DC voltage is applied between the cathode and the anode. Therefore, it is a DC discharge of Ar, but it occurs under much higher pressure than in most low-pressure DC discharges, and the gas travels very fast in one direction in the generator. The basic process of ionization of Ar takes place in the cascade arc generator, which can be depicted as follows. 

Torr and flow rate of 200 standard cm s was used. The buffer gas is He with up to 5% Ar added to stabilize the DC discharge source. Approximately 10 collisions with the buffer gas (and precursor molecules) in the flow tube ensure that the ions are cooled to room temperature." ... 

Excitation method DC discharge DC discharge DC discharge Ar laser pump Krypton arc lamp DC injection... 

The Hornbeck-Molnar process (13) is indicated by the linear relation obtained when the ratio Ar2 /Ar is plotted against reciprocal pressure. This has been observed by Pahl for the positive column of a dc discharge of Ar. The variation in electron energy with pressure is not expected to be important in this case because the energy levels of the excited argon lie close to the ionization continuum. 

FIG. 44. Plasma parameters as deduced from the lEDs and material properties as a function of power delivered to the SiHa-Ar discharge at an excitation frequency of 50 MHz and a pressure of 0.4 mbar (a) the plasma potential Vp (circles) and dc self bias (triangles), (b) the sheath thickness d, (c) the maximum ion flux r ax. (d) the growth rate r,/. (e) the microstructure parameter R. and (f) the refractive index ni ev- (Compiled from E. A. G. Hamers. Ph.D. Thesis, Universiteit Utrecht, Utrecht, the Netherlands. 1998.)... 

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