Discharge and Onion Layer Structure

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. 

In alternating current discharge for LCVD, up to about 100 kHz, the DG adhering to the electrode surface (in the cathodic cycle) is the core. The discharge system has two cores, and the interelectrode space is filled with two onion structures overlapping in part, which approach each other when the value of Wjpd increases. 

In radio frequency discharge, the electrode does not function as electrode in the lower frequency discharge. Consequently, the core of discharge moves away from the electrode surface, i.e., two cores for DG, which are located away from electrodes but near the electrode surface (in the case with internal electrodes). Because DG does not adhere to the electrode surface, the main medium of material deposition shifts to the interelectrode space, which leads to the higher deposition rate observed in the interelectrode space under otherwise identical discharge conditions carried out by different power source (see Chapter 8). 

In microwave plasma, electrons adhere to the wall because the microwave energy propagates on surface. In this case, the inner surface of the vacuum chamber becomes the core of the luminous gas phase for LCVD. If the inner surface of a vacuum chamber is the main substrate surface on which LCVD coating is aimed, such as the case of the coating the irmer surface of a plastic bottle, the microwave discharge is the most efficient LCVD. 

When the system pressure of such a luminous gas phase is raised, it is generally considered that the electron temperature, 7)., ion temperature, T, and temperature of neutral species, Tji approach an equilibrium state (thermal equilibrium), and the plasma becomes hot at round lOOtorr. On the other hand, there is a type of glow discharge that is termed atmospheric-pressure glow discharge, which is claimed to be atmospheric low-temperature plasma. Obviously, such low-temperature plasma 

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