Influence of the different operations of gas in the large microwave plasmas

The study of discharge performance was performed for argon, nitrogen, and t he H-2-C2H5OH gas mixture in a power range from 250 to 1000 W, and a pressu re range from 10 to 1000 Pa. With argon, a surface wave at the plasma-quart z interface can be excited above 250 W. The surface wave modes can be ident ified as m = 4 and m = 6 with pressures of 10 and 230 Pa. With nitrogen, su rface waves propagate in two or more modes superposed with a different valu e of m below the pressure of 133 Pa. In contrast to the above gases, the H- 2-C2H5OH gas mixture showed no surface wave generation for power levels up to 1000 W; only a hemisphere plasma with a diameter of 8 cm was observed ju st above the substrate. The plasma, having a diameter of 160 mm, is uniform below the pressure of 133 Pa in nitrogen discharges, but the plasma densit y is lower than in argon discharges. The radial distributions of electron d ensity in the quartz tube also prove the existence of surface waves for arg on and nitrogen. In addition, the axial distributions of electron density p rove that the traveling and standing surface waves can be excited by argon discharges in each case: with or without the short plunger at the top of th e setup. (C) 2001 American Vacuum Society.