(a) 1: vacuum chamber; 2: replaceable platinum probe, U b , bias voltage, either dc or rectangular pulses with 50 μs duration; 3: ferromagnetic core of the FIC plasma source, inner diameter 10 cm, outer diameter 15 cm, thickness 2.5 cm, 15 turns of winding; 4: large planar probe (S = 7 cm2); 5: thin tungsten filament (hot probe); 6: hot cathode, U heat pulse duration 0.2 s, repetition rate 5 s; 7: dc injector; 8: combination of insulated coaxial waveguide adaptors. (b) Left: cathode emitted current I emis , U heat = 10.5 V, U a = 100 V, Xe gas; right: ion saturation current , collected by planar probe, ∼ n p .
(a) 1: cathode emitted current I emis ; 2: electron current I pr , collected by the thin (0.05 mm) probe. (b) Expanded waveforms near I emis ≈ 40 mA (n p ∼ 109 cm−3); 2: electron current I pr ; 3: bias voltage U b ; 4: plasma potential Uh with respect to the chamber walls; 5: UHF spike in the probe current I pr . (c) Expanded UHF spike, f p ≈ 290 MHz. (d) the same probe, used as a resonance probe, maximal reflected signal at the same frequency.
(a) 1: emitted current I emis ; 2: ion saturation current , collected by the planar probe during FIC rf driving pulse. (b) 2: expanded pulse; 3: bias pulse U b . (c) 1: plasma potential Uh ; 2: ion saturation current; 3: electron current I pr , collected by the thin (0.05 mm) probe. (d), plasma density n p vs U ind for various pressures of Xe gas. Derived from to the large planar probe, T e ∼ 4 eV.
(a) Xe gas. (b) Ar gas. 1: bias voltage U b ; 2: electron current I pr , collected by the thin (0.05 mm) probe; 3: detected UHF signal. (c) The same, but the probe diameter is 1.1 mm. (d) The thin (0.05 mm) probe, but the current I pr is high (25 A).
Xe gas. (a) 1: microwave signal U UHF vs gas pressure P; 2: optimal probe current I pr , U ind ∼ (350–400) V. (b) Bias voltage U b vs U ind for various pressures P. (c) Microwave signal U UHF vs U ind for various pressures P. (d) “Breaking points” of microwave signal for low and high pressures.
Microwave signal, obtained with narrow-band detector, 1: bias voltage U b ; 2: probe current I pr ; 3: microwave signal U UHF .
Theoretical values of the transit angles (in π units), which correspond to the experimentally measured threshold potentials . Top-filled circles, pressure 0.8 mTorr; bottom-filled circles, pressure 0.2 mTorr. All other experimental points, which correspond to pressures between 0.2 mTorr and 0.8 mTorr, are located between the depicted curves.
Article metrics loading...
Full text loading...