From the width of the 656.3 nm Balmer α line emitted from microwave and glow discharge plasmas, it was found that a strontium–hydrogen microwave plasma showed a broadening similar to that observed in the glow discharge cell of 27–33 eV; whereas, in both sources, no broadening was observed for magnesium–hydrogen. Microwave helium–hydrogen and argon–hydrogen plasmas showed extraordinary broadening corresponding to an average hydrogen atom temperature of 180–210 eV and 110–130 eV, respectively. The corresponding results from the glow discharge plasmas were 33–38 eV and 30–35 eV respectively, compared to ≈4 eV for plasmas of pure hydrogen, neon–hydrogen, krypton–hydrogen, and xenon–hydrogen maintained in either source. Similarly, the average electron temperature Te for helium–hydrogen and argon–hydrogen microwave plasmas were high, 30 500±5% K and 13 700±5% K, respectively; compared to 7400±5% K and 5700±5% K for helium and argon alone, respectively. External Stark broadening or acceleration of charged species due to high fields can not explain the microwave results since no high field was present, and the electron density was orders of magnitude too low for the corresponding Stark effect. Rather, a resonant energy transfer mechanism is proposed.
Optical emission study of the laser ablation plasma plume during the preparation of diamond-like carbon (DLC) films using KrF excimer (248 nm) pulsed laser deposition (PLD) has been carried out by means of a monochromator equipped with an intensified optical multichannel analyzer. In high vacuum (1×10−7 Torr), the emission lines from carbon ions of C+, C2+, and C3+ are observed in addition to atomic carbon emission lines, while no emission from the diatomic carbon molecule (C2) is observed. With increasing background nitrogen pressure up to 500 mTorr, the emission intensities of the C2 Swan band and the carbon nitride (CN) violet band increase. The diamond-like character of deposited DLC film degrades with background nitrogen pressure. The vibrational temperature of C2 and CN molecules decreases with the increasing of nitrogen pressure. The CN vibrational temperature for the first 2 μs after the laser pulse is very high and in agreement with the kinetic energy of monatomic carbon ions. The C2 vibrational temperature is as low as 0.6 eV and is consistent with the electron temperature of about 0.8–3.0 eV. It is conjectured that CN molecules are formed directly in reactions involving energetic ionic monatomic carbon, and that the formation of excited C2 molecules is the result of molecular recombinations of C atoms and ions. From the emission intensity measurements and the estimation of the vibrational temperature, it is suggested that the C2 molecule in the ablated plasma plume is not important, but energetic species, such as C+, are very important for producing high quality DLC films using PLD.
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