Time resolved metal line profile by near-ultraviolet tunable diode laser absorption spectroscopy

Abstract

Pulsed systems are extensively used to produce active species such as atoms, radicals, excited states, etc. The tunable diode laser absorption spectroscopy (TD-LAS) is successfully used to quantify the density of absorbing species, but especially for stationary or slow changing systems. The time resolved-direct absorption profile (TR-DAP) measurement method by TD-LAS, with time resolution of μs is proposed here as an extension of the regular use of diode laser absorption spectroscopy. The spectral narrowness of laser diodes, especially in the blue range (∼0.01 pm), combined with the nanosecond fast trigger of the magnetron pulsed plasma and long trace recording on the oscilloscope (period of second scale) permit the detection of the sputtered titanium metal evolution in the afterglow (∼ms). TR-DAP method can follow the time-dependence of the temperature (Doppler profile) and the density (deduced from the absorbance) of any medium and heavy species in a pulsed system.

Are the argon metastables important in high power impulse magnetron sputtering discharges?

“…Then a low voltage is maintained between the high power pulses. Such an arrangement of an argon discharge with aluminum target was explored by Vitelaru et al 25 who found that the steady state metastable density between the high power pulses is up to 10% of the maximum metastable density in the pulse. The same order of magnitude was found independently by Britun et al, 14 however without pre-ionization.…”

Argon metastables in HiPIMS: time-resolved tunable diode-laser diagnostics

“…The TD-LAS technique is usually employed for stationary plasmas [30]or time averaged measurements in pulsed plasmas [31], but has been adapted in various ways to perform time resolved measurements [21,22,24]. The method proposed in this paper uses the diode laser in its regular scanning mode, at very low scanning frequency (less than 0.2 Hz).…”

“…An absorption spectroscopy technique, which directly performs time resolved measurements in the afterglow of a pulsed discharge, has recently been proposed in [21]. This technique uses diode lasers in their regular scanning regime, at frequencies around 1Hz, and the precise synchronization between the laser scan and plasma pulses.…”

“…Although this technique is very efficient and easy to implement in continuous steady state discharges or time averaged measurements of plasma species [18,19,20], the pulsed regime raises additional problems due to the fast time variations [21]. Time resolved measurements of atomic species have been performed by locking the laser to a fixed wavelength (usually the resonance wavelength λ 0 ) [22,23].…”

Modulated Electron Cyclotron Drift Instability in a High-Power Pulsed Magnetron Discharge

“…The planar magnetron used in experiments is operated with a 10 cm-diameter titanium cathode and run in dc and pulsed excitation regimes with argon as a working gas; a detailed description of the source and chamber is provided elsewhere [10]. The magnetic field is radial and is set using concentric permanent magnets (a cylindrical magnet at the cathode center and an annular magnet at the outer edge of the cathode^.…”