Tunable diode-laser induced fluorescence on Al and Ti atoms in low pressure magnetron discharges

Abstract

Two different blue light laser diodes were used to investigate two types of atoms, namely Ti with resonance transition centred at λ0(Ti) = 398.289 nm and Al with λ0(Al) = 394.512 nm. Tunable diode-laser induced fluorescence offers local information on two groups of sputtered particles—non-thermalized and thermalized. The anisotropic velocity distribution functions (vdfs) are characterized probing the plasma along two directions: parallel to the target, vr, and perpendicular to it, vz. Measurements were performed in two plasma reactors both having planar magnetron cathodes with circular symmetry but with Ti and Al targets of different magnet strengths and diameters. The similar results of the vdf space dependence for these magnetron systems confirm the general behaviour of sputtered species transport. These similarities are related to the circular geometry and fundamentals of sputtering whereas differences are due to each specific sputtered element. The experimental results also show the effect of current density on the shape of vdf for Ti and Al. An increase in the current intensity implies a linear increase in the relative density of energetic sputtered atoms while the group of thermalized ones appears unaffected in the high current density regime.

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

“…By coupling the value of this flight velocity with relatively high value of atom temperature, about 1000 K, one can see that this first peak is the signature of quasiballistic sputtered atoms which have made very few collisions with the buffer gas during their transport from the target to the probed volume. 10,22 After this first peak there is a fast relaxation of the Ti atom temperature due to collisions with buffer gas atoms, which takes place roughly in the first 200 ls. In other words, 200 ls is the typical time necessary to thermalize Ti atoms by scattering on argon gas atoms, or at least to make them lose almost all of their initial energy they got when ejected from the target.…”

On Both Spatial And Velocity Distribution Of Sputtered Particles In Magnetron Discharge

“…The LIF signal was registered in different positions along a diameter of the magnetron target, for a distance of 1 mm from the cathode surface. More details about this classical system of operation have been already presented [9][10][11]. As it was already pointed out, the velocity distribution of sputtered metal species measured in the radial direction at low pressure, typically less than 10 mTorr, has twocomponent shape [9].…”

“…These methods primarily used for DC steady state magnetron discharge [9][10][11] were also developed and used for investigation of the specified kinetic parameters within pulsed system as time resolved -direct absorption profile (TR-DAP) [12].…”

“…In this case the laser beam is injected perpendicular to the target surface probing the velocity component perpendicular (normal) to the target. The measurement made in y direction perpendicular to target surface shows clear dependence of the velocity and energy distribution of the sputtered atoms on the distance from the cathode surface, on discharge current intensity and the gas pressure[9][10][11].…”

Laser-Induced Fluorescence of Hydroxyl (OH) Radical in Cold Atmospheric Discharges

“…This technique offers the lowest spectral width of the output line among the mentioned methods, but as the tuning range is strongly limited, it is often insufficient to cover a satisfying number of rotational lines in the molecular spectra. Notable work on atomic LIF by TDL is, for example, [25].…”