Diode laser-induced fluorescence measurements of metastable argon ions in a magnetized inductively coupled plasma

Abstract

Velocity distribution functions of metastable argon ions ͑3dЈ4 F 7/2 ͒ have been measured to obtain metastable ion density and temperature by the diode laser-induced fluorescence ͑LIF͒ technique in magnetized inductively coupled plasma as a function of pressure, rf power, and magnetic field strength. Calculated density from a rate equation agrees with the trends observed in the experimental data. From the calculation, the metastable ion density should be over 10 7 cm −3 to obtain a LIF signal. From a dc bias experiment, it is suggested that the spatial potential can be the dominant ion heating source, and a simple global model for ion temperature is constructed. In this model, approximately 0.01% and 10% of total spatial potential energy can contribute to ion and neutral temperatures, respectively. The measured ion temperature agrees with the calculation.

Time-resolved laser-induced fluorescence spectroscopy using CW diode laser for diagnostics of argon-ion velocity distribution near AC-biased electrode

“…Because the IVDFs in bulk plasmas and ion-acceleration fields are crucial in various plasma technologies, the LIF method has been extensively used to obtain the IVDFs, and its capability has been confirmed based on comparison with measurement results yielded by RFEAs. [27][28][29] To investigate the behavior of rare-gas ions in lowtemperature plasmas in the steady state, the LIF method has been utilized to diagnose bulk plasmas, [30][31][32][33] pre-sheaths, [34][35][36][37][38] ion sheaths formed on floated, 39,40 and DC-biased electrodes, [41][42][43][44][45] and plumes of electric propulsion devices. [46][47][48][49][50][51][52] To understand the dynamic behaviors of ions in plasmas, time-resolved LIF systems have been developed and applied to diagnose spatiotemporal fluctuations in plasma thrusters, [53][54][55][56][57] the temporal evolution of discharge and afterglow phases in pulsed plasmas, 58,59 and ion sheaths formed on AC-biased electrodes.…”

Laser induced fluorescence diagnostic for velocity distribution functions: applications, physics, methods and developments

“…LIF measurements of IVDFs of a pulsed inductively coupled plasma with have been reported by Jacobs et al [165] with a two-dimensional flow pattern of the ion velocity above the substrate. Jun et al have also been measured metastable ion density and temperature by the diode LIF technique in magnetized inductively coupled plasma as a function of pressure, RF power, and magnetic field strength [166]. The 2D ion velocity distribution of inductively coupled RF plasma had been measured with optical tomography via LIF in the bulk plasma and in the presheath of a plate with LIF and optical tomography, Zimmerman at al found that ion temperature depends on RF frequency and is weakly dependent on pressure [167].…”

2-dimensional ion velocity distributions measured by laser-induced fluorescence above a radio-frequency biased silicon wafer

“…In the context of low pressure plasmas for materials processing, the technique has been used to measure ion densities, drift velocities, and energy distribution functions in dc and rf sheaths. [28][29][30][31][32][33][34][38][39][40][41][42] The electric field inside an rf sheath has also been measured by using a two-step process called LIF-dip in which the field is calculated from the Stark shifted fluorescence from ions. 43,44 Our implementation of the LIF technique uses the 3d 02 G 9/2 -4p 07 F 7/2 transition in argon.…”