Influence of surface condition in Langmuir probe measurements

Abstract

The surrounding sheath focuses the charged particles to distinct parts of the probe surface resulting in nonuniform physical and/or chemical properties. Then, after a time interval dependent of the degree of plasma contamination, this process results in well-defined regions with different work functions that shape the probe characteristic leading to erroneous measurement of plasma temperature and ion density. For Ar/O2 and Ar/SF6 plasmas produced within a multipolar magnetically confined device we investigated bombardment by positive or negative charges and indirect heating to modify the surface of a planar probe.

Spatially Resolved Optoelectronic Properties of Al-Doped Zinc Oxide Thin Films Deposited by Radio-Frequency Magnetron Plasma Sputtering Without Substrate Heating

“…While surface characterization techniques such as XPS, TOF-SIMS and XRD allows one to perform spatially resolved analytical investigations, this possibility alone cannot unveil the growth mechanism due to the need for coupling with spatially resolved plasma diagnostics. While electrostatic probes are subject to contamination and electromagnetic field distortions [48,49], optical diagnostics need complex 2D laser-induced fluorescence setups [50] to reveal the needed information.…”

Properties of highly electronegative plasmas produced in a multipolar magnetic-confined device with a transversal magnetic filter

“…The electrical probe circuit and the details of the "Test Function" procedure for extracting the bulk and hot electron densities (n e and n eh ) and temperatures (T e and T eh ) and the negative ion parameters (n ni and T ni ) are presented in detail elsewhere [39,40]. Special care was devoted to avoid recording erroneous probe characteristics affected by contaminations effects reported for reactive plasmas [52,53]. It has been shown that the DC discharges with magnetic confinement exhibit three groups of electrons, namely the anisotropic primary electrons emitted by filament and accelerated to an energy correlated to the discharge voltage in a very thin sheath surrounding the cathode (filament) [54].…”

Improvement of the dose uniformity in plasma immersed ion implantation by introducing a vertical biased ring

“…Later, a similar explanation was adopted for the ion dose non-uniformity found in the PIII case [8]. In order to avoid this problem the introduction of a guard ring, just as in the case of the planar probe [9], was proposed [8]. However, so far, no rigorous treatment was devoted to prove either experimentally or theoretically the reliability of the ion dose uniformity improvement by introducing such a guard ring or to propose alternative solutions.…”