Bremen 2017 – wissenschaftliches Programm
P 7.4: Poster
Montag, 13. März 2017, 16:30–18:30, HS Foyer
Fast Langmuir probe measurements during nanoparticle growth in a CCRF plasma — •Erik von Wahl1, Yerbolat A. Ussenov2, T. S. Ramazanov3, and Holger Kersten1 — 1Institute of Experimental and Applied Physics (IEAP), Kiel University, Germany — 2National Nanotechnology Laboratory of Open type (NNLOT), Al - Farabi KazNU, Almaty, Kazakhstan — 3Institute of Experimental and Theoretical Physics (IETP), Al-Farabi KazNU, Almaty, Kazakhstan
The oldest and well established technique to measure electron temperatures and electron densities in a plasma is the Langmuir probe, introduced by Mott-Smith and Langmuir.
However, in dust forming plasmas the current onto the probe may be distorted by charged dust particles and non-conductive contamination due to film forming radicals and ions. One approach to overcome this problem is by shielding the probe tip from its environment. In the present study ion bombardment by a negatively biased probe was used instead to keep it clean. Additionally, the V-I-characteristics were obtained by an advanced and fast voltage sweep pattern for the probe bias. By keeping the duration of positive bias shorter than the inverse of the nanoparticle’s plasma frequency τd=1/ωpd the negatively charged dust particles are not able to overcome the on average negative probe potential and, thus, cannot contaminate the probe.
Measured changes in electron density and temperature are presented during the entire growth cycle of nanoparticles. An upper limit for the dust plasma frequency will also be presented.