Stuttgart 2012 – scientific programme
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P: Fachverband Plasmaphysik
P 19: Komplexe und staubige Plasmen
P 19.4: Talk
Thursday, March 15, 2012, 15:10–15:25, V57.02
Three growth modes of nanoparticles generated in reactive plasmas — •Kazunori Koga1,2, Kunihiro Kamataki1, Shota Nunomura3, Shinya Iwashita2, Giichiro Uchida1, Hyunwoong Seo1, Naho Itagaki1, Masaharu Shiratani1, and Uwe Czarnetzki2 — 1Kyushu University, Fukuoka, Japan — 2Ruhr-University Bochum, Bochum, Germany — 3AIST, Tsukuba, Japan
Nanoparticles formed in reactive plasmas can be employed as building blocks of nanostructures [1]. To study growth kinetics of nanoparticles in reactive plasmas, a diagram of the particle growth modes was obtained as a function of the density ratio of a nanoparticle density to an ion density np/ni and a nanoparticle size d. For d= 20nm, particle growth rate increases with np for np/ni> 20 by coagulation between nanoparticles. In such positive feedback growth mode, the collision frequency between nanoparticles, most of which are neutral, increases with increasing np. For np/ni< 20, the coagulation is suppressed by electrostatic repulsive force exerted on nanoparticles. In this case, a main growth process is a deposition of radicals to the nanoparticles. In the np/ni range between 2× 10−5 and 20, the growth rate decreases with increasing np. In such negative feedback growth mode, the flux of radicals to a nanoparticle decreases with increasing np because nanoparticles act as a major sink of the radicals. For np/ni< 2× 10−5, the growth rate is independent on np. In this independent growth mode, the radical flux to a nanoparticle is irrelevant to np because the chamber wall is the main sink of the radicals.
[1] M. Shiratani, et al., J. Phys. D: Appl. Phys. 44 (2011) 174038.