AVS 62nd International Symposium & Exhibition
    Plasma Science and Technology Monday Sessions
       Session PS+EM-MoA

Paper PS+EM-MoA8
Nucleation of Silicon Nanocrystals in a Remote Plasma without Subsequent Coaguation

Monday, October 19, 2015, 4:40 pm, Room 210B

Session: Directed Self Assembly and Plasma Synthesis of Novel Materials
Presenter: Ilker Dogan, Eindhoven University of Technology, Netherlands
Authors: I. Dogan, Eindhoven University of Technology, Netherlands
S.L. Weeks, Colorado School of Mines
S. Agarwal, Colorado School of Mines
M.C.M. van de Sanden, Dutch Institute for Fundamental Energy Research (DIFFER), Netherlands
Correspondent: Click to Email
We report on the growth mechanism of spherical silicon nanocrystals (Si-NCs) in a remote expanding Ar plasma using a time-modulated SiH4 gas injection in the microsecond time range. Under identical time-modulation parameters, we varied the local density of the SiH4 gas by changing its stagnation pressure on the injection line over the range 0.1-2.0 bar. We observed that nanocrystals were synthesized in a size range from 2 nm to 50 nm with monocrystalline morphology. Smaller nanocrystals (2-6 nm) with narrower size distributions and with higher number densities were synthesized with an increase of the SiH4 gas-phase density. We related this observation to the rapid depletion of the number density of the molecules, ions and radicals in the plasma during nanocrystal growth, which can primarily occur via nucleation with no significant subsequent coagulation. In addition, in our remote plasma environment, rapid cooling of the gas in the particle growth zone from 1500 K to 400 K significantly reduces the coalescence rate of the nanoparticles, which makes the coagulation process highly unlikely. Our observations on nanocrystal formation via nucleation indicated that subsequent coagulation for further growth is not always an essential step on nanoparticle formation.