| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS+AS+NS+SS-ThM |
| Session: | Plasma Synthesis of Nanostructures |
| Presenter: | T. Lopez, University of California, Riverside |
| Authors: | T. Lopez, University of California, Riverside L. Mangolini, University of California, Riverside |
| Correspondent: | Click to Email |
The use of continuous flow non-thermal plasma reactor for the formation of silicon nanoparticles has attracted great interest because of the advantageous properties of the process [1]. Despite the short residence time in the plasma (around 10 milliseconds), a significant fraction of precursor, silane, is converted and collected in the form of nanopowder. The structure of the produced powder can be tuned between amorphous and crystalline by adjusting the power of the radio-frequency power excitation source, with high power leading to the formation of crystalline particles [2]. Numerical modelling suggests that higher excitation power results in a higher plasma density, which in turn increases the nanoparticle heating rate due to interaction between ions, free radicals, and the nanopowder suspended in the plasma [3]. An understanding of the mechanism that leads to the crystallization of the powder while in the plasma is lacking. In this work, we present an experimental investigation on the crystallization kinetic of plasma-produced amorphous powder. Silicon nanoparticles are nucleated and grown using a non-thermal plasma reactor similar to the one described in [1], but operated at low power to give amorphous nanoparticles. The particles are then extracted from the reactor and flown through a tube furnace capable of reaching temperatures up to 1000°C. Raman and TEM have been used to monitor the crystalline fraction of the material as a function of the residence time and temperature. A range of crystalline percentages can be observed from 750 °C to 830 °C. We have also used in-situ FTIR to monitor the role of hydrogen on the crystallization kinetic. It has been proposed that that hydrogen induced crystallization is the mechanism for deposition of microcrystalline silicon thin films in PECVD systems. We find that the plasma-produced amorphous silicon powder is rich with surface SiHx species, but no detectable signature from bulk Si-H bonds has been observed. A discussion of particle growth and plasma-particle interaction will be presented with its relation to the overall effect on crystallization mechanisms.
1. Mangolini, L.; Thimsen, E.; Kortshagen, U., High-yield plasma synthesis of luminescent
silicon nanocrystals. Nano Letters 2005, 5 (4), 655-659.
2. O. Yasar-Inceoglu, T. Lopez, E. Farshihagro, and L. Mangolini, Silicon nanocrystal
production through non-thermal plasma synthesis: a comparative study between silicon
tetrachloride and silane precursors. Nanotechnology, 23(25): p. 255604.(2012)
3. Mangolini, L.; Kortshagen, U., Selective nanoparticle heating: another form of
nonequilibrium in dusty plasmas. Physical review E 2009, 79, 026405 1-8.