Aim
Gasphase plasma reactors are particularly suitable for the synthesis of non-aggregated, highly specific nanomaterials, especially based on silicon. Silicon is a basic material in semiconductor industry. It is used in applications like computer chips, photvoltaic cells and sensors. In combination with germanium it is a frequently-discussed material for high-temperature thermoelectrics. Nanostructuring of silicon reveals several new properties of a well-known material, e.g. tunable photoluminescence, enhanced thermoelectric performance and properties that makes it suitable for applications in lithium-ion batteries with increased storage capacity. This reactor enables for the synthesis of tailored, crystalline nanoparticles in quantities that are sufficient for the exploration of their benefits to numerous applications. It also allows to investigate the particle formation process and the influence of synthesis parameters on the particles’ size, morphology and properties.

Approach
The microwave flow reactor generates an argon/hydrogen plasma, which decomposes gaseous precursors, e.g. silane (SiH₄) into components, forming a supersaturated vapor. Depending on the conditions during synthesis, this vapor forms solid, crystalline materials with diameters between 5 and 100 nm. Production rates from 0.5 to 10 gram per hour are possible. The resulting product is carried by the gas flow into a strainer and collected by a filter device. It can be bottled under inert gas atmosphere. Surveillance of quantitative conversion from precursor to particles is validated by mass spectrometry. The synthesis takes place at 10 to 200 mbar, a microwave-power between 1 to 2.5 kW and an overall mass flow between 5 to 15 slm, while the precursor flow varies between 10 to 200 sccm.
Plasma-based approaches allow for the synthesis of different oxidic and non-oxidic nanoparticles from gaseous and vaporized precursors.

References
J. Knipping, H. Wiggers, B. Rellinghaus, P. Roth, D. Konjhodzic, C. Meier „Synthesis of high purity silicon nanoparticles in a low pressure microwave reactor“ J. Nanosci. Nanotech. 4, 1039-1044, (2004).

Contact
apl. Prof. Dr. habil. H. Wiggers, Hartmut Wiggers, Tel: +49 (0)203 - 379 8087, IVG