High-Throughput Low Frequency Reactor for Non-Thermal Plasma Synthesis of Amorphous Silicon Nanoparticles

The purpose of this article is to increase availability and applicability of laboratory and industrial scale non-thermal plasma synthesis of nanoparticles. To that end, the article describes an original apparatus setup for the preparation of amorphous silicon nanoparticles from silane, as well as identification and characterization of the product. Glow discharge is generated through direct contact of a gas mixture with electrodes, an accessible 8 kHz power source is used. Hydrogen, argon, air, and mixtures thereof are considered as the dilutant gases. The methods employed include SEM, vibrational spectroscopy and total reflection XRF spectroscopy. On the basis of vibrational spectra interpretation the particles are found to consist of hydrogenated amorphous silicon. According to IR spectroscopy data, the surface passivation is largely with SiH 2 groups when hydrogen or argon are used, in the case of air dilution the particles are readily surface oxidized. Attained mean sizes are on the order of 30–60 nm, as estimated with SEM. Possible electrode-borne impurities are determined to constitute less than 100 ppm of the samples. Partial crystallization, evident from Raman spectra, is observed only for high (60:1) hydrogen dilution with a low silane flow rate. Intermediate values of plasma power are found to be optimal for maximization of the production rate (up to 690 mg/h). Near total conversion of the precursor is demonstrated. The presented reactor design shows record performance in terms of the production rate, high efficiency in the reactant usage. Crucially, elemental purity of the product is not affected by electrode sputtering.