Electrostatic enhancement factor for the coagulation of silicon nanoparticles in low-temperature plasmas

TL;DR

This study numerically investigates how electrostatic interactions, including polarization effects, enhance silicon nanoparticle coagulation in low-temperature plasmas, revealing significant effects even between like-charged particles.

Contribution

It introduces a rigorous multipole-based electrostatic interaction model for dielectric nanoparticles, improving understanding of coagulation enhancement mechanisms.

Findings

Polarization significantly enhances coagulation rates.

Like-charged particles can attract due to dielectric effects.

A simplified analytic potential is proposed for practical use.

Abstract

The coagulation enhancement factor due to electrostatic (Coulomb and polarization-induced) interaction between silicon nanoparticles was numerically computed for different nanoparticle sizes and charges in typical low-emperature argon-silane plasma conditions. We used a rigorous formulation, based on a multipole moment coefficients, to describe the complete electrostatic interaction between dielectric particles. The resulting interaction potential is non-singular at the contact point, which allows to adapt the orbital-motion limited theory to calculate the enhancement factor. It is shown that, due to induced polarization, coagulation is enhanced in neutral-charged particles encounters up to several orders of magnitude. Moreover, the short-range force between like-charged nanoparticles can become attractive as a direct consequence of the dielectric nature of the nanoparticles. The multipolar coefficient potential is compared to an approximate analytic form which can be readily used to simplify the calculations. The results presented here provide a better understanding of the electrostatic interaction in coagulation and can be used in dust growth simulations in low-temperature plasmas where coagulation is a significant process.