Plasma gas aggregation cluster source: Influence of gas inlet configuration and total surface area on the heterogeneous aggregation of silicon clusters

Abstract

In nanotechnology, individual clusters can be produced using a plasma gas aggregation cluster source through a homogeneous nucleation process of atoms. The size of the clusters is typically controlled by varying the length of the aggregation zone, the pressure differential between the aggregation and the deposition zones, and the deposition power. To assess whether the size of the clusters could also be affected by the level of interactions with the walls of the chamber (heterogeneous nucleation process), we modified the gas inlet geometry and placed additional internal walls in the aggregation zone. This paper presents the effects of the gas flow lines on the distribution of particles size and provides evidence of the heterogeneous nucleation of clusters through interactions with the walls.We observed increases in either the number density of particles or in the size of particles for a downward facing or inward facing gas inlet configurations, respectively. Our simulation results revealed a strong dependence of the gas flow lines patterns on the gas inlet geometry. By expanding the available surface of interaction, the mean size of the clusters increased. In conclusion, the gas flow lines are critical in the aggregation of atoms and the clusters nucleation can be controlled through surface interaction; this gas and wall dependence will need to be considered for designing new large-scale aggregation chambers for the development of nanocomposite coatings.