Novel in situ method to detect subnanometer‐sized particles in plasmas and its application to particles in helium‐diluted silane radio frequency plasmas

A new Langmuir probe method is proposed to reveal processes of particulate nucleation and its subsequent early growth in silane radio frequency (rf) plasmas. In the method, subnanometer‐sized particles grown during the rf‐discharge‐on phase are detected as negative ions in the subsequent afterglow phase in which temperature and density of electrons have decayed. Preliminary experiments applying the method to helium‐diluted silane rf plasmas have the following features of particle growth: subnanometer‐sized particles are mainly generated around the plasma/sheath boundary near the rf electrode; they grow with increase in the rf‐discharge‐on period, Ton, for Ton≲a gas residence time of the discharge.