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.