High densities of submicron particles have been created in an Ar/SiH4 parallel plate radio-frequency (rf) discharge. The particles were collected and measured by electron microscopy and the mean particle diameter was found to be 230±60 nm. Laser scattering from the dense clouds of such particles showed that the concentration was 1×108 cm−3. A laser Doppler anemometer was used to measure the particle velocity distribution and hence the mean particle mass. This is consistent with the specific density of the hydrogenated amorphous silicon. The mean velocities of particles were measured at two different gas flows when the discharge was extinguished, so that the particles are neutral and do not interact, and the particles move with the gas velocity. However, during the discharge the particles have almost no mean axial velocity, even though the gas flow is as large as before. This is due to the strong interparticle interactions that keep the particle cloud, as a whole, stationary. The charge on the particles is estimated, leading to a value of the Coulomb coupling parameter of Γ=10. This large value suggests that the particle cloud can be viewed as a Coulomb liquid.

In this article we focus on the time evolution of macroscopic and microscopic properties of a dust forming plasma in a silane–argon low pressure radio frequency (rf) discharge. The time evolution of electron density, ion density, dust particle concentration, and the current density were recorded in a low pressure (0.1 Torr) rf Ar–SiH4 discharge. From these data and optical emission spectroscopy simultaneous measurements, the time evolution of the electron mean energy and the particle mean charge are determined. Together with previous experimental data concerning the nucleation and growth of dust particles, a complete experimental set of microscopic and macroscopic data is available and it is compared to a theoretical model including both particle growth and dusty discharge parameters. A clear representation of this closely coupled time evolution of the particles’ formation and plasma properties is given. It includes the nucleation and coagulation phenomena for particles, and the strong increase of the rf electric field in the plasma volume and the increase of the excitation rates of electrons.

Dust generation in plasma reactors used for PECVO is a general 1:m:ting effect which occurs when tryhg to obtain high deposition rates in the fabrication of thin films. In sJch dust-forming processes, for instance silane dscharges. very high concentrations of submicrometre s'zed particulates are readily produced. The theoretical approach and the modelling of these dusty dense pasmas suggest that they have very pecJliar properties with spectacular effects concerning tne plasma equil:br'um and the behaviour of the particulate cloud.argon-silane or in pure argon RF discharges and experimental data obtained in these situations are reported here, in connection w:th the theoretical predictions.In terms of plasma properties the drastic modification of the free electron population, induced by the presence of the part;cles, is one of the most important resu.ts, with sigdficant effects on the chem'cal equilibrium of the plasma.In terms of the particle cloud behaviour the strong electrostatic interaction between the negatively charged particulates is shown to be an order of magnitude hgher than their ltinetic energy and this particle cloud has to be described a s a 'Coulomb liquid'. An overview of oJr experimental studies of these effects in a dJsty dense plasma situation is given, including the most recent results.