Phase transitions of dense systems of charged ‘‘dust’’ grains in plasmas

The behavior of ‘‘dust’’ grains (particulates) in microelectronics process plasmas has been studied using N‐body simulations. Grains are assumed to be negatively charged and interact through a screened Coulomb potential Φ(r). The dimensionless parameters κ=a/λ and Γ=Φ(a)/kBT characterize the thermodynamics of the particulate system, where λ is the ion Debye length, a=(3/4πnD)^1/3 is the mean intergrain distance, and nD and T are the dust density and temperature. The simulations exhibit a transition between ‘‘fluid’’ and ‘‘solid’’ phases at a critical value Γc that depends on κ and weakly on the system history (i.e., whether it ‘‘melts’’ from an ordered state or ‘‘freezes’’ from a random one).