Plasma transport around dust agglomerates having complex shapes

Dust particles generated in low temperature plasmas as used for microelectronics fabrication are often agglomerates of smaller monodisperse particles. The transport of these agglomerates, and the subsequent contamination of surfaces, depends on the details of ion-momentum transfer ~ion drag! to, and electrostatic forces on, the agglomerate. Given that the charge distribution on the surface of the agglomerate and local electric fields in the vicinity of the agglomerate depend on its shape, the subsequent forces on the agglomerate will also be a function of shape. In this article, we describe results from a simulation in which plasma transport around, and the charging of, agglomerates are investigated. We find that the charge distribution on the agglomerates is generally nonuniform, a consequence of both shadowing and charge depletion. The ion-momentum transfer cross section, calculated using a Monte Carlo simulation, also depends on the shape of the agglomerate. © 1998 American Institute of Physics. @S0021-8979~98!04711-2#