The thermophoretic force acting on a small particle suspended in the near-wall region of a low-pressure plasma processor

Abstract

Analytical results are presented concerning the thermophoretic force acting on a spherical particle suspended in the near-wall region of a low-pressure plasma processor. Because the mean free path length of gas molecules is not negligibly small in comparison with the characteristic dimension of the plasma processor, for this case, a complex temperature variation will occur near the processor wall which can be approximately treated by using a temperature jump at the wall associated with a linear temperature distribution extended from the wall to bulk gas. The temperature jump at the processor wall has been included in the present analysis to determine the temperature of the molecules coming from the bulk gas and incident upon the suspended particle. It is shown that the thermophoretic force acting on the near-wall particle depends not only on the temperature gradient within the bulk gas but also on the magnitude of temperature jump at the processor wall. Dependent on the gas type, the thermophoretic force acting on the near-wall particle may even be greater than its counterpart without accounting for the near-wall effect.