Combined effects of thermophoresis and electrophoresis on particle deposition onto a wafer

A theoretical study of aerosol particles responding io thermophoresis and electrophoresis, and the deposition rate of the particles onto an axisymmetric wafer, is proposed. The flow is modeled as a two-dimensional, incompressible and steady-state laminar forced convective flow. The mechanisms of particle deposition by convection, Brownian diffusion, sedimentation, thermophoresis and electrophoresis are coupled. Similarity analysis is used to transform the governing equations for mass, momentum and concentration into a system of ordinary differential equations. Through numerical integration of the equation for particle concentration, concentration profiles and deposition rates are obtained. While the results are compared with the simple-addition method for a one-dimensional stagnant film model, the error on the film model increases with an increase in the temperature gradient, particularly when thermophoresis is the dominating mechanism. Comparing the experimental results from previous works with the calculated results of deposition velocity, we find that the comparison shows a very good agreement. (C) 1998 Elsevier Science Ltd. All rights reserved.