Two analyses of steadyhyphen;state mass transport during laser chemical vapor deposition (LCVD) are compared for a hemispherical source/sink geometry. The first considers only diffusion while the second includes diffusion and also convection due to the mole number change of vapor species in the reaction, which is modeled as the radial outflow of an incompressible gas from a point source. The results of the two analyses differ markedly for high deposition fluxes and large radii. For example, in the LCVD of Ni from Ni(CO4), reactant partial pressures at the hemispherical surface predicted by the diffusion plus convection analysis are less than those predicted by the diffusion analysis because the inward diffusion of the reactant species is hindered by the convective outflow of the product species. The diffusion analysis predicts an increase in total pressure at the hemispherical surface, which normally is relieved by the neglected convective flow. Bounds for transport controlled deposition and for deposition where convection can be safely neglected are specified. The diffusion plus convection analysis is generalized to cover a surface distribution of sources/sinks, and can be employed to predict local partial pressures in steadyhyphen;state LCVD.
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