Answer Happy

Now we turn to the combined effect of diffusion and deposition. By using the expressions below, show that the statement is correct that at higher pressures the diffusion controlled deposition sets in at a lower temperature. Hint: realize that D times pressure is constant 9 = = F C,N Rd N 8D + 1/ks Rd is the overall deposition rate, F is the flux of molecules through the boundary layer, N is the number of atoms per unit volume in the deposited film, is the boundary-layer thickness, C, is the concentration at the outer edge of the gaseous boundary layer, D is the gas-phase diffusivity of the reactant, and kg is the surface reaction-rate coefficient, which depends exponentially on the reciprocal of temperature, with an activation energy E, [kg = koerp (-E,KT)). g S =