Spatially controlled atomic layer deposition in porous materials

We describe a technique for depositing materials at controlled depths within porous substrates based upon the passivating effect produced by one precursor to prevent the adsorption of a second precursor. For example, a surface exposed to trimethyl aluminum is not reactive toward diethyl zinc. This effect, combined with Knudsen diffusion in which the precursor exposure times dictate the depth of penetration of the deposited layer, enables spatially controlled "stripe coating" within porous supports. We demonstrate ZnO stripes in anodic alumina and model the results using Monte Carlo simulations. Etching is identified as a potential problem for certain precursor combinations. (C) 2007 American Institute of Physics.