Patent ID: 7947579

Claim:
A method for forming a barrier layer on a porous material comprising: using a plasma defined ALD process wherein: a) a plasma is used during the ALD process for localizing the barrier layer to an external surface of the porous material and without compromising porosity of the porous material; b) ALD precursors are selected to be non-reactive to each other unless activated by plasma, ALD deposition cannot take place unless assisted by plasma, and takes place only in places irradiated by plasma; c) plasma parameters comprise a Debye length and molecular mean free path each larger than a pore size of the porous material, wherein internal pores comprising the pores in the porous material are at least 5 nm below the external surface; and d) deposition of the barrier layer inside internal pores of the porous material is avoided and deposition takes place only on the external surface of the porous material.