A transparent glass or ceramic or glass-ceramic substrate, coated with a functional layer or with a stack of at least two functional layers, the functional layer or at least one of the functional layers of the stack being porous and made of an inorganic material M1, wherein the or at least one of the porous functional layer(s) of inorganic material M1 has, at the surface of at least one portion of the pores thereof, at least one inorganic material M2 different from M1.