The inexpensive fabrication of large three-dimensional and highly oriented porous microrod array of n-type ZnO semiconductor with a unique designed architecture consisting of well-defined, length-tailored, monodisperse, perpendicularly oriented single-cryst. hexagonal rods, grown directly onto polycryst., single-cryst., or amorphous substrates, from an aq. soln. of Zn salt at low temp. is reported.