Preferred heteroepitaxial orientations of ZnO nanorods on Ag

Wurtzite ZnO nanorods were grown from solution onto coarse-grain bulk polycrystalline Ag substrates to explore the nature of preferred heteroepitaxial orientations. ZnO nanorods grow copiously on grains with <111> and <001> surface normals. Two epitaxial orientations were observed: {0001} ZnO ‖ {111} Ag with <20> ZnO ‖ <10> Ag and {0001} ZnO ‖ {001} Ag with <20> ZnO ‖ <10> Ag. Both feature ZnO basal plane growth, and the specific in-plane orientation relationships both feature alignment of close-packed directions in the interface. Nanorod growth was strongly suppressed on Ag grains in most other orientations. Although strain energy minimization is often invoked to explain the {0001} ZnO ‖ {111} Ag with <20> ZnO ‖ <10> Ag orientation, associated with an almost ideal near-coincidence site lattice matching, our data suggests that strain may not be the sole, or even the most important, determinant of the preferred orientations during solution-based epitaxial growth in this system.