We have grown high-quality Co/Cu(001) superlattices by molecular beam epitaxy on R-plane sapphire (<1(1)over bar 02>) substrates using a complex buffer layer system consisting of Nb(001), Cr(001) and Cu(001). The samples were structurally characterized in-situ by reflection high-energy electron diffraction measurements and ex-situ X-ray scattering experiments. Small-angle reflectivity and high-angle Bragg diffraction scans were performed in order to obtain structural information on different length scales in the direction parallel to the growth direction. The in-plane epitaxial relations of the buffer layers and the superlattice was determined with glancing-angle surface scattering. The orientational relationship of Nb on Al2O3 (<1(1)over bar 02>) induces a characteristic tilt angle of the samples.