Structural, magnetic, and optical properties of Co- and Gd-implanted ZnO(0001) substrates. - Ney, V.; Ye, S.; Kammermeier, T.; Ney, A.; Zhou, H.; Fallert, J.; Kalt, H.; Lo, F.-Y.; Melnikov, A.; Wieck, A. D. (Journal of Applied Physics, 2008)