Room-temperature ferromagnetism in Cu+ implanted ZnO nanowires

We experimentally showed ferromagnetism at above 300 K for ZnO nanowires prepared by reactive vapour deposition and subsequently implanted with 2 at% of Cu. The magnetic moments of the samples annealed in oxygen and in argon at 600 degrees C for 120 min are about 0.42 mu(B) and 0.33 mu(B) per Cu atom, respectively. No ferromagnetism-related secondary phase existed according to the results of x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy including HRTEM and EELS mapping. It can be concluded that the d(9) configuration in the ground state of Cu2+ plays an important role in ferromagnetism. This controllable and shallow doped ion implantation technique may find potential applications in spintronic, especially nano-spintronic, devices.