Room-temperature ferromagnetism in N+-implanted ZnO:Mn thin films

Mn–N co-doped ZnO films with wurtzite structure were fabricated by RF magnetron sputtering together with the ion-implantation technique. Then a post-annealing at 650 °C for 10 min in a N2 atmosphere was performed to activate the implanted N+ ions and recover the crystal quality, and a p-type ZnO:Mn–N film with a hole concentration of about 2.1×1016 cm−3 was obtained. It is found that the Mn mono-doped ZnO film only exhibits paramagnetic behavior, while after N+-implantation, it shows ferromagnetism at 300 K, and the magnetization of the ZnO:Mn–N films can be further enhanced by thermal annealing due to the activation of the N acceptors. Our experimental results confirm that the codoping N acceptors are favorable for ferromagnetic ordering of Mn2+ ions in ZnO, which is consistent with the recent theoretical calculations.

► Mn–N codoped ZnO thin films were achieved by implanting nitrogen ions (N+) into the sputtered ZnO:Mn films. ► The p-type ZnO:Mn–N film with a hole concentration of 2.1×1016 cm−3 was obtained. ► N doping plays a crucial role in the activation of ferromagnetism ordering in ZnO:Mn films. ► The p-type ZnO:Mn–N film shows the strongest room temperature ferromagnetism. ► The existence of ferromagnetism in ZnO:Mn system has no direct correlation with the conductivity type for the specific samples.