Nano-clusters structure and magnetic properties of high fluence Mn+ ion-implanted GaN

The n-type GaN film was grown on sapphire substrate by metal organic chemical vapour deposition (MOCVD). Mn+ ions of 75 keV with the fluence of 8 × 1017/cm2 were implanted in the GaN at 350 °C. The implanted sample was annealed at 850 °C to recrystallize the sample and to remove implantation damage. We investigated the structural and magnetic properties of Mn+ ion-implanted GaN by using Rutherford back-scattering (RBS), high resolution transmission electron microscopy (HRTEM) and superconducting quantum interference device (SQUID). RBS results showed the Mn+ ions were concentrated near the surface. HRTEM results showed nano-clusters structure in the sample. The temperature dependence of magnetization taken in zero-field-cooling and field-cooling conditions with the block temperature was 267 K and hysteresis loops which exhibited a transformation from ferromagnetism to superparamagnetism showed the features of magnetic nano-clusters system. And it could be explained the magnetic property of this film originated from Mn-rich clusters.