Robust room-temperature ferromagnetism and the effect of doping concentration in (Co, Tb) co-implanted GaN films

Abstract

The present study reports a large room temperature ferromagnetism in Co and Tb co-doped GaN films and further investigates the correlation between the doping concentration and the magnetic moment. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements confirm that most of the dopants are incorporated into the GaN lattice. Photoluminescence (PL) and Raman spectra results reveal that post-annealing repaired most of lattice defects induced by ion implantation. The ZFC/FC curves show a blocked phase related to Co precipitates in Co single-doped GaN system and this phase is suppressed by the incorporation of Tb ions in the co-doped GaN systems. Although the magnetic properties were enhanced with the co-implantation of Co and Tb ions, the magnetic moment introduced by each ion slightly decreased with increasing Tb concentration. Density functional theory (DFT) calculations suggest that a high doping concentration of Tb atoms leads to the antiferromagnetic phase in the nearest position between Co and Tb ions. Appropriate co-doping with Co and Tb ions in GaN favors the development of enhanced ferromagnetism with no secondary phase. Our study not only offers valuable insights for understanding the magnetic characteristics of co-doped GaN, but also highlights the viability of developing room-temperature diluted magnetic semiconductors by appropriately co-doping TM and RE elements.