Tunable ferromagnetic behavior in Cr doped ZnO nanorod arrays through defect engineering

Abstract

Zn vacancy (V_Zn) effects on the microstructure and ferromagnetism (FM) of Zn_0.94Cr_0.06O nanorod arrays have been investigated using a combination of experimental measurements and first-principles calculations. The well-aligned Zn_0.94Cr_0.06O nanorod arrays were synthesized by radio frequency magnetron sputtering deposition at different substrate temperatures. The Cr K-edge X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy results revealed that the Cr³⁺ ions were located at the substitutional Zn sites. Moreover, the O K-edge XANES analysis and resonance Raman scattering indicated the existence of numerous V_Zn. The stable FM observed at room temperature was an intrinsic property of Zn_0.94Cr_0.06O nanorod arrays. With increasing substrate temperature, improved crystallinity along with the increase in V_Zn was observed in Zn_0.94Cr_0.06O nanorod arrays, and an enhancement of magnetic moment in the samples came forth. First-principles calculations revealed that the enhanced magnetism mainly comes from the unsaturated 2p orbitals of the surrounding O atoms, which is caused by the presence of the Zn vacancy. This research represents a novel promising route for tuning the magnetic behavior of nano-dilute magnetic semiconductor systems via V_Zn changes.