Theoretical examination of defect structures and spin Hamiltonian parameters of manganese (II)- and cobalt (II)-doped ZnO nanowires. (June 2022)

• Record Type: Journal Article
• Authors: Wu, Li-Na; Zhang, Gao-Jun; Yang, Si-Tong; Guo, Jia-Xing; Wu, Shao-Yi
• Is Part Of: Journal of physics and chemistry of solids. Volume 165(2022)
• Publication Date: 2022-06
• Subjects: Electron paramagnetic resonance -- Defect structures -- Co2+ -- Mn2+ -- ZnO nanowires; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2022.110657
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: This study theoretically investigates the defect structures of Mn 2+ at 3 and 10 at. % as well as those of Co 2+ at 5 at. % in ZnO nanowires by analyzing their experimental spin Hamiltonian parameters (g factors, hyperfine structure constants A, and zero-field splitting D) based on perturbation formulae in trigonally distorted tetrahedral 3 d 5 and 3 d 7 clusters, respectively. Unlike the trigonal distortion of the host Zn 2+ site in ZnO nanowires, the impurities Mn 2+ and Co 2+ underwent displacements Δ Z (≈0.0223 and 0.0233 Å for Mn 2+, and 0.040 and 0.043 Å for the two Co 2+ centers) away from the ligand oxygen triangles along the C3 axis at 3 and 10 at. %, and at 5 at. %, respectively. In light of the significant covalent interactions of the two Co 2+ centers, their contributions to the spin Hamiltonian parameters due to the charge transfer mechanism need to be included in the theoretical calculations. The defect structures and spectral properties are also discussed in view of the different crystalline morphologies of the doped samples, which indicate that the values of Δ Z of the Mn 2+ centers decreased in low-dimensional materials, whereas those of the Co 2+ centers remained nearly constant owing to strong covalence. Graphical abstract: Image 1 Highlights: This study theoretically investigates the SHPs and defect structures of Mn 2+ and Co 2+ in ZnO nanowires. Impurity displacements away from oxygen triangles along the C3 axis were obtained by analyzing the SHPs. Reductions in the displacement of Mn 2+ centers were noted in low-dimensional ZnO materials. Nearly the same displacements were observed for the Co 2+ centers in various ZnO materials owing to strong covalency.