Magnetic and optical properties of printed ZnO:Co polycrystalline layers

• Published in: Materials science in semiconductor processing Vol. 135; p. 106054
• Main Authors: Pekar, G.S., Singaеvsky, A.F., Kolomys, O.F., Strelchuk, V.V., Lytvyn, P.M., Osipyonok, M.M., Vasin, I.A., Skoryk, M.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.11.2021
• Subjects: Co-doped ZnO; Magnetization at room temperature; Printed polycrystalline layers; Uniform distribution of Co ions In the Zn sites; Printed polycrystalline layers; Uniform distribution of Co ions In the Zn sites; Co-doped ZnO; Magnetization at room temperature
• ISSN: 1369-8001; 1873-4081
• DOI: 10.1016/j.mssp.2021.106054

The results of studies of printed ZnO:Co polycrystalline layers are first described. The layers with Co concentration of 0.78, 2.09 and 5.42 at.% were printed by a new stencil-free method developed by the authors and then were recrystallized at a temperature 1000–1100 °C. It was shown that the layers were polycrystalline with a typical grain size about 500 nm, were densely packed and had a rather uniform single-phase wurtzite structure. The influence of Co doping on the structure, composition, photoluminescence, optical absorption, confocal micro-Raman spectra and the magnetic properties of the layers was investigated. It was shown that Co ions substituted Zn2+ ions and were uniformly distributed in the ZnO lattice whereas in previous publications on ZnO:Co only the statistical average distribution of Co in ZnO films was reported. In was also found that, with increasing Co contamination, Raman spectra showed systematic frequency shift and broadening of the E2(high) and E2(low) phonon modes. The optical band gap of the layers decreased with increasing Co contamination and the lattice parameters a and c were found to depend slightly on the Co content. At cryogenic temperatures the donor bound excitons dominated in the photoluminescence spectra of ZnO:Co layers which indicated that the layers were of a good crystalline quality and had a n-type conductivity. Magnetization measurements made by the method of magnetic force microscopy (MFM) revealed a clear magnetic contrast in 2D magnetization maps, providing the evidence of in-plane ferromagnetic magnetization at room temperature. Magnetization was shown to be increased with increasing Co content. The direct correlation between the magnetic behavior of ZnO:Сo polycrystalline layers and their microstructure was identified. In particular, it was shown that secondary Co-related spinel phases, if any, were localized at the grain boundaries of the ZnO:Co microcrystallites. •Сo-doped ZnO polycrystalline layers with a different cobalt content have been printed by the developed stencil-free technique.•Cobalt ions are shown to be uniformly distributed in the Zn sites of the ZnO lattice.•The printed ZnO:Co layers exhibit inplane magnetization at room temperature.