Temperature dependence and defect related structure, photoluminescence, (ferro)magnetism and ammonia sensitivity of un-doped nanocrystalline ZnO

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Vol. 262; p. 114748
• Main Authors: Mihalache, V., Secu, M., Negrila, C., Bercu, V., Mercioniu, I., Leca, A.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-12-2020; Elsevier BV
• Subjects: Ammonia; Crystal defects; Crystallites; Curie temperature; Defect annealing; Electron paramagnetic resonance; Extended defects; Ferromagnetism; FTIR; Magnetic saturation; Magnetism; Microstrain; Microstructure; Morphology; Nanoparticles; Native point defects; NH3 adsorption; Optoelectronic devices; Photoluminescence; Room temperature; Room temperature ferromagnetism; Temperature dependence; Unit cell; UV–vis; XPS; Zinc oxide; ZnO nanostructures; UV–vis; Room temperature ferromagnetism; NH3 adsorption; FTIR; Photoluminescence; Native point defects; ZnO nanostructures; XPS; Electron paramagnetic resonance; Microstructure; Extended defects; Curie temperature
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2020.114748

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•ZnO prepared by decomposition of Zn-propionate and annealing at 400–970 °C show RTFM.•g = 2.0065 and g = 1.9632 EPR signals. A prominent violet-blue PL emission for 470–800 °C.•Very intense green-yellow PL emission and large number of GBs for 800–970 °C.•Strained lattice for 400 °C; Ms enhanced to 0.022 emu/g; TC > 700 °C; high NH3 adsorption.•Intrinsic defects in a distorted lattice or pinned by GBs generate RTFM.
ZnO nanostructures with intrinsic and extended defects were prepared by rapid decomposition of zinc-propionate and annealing at 400 °C–970 °C. The correlation between the structure/morphology, type of native defects (photoluminescence (PL), EPR) and ferromagnetism was investigated, together with ammonia adsorption capacity. All the samples show room temperature ferromagnetism (RTFM). Crystallite size increases while the unit cell volume, c-axis constant, microstrain and saturation magnetization relax with increasing temperature; morphology varies from aggregated nanoparticles to frameworks of well-welded crystals. 400 °C–800 °C annealed samples show a broad visible and/or a prominent violet-blue PL emission and, two narrow g = 2.0065 and g = 1.9632 EPR signals. 800 °C–970 °C annealed samples exhibit very intense green-yellow photoluminescence. The intrinsic defects in conjunction with a deformed lattice and/or pinned by grain-boundaries appear responsible for RTFM and Curie temperature exceeding 700 °C. Tuning the morphology, PL intensity and ferromagnetic signal by choice of annealing temperature can find applications in (gas) sensing, photonic/optoelectronic and spintronic devices.