Effect of Dopant Oxidation State and Annealing Atmosphere on the Functional Properties of Zinc Oxide-Based Nanocrystalli
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Effect of Dopant Oxidation State and Annealing Atmosphere on the Functional Properties of Zinc Oxide-Based Nanocrystalline Powder and Thin Films Miguel A. Santiago Rivera1, Gina M. Montes Albino2, and Oscar Perales Pérez3 1 Dept. of Physics, University of Puerto Rico, Mayagüez PR 00681-9000, U.S.A. 2 Mechanical Engineering Department, University of Puerto Rico, Mayagüez PR 00681-9000, U.S.A. 3 Engineering Science and Materials Department, University of Puerto Rico, Mayagüez PR 00681-9000, U.S.A. ABSTRACT The effective incorporation of dopant species into ZnO host structure should induce changes in its physical and chemical properties enabling the establishment of novel multi-functional properties. Doping with transition metal ions and the subsequent exchange interaction between available spins of the magnetic species are expected to induce a ferromagnetic behavior. This ferromagnetic functionality will enable the application of this material in data storage and spintronics-based devices. The present research addresses the study of the effect of the oxidation state of Fe species and the influence of the annealing atmosphere on the structural and functional properties of nanocrystalline ZnO-based powders.
INTRODUCTION Among various semiconductor oxides that are expected to become suitable platforms for multifunctional applications, zinc oxide (ZnO) is one of the most attractive alternatives. ZnO is a wide-bandgap semiconductor of the II-VI semiconductor group and exhibits several favorable properties, including good transparency, high electron mobility, wide band-gap, and strong room-temperature luminescence. These properties makes ZnO an excellent candidate for emerging applications such as transparent electrodes in liquid crystal displays, energy-saving or heat-protecting windows, thin-film transistors for electronics, and light-emitting diodes (LED’s) 1,2 . The effective incorporation of dopant species into ZnO host structure should induce changes in its physical and chemical properties enabling the establishment of novel multi-functional properties. In the case of doping with transition metal ions, such as Fe, Mn and V ions, the subsequent exchange interaction from magnetic spins should induce a ferromagnetic behavior in the so-called ZnO-based diluted magnetic semiconductor. This ferromagnetic functionality will enable the application of this material in data storage and spintronics-based devices. On the other hand, among the acceptor impurities that affect ZnO, nitrogen (N) has been considered to be the most suitable p-type dopant due to atomic size and electronic structure considerations. The energy of the valence 2p states and the electronegativity of nitrogen are also the closest to those of the oxygen atom, particularly when compared with other column-V dopants. Several groups have reported the incorporation of N in ZnO, and many have claimed that N substitutes oxygen (O) species into the ZnO structure1.
EXPERIMENTAL Materials Pure and Fe-doped ZnO powders and films were synthesized via a sol-gel techn
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