Recent theoretical predictions of ferromagnetic behavior in transition metal (TM)-doped ZnO have focused significant
attention on these materials for use as spintronic materials. Moreover, rare earth (RE) elements in wide bandgap
semiconductors would be useful not only in spintronics but also in optoelectronic applications. This work presents
results obtained from an investigation into the optical, magnetic, and structural properties of transition-metal (TM)-
doped ZnO and rare earth (RE) doped ZnO (TM = Mn, Co, Ni, and Fe; RE = Gd, Eu, and Tb) bulk crystals and thin
films. Properties of TM- and RE-doped ZnO bulk crystals and thin films were studied and compared in order to better
understand the nature of these dopant centers and their effects on the properties of the host crystal. Optical properties
confirm the incorporation of substitutional transition metal ions on cation sites. While most thin film samples show
ferromagnetic behavior, the magnetic response of the bulk crystals varies. This suggests that the magnetic behavior of
TM-doped ZnO is highly dependent on growth conditions, and growth conditions which favor the formation of grain
boundaries and interfaces may be more likely to result in ferromagnetic behavior. Origins of this ferromagnetic behavior
are still under investigation. Defect luminescence observed in the RE-doped samples suggests that these materials may
prove useful in optoelectonic applications as well.
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