Solubility Enhancement of Fe in ZnO Nanoparticles Prepared by Co-Precipitation Method

Crystalline ZnO offers an excellent host matrix to create a dilute magnetic semiconductor (DMS) owing to its facile Zn-atom substitution with the transition metal dopant atom. The exchange interactions between the spin of the dopant atoms and the carriers in the ZnO matrix results in the room-temperature ferromagnetic order in the entire lattice. In this work, we report on the enhanced solubility (doping) of Fe atoms in ZnO matrix. Zn1-x FexO DMS nanoparticles were synthesized with different doping concentrations (x = 0.01, 0.05, 0.20, 0.22, and 0.25) via a modified version of co-precipitation method, in which the precursors’ solution was heated at 60 ℃ during the stirring process. Only the wurtzite phase was obtained for all Zn1-x FexO samples in X-ray diffraction, and no secondary phase was observed, which supports the idea of an enhanced solubility limit of Fe doping up to 25%. A systematic broadening of the Raman characteristic peak at 525 cm−1 associated with Fe substitution across the entire range of doping accompanied with the suppression of ZnO peak at 371cm−1 and 435 cm−1, supporting the enhanced doping effect further. The bandgap exhibited a systematic trend — it first increased from 3.13 eV for undoped to 3.23 for x = 0.1 and dropped to the value of 2.94 for the highest concentration (x = 0.25) with few in band transitions for high doping. VSM results showed magnetic behavior for all the doped samples at room temperature.