Electronic and magnetic properties of ZnO:Er(Ga) thin films

Er- and Ga-substituted ZnO diluted magnetic semiconductor polycrystalline thin films were deposited on sapphire substrates via DC sputtering at 700 °C under an oxygen plasma atmosphere. The electronic structure, local coordination, and magnetic behavior of these materials were systematically examined. While pure ZnO is diamagnetic, the substitution of Er³⁺ (Ga³⁺) at the Zn²⁺ site introduces donor states, increases the carrier concentration, and distorts the lattice owing to ionic size mismatch. These structural modifications promote room-temperature ferromagnetism while preserving the lattice structure, with a slight change in the lattice parameter. The substitution of Er(Ga) in ZnO increases structural disorder and intrinsic defects, including zinc vacancies (V_Zn), and oxygen vacancies (V_O). Combined X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure spectroscopy confirmed the substitutional incorporation of Er(Ga) in the ZnO system. The spectroscopic results indicate hybridization and charge transfer within Er(Ga)-O-Zn bonds. In ZnO:Er, V_O trap electrons and enhance magnetic exchange interactions; whereas ZnO:Ga does not. Consequently, the ZnO:Er system shows a stronger ferromagnetic response than ZnO:Ga. These findings highlight Er(Ga)-substituted ZnO as a promising material for optoelectronic applications.