Enhancing ZnMgO Ferroelectric Properties by Defect Engineering: First-Principles and Experimental Study

Although ZnMgO has regained attention as a ferroelectric material, the influence of defects on its ferroelectric properties remains unclear. The effects of common defects (vacancies: VO, VZn, VMg, and interstitials: IO, IZn, IMg) on the ferroelectric properties of ZnMgO were investigated by combining first-principles with magnetron sputtering along with their formation energies and carrier concentrations. First, VO2+, IZn2+, and IMg2+ exhibit lower formation energies under O-poor conditions, while VZn2–, VMg2–, and IO1+ are stabilized under O-rich conditions. Second, O-rich conditions were found to reduce the net carrier concentration. Furthermore, for defect-free ZnMgO, increased Mg content reduces the spontaneous polarization magnitude (Ps) but widens the bandgap (Eg), while the polarization reversal barrier (Ea) drops sharply near 50 atom % Mg, suggesting a transition from nonuniform to uniform polarization reversal. Meanwhile, low-concentration defects (2.778 atom %) reduce Ea, Ps, and Eg. This indicates that a moderate level of defects can effectively facilitate polarization reversal, while a high concentration may lead to an undesirable Eg. Finally, magnetron-sputtered ZnMgO films grown under varying Ar/O2 mixtures confirm defect evolution trends and demonstrate that O-rich conditions significantly enhance breakdown field strength (Ebd). This work provides deep insight into defect formation and ferroelectric modulation, providing essential guidance for process optimization.