Impact of N+ Ion Irradiation on the Electrochemical Behavior of ZnO Thin Film Electrode–Electrolyte Interfaces

Defect engineering serves as a crucial technique for enhancing the performance of advanced next-generation devices. Ion beam irradiation stands out as a highly promising method for introducing defects in a controlled manner. This study investigates the impact of nitrogen ion (N⁺) irradiation-induced defects on the electrochemical behavior of ZnO thin-film electrode-electrolyte interface. The oxygen vacancy defects were introduced and tuned by varying the fluence of ion irradiation. The increased Urbach energy in the irradiated samples confirms the enhanced disorder. Photoluminescence data show the emergence of new defect states upon irradiation. The behavior of the ZnO thin-film electrode-electrolyte interface was studied using cyclic voltammetry and electrochemical impedance spectroscopy. At a fixed scan rate, the enhanced peak current was observed in cyclic voltammetry in N⁺ Irradiated electrodes. Furthermore, reduced charge transfer resistance was observed in the case of irradiated electrodes. To unravel the underlying mechanism, we analyze the AC conductivity, which shows varying dependency on the frequency. It shows the existence of multiple ion-ion correlations in irradiated electrodes. Furthermore, the AC conductivity in the entire frequency region is enhanced significantly. Dielectric permittivity spectra suggest low-frequency dipole interactions and increased dielectric losses after irradiation, indicating non-Debye type relaxation processes. Understanding irradiation-induced changes will help engineer thin film electrodes for batteries, supercapacitors, and other electrochemical applications.