The ion beam-induced domain growth in Y-cut MgO-doped lithium niobate (MgOLN) covered by the resist layer was studied. A comparative study of domain structure in the samples with and without surface dielectric layer is crucial for periodical poling. Differences in the domain shape with changes in the irradiation dose, energy, and current of the ion beam were revealed. The maximum domain depth was 400 nm at 100 pC. A detailed analysis of interaction for different distance between irradiated dots in row revealed formation of 1 D arrays with variating length of the wedge-like domains. These findings allow optimizing the poling process. © 2023 Taylor & Francis Group, LLC.