Morphology change in (K_0.5Na_0.5)(Mn_0.005Nb_0.995)O₃ thin films caused by gamma-ray irradiation

We investigated the effects of gamma-ray (γ) irradiation on the morphology properties of (K_0.5Na_0.5)(Mn_0.005Nb_0.995)O₃ (KNMN) thin films. The KNMN thin films were prepared on Pt/Ti/SiO₂/Si substrate using a chemical solution deposition method through a spin-coating process and were subject to γ radiation at various total doses from 0–3000 kGy. The grain size of the KNMN films changed visibly with an increase in the total γ irradiation dose. Williamson-Hall plot analysis revealed that the microstrain of the films increased from 0.222% (at 0 kGy) to 0.266% (at 3000 kGy) after the irradiation. The observed variation of the morphology properties on the total dose might be mainly associated with the microstrain in Mn-doped KNN thin films. In addition the migration of defects and/or impurities bound inside the grain by the gamma-ray energy in Mn-doped KNN thin films can enhance the grain size decrease process. The mobile impurities in our polycrystalline samples can congregate at the domain boundary, which can lead to partial amorphization inside the grain.