Structure and Ferroelectric Properties of Thin Heteroepitaxial NaNbO3 Films Obtained by RF Cathode Sputtering

Abstract

Thin films of sodium niobate (NaNbO3) on a MgO(001) substrate with a predeposited SrRuO3 layer were obtained for the first time by the method of RF cathode sputtering in an oxygen atmosphere. X‑ray diffraction data showed the obtained films to be single-phase and single-crystalline. The parameters of the unit cells of NaNbO3 and SrRuO3 layers in the tetragonal approximation were found to be $${{c}_{{{\text{NaNb}}{{{\text{O}}}_{3}}}}}$$ = 0.3940(1) nm, $${{a}_{{{\text{NaNb}}{{{\text{O}}}_{3}}}}}$$ = 0.389(1) nm, $${{c}_{{{\text{SrRu}}{{{\text{O}}}_{3}}}}}$$ = 0.4004(1) nm, and $${{a}_{{{\text{SrRu}}{{{\text{O}}}_{3}}}}}$$ = 0.392(3) nm. Misfit strain of the unit cell of NaNbO3 amounted to e33 = 0.007 and e11 = 0.002. The results of dielectric and piezoelectric measurements showed that the films occurred in a ferroelectric state.