Induced polarized state in intentionally grown oxygen deficient KTaO3 thin films (original) (raw)

2013, Journal of Applied Physics

Deliberately oxygen deficient potassium tantalate thin films were grown by RF magnetron sputtering on Si/SiO 2 /Ti/Pt substrates. Once they were structurally characterized, the effect of oxygen vacancies on their electric properties was addressed by measuring leakage currents, dielectric constant, electric polarization, and thermally stimulated depolarization currents. By using K 2 O rich KTaO 3 targets and specific deposition conditions, KTaO 3 d oxygen deficient thin films with a K/Ta ¼ 1 ratio were obtained. Room temperature X-ray diffraction patterns show that KTaO 3 d thin films are under a compressive strain of 2.3% relative to KTaO 3 crystals. Leakage current results reveal the presence of a conductive mechanism, following the Poole-Frenkel formalism. Furthermore, dielectric, polarization, and depolarization current measurements yield the existence of a polarized state below T pol $ 367 C. A Cole-Cole dipolar relaxation was also ascertained apparently due to oxygen vacancies induced dipoles. After thermal annealing the films in an oxygen atmosphere at a temperature above T pol , the aforementioned polarized state is suppressed, associated with a drastic oxygen vacancies reduction emerging from annealing process.