Self-polarization induced by lattice mismatch and defect dipole alignment in (001) BaTiO₃/LaNiO₃ polycrystalline film prepared by magnetron sputtering at low temperature

Abstract

ARTICLE This journal isUpward self-polarization phenomenon was observed and studied in the highly (001)-oriented BaTiO 3 /LaNiO 3 polycrystalline film, and the polycrystalline film was in situ prepared by radio frequency magnetron sputtering at 400°C without post treatment. The low temperature crystallization and high orientation of BaTiO 3 polycrystalline film may be caused by the better compatibility between BaTiO 3 and LaNiO 3 . The upward self-polarization phenomena was characterized by piezoelectric force microscopy (PFM), and the coupling effects of low crystallization temperature, high (001) orientation, large compressive strain gradient and preferred orientation of defect dipoles are considered to be responsible for the upward self-polarization phenomena in the BaTiO 3 /LaNiO 3 polycrystalline film during the cooling process, especially when ferroelectric domains nucleate and grow near 120°C.

Self-Poling of BiFeO3 Thick Films

“…In the first part of the study we provide evidence of the self-poling effect in ~23-µm-thick BFO films and show that the effect is only large when the BFO film experiences the ferroelectric- In order to verify whether the large difference in the d 33 responses between the two films indeed originates mostly from the self-poling effect, both the samples were poled at room temperature by application of an external DC electric field of 50 kV/cm for ~5 minutes. The The appearance of the macroscopic piezoelectricity in the as-sintered samples ( Fig.…”

“…21,22,27,33,34 The BFO thick-film structure sintered above the T C exhibited a significant self-poling effect, thus we used high-resolution (HR) TEM imaging and …”

“…22,27,33,57 We also note that the observed significant change in the microstructure of the film (from an equiaxed to a columnar grain morphology) by cooling through the T C ( Fig. 3 and S2), can also be a result of the strain distribution in the film and possibly related to the self-poling effect, though the exact mechanisms are still to be investigated.…”

“…Piezoresponse force microscopy amplitude images were recorded with an atomic force microscope (AFM; Asylum Research, Molecular Force Probe 3D, Santa Barbara, CA, USA) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 7 equipped with a piezoresponse force mode (PFM The converse d 33 response at weak (sub-coercive) fields was recorded on self-poled samples using a setup based on an optical-fiber sensor, as described in ref. 39 The displacement signals were recorded with an oscilloscope and a lock-in amplifier (the d 33 and the piezoelectric phase angle were determined from the first-harmonic strain response).…”

“…39 The displacement signals were recorded with an oscilloscope and a lock-in amplifier (the d 33 and the piezoelectric phase angle were determined from the first-harmonic strain response). The measurements were carried …”