Ion modification techniques for improving the insulating and ferroelectric properties of BiFeO 3 (BFO) thin films are reported. Rare-earth-substituted BFO films with chemical compositions of Bi 1:00Àx RE x Fe 1:00 O 3 [RE = La and Nd] were fabricated on (111)Pt/TiO 2 /SiO 2 /(100)Si substrates using a chemical solution deposition technique. Well-saturated P-E curves were obtained for La 3þ -and Nd 3þ -substituted BFO films, while the curve of a nonsubstituted BFO film was distorted due to the leakage current. Remanent polarization (P r ) values measured at 10 K were respectively 44 and 51 mC/cm 2 , for La 3þ -and Nd 3þ -substituted BFO films, which are significantly superior to conventional Pb-free ferroelectrics.
Thin films of Bi(Fe1−xScx)O3 (BFSO) system were fabricated on (111)Pt∕TiO2∕SiO2∕(100)Si substrates by chemical solution deposition to improve the electrical resistivity by substituting electrically unstable Fe3+ cations for stable Sc3+ cations. A single phase of perovskite was obtained in the range of x=0–0.30, in which selective replacement of Fe3+ and Sc3+ was confirmed in x=0–0.15 by using Raman measurement. The leakage current density of the BFSO films was reduced by increasing x. A well-saturated polarization–electric field hysteresis loop was obtained for BFSO films with x=0.15, showing remanent polarization of approximately 35μC∕cm2.
The authors grew (001)- and (001)∕(100)-oriented epitaxial PbTiO3 films with various thicknesses on (100)SrTiO3 substrates. They used x-ray diffraction to measure the angles between surface normal [001] of (001)-oriented domains and [100] of (100)-oriented domains. The angles were found to be approximately 3.6° when the film thickness exceeded 1100nm. This value is consistent with the value obtained by a geometric calculation for strain-free PbTiO3. This result suggests that thick epitaxial PbTiO3 films grown on (100)SrTiO3 substrates have a fully strain-relaxed structure.
(100)/(001)-oriented tetragonal Pb(Zr,Ti)O3 (PZT) films, which were thicker than 2 µm, were epitaxially grown on SrRuO3-covered (100)Si, (100)KTaO3, (100)SrTiO3, and (100)CaF2 substrates by metal organic chemical vapor deposition. The volume fraction of the (001)-orientation almost linearly increased as the thermal strain increased during the cooling process from the deposition temperature to the Curie temperature. Consequently, perfectly (001)-oriented, i.e., polar-axis-oriented, thick films were obtained on CaF2 substrates with a remanent polarization of 71 µC/cm2. This approach to grow polar-axis-oriented PZT thick films enabled the intrinsic piezoelectricity of PZT itself to be clarified, and has potential in novel applications.
Estimation of intrinsic contribution to dielectric response of Pb0.92La0.08Zr0.52Ti0.48O3 thin films at low frequencies using high bias fields Appl. Phys. Lett. 102, 062906 (2013); 10.1063/1.4792529 Piezoelectric properties of epitaxial Pb(Zr0.525, Ti0.475)O3 films on amorphous magnetic metal substrates J. Appl. Phys. 111, 07D916 (2012); 10.1063/1.3677864 Influence of Mn doping on domain wall motion in Pb(Zr0.52Ti0.48)O3 films J. Appl. Phys. 109, 064105 (2011);
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