SEM images for (a) BFO and (b) thin films deposited on substrates.
XPS survey spectra of BFO and films annealed at 873 K for 60 min under a ambience.
The fitted narrow-scan spectra of (a) , (b) , (c) , and (d) peaks for the BFO and films. The black solid lines represent experimental results, red short dots represent the fitting results after Shirley-type background subtraction, and the dashed peaks with colors of blue, magenta, violet, and green are fitted subpeaks using the XPSPEAK Version 4.1 software. Iterations are performed until a minimum for the square of the difference between the experimental curve and the fitted curve is reached for each fitted sum curve.
(a) Comparison of XPS valence band spectra between the BFO and films. Their uppermost valence band edges are located at 0.41 and 0.84 eV lower than the Fermi level , respectively. The spectra are aligned at . (b) Plots of vs photon energy for the BFO and films. The optical bandgap energy is deduced from extrapolation of the dashed straight line to . The inset of (b) gives transmission spectra as a function of the wavelength for the BFO and films deposited on FTO/glass substrates. (c) Energy band diagram for Pt/BFO contact. The of the BFO film lies 0.41 eV below . Band bending for the and conduction band of the -type BFO film is downward and small in magnitude of 0.11 eV. Schottky barrier height of the BFO/Pt interface is calculated to be 0.52 eV.
XRD patterns of (a) (, 0.05, 0.1, 0.15, and 0.2) films deposited on substrates and (b) subtle (104) and (110) peaks of the corresponding films.
Raman spectra of ( and 0.2) films deposited on substrates.
Dielectric constants and loss tangents of the film capacitors as a function of frequency.
Polarization–electric field hysteresis loops as a function of applied electric field for (a) BFO and (b) film capacitors. (c) Remnant polarization and coercive field for the BFO and capacitors as a function of the electric field in the range of 155–621 kV/cm.
(a) Current density–applied voltage curves for capacitors. (b) and (c) show as a function of applied voltage with absolute value ( or ) under the conditions of and , respectively. Discrete symbols are experimental data and solid lines are linear fits to the data. , , , and are slopes of the fitted straight lines. The and subscripts signify that the top Pt electrode is positively and negatively biased with respect to the bottom electrode, respectively.
(a) In-plane and (b) out-of-plane magnetization–magnetic field hysteresis loops for films: (1) , (2) , (3) , and (4) . (c) Saturation magnetization values for the films applied with in-plane magnetic field and out-of-plane magnetic field and ratios as a function of Ce concentration.
Fraction of covalency and fraction of ionicity for Bi–O, Ce–O, and Fe–O bonds.
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