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We report the enhancement of ferroelectric properties in vanadium-doped Bi[sub 4]Ti[sub 3]O[sub 12] (BIT) thin films deposited by a sol-gel method. Compared to the undoped BIT, V-doped BIT (BTV) showed higher polarizations and a better fatigue resistance as reported in ceramic systems recently [Noguchi et al., Appl. Phys. Lett. 78, 1903 (2001)]. BTV showed a remanent polarization (2P[sub r]) of 15.9 µC/cm², higher than the value for BIT, 12.5 µC/cm². The polarization of the BTV thin film capacitor decreased by 19%, while that of the BIT decreased by 23% after the fatigue test with 4 × 10[sup 10] switching cycles. [ABSTRACT FROM AUTHOR]

Pure Bi6Fe2Ti3O18and vanadium (V) doped Bi6Fe2Ti3O18(Bi5.99Fe2Ti2.75V0.03O18) thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by a chemical solution deposition method. The Bi5.99Fe2Ti2.75V0.03O18thin film exhibited improved electrical and multiferroic properties, such as leakage current densities, dielectric properties, ferroelectric and ferromagnetic properties. We consider that the improved properties might be related to the reduced concentration of oxygen vacancies and the decreased mobility of oxygen vacancies by V doping. [ABSTRACT FROM PUBLISHER]

We have evaluated the ferroelectric and electrical properties of pure BiFeO3(BFO) and (Bi0.9Ho0.1)(Fe0.975Ti0.025)O3+δ(BHFTO) thin films on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. The improved electrical properties were observed in the BHFTO thin film. The leakage current density of the co-doped BHFTO thin film showed three order lower than that of the pure BFO, 1.22 × 10−6A/cm2at 100 kV/cm. The remnant polarization (2Pr) and the coercive electric field (2Ec) of the BHFTO thin film were 61 μC/cm2and 1190 kV/cm at an applied electric field of 800 kV/cm and at a frequency of 1 kHz and these values decreased with increasing measurement frequency, 35 μC/cm2and 920 kV/cm at 10 kHz, respectively. Also, the 2Prand the 2Ecvalues were fairly saturated above 30 kHz. [ABSTRACT FROM PUBLISHER]

Randomly oriented and c-axis-oriented Bi3.15Pr0.85Ti3O12 (BPT) thin films were prepared by a chemical solution deposition method. Ferroelectric and leakage current properties were strongly related to the crystallographic orientation of BPT thin film. The values of remnant polarization (2Pr) and leakage current density were 74 μC/cm2 at 250 kV/cm and 3.4 × 10-8 A/cm2 at 125 kV/cm for the randomly oriented thin film, respectively, and 16 μC/cm2 and 6.9 × 10-6 A/cm2 for the c-axis-oriented thin film, respectively. The result indicates that the polarization vector of BPT thin films is not oriented along the c-axis. [ABSTRACT FROM AUTHOR]

Ferroelectric Na0.5Bi4.5Ti4O15 (NaBTi) thin films, selectively controlled in c-axis and random orientation, were fabricated on a Pt(111)/Ti/SiO2/Si(100) substrate by using a chemical solution deposition method. The preferred orientation of the thin films annealed at 750°C under oxygen atmosphere was confirmed by X-ray diffraction and scanning electron microscope studies. We found that ferroelectric, dielectric, and leakage current properties were strongly related to the crystallographic orientation of NaBTi thin films; the randomly oriented NaBTi thin film exhibited better properties than the c-axis oriented thin film. The values of remnant polarization (2Pr), dielectric constant, and leakage current density were 21 μC/cm2 at 300 kV/cm, 630 at 100 kHz, and 7.4 × 10-6 A/cm2 at 100 kV/cm for the randomly oriented thin film, respectively, and 6 μC/cm2, 420, and 1.1 × 10-1 A/cm2 for the c-axis oriented thin film, respectively. Also, no polarization fatigue was observed in both NaBTi thin films up to 107 switching cycles. [ABSTRACT FROM AUTHOR]

Ferroelectric CaBi4Ti4O15 (CBTi) thin films with random orientation and high c-axis orientation were prepared on a Pt(111)/Ti/SiO2/Si(100) substrate by a chemical solution deposition method. We observed a strong dependence of ferroelectric and dielectric properties on the film orientation. The CBTi thin film with random orientation exhibited remnant polarization (2Pr) of 54 μ C/cm2 at an applied electric field of 250 kV/cm and dielectric constant (ε) of 412 at a frequency of 1 kHz. The values of 2Pr and ε were larger than those observed in the CBTi thin film with high c-axis orientation. In addition, the randomly oriented thin film showed lower leakage current density than the highly c-axis-oriented thin film. [ABSTRACT FROM AUTHOR]

Cr-substituted BiFeO3 (BFCr-3 mol%) thin films were deposited on Pt(200)/TiO2/SiO2/Si substrates by a chemical solution deposition. The coated films were annealed in the temperature range of 500°C∼ 600°C for 30 min under nitrogen atmosphere. The electrical properties of BFCr thin films were found to be sensitive to the annealing temperature. It was found that BFCr thin films exhibited good ferroelectric properties, such as an improved leakage-current density and P-E hysteresis characteristics. The BFCr thin film annealed at 525°C exhibits a low leakage current density of 9.2 × 10- 7 A/cm2 at an applied electric field of 100 kV/cm. The films exhibited a well-saturated hysteresis loop with a remanent polarization (Pr) of 47 μC/cm2 at room temperature. The reason for the improved leakage current and ferroelectric properties in BFCr thin films can be attributed to the effects of increased grain size and oxygen vacancies reduced by Cr doping. [ABSTRACT FROM AUTHOR]

5 mol % La3 +, Nd3 + or Y3 +-cosubstituted BiFe0.97Cr0.03O3 thin films (denoted by BLaFCr, BNdFCr, and BYFCr, respectively) have been successfully deposited on Pt (200)/TiO2/SiO2/Si substrates by a chemical solution deposition method. Well-saturated ferroelectric hysteresis loops and low leakage current densities have been observed in BLaFCr, BNdFCr, and BYFCr thin films with single-phase structure. The values of remanent polarization (Pr) and coercive field (Ec) were 64 μ C/cm2 and 275 kV/cm, 61 μC/cm2 and 290 kV/cm, and 31 μ C/cm2 and 315 kV/cm for BLaFCr, BNdFCr and BYFCr thin films at the maximum electric field of 712 kV/cm, respectively. In the present study, the differences in values of Pr seem to be related to the doped ionic radii. [ABSTRACT FROM AUTHOR]

Recently perovskite niobates were paid much attention as lead-free piezoelectric materials to replace lead-based Pb(Zr,Ti)O3 or relaxor systems which cause much environmental problems. Piezoelectric and ferroelectric properties of electromechanical coupling coefficient and quality factor in (K0.5Na0.5)NbO3 ceramic were studied. Dielectric properties of niobates including Ag ion; AgNbO3 and (Ag0.5Na0.5)NbO3 were studied. Phase transitions and dielectric relaxations were studied from the frequency and temperature dependent dielectric constant measurements. The piezoelectric properties were hardly observed in silver niobate systems. [ABSTRACT FROM AUTHOR]

Neodymium-substituted Bi4Ti3O12 (BNdT) thin films were prepared by a chemical solution deposition technique on platinum- coated silicon substrates. All of the samples were annealed at the relatively low temperature of 600 °C by a rapid thermal annealing process in different atmospheres, such as O2, air, and nitrogen, and vacuum. Irrespective of different annealing atmospheres, all of the BNdT thin films exhibit good ferroelectric properties, such as a saturated hysteresis loop, good fatigue endurance, and low leakage current density. A large remanent polarization (Pr) of ∼48 μC/cm2 with an electric field of 240 kV/cm was observed from the BNdT thin film annealed in O2 atmosphere. The BNdT thin films annealed in nitrogen and vacuum, at reduced oxygen partial pressures, exhibit smaller Pr than that annealed in oxygen. The difference of Pr of the BNdT thin films annealed in different atmospheres may originate from differences in the grain sizes and the number of oxygen vacancies. [ABSTRACT FROM AUTHOR]

A new type of bismuth-based relaxor, such as Bi 2 (Y 1/2 Nb 1/2 ) 2 O 7 and Bi 2 (Mg 1/3 Nb 2/3 ) 2 O 7 thin films were fabricated on Pt/Ti/SiO 2 /Si substrate by a sol-gel spin coating process. The films exhibit characteristic diffused phase transition. The temperature dependent reciprocal dielectric constant characteristics of the films deviates from the Curie-Weiss law in the temperature range over the dielectric constant maximum temperature ( T m ). The diffuseness of the phase transition of the thin films was estimated by calculating the difference between T m and T cw (starting temperature following the Curie-Weiss law). For the thin films annealed at 750°C, the temperature T m , the Curie-Weiss temperature Θ, the Curie-Weiss constant c and the temperature T cw were measured at frequency of 10 3 Hz, respectively. [ABSTRACT FROM AUTHOR]

Nd-substituted bismuth titanate Bi3.54Nd0.46Ti3O12 (BNT) thin films were prepared on (111)Pt/Ti/SiO2/Si substrates by a sol–gel method. The BNT thin films processed at a low annealing temperature of ∼600 °C showed good ferroelectric properties. The randomly oriented BNT single phases and the improved ferroelectric properties were confirmed by X-ray diffraction and polarization–electric field hysteresis loops, respectively. The remanent polarization of the BNT thin films is 64 μC/cm2, which is larger than that of Bi3.25La0.75Ti3O12 (BLT) thin films. After 1010 read/write switching cycles, the effective non-volatile charges showed no polarization fatigue. Regardless of the low annealing temperature of 600 °C, the BNT thin films had good ferroelectric properties with high remanent polarizations and strong fatigue resistances. [ABSTRACT FROM AUTHOR]

The formation of phase-pure BiFeO 3 (BFO) thin films using a chemical solution deposition on platinium electrode has been investigated systematically by changing the annealing condition of the films. From the X-ray diffraction results, it was found that the formation of the phase-pure BFO was favorable under lower oxygen partial pressure, slower heating rate and Pt(200)/Ti/SiO 2 /Si(100) substrate. The remanent polarization ( P r ) and coercive field ( E c ) values of the phase-pure BFO thin film annealed at 600°C in nitrogen atmosphere by conventional furnace annealing method are approximately 0.9 μC/cm 2 and 20 kV/cm, respectively. [ABSTRACT FROM AUTHOR]