Enhancement of fatigue endurance and retention characteristic in Bi3.25Eu0.75Ti3O12 thin films

The effects of moderate annealing temperature (600–800 °C) on the microstructure, fatigue endurance, retention characteristic, and remnant polarization (2P_r) of Bi_3.25Eu_0.75Ti₃O₁₂ (BET) thin films prepared by metal-organic decomposition (MOD) were studied in detail. 2P_r (66 µC/cm² under 300 kV/cm), fatigue endurance (3% loss of 2P_r after 1.2 × 10¹⁰ switching cycles), and retention characteristic (no significant polarization loss after 1.8 × 10⁵s) for BET thin film annealed at 700 °C are better than those for thin films annealed at other temperature. The mechanisms concerning the dependence of microstructure and ferroelectric properties on the annealing temperature were discussed.     

Enhanced performance of sandwich structure Pb0.8La0.1Ca0.1Ti0.975O3 thin film for pyroelectric applications

Using the advantages of low-temperature crystallization and high orientation in Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ (PLCT) film, a dense PLCT/porous PLCT/dense PLCT sandwich structure was obtained in the present study. It is found that dense PLCT layer can both sustain the porous density in the core layer and also lead to better preferential orientation of the sandwich structure. In the sandwich structure, low dielectric constant (ε_r = 43) and leakage current density (J < 9 × 10^− 5A/cm²) are simultaneously achieved. Because of high orientation in sandwich structure, the pyrocoefficient (p > 185 µC/m² K) is still keeping a relatively large value. The resulting high figure of merit (F_V′ = 4.5 µC/m² K, F_d′ = 228 µC/m² K) make the sandwich structure films good candidate for pyroelectric thin-film devices.     

Enhanced ferroelectric properties of epitaxial Pb(Zr,Ti)O3 film with LaAlO3 buffer

PbZr_0.52Ti_0.48O₃ films (PZT) have been grown epitaxially on SrRuO₃/LaAlO₃ (SRO/LAO) substrates using pulse laser deposition. In order to improve the ferroelectric properties of the PZT, one LAO buffer was introduced into the interface of PZT/SRO. The dependence of the electrical properties of the PZT films on the buffer thickness was studied. When a 10-nm-thick buffer was used, the remnant polarization (Pr) of the PZT film reached 58 ± 5 μC/cm², 2 times larger than the sample without any buffer layer. The leakage current was reduced 1-2 orders of magnitude. Besides, the PZT film with 10-nm-thick LAO buffer also exhibited good fatigue endurance after 10⁹ switching cycles. These results could propose one effective way to improve the properties of ferroelectric films deposited on oxide electrodes.     

Ferroelectric properties of Mn-Doped Bi3.15Nd0.85Ti3O12 thin films prepared under different annealing conditions

Mn-doped Bi_3.15Nd_0.85Ti₃O₁₂ (BNTM) thin films were fabricated on Pt/Ti/SiO₂/Si(100) substrates by a chemical solution deposition technique and annealed at different temperatures from 650 to 800 °C. The structures of the films were analyzed using X-ray diffraction, which showed that the BNTM films exhibit polycrystalline structures and random orientations. The surface morphologies of the samples were investigated using scanning electron microscopy. The average grain size of the films increases with increasing annealing temperature. Electrical properties such as remanent polarization (2P_r) are quite dependent on the annealing temperature of BNTM films. It is found that the film annealed at 750 °C exhibits excellent ferroelectricity with a remanent polarization of 2P_r = 89.3 μC/cm² and a coercive field of E_c = 99.2 kV/cm respectively.     

Effect of film thickness on ferroelectric domain structure and properties of Pb(Zr0.35Ti0.65)O3/SrRuO3/SrTiO3 heterostructures

Epitaxial Pb(Zr_0.35Ti_0.65)O₃ (PZT) thin films with tetragonal symmetry and thicknesses ranging from 45 to 230 nm were grown at 540 °C on SrRuO₃-coated (001)SrTiO₃ substrates by pulse-injected metalorganic chemical vapor deposition. The effect of the film thickness on the ferroelectric domain structure and the dielectric and ferroelectric properties were systematically investigated. Domain structure analysis of epitaxial PZT films was accomplished with high-resolution X-ray diffraction reciprocal space mapping and high-resolution transmission electron microscopy. Fully polar-axis (c-axis)-oriented epitaxial PZT thin films with high ferroelectric polarization values [e.g., remanent polarization (P _r) ~ 90 μC/cm²] were observed for film thicknesses below 70 nm. Films thicker than 70 nm had a c/a/c/a polydomain structure and the relative volume fraction of c-domains monotonously decreased to about 72% on increasing the film thickness up to 230 nm , and finally P _r diminished to about 64 μC/cm² for the 230-nm-thick epitaxial film. These polarization values were in good agreement with the estimated values taking into account the volume fraction of the c-axis-oriented domains while assuming a negligible contribution of 90° domain reorientation caused by an externally applied electric field.     

Influence of ZnO additions to 0.8(Mg0.95Co0.05)TiO3–0.2Ca0.6La0.8/3TiO3 ceramics on sintering behavior and microwave dielectric properties

The effects of ZnO addition on the microstructures and microwave dielectric properties of 0.8(Mg_0.95Co_0.05)TiO3–0.2Ca_0.6La_0.8/3TiO₃ ceramics were investigated. ZnO was selected as liquid phase sintering aids to lower the sintering temperature of 0.8(Mg_0.95Co_0.05)TiO3–0.2Ca_0.6La_0.8/3TiO₃ ceramics. With ZnO additives, the densification temperature of 0.8(Mg_0.95Co_0.05)TiO₃–0.2Ca_0.6La_0.8/3TiO₃ can be effectively reduced from 1450 to 1200–1325 °C. The crystalline phase exhibited no phase difference at low addition levels (0.25–2 wt.%). It is found that low-level doping of ZnO (0.25–2 wt.%) can significantly improve the density and dielectric properties of 0.8(Mg_0.95Co_0.05)TiO₃–0.2Ca_0.6La_0.8/3TiO₃ ceramics. The quality factors Q × f were strongly dependent upon the amount of additives. Q × f values of 36 000 and 13 000 GHz could be obtained at 1200–1325 °C with 1 and 2 wt.% ZnO additives, respectively. During all additives ranges, the relative dielectric constants were significantly different and ranged from 23.1 to 27.96. The temperature coefficient varies from 14.1–24.3 ppm/°C.     

Microstructures, ferromagnetic, and ferroelectric properties in polyvinylpyrrolidone-assisted CoFe2O4/Pb(Zr0.53Ti0.47)O3 multiferroic composite thick films

CoFe₂O₄/Pb(Zr_0.53Ti_0.47)O₃ (CFO/PZT) multiferroic composite thick films with different CFO mass fractions have been prepared onto Pt/Ti/SiO₂/Si substrate by a hybrid sol–gel process and spin coating technique. Polyvinylpyrrolidone (PVP) was employed to be an assistance to the sol–gel solution for enhancing the film thickness and promising a crack-free film surface. After annealing at 650 °C in air for 1 h, phase structure, microstructure, magnetic and ferroelectric properties as well as leakage current of multiferroic thick films were investigated. X-ray diffraction indicated a deeply buried distribution of CFO particles in the PZT matrix. Scanning electronic microscopes showed crack-free surfaces and a decreasing film thickness from 7.2 μm to 6.2 μm with increasing CFO content. Furthermore, the saturated magnetization and remanent magnetization were also hence increased. In addition, mass fraction of CFO in PZT matrix was also estimated from 0.36% to 4.58% according to the relationship between M _s and magnetic content. Ferroelectric hysteresis loops revealed saturated polarization (P _s) and remanent polarization (P _r) were diluted by CFO till its mass fraction rising to 1.8%. After that, polarization was increased with further increasing CFO content. Enhanced leakage was demonstrated to be partially contributed to them. A critical content of 1.8% was hence confirmed, where ferroelectric and magnetic properties can be balanced, indicating a possible stress-transferred magnetoelectric coupling effect in this composite.     

Ferroelectric and dielectric properties of Bi4-xNdxTi3O12 thin films prepared by sol–gel method

Bi_4-xNd_xTi₃O₁₂ (BNT-x, x = 0, 0.25, 0.50, 0.75 and 1.0) thin films were prepared on Pt/Ti/SiO₂/Si substrates by a sol–gel method. The microstructure, ferroelectric and dielectric properties of BNT-x thin films were investigated. The single-phase BNT-x thin films were obtained. With increasing Nd content, the preferred orientation changed from random to (117) and surface morphologies changed from the mixture of rod- and plate-like grains to rod-like grains. The Nd substitution improved the ferroelectric and dielectric properties of BTO films. BNT-x films showed better electrical properties at x = 0.50—1.0. BNT-0.75 film exhibited the best electrical properties with remanent polarization (2P _r) of 26.6 μC/cm², dielectric constant (ε _r) of 366 (at 1 MHz), dielectric loss (tanδ) of 0.034 (at 1 MHz), leakage current density (J) of ±3.0 × 10⁻⁶ A/cm² (at ± 5 V) and fatigue-free characteristics.     

Magnetoelectric effect in Pb(Zr0.95Ti0.05)O3 and CoFe2O4 heteroepitaxial thin film composite

Multiferroic epitaxial films, include SrRuO₃/Pb(Zr_0.95Ti_0.05)O₃/CoFe₂O₄ has been successfully deposited on SrTiO₃ substrate by pulsed-laser deposition technique. The results show that the prepared films exhibit a single phase. The Pb(Zr_0.95Ti_0.05)O₃ (PZT) film was highly textured with (1 0 0) orientation and gives good ferroelectric properties with saturated polarization of 15 μC/cm². The magnetic coercivity of CoFe₂O₄ film on Pb(Zr_0.95Ti_0.05)O₃ has been dampened to 0.9 kOe. The anisotropic magnetically behavior of CoFe₂O₄ film was changed to isotropic by using high Zr concentrated PZT as underneath layer. Heterostructure films show a good ferromagnetic and ferroelectric coupling that lead to the large magnetoelectricity of 287 mV/cm Oe.     

Distribution of pyrochlore phase in Pb(Mg1/3Nb2/3)O3-PbTiO3 films and suppression with a Pb(Zr0.52Ti0.48)O3 interfacial layer

Thin films of the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) on Pt/Ti/SiO₂/Si (Pt/Si) substrates both with and without a Pb(Zr_0.52Ti_0.48)O₃ (PZT) interfacial layer were investigated. Perovskite and pyrochlore coexistence was observed for PMN-PT thin films without a PZT interfacial layer. Interestingly, most of the pyrochlore phase was observed in single-coated films and in the first layer of multi-coated films. The pyrochlore phase exhibited grains with an average size of about 25 nm, which is smaller than those of the perovskite phase (about 90 nm). In contrast, for PMN-PT thin films grown on a PZT interfacial layer, the formation of a pyrochlore phase at the interface between PMN-PT layers and the substrate is completely suppressed. Moreover, small grains are not observed in the films with a PZT interfacial layer. The measured polarization-electric field (P-E) hysteresis loops of PMN-PT films with and without PZT layers indicate that enhanced electrical properties can be obtained when a PZT interfacial layer is used. These enhanced properties include an increase in the value of remanent polarization P_r from 2.7 to 5.8 μC/cm² and a decrease in the coercive field E_c from 60.5 to 28.0 kV/cm.     

Annealing temperature dependence of effective piezoelectric coefficients for Bi3.15Eu0.85Ti3O12 thin films

The effects of annealing temperatures 600, 650, 700, and 750 °C on microstructure, chemical composition, leakage current, ferroelectric, dielectric, and piezoelectric properties of Bi_3.15Eu_0.85Ti₃O₁₂ (BET) thin films prepared by metal–organic decomposition were studied in detail. The largest spontaneous polarization 2P _s (98.7 μC/cm² under 300 kV/cm), remnant polarization 2P _r (81.7 μC/cm² under 300 kV/cm), dielectric constant ε_r (889.4 at 100 kHz), effective piezoelectric coefficient d ₃₃ (46.7 pm/V under 260 kV/cm), and lowest leakage current (1.3 × 10⁻⁶ A/cm² under 125 kV/cm) of BET thin film were obtained with annealing at 700 °C. The mechanisms concerning the dependence of the enhancement d ₃₃ are discussed according to the phenomenological equation, and the improved piezoelectric performance could make BET thin film a promising candidate for piezoelectric thin film devices.     

Effect of TiOx seed layer on the texture and electric properties in La and Ca modified PbTiO3 thin films

Lanthanum-and calcium-modified PbTiO₃ (PLCT) ferroelectric thin films were successfully prepared on Pt(111)/Ti/SiO₂/Si substrates by pulsed laser deposition. Influence of TiO_x seed layer on texture and electric properties of PLCT films was investigated. It is found the PLCT films without seed layer exhibited highly (100)-textured, while using about 9 nm TiO_x as seed layer lead to highly (301)-textured. The PLCT film with TiO_x seed layer possess higher remnant polarization (Pr = 26 µC/cm²), better pyroelectric coefficient and figure of merit at room temperature (p = 370 µC/m²k, F_d = 190 × 10^− 5 Pa^− 1/2) than that of film without seed layer. The mechanism of the enhanced electric properties was also discussed.     

Enhanced ferroelectric properties of Pb(Zr0.80Ti0.20)O3/PbO thin films prepared by radio frequency magnetron sputtering

The Pb(Zr_0.80Ti_0.20)O₃ (PZT) thin films with and without a PbO buffer layer were deposited on the Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by radio frequency (rf) magnetron sputtering method. The PbO buffer layer improves the microstructure and electrical properties of the PZT thin films. High phase purity and good microstructure of the PZT thin films with a PbO buffer layer were obtained. The effect of the PbO buffer layer on the ferroelectric properties of the PZT thin films was also investigated. The PZT thin films with a PbO buffer layer possess better ferroelectric properties with higher remnant polarization (P_r = 25.6 μC/cm²), and lower coercive field (E_c = 60.5 kV/cm) than that of the films without a PbO buffer layer (P_r = 9.4 μC/cm², E_c = 101.3 kV/cm). Enhanced ferroelectric properties of the PZT thin films with a PbO buffer layer is attributed to high phase purity and good microstructure.     

The effect of Sb2O5 additions on the dielectric properties of Ag(Nb0.8Ta0.2)O3 ceramics

The sintering behavior and dielectric properties for perovskite Ag(Nb_0.8Ta_0.2)O₃ ceramic with Sb₂O₅ doping was explored. A small amount of Sb₂O₅ (2.5 wt.%) led to high densification at temperatures < 1060 °C. The dielectric constant increased and the temperature coefficient decreased with increasing concentration of Sb₂O₅, and the dielectric constant reached 673, combined with a low temperature coefficient of 147 ppm/°C, and dielectric loss of 0.0044 (at 1 MHz) for the sample with 3.5 wt.% Sb₂O₅ sintered at 1080 °C.     

Electrical and optical properties of 12CaO·7Al2O3 electride doped indium tin oxide thin film deposited by RF magnetron co-sputtering

12CaO·7Al₂O₃ electride (C12A7:e⁻) doped indium tin oxide (ITO) (ITO:C12A7:e⁻) thin films were fabricated on a glass substrate by an RF magnetron co-sputtering system with increasing number of C12A7:e⁻ chips (from 1 to 7) and at various oxygen partial pressure ratios. The optical transmittance of the ITO:C12A7:e⁻ thin film was higher than 70% in the visible wavelength region. In the electrical properties of the thin film, a decrease of the carrier concentration from 2.6 × 10²⁰ cm^− 3 to 2.1 × 10¹⁸ cm^− 3 and increase of the resistivity from 1.4 × 10^− 3 Ω cm to 4.1 × 10^− 1 Ω cm were observed with increasing number of C12A7:e⁻ chips and oxygen partial pressure ratios. It was also observed that the Hall mobility was decreased from 17.27 cm²·V^− 1·s^− 1 to 5.13 cm²·V^− 1·s^− 1. The work function of the ITO thin film was reduced by doping it with C12A7:e⁻.     

Highly a-oriented SrBi2Ta2O9 thin film on (111) Pt/TiO2/SiO2/Si substrate by eclipse pulsed laser deposition

A highly a-oriented SrBi₂Ta₂O₉ thin film with a polycrystalline structure was deposited on a preferentially oriented (111) Pt/TiO₂/SiO₂/Si substrate by eclipse pulsed laser deposition (PLD) method. The SrBi₂Ta₂O₉ thin film exhibited flat and smooth surface with the surface roughness of about 0.5 nm resulting from reducing particulates generated by on-axis PLD. The SrBi₂Ta₂O₉ thin film showed a good ferroelectric property with the high remanent polarization of 12 μC/cm² and the low coercive electric field of 140 kV/cm. For the highly a-oriented SBT thin film, domain switching and reading were performed by Kelvin probe force microscope (KFM). The KFM data indicate a good ferroelectric property of the highly a-oriented SrBi₂Ta₂O₉ thin film with high KFM signals that reflect ferroelectric polarizations.     

Enhanced ferro- and piezoelectric properties in (100)-textured Nb-doped Pb(ZrxTi1 − x)O3 films with compositions at morphotropic phase boundary

To develop high-performance piezoelectric films on conventional Pt(111)/Ti/SiO₂/Si(100) substrates, sol-gel-derived highly [100]-textured Nb-doped Pb(Zr_xTi_1 − x)O₃ (PNZT) thin films with different Zr/Ti ratios ranging from 20/80 to 80/20 were prepared and characterized. The phase structure, ferroelectric and piezoelectric properties of the PZNT films were investigated as a function of Zr/Ti ratios, and it was confirmed that there was distinct phase transition of the PNZT system from tetragonal to rhombohedral when the Zr/Ti ratio varied across the morphotropic phase boundary (MPB). The Nb-doped PZT films showed enhanced remanent polarization but reduced coercive field, whose best values reached 75 μC/cm² and 82 kV/cm, respectively at the composition close to MPB. In addition, the [100]-textured PNZT film at MPB also shows a high piezoelectric coefficient up to 161 pm/V. All these properties are superior to those for undoped PZT films.     

Deflection of wafers and cantilevers with Pt/LNO/PZT/LNO/Pt/Ti/SiO2 multilayered structure

The present paper describes a Pt/LNO/PZT/LNO/Pt/Ti/SiO₂ multilayers deposited on 4-inch Si wafers. We have evaluated the variation of the deflection of the Si wafers with deposition of each of the thin films. The deposition of the multilayers has resulted in downward deflection (center is higher than edge) of the Si wafers. The multilayers have been also deposited onto SOI wafers and fabricated into piezoelectric micro cantilevers through MEMS bulk micromachining. The micro cantilevers have shown the upward deflection. We have characterized the ferroelectric and piezoelectric properties of the PZT thin films through electrical tests of the micro cantilevers. The dielectric constant, saturation polarization, remanent polarization and coercive field were measured to be 1050, 31.3 μC/cm², 9.1 μC/cm² and 21 kV/cm, respectively. The transverse piezoelectric constant, d₃₁, was measured to be − 110 pm/V from the DC response of the micro cantilevers.     

Pb(Zr0.52Ti0.48)O3/TiNi multilayered heterostructures on Si substrates for smart systems

Ferroelectric/shape memory alloy thin film multilayered heterostructures possess both sensing and actuating functions and are considered to be smart. In this article, Pb(Zr_0.52Ti_0.48)O₃ (PZT) ferroelectric thin films and Ti-riched TiNi shape memory alloy thin films have been deposited on Si and SiO₂/Si substrates in the 400-600 °C temperature range by pulsed laser deposition technique. Deposition processing, microstructure and surface morphology of these films are described. The TiNi films deposited at 500 °C had an austenitic B2 structure with preferred (110) orientation. The surfaces of the films were very smooth with the root-mean-square roughness on a unit cell level. The structure of the TiNi films had a significant influence on that of the subsequently deposited PZT films. The single B2 austenite phase of the TiNi favored the growth of perovskite PZT films. The PZT/TiNi heterostructures with the PZT and TiNi films respectively deposited at 600 and 500 °C exhibited a polarization-electric field hysteresis behavior with a leakage current of about 2 × 10^− 6 A/cm².     

Effects of porosity on ferroelectric properties of Pb(Zr0.2Ti0.8)O3 films

The sol-gel deposition method has been successfully applied to obtain Pb(Zr_0.2Ti_0.8)O₃ thin films on platinized silicon wafers. Addition of different amounts (7-15 wt.%) of organic macromolecular polyvinylpyrrolidone in the precursor solution prior to spin coating proves to be an excellent method for obtaining porous films. The crystal structure of as deposited films was analyzed by X-ray diffraction. The porous films show perovskite phase after annealing at 650 °C. The surface morphology has been studied by Atomic Force Microscopy and Scanning Electron Microscopy. The surface profile indicates a roughness of the film of 5 nm and no microcracks on the surface. The ferroelectric behavior was proved for each film, by hysteresis loops and by the “butterfly” shape of the capacitance-voltage characteristics. The remnant polarization and the coercive field decrease while the amount of added PVP increases.