Solution-based fabrication and electrical properties of CaBi4Ti4O15 thin films

Ferroelectric CaBi₄Ti₄O₁₅ (CBT) thin films were prepared by spin coating technology using solution-based fabrication. The as-deposited CBT thin films were crystallized below 600 °C and the layered perovskite were crystallized at 700 °C using CFA processing in air. The enhancement of ferroelectric properties in CBT thin films for MFIS structures were investigated and discussed. Compared the Bi₄Ti₃O₁₂ (BIT), the CBT showed the better physical and electrical characteristics. The 700 °C annealed CBT thin films on SiO₂/Si substrate showed random orientation and exhibited large memory window curves. The maximum capacitance, memory window and leakage current density were about 250 pF, 2 V, and 10^?5 A/cm², respectively.     

Structural and electrical properties of Pb(Zr0.53Ti0.47)O3 films prepared on La0.5Sr0.5CoO3 coated Si substrates

PbZr_0.53Ti_0.47O₃ (PZT) thin films with thickness of 0.9 μm were prepared on La_0.5Sr_0.5CoO₃ (LSCO) coated Si substrates. Both PZT and LSCO were prepared by the sol–gel method. The concentration of LSCO sol was varied from 0.3 to 0.1 mol/L, which could modify the preferential orientation of PZT thin films and consequently affect the dielectric and ferroelectric properties. The LSCO electrode layers derived from lower sol concentration of 0.1 mol/L have much more densified structure, which facilitates the formation of (1 0 0) textured PZT films with smooth and compact columnar grains. PZT thin films prepared on the optimized LSCO films exhibit the enhanced dielectric constant and remnant polarization of 980 and 20 μC/cm², respectively.     

Dip-coated La2Ti2O7 as a buffer layer for growth of Bi3.25La0.75Ti3O12 films with enhanced (0 1 1) orientation

Thin-films of La₂Ti₂O₇ were obtained by dip-coating process using a precursor salt in nitric acid solution. The effects of solution concentration, withdrawal speed, post-annealing duration and temperature were investigated both on grain size and orientation of the La₂Ti₂O₇ thin layers. In addition, a target with the required stoichiometry for PVD deposition of La-substituted Bi₄Ti₃O₁₂ (BLT) was successfully sintered by spark plasma sintering (SPS) at 750 °C. Finally (0 1 1)-oriented BLT ferroelectric films have been grown by RF sputtering on (1 1 0)-oriented La₂Ti₂O₇ polycrystalline thin-film. A preferential orientation of BLT thin films has been obtained after annealing at a temperature lower than 650 °C.     

Effect of annealing temperature on ferroelectric electron emission of sol–gel PZT films

In this work, the influence of annealing temperature on the ferroelectric electron emission behaviors of 1.3-μm-thick sol–gel PbZr_0.52Ti_0.48O₃ (PZT) thin film emitters was investigated. The results revealed that the PZT films were crack-free in perovskite structure with columnar-like grains. Increasing annealing temperature led to the growth of the grains with improved ferroelectric and dielectric properties. The remnant polarization increased slightly from 35.3 to 39.6 μC/cm² and the coercive field decreased from the 56.4 to 54.6 kV/cm with increasing annealing temperature from 600 to 700 °C. The PZT film emitters exhibited remarkable ferroelectric electron emission behaviors at the threshold voltage above 95 V. The film annealed at 700 °C showed a relatively lower threshold voltage and higher emission current, which is related to the improved ferroelectric and dielectric properties at higher annealing temperature. The highest emission current achieved in this work was around 25 mA at the trigger voltage of 160 V.     

Pulsed laser deposition BTS thin films: The role of substrate temperature

BaSn_0.15Ti_0.85O₃ (BTS) thin films were deposited on Pt/Ti/SiO₂/Si(1 0 0) substrate by pulsed laser deposition and the effects of substrate temperature on their structure, dielectric properties and leakage current density were investigated. The results indicate that the substrate temperature has a significant effect on the structural and dielectric properties of the BTS thin films which exhibit a polycrystalline perovskite structure if the substrate temperature ranges within 550–750 °C. The dielectric constant and loss tangent of the BTS thin films deposited at 650 °C are 341 and 0.009 at 1 MHz, respectively, the tunability is 72.1% at a dc bias field of 400 kV/cm, while the largest figure of merit (FOM) is 81.1. The effect of the substrate temperature on the leakage current of the BTS thin films is discussed.     

Structural and electrical properties of Na0.5Bi4.0RE0.5Ti4O15 (RE=Tm,Yb and Lu) thin films

In the current study, a series of lanthanide ions, Tm, Yb and Lu, were used for doping at the Bi-site of the Aurivillius phase Na_0.5Bi_4.5Ti₄O₁₅ (NaBTi) to investigate the structural, electrical and ferroelectric properties of the thin films. In this regard, Na_0.5Bi_4.5Ti₄O₁₅ and the rare earth metal ion-doped Na_0.5Bi_4.0RE_0.5i₄O₁₅ (RE=Tm, Yb and Lu, denoted by NaBTmTi, NaBYbTi, and NaBLuTi, respectively) thin films were deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by using a chemical solution deposition method. Formations of the Aurivillius phase orthorhombic structures for all the thin films were confirmed by X-ray diffraction and Raman spectroscopic studies. Based on the experimental results, the rare earth metal ion-doped Na_0.5Bi_4.0RE_0.5Ti₄O₁₅ thin films exhibited a low leakage current and the improved ferroelectric properties. Among the thin films, the NaBLuTi thin film exhibited a low leakage current density of 6.96×10⁻⁷ A/cm² at an applied electric field of 100 kV/cm and a large remnant polarization (2P_r) of 26.7 μC/cm² at an applied electric field of 475 kV/cm.     

Enhanced ferroelectric properties of 0.95Pb(Sc0.5Ta0.5)O3–0.05PbTiO3 thin films with Pb(Zr0.52,Ti0.48)O3 seed layer

0.95Pb(Sc_0.5Ta_0.5)O₃–0.05%PbTiO₃ (PSTT5) thin films with and without a Pb(Zr_0.52,Ti_0.48)O₃ (PZT52/48) seed layer were deposited on Pt/Ti/SiO₂/Si(1 0 0) substrates by RF magnetron sputtering. X-ray diffraction patterns indicate that the PSTT5 film with a PZT52/48 seed layer exhibited nearly pure perovskite crystalline phase with highly (4 0 0)-preferred orientation. Piezoresponse force microscopy observations reveal that a large out-of-plane spontaneous polarization exists in the highly (4 0 0)-oriented PSTT5 thin film. The PSTT5/PZT(52/48) possesses good ferroelectric properties with large remnant polarization P_r (12 μC/cm²) and low coercive field E_c (110 kV/cm). Moreover, The perfect butterfly-shaped capacitance–voltage characteristic curve and the relative dielectric constant as high as 733 is obtained in this PSTT5 thin film at 100 kHz.     

The effect of Nb doping on dielectric and ferroelectric properties of PZT thin films prepared by solution deposition

Niobium (Nb)-doped lead zirconate titanate thin films (PNZT) were produced by solution deposition with nominal compositions, Pb_(1?0.5x)(Zr_0.53Ti_0.47)_1?xNb_xO₃ where x = 0.00–0.07. The effects of sintering temperature, sintering time, variation of thickness in the films and change of niobium content were investigated with regard to phase development, microstructure, and ferroelectric and dielectric characteristics. The best results were obtained in double-layered films (390 nm) sintered at 600 °C for 1 h. Optimum doping level was found in 1% Nb-doped films. For 1% Nb-doped [Pb_0.995(Zr_0.53Ti_0.47)_0.99Nb_0.01O₃] films, remanent polarization (P_r) of 35.8 μC/cm² and coercive field (E_c) of 75.7 kV/cm have been obtained. The maximum dielectric constant was achieved in 1% Nb-doped films which was 689. Ferroelectric and dielectric properties decreased at higher Nb doping levels because of the changes in the grain size and perovskite lattice parameters.     

Effects of Ta-substitution on the dielectric properties of Ba6Ti2(Nb1−xTax)8O30 thin films

Tunable Ba₆Ti₂(Nb_1−xTa_x)₈O₃₀ (BTN-xTa; x = 0, 0.25, 0.4) thin films with a tetragonal tungsten bronze structure (TTB) were deposited on platinized Si substrates using the pulsed laser deposition (PLD) technique and their properties were investigated from the viewpoint of orientation and ferroelectric phase transition. Crystal structures and dielectric properties were characterized using an X-ray diffractometer and an impedance analyzer. Pure BTN (BTN-0Ta) thin films showed tunability as high as 60% and the tunability decreased as the amounts of Ta-substitution increased at 150 kV/cm and at 1 MHz. The dielectric constants also decreased from 436 to 88 at 1 MHz through the Ta-substitution. The low tunability and dielectric constants of Ta-substituted thin films were mainly ascribed to the lowered ferroelectric transition temperature (T_c). Ferroelectric BTN (BTN-0Ta) thin films may have been changed into a paraelectric state through the Ta-substitution since the T_c of BTN thin films were shifted to temperatures far below room temperatures (approximately −60 °C).     

Dielectric and optical properties of electroceramic PBZNZT thin films prepared by pulsed laser deposition process

The 0.6[0.94Pb(Zn_1/3Nb_2/3)O₃ + 0.06BaTiO₃] + 0.4[0.48(PbZrO₃) + 0.52(PbTiO₃)], PBZNZT, thin films were synthesized by pulsed laser deposition (PLD) process. The PBZNZT films possess higher insulating characteristics than the PZT (or PLZT) series materials due to the suppressed formation of defects, therefore, thin-film forms of these materials are expected to exhibit superior ferroelectric properties as compared with the PZT (or PLZT)-series thin films. Moreover, the Ba(Mg_1/3Ta_2/3)O₃ thin film of perovskite structure was used as buffer layer to reduce the substrate temperature necessary for growing the perovskite phase PBZNZT thin films. The PBZNZT thin films of good ferroelectric and dielectric properties (remanent polarization P_r = 26.0 μC/cm², coercive field E_c = 399 kV/cm, dielectric constant K = 737) were achieved by PLD at 400 °C. Such a low substrate temperature technique makes this process compatible with silicon device process. Moreover, thus obtained PBZNZT thin films also possess good optical properties (about 75% transmittance at 800 nm). These results imply that PBZNZT thin films have potential in photonic device applications.     

Electrical properties of chemical solution deposited (Bi0.9RE0.1)(Fe0.975Cu0.025)O3−δ (RE=Ho and Tb) thin films

Pure BiFeO₃ (BFO) and (Bi_0.9RE_0.1)(Fe_0.975Cu_0.025)O_3?δ (RE=Ho and Tb, denoted by BHFCu and BTFCu) thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by using a chemical solution deposition method. The BHFCu and BTFCu thin films showed improved electrical and ferroelectric properties compared to pure BFO thin film. Among them, the BTFCu thin film exhibited large remnant polarization (2P_r), low coercive field (2E_c) and reduced leakage current density, which are 89.15 C/cm² and 345 kV/cm at 1000 kV/cm and 5.38×10^?5 A/cm² at 100 kV/cm, respectively.     

Impact of Sr-doping on structural and electrical properties of Pb(Zr0.52Ti0.48)O3 thin films on RuO2 electrodes

In this paper, we investigated the impact of Sr-doping on the structural properties and electrical characteristics of lead zirconate titanate [Pb(Zr_0.52Ti_0.48)O₃, PZT] thin films deposited on RuO₂ electrodes by a sol-gel process and spin-coating technique. We used X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and field-emission transmission electron microscopy to explore the structural, morphological, chemical, and microstructural features, respectively, of these films as a function of the growth condition (strontium doping concentrations varied from 1, 3, and 5 mol%). The PZT thin film processed at the 3 mol% Sr exhibited the best electrical characteristics, including a low leakage current of 2.27×10⁻⁷ A/cm² at an electric field of 50 kV/cm, a large capacitance value of 2.74 μF/cm² at a frequency of 10 kHz, and a high remanent polarization of 37.95 μC/cm² at a frequency of 5 kHz. We attribute this behavior to the optimal amount of strontium in the PZT film forming a perovskite structure and a thicker interfacial layer at the PSZT film-RuO₂ electrode interface.     

Effects of annealing temperature on the microstructure,ferroelectric and dielectric properties of W-doped Na0.5Bi0.5TiO3 thin films

The effects of annealing temperature on the structure, morphology, ferroelectric and dielectric properties of Na_0.5Bi_0.5Ti_0.99W_0.01O_3+δ (NBTW) thin films are reported in detail. The films are deposited on indium tin oxide/glass substrates by a sol-gel method and the annealing temperature adopted is in the range of 560–620 °C. All the films can be well crystallized into phase-pure perovskite structures and show smooth surfaces without any cracks. Particularly, the NBTW thin film annealed at 600 °C exhibits a relatively large remanent polarization (P_r) of 20 μC/cm² measured at 750 kV/cm. Additionally, it shows a high dielectric constant of 608 and a low dielectric loss of 0.094 as well as a large dielectric tunability of 62%, making NBTW thin film ideal in the room-temperature tunable device applications.     

Effects of Li2CO3 and Sm2O3 additives on low-temperature sintering and piezoelectric properties of PZN-PZT ceramics

To assist the development of applications for multilayer piezoelectric devices, the low-temperature sintering piezoelectric ceramics of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ with Li₂CO₃ and Sm₂O₃ additives were fabricated by a conventional solid-state reaction, and their structural and piezoelectric properties were studied. With the addition of Li₂CO₃, the minimum sintering temperature of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ piezoelectric ceramics was reduced from 1125 °C to 950 °C through the formation of a liquid phase and its piezoelectric properties showed almost no degradation. When the sintering temperature was below 950 °C, however, the piezoelectric properties degraded obviously. The additional Sm₂O₃ resulted in a significant improvement in the piezoelectric properties of 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ ceramic with added Li₂CO₃. When sintered at 900 °C, the optimized properties of the 0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.49Ti_0.51)O₃ piezoelectric ceramic with 0.3 wt% Li₂CO₃ and 0.3 wt% Sm₂O₃ were obtained as d₃₃ = 483 pC/N, k₃₁ = 0.376, Q_m = 73, ɛ_r = 2524, tan δ = 0.0178.     

Lead zirconium titanate thin films prepared by thermal annealing of multilayer structures composed of PbO,ZrO2 and TiO2

Lead zirconium titanate [Pb(Zr_xTi_1?x)O₃ or PZT] thin films were prepared by the thermal annealing of multilayer films composed of binary oxide layers of PbO, ZrO₂ and TiO₂. The binary oxides were deposited by metal organic chemical vapor deposition. An interdiffusion reaction for perovskite PZT thin films was initiated at approximately 550 °C and nearly completed at 750 °C for 1 h under O₂ annealing atmosphere. The composition of Pb/Zr/Ti in perovskite PZT could be controlled by the thickness ratio of PbO/ZrO₂/TiO₂ where the contribution of each binary oxide at the same thickness was 1:0.55:0.94. The electrical properties of PZT (Zr/Ti = 40/60, 300 nm) prepared on a Pt-coated substrate included a dielectric constant ?_r of 475, a coercive field E_c of 320 kV/cm, and remnant polarization P_r of 11 μC/cm² at an applied voltage of 18 V.     

Enhanced photocatalytic activity of TiO2-ZnO thin films deposited by dc reactive magnetron sputtering

The effect of deposition conditions on the photocatalytic activity of TiO₂-ZnO thin films was studied. By using a (Ti)₉₀-(Zn)₁₀ alloy target, the samples were deposited at room temperature on glass substrates by dc reactive magnetron sputtering and post-annealed in air at 500 °C. The dependence of the physical properties of the films on the O₂/Ar gas ratio and the deposition working pressure was investigated. XRD patterns showed mainly the formation of the anatase phase of TiO₂. Optical absorption measurements exhibited a blue shift of the band-gap energy with increasing working pressure. XPS spectra indicated the presence of the Ti⁴⁺ and Zn²⁺ oxidation states, which correspond to TiO₂ and ZnO, respectively. The chemical state of Ti was further analyzed by means of the modified Auger parameter, α’, which gave a value of ca. 873 eV. The photocatalytic property of the films was assessed by the degradation of a methylene blue aqueous solution. The maximum photocatalytic performance was observed for the samples deposited at 3.0 mTorr and O₂/Ar gas ratio of 10/90. These results are explained in terms of the structural, optical, and morphological properties of the films.     

Structural,dielectric and piezoelectric properties of (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3–Bi(Zn0.5Ti0.5)O3 thin films prepared by sol–gel method

Lead free (1−x)(0.8Bi_0.5Na_0.5Ti_0.5O₃–0.2Bi_0.5K_0.5TiO₃)–xBiZn_0.5Ti_0.5O₃ (x=0–0.06) (BNT–BKT–BZT) thin films were deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by a sol–gel processing technique. The effects of BZT content on the structural, dielectric, ferroelectric and piezoelectric properties of the BNT–BKT–BZT thin films were investigated systematically. The BNT–BKT–BZT thin films undergo a transition from ferroelectric to relaxor phase with increasing temperature. The phase transition temperature decreases with the increase of BZT content. The BNT–BKT–BZT thin film with x=0.04 exhibits the best ferroelectric properties (P_max=40 µC/cm² and P_r=10 µC/cm²), largest dielectric constant (ε=560) and piezoelectric constant (d₃₃=40 pm/V). This finding demonstrates that the BNT–BKT–BZT thin film has an excellent potential for demanding high piezoelectric properties in lead free films.     

Light controlled resistive switching and photovoltaic effects in ferroelectric 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 thin films

In this work, the structural and ferroelectric properties of 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ (0.5BZT-0.5BCT) thin films deposited at different pulse repetition rates were studied. The films deposited at pulse repetition rate of 1 Hz display the optimum values of ferroelectric polarization and dielectric permittivity and are chosen for the investigation of resistive switching and photovoltaic studies. The Pt/0.5BZT-0.5BCT/ITO capacitors show the electroforming free resistive switching (RS) and is explained based on the polarization modulation of the Schottky barrier at the 0.5BZT-0.5BCT/ITO interface. Furthermore, it is shown that the RS ratio and switching voltage can be tuned with white light illumination. The capacitors display photovoltaic effect with the open circuit voltage ≈0.8 V and the short circuit current density ≈72.6 μAcm⁻². The photovoltaic efficiency is found to be ≈0.010% and is greater than that of other perovskite ferroelectric thin films. The underlying mechanism for enhanced RS and photovoltaic effects is highlighted.     

Dielectric dispersion and impedance spectroscopy of B3+-doped Ba(Ti0.9Sn0.1)O3 ceramics

In this study, the B₂O₃ doped Ba(Ti_0.9Sn_0.1)O₃ ceramics were prepared by using a solid state reaction method. Wide ranges of frequency (0.1 Hz to 1 MHz) and temperature (20–280 °C) dependence of the impedance relaxation were investigated. The impedance study indicates the presence of both dielectric relaxation in bulk and grain boundary effects in the material. The relaxation times for grain and grain boundary estimated from Cole–Cole plots varied with temperature according to the Arrhenius relation. The activation energy for grain and grain boundary were estimated to be 0.73 and 0.85 eV, respectively.     

Enhanced energy-storage performance of 0.94NBT-0.06BT thin films induced by a Pb0.8La0.1Ca0.1Ti0.975O3 seed layer

0.94(Na_0.5Bi_0.5TiO₃)-0.06BaTiO₃ ferroelectric thin films with and without the Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer were deposited on platinum-buffered silicon substrates by using Sol–Gel process. The influence of Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer and annealing temperatures on the microstructures, ferroelectric properties and energy-storage performances of the as-prepared films were investigated in details. The low annealing temperature and Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer could improve the values of electric break-down field strength and P_max-P_r, which play a vital role for high recoverable energy-storage density. Owing to the high electric break-down field strength value of 3310 kV/cm, a large recoverable energy density of W=17.2 J/cm³ and a high energy efficiency of η=74.3% were obtained for the 0.94(Na_0.5Bi_0.5TiO₃)-0.06BaTiO₃ thin film with the Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ seed layer, which was annealed at 450 °C.