Properties Of BaTiO3 Thin Films Research Articles

Ni-modified BaTiO3 film prepared by sol-gel with high energy storage performance

The development of lead-free dielectric capacitors with high recoverable energy storage density and high energy storage efficiency is important for improving the overall performance of electronic and power systems. BaTiO3 (BTO) is one of the most common ferroelectric materials and has attracted much attention for energy storage applications in the past decades due to its excellent dielectric and ferroelectric properties. However, high remnant polarization and low electrical breakdown strength of BTO limit its development in energy storage applications. Many efforts (e.g., elements doping, interface/heterostructure, etc.) have been made to improve the energy storage density of BTO thin films. In this paper, Ba1-xNixTiO3 thin films (x = 0, 0.02, 0.04, 0.06, 0.08; abbreviated as BNxT) were synthesized via sol-gel and spin-coated method. The effect of Ni doping on the structural, dielectric, ferroelectric and energy storage properties of BTO thin films has been studied. The results confirmed that with the increase of Ni doping, a second phase arises and the dielectric constant decreases. While appropriate Ni doping led to the improvement of the breakdown strength, further increase of Ni deteriorated the energy storage because of the high oxygen vacancy. Finally, optimized energy storage performance was obtained for BN0.04T thin film: dielectric constant of 401, dielectric loss of 0.002, recoverable energy density of 20.2 J/cm3 and energy storage efficiency of 83.6% at 965 kV/cm. Meanwhile, the remnant and maximum polarization of the films were 0.06 μC/cm2 and 50 μC/cm2, respectively. BN0.04T thin film has an excellent application prospect and is expected to appear as a component in the future composite energy storage film system.

Deposition-rate-dependent ferroelectric properties of epitaxially grown BaTiO3 thin films

We report the deposition-rate-dependent ferroelectric properties of BaTiO3 thin films fabricated through pulsed laser deposition. BaTiO3 thin films were epitaxially grown on single-crystal (001) Rh substrates. The BaTiO3 thin films exhibited strained tetragonal structures with c/a ratios of 1.05 (0.02 nm/pulse) and 1.03 (0.3 nm/pulse), depending on the film deposition rate. The increased tetragonality enhances the ferroelectric properties of the films. In addition, their deposition rate determines their leakage current and bandgap energy. Using scanning probe microscopy, we observed the surface morphologies and ferroelectric domain structures of the films. Furthermore, a ferroelectric domain analysis based on the Landau–Lifshitz–Kittel scaling law indicated that a reduction in the growth rate leads to an increase in the domain size and domain wall energy of BaTiO3 thin films. Finally, it was demonstrated that the optical bandgap of BaTiO3 thin films is related to their tetragonality.

Role of ferroelectric polarization during growth of highly strained ferroelectric materials

In ferroelectric thin films and superlattices, the polarization is intricately linked to crystal structure. Here we show that it can also play an important role in the growth process, influencing growth rates, relaxation mechanisms, electrical properties and domain structures. This is studied by focusing on the properties of BaTiO3 thin films grown on very thin layers of PbTiO3 using x-ray diffraction, piezoforce microscopy, electrical characterization and rapid in-situ x-ray diffraction reciprocal space maps during the growth using synchrotron radiation. Using a simple model we show that the changes in growth are driven by the energy cost for the top material to sustain the polarization imposed upon it by the underlying layer, and these effects may be expected to occur in other multilayer systems where polarization is present during growth. This motivates the concept of polarization engineering as a complementary approach to strain engineering.

Ferroelectric properties of BaTiO3 thin films co-doped with Mn and Nb

We report on properties of BaTiO3 thin films where the bandgap is tuned via aliovalent doping of Mn and Nb ions co-doped at the Ti site. The doped films show single-phase tetragonal structure, growing epitaxially with a smooth interface to the substrate. Using piezoforce microscopy, we find that both doped and undoped films exhibit good ferroelectric response. The piezoelectric domain switching in the films was confirmed by measuring local hysteresis of the polarization at several different areas across the thin films, demonstrating a switchable ferroelectric state. The doping of the BaTiO3 also reduces the bandgap of the material from 3.2 eV for BaTiO3 to nearly 2.7 eV for the 7.5% doped sample, suggesting the viability of the films for effective light harvesting in the visible spectrum. The results demonstrate co-doping as an effective strategy for bandgap engineering and a guide for the realization of visible-light applications using its ferroelectric properties.

Enhanced energy storage properties of BaTiO3 thin films by Ba0.4Sr0.6TiO3 layers modulation

Electrostatic dielectric energy storage capacitors have attracted much attention recently for their fast charging-discharging speed and high power density. Trilayered Ba0.4Sr0.6TiO3/BaTiO3/Ba0.4Sr0.6TiO3 (BST/BT/BST) thin films were prepared by spin-coating technique. The sandwich-structured thin films showed high dielectric constant (εr = 952) and low dielectric loss (tanδ = 0.034) at room temperature (10 kHz). Moreover, the dielectric constant of the thin films demonstrated good frequency stability within the measured frequency range and broad capacitance variation (20 °C–160 °C, ΔC/C25°C<±10%). The electric-field dependence of dielectric response was investigated and the dielectric tunability was 13.3% at 100 kV/cm. Compared with pure BT thin films, the heterostructure exhibited enhanced electric breakdown strength and energy storage density. The recoverable energy storage density and efficiency of BST/BT/BST thin films were 14.69 J/cm3 and 33.9% at 1.44 MV/cm, respectively. The results indicated that BST/BT/BST heterostructure films would be an alternative way to improve the energy storage density of dielectrics for applications.

Fabrication and Ferroelectric Properties of BaTiO3 Thin Films Deposited on Silicon Substrate Using PLD

In this work, thin films of BaTiO3 have been fabricated by pulsed-laser ablation on silicon substrate. The x-ray diffraction pattern of the polycrystalline and post annealed films in presence of oxygen indicates perovskite tetragonal phase. The room temperature ferroelectric response measured by “Positive-Up-Negative-Down” PUND method shows hysteretic behaviour in polarization versus electric field loops, confirms the traditional ferroelectric nature. The polarization switching dynamics can be described by Kolmogorov-Avrami-Ishibashi (KAI) model based on nucleation and growth of domains. The room temperature ferroelectricity of BaTiO3 deposited on silicon substrate is promising for application in electronic and memory devices.

Tuning the growth and strain relaxation of ferroelectric BaTiO3 thin films on SrRuO3 electrode: influence on electrical properties

This study is focused on the link between the structural and electric properties of BaTiO3 thin films grown on SrRuO3-buffered (001) SrTiO3 substrates, SrRuO3 acting as bottom electrode. The growth regime and film structure are here tuned through the growth pressure for pulsed laser deposition in the 1–200 mTorr range. The dielectric, ferroelectric and leakage current properties are systematically measured for the different strain states of the BaTiO3 thin films on SrRuO3. The results are discussed with the help of ab initio calculations on the effects of Ba- and Ti-vacancies on BaTiO3 lattice parameters. A sharp increase of the dielectric constant is evidenced in the high pressure region, where the tetragonality of the BaTiO3 is decreasing rapidly with growth pressure. We interpret this divergence of the dielectric function as the signature of the vicinity of the phase boundary between the out-of-plane and in-plane orientations of the tetragonal BTO films.

Effects of defects, grain size, and thickness on the optical properties of BaTiO3 thin films

Barium titanate (BaTiO3) thin films were grown on Au/Si:B (111) substrates using an electron beam physical vapor deposition (EB-PVD) method. Investigation was made of the effects of grain size and strain on the temperature-dependent optical properties of these thin films, controlled using post-deposition annealing treatments at 400°C and 550°C. The structural, morphological, and optical properties of the deposited films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM), and luminescence spectroscopy, respectively. The XRD and AFM analyses revealed the tetragonal crystal structure of the films. The luminescence spectra properties were attributed to recombination of the self-trapped excitons that formed localized states in the forbidden gaps (produced by impurities and oxygen vacancies), modulated by thermal treatment and the presence of oxygen. With increasing thickness, the blue and violet emission energies increased from 2.60 to 2.66eV, and from 2.82 to 2.90eV, respectively. This work shows that extrinsic and intrinsic defects can induce and enhance luminescence.

Room Temperature Fabrication of MIMCAPs via Aerosol Deposition

We report the microwave dielectric properties of BaTiO3 thin films fabricated via aerosol deposition, which is capable of applying functional ceramic films to Si-based semiconductor fabrication at room temperature. As the starting powder, BaTiO3 powder with an average particle size of 300 nm afforded a dense thin film with a thickness of 500 nm as well as a smooth interface with the Pt/Ti/SiO2/Si substrate. In comparison, the interface roughness of BaTiO3 thin film was degraded (>100 nm) when BaTiO3 powder with an average particle size of 450 nm was used as the starting powder, owing to the excessive impact energy during film growth. Metal-insulator–metal capacitors were realized on a Si wafer via electron beam evaporation and inductively coupled plasma etching in order to determine the relative permittivity, loss tangent, and current-voltage characteristics. The average values of the relative dielectric permittivity and loss tangent of the BaTiO3 thin film were 78 and 0.03, respectively, in the frequency range of 1–6 GHz.

Effect of ion beam irradiation on dielectric properties of BaTiO3 thin film using surface plasmon resonance

The effects of swift heavy ions on the structure, surface morphology and dielectric behaviour of barium titanate (BaTiO3, known as BTO) thin films have been investigated by irradiating the films with 100 MeV Au+8 ions at an ion fluence of 1 × 1012 ions cm−2. BTO thin films were deposited on Pt/Si substrate by pulsed laser deposition technique. The structure of the film was crystalline with tetragonal phase. Surface topography was studied by atomic force microscope. The dielectric properties of BTO have been studied using surface plasmon resonance (SPR) technique in Otto configuration. SPR is a highly sensitive technique for investigating the dielectric and optical properties of dielectrics. Gold-coated glass prisms have been utilized to excite the surface plasmon waves (SPWs) at the metal–air interface. When BTO thin film is integrated with the surface of Au thin film, a significant shift in the SPR curve has been observed due to change in the propagation constant of SPW at metal–dielectric interface. The optical and dielectric parameters of BTO thin film were obtained by fitting the experimental SPR data with the Fresnel’s equations. The observed increase in the dielectric constant of BTO thin film after irradiation may be attributed to packing density.

Thickness dependence of structural, optical and luminescence properties of BaTiO3 thin films prepared by RF magnetron sputtering

BaTiO3 thin films were deposited onto quartz substrates by RF magnetron sputtering. X-ray diffraction pattern showed the formation of BT thin films with a tetragonal structure with orientations along (101) plane. Average crystallite size increased from 12.52 to 14.87 nm as the film thickness increased from 207 to 554 nm. With the increase in film thickness, the structural disorder decreases and the crystalline quality of the films gradually improved. The film exhibited good adherence to the substrate and are crack free. X-ray photoelectron spectroscopy revealed the presence of barium, titanium and oxygen in BT film. An average transmittance of >80 % was observed for all the films. This high transmittance BT films in the visible region is suitable for various electro-optic applications. The transmittance spectra showed high UV-shielding properties. Optical band gap was found to decrease from 4.55 to 3.70 eV with increase of film thickness, whereas the refractive index was found to increase. The refractive index of the BT films can be tuned between 2.11 and 2.21 at 550 nm. The real and imaginary dielectric constants with increase in film thickness were investigated. The low dissipation factor of BT thin films makes it a promising material for frequency agile applications. The emission spectra of BT thin films consist of near band edge excitonic UV emission and defect related emission in the visible range. The PL emission bands in UV and visible region of BT thin films make them suitable for electro-optic devices and light emitters.

Influence of epitaxial strain on elastocaloric effect in ferroelectric thin films

We report the influence of epitaxial strain um on the elastocaloric properties of BaTiO3 thin films. Using thermodynamic calculations, we show that there exists a critical compressive stress σ3c at which the elastocaloric effect is maximized for any compressive misfit strain we investigate. Moreover, it is found that |σ3c| decreases significantly with decreasing |um|, which is accompanied by a reduction of the elastocaloric response. Interestingly, a several fold enhancement in the electrocaloric effect can be achieved for stress in proximity of σ3c. The elastocaloric effect predicted here may find potential cooling applications by combining the stress-mediated electrocaloric effect or designing hybrid elastocaloric/electrocaloric devices in the future.

Effect of a Second Annealing Process on the Properties of BaTiO3 Thin Films on Polycrystalline Nickel Substrates Grown by Polymer-Assisted Deposition

Ferroelectric BaTiO3 thin films were successfully deposited on nickel foils by a chemical solution technique named polymer-assisted deposition. It is found that a second annealing in oxygen using a rapid thermal annealing furnace would strongly affect the electric properties of the as-prepared thin films. Dielectric and ferroelectric properties have been systematically studied. The correlation between the second annealing conditions and dielectric properties was established and discussed. Optimized second annealing condition was found.

(Invited) Fabrication and Dielectric Properties of BaTiO3 Thin Films on Polycrystalline Ni Foils

The BaTiO3 (BTO) thin films were deposited on polycrystalline Ni foils using a chemical solution approach. We show that the interface between the BTO film and the Ni foil plays a critical role in determining the dielectric and magnetoelectric (ME) properties of this flexible assembly. A pretreatment process of nickel foils with hydrogen peroxide (H2O2) solution has been conducted to form thin nickel oxide layers on the surfaces for the growth of BTO films. Both the concentration of H2O2 solution and the pretreated time were found to strongly affect the dielectric constant of BTO films, which is likely to be related to the evolution of nickel oxide at the interface during the growth of BTO films. The growth dynamics was systematically studied to optimize the single phase BTO films with good dielectric properties. Our results have demonstrated that not only a well-controlled interface between the BTO film and the Ni substrate can be achieved, but also an good dielectric and ME performance can be accomplished.

(Invited) Fabrication and Dielectric Properties of BaTiO3 Thin Films on Polycrystalline Ni Foils

The BaTiO3 (BTO) thin films were deposited on polycrystalline Ni foils using a chemical solution approach, polymer-assisted deposition. We show that the interface between the BTO film and the Ni foil plays a critical role in determining the dielectric and ferroelectric properties of this flexible assembly. A pretreatment process of nickel foils with hydrogen peroxide (H2O2) solution has been conducted to form thin nickel oxide layers on the surfaces for the growth of BTO films. A rapid thermal post-annealing in oxygen would also strongly affect the electric properties of the as-prepared thin films. The growth dynamics was systematically studied to optimize the single phase BTO films with good dielectric and ferroelectric properties.

Structural characterization and dielectric properties of BaTiO3 thin films obtained by spin coating

Barium titanate thin films were prepared by spin coating deposition technique of an acetic precursor sol and sintered at 750, 900 and 1050?C. Phase composition of the obtained thin films was characterized by X-ray diffraction and Raman spectroscopy. Their morphology was analysed by scanning electron microscopy and atomic force microscopy. Dielectric properties of thin films sintered at 750 and 900 ?C were characterized by LCD device, where the influence of sintering temperature on dielectric permittivity and loss tangent was inspected. It was concluded that higher sintering temperature increases grain size and amount of tetragonal phase, hence higher relative permittivity was recorded. The almost constant relative permittivity in the measured frequency (800Hz-0.5MHz) and temperature (25-200?C) ranges as well as low dielectric loss are very important for the application of BaTiO3 films in microelectronic devices.

The Influence of the Photovoltaic Effect on the Ferroelectric Properties of BaTiO&lt;sub&gt;3&lt;/sub&gt; Thin Film

This article simulates the ferroelectric properties of a model of BaTiO3 thin film sandwiched between metal electrodes at the state of short circuit. We discussed the change of the depolarization and the Photocurrent generated within the film under UV irradiation. Comparing the polarization before and after the irradiation, the influence of the photovoltaic effect on the ferroelectric properties of BaTiO3 Thin Film is gained.

Ferroelectric Instability and Dimensionality in Bi-Layered Perovskites and Thin Films

The dielectric and thermal properties of Bi (bismuth)-layered perovskite SrBi2Ta2O9(SBT) are discussed in comparison with ferroelectric thin BaTiO3films. Although these two perovskites exhibit quite a different nature, the dielectric properties of BaTiO3thin film are similar to those in bulk SBT. The dielectric properties and pseudo-two-dimensional structure between SBT and thin film suggest that the bulk layered ferroelectric SBT is a good model of ultra-thin ferroelectric film with two perovskite layers, free from any misfit lattice strain with substrate and surface charge at the interface with electrodes. Based on the mechanism of ferroelectric phase transition of SBT, it seems plausible that the ferroelectric interaction is still prominent but shows a crossover from ferroelectric to antiferroelectric interaction in perovskite ultra-thin films along the tetragonal axis.

Effect of Stress Engineering on the Electrical Properties of BaTiO3 Thin Film

Nano porous LaNiO3 (LNO) thin-film oxide electrodes were deposited on Si substrates by a chemical solution deposition (CSD) to control the residual stress in sputtered BaTiO3 (BTO) thin film. The BTO thin film was deposited on the LNO/Si substrate by RF magnetron sputtering to elucidate the effect of the LNO thin-film electrode on the ferroelectric and dielectric properties of the resulting BTO thin film. The orientation of the LNO thin film was successfully controlled in the (100) direction even on the Si substrates, and therefore, the resulting BTO thin films also exhibited preferred orientation in the (001) direction. The BTO thin films deposited at a relatively low temperature of 500 °C exhibited a good hysteresis loop, indicating the usefulness of our CSD-derived LNO thin-film electrode. We also investigated the effect of the thickness of the LNO thin-film electrode on the ferroelectric property of the resulting BTO thin films.

Sizable electrocaloric effect in a wide temperature range tuned by tensile misfit strain in BaTiO3 thin films

The effects of misfit strain on the electrocaloric (EC) properties of BaTiO3 thin films arestudied by using the Landau-Devonshire thermodynamic theory. The “misfit-strain temperature” phase diagrams for different electric fields are constructed. It was found that the EC effect of a BaTiO3 thin film is strongly dependent on misfit strain. More interestingly, we found that BaTiO3 thin films with tensile misfit strain exhibit a sizable EC effect in a wider temperature range in comparison with those with compressive misfit strain.