BaTiO3 Films Research Articles

Understanding the electronic properties of BaTiO3 and Er3+ doped BaTiO3 films through confocal scanning microscopy and XPS: the role of oxygen vacancies.

Photonic and electronic properties exist inherently in ferroelectric barium titanate (BaTiO3); severe luminescence quenching also exists due to the insufficient confinement of excitons. In this sense, high optical emission can only be achieved by its chemical and structural modification. Thin BaTiO3 and Er:BaTiO3 films were grown by the spin coating method on a glass substrate at room temperature. Self-trapping of excitons in the thin BaTiO3 film and its structural modification due to the doping with Er3+ ions (Er:BaTiO3) are verified using scanning confocal fluorescence microscopy (SCFM), where self-trapping excitons never occured in its pure state. By thermal treatment and doping (BaTiO3 and Er:BaTiO3) we obtained localization of the excitons, which would further induce lattice strain around the surface defects, to accommodate the self-trapped excitons. With such a self-trapped state, the structure of BaTiO3 generates broadband emission of several overlapping bands between 1.95 and 2.65 eV at room temperature, while the structure Er:BaTiO3 showed defined emission bands at 2.24 and 2.35 eV, with very weak contributions of the emission due to the self-trapping state. The influence of the variation of the excitation wavelength using 1PE and 2PE on the emission bands of BaTiO3 and Er:BaTiO3 is also investigated. The results of enhanced emission bands suggest a clear dependence of the emission intensity on the excitation energy, where a ∼3 fold enhancement in emission has been demonstrated under Er3+ (1.55 eV) excitation, which can be attributed to effective energy transfer between the Er3+ ions. As a result, it is concluded that the developed BaTiO3 and Er:BaTiO3 can pave the way for future photonic devices.

Investigation of Rh–titanate (ATiO3) interactions on high-surface-area perovskite thin films prepared by atomic layer deposition

Thin, ∼1 nm films of CaTiO3, SrTiO3, and BaTiO3 were deposited onto MgAl2O4 by Atomic Layer Deposition (ALD) and studied as catalyst supports for Rh.

Effects of substrate-controlled-orientation on the electrical performance of sputtered BaTiO3 thin films

In this work, the relationships between bottom electrode/substrate configuration, crystalline microstructure, and electrical performances of BaTiO3 (BTO) thin films were investigated. The films were fabricated via RF magnetron sputtering on (Sr0.5La0.5)CoO3 (LSCO) buffered (110)-, (111)-SrTiO3 (STO) and SrRuO3 (SRO) buffered (110)-, (111)-MgO (MGO) substrates. The x-ray diffractometer results show that the LSCO/STO substrate resulted in films with high-quality epitaxial orientation, whereas the SRO/MGO substrate resulted in films having a strong (110) texture. The electrode/substrate configurations were designed to control the crystalline microstructure, which in turn affects the electrical performances of the films. The electrical performances were studied by employing a metal/ferroelectric/metal model. The J-V characteristics show obvious asymmetry with bias, which is mainly due to the varying transport state of oxygen vacancies. BTO films grown on LSCO/STO substrates exhibit large dielectric frequency dispersion, while those grown on SRO/MGO substrates display a nearly frequency independent response. All electrical parameters of these films were strongly affected by the polarization-tilting angle and the preferred orientation degree. Epitaxial and textured (110)-oriented films show higher permittivity but lower loss tangent, free-carrier concentration, built-in voltage, and leakage current density as compared to the epitaxial (111)-oriented film.

Space charge limited conduction in pulsed laser deposited BaTiO3/LaNiO3 hetero-junctions

We report the charge transport mechanism in BaTiO3 (BTO) thin film deposited on LaNiO3 (LNO) buffer layer using pulsed laser deposition technique thus, forming the metal – insulator – metal junction (Au/BTO/LNO). The temperature dependent Current density- Voltage (J-V) characteristics were measured, analyzed and compared with the La0.67Ca0.33MnO3 (LCMO) buffered BTO film (Au/BTO/LCMO). Although the mechanism was found to be space charge limited conduction (SCLC) as in case of BTO/LCMO but the absence of Ohmic region in Log J-Log V plot indicates higher injection rate. Various parameters such as trap density, activation energy, and ratio of free to trapped carriers (θ) were extracted out from the fitted J-V plot and subsequently their temperature dependence was studied and compared with BTO/LCMO. Higher current density, lower activation energy, lower trap density and higher ratio of free to trapped carriers (θ) were observed in BTO/LNO in contrast to BTO/LCMO. Furthermore, the lower activation energy indicates the presence of shallow trap level.

Negative-pressure enhanced ferroelectricity and piezoelectricity in lead-free BaTiO3 ferroelectric nanocomposite films

Negative pressure enhances the ferroelectric Curie temperature and piezoelectric coefficient in lead-free monoclinic BaTiO3 films for high-temperature ferroelectric applications.

Fabrication and characterization of metal-ferroelectric-semiconductor non-volatile memory using BaTiO3 film prepared through sol–gel process

In the present work, a metal-ferroelectric-semiconductor (MFS) structure for non-volatile memory application using barium titanate (BaTiO3) thin film is proposed. Sol–gel method is used to prepare the material, while deposition is done through spin-coating. A thin layer of BaTiO3 (BTO) film on a silicon substrate with MFS structure is fabricated followed by N2 dominant gas annealing. The electrical properties and the non-volatile memory operations characteristics of prepared MFS structure with BTO as the ferroelectric thin film are observed and discussed. Two different solvents are used to prepare the sol–gel of BTO material and prepared films are compared on the basis of morphological and electrical properties. It is found that the film prepared by 2-methoxyethol is better than the film prepared by ethanol. The device’s performance is evaluated by changing the annealing temperature and variable sweep voltages. Memory window and leakage current improve at higher annealing temperature with saturation at 650 °C. A maximum of 6 V memory window is achieved for 650 °C annealed device. Saturation in memory window is also observed with respect to the voltage sweep up to − 6 V to + 6 V with a considerable remnant polarization value. Endurance property for the MFS structure shows promising result for the iteration cycle of 1013 using positive up negative down pulse testing. To the best of author’s knowledge, this is the first report on BTO based MFS structure for memory application prepared through sol–gel process.

Barium titanate film based fiber optic surface plasmon sensor with high sensitivity

An optical fiber/Au film/barium titanate (BaTiO3) thin film surface plasmon resonance (SPR) sensor is proposed. Improving sensitivity by charge transfer between Au and BaTiO3. The calculation of transfer matrix method shows that BaTiO3 are coated on the surface of the sensing area, the simulation sensitivity of the sensor reaches 2820 nm/RIU. The finite element method simulation shows that BaTiO3 can improve the electric field intensity in the sensing region. The experimental results of refractive index show that the sensitivity of optical fiber/Au film/ BaTiO3 film SPR sensor is 2543 nm/RIU in the low refractive index range, 495 nm/RIU higher than that of traditional Au film SPR sensor. In the high refractive index range, the sensitivity of the sensor can reach 6040 nm/RIU. The sensor has broad application prospects in the field of biosensor.

Self‐Polarized BaTiO3 for Greatly Enhanced Performance of ZnO UV Photodetector by Regulating the Distribution of Electron Concentration

AbstractZnO film ultraviolet photodetectors (UV PDs) have always suffered from slow speed and low photosensitivity that restrict their broader applications. To break through those barriers, high‐performance ZnO UV PD based on self‐polarized BaTiO3 (BTO) is first introduced through a facile one‐step spin‐coating method. Compared with pure ZnO film UV PD with low on/off ratio (65) and slow speed (4.1/7.5 s) at 3 V bias under 350 nm UV light, the BTO‐ZnO bilayer film device exhibits an ultrahigh on/off ratio (14 300) and ultrafast response speed (0.11/5.80 ms), which is much faster than that of the most reported ZnO film‐based UV PDs. The numerical simulation demonstrates that the spatial distribution of electron concentration of ZnO film is regulated by the self‐polarization of BTO film, resulting in low dark current and fast response time of the BTO‐ZnO PD. This work provides a new approach to fabricate high‐performance PDs based on self‐polarized ferroelectric materials.

The Anneal Temperature Effect on the BTO and NZFO Flims and Their Capacitance - Inductance Integrated Device

In this paper, a novel capacitor-inductor integrated structure was proposed. The dielectric material BaTiO3 (BTO) and ferromagnetic material Ni0.5Zn0.5Fe2O4 (NZFO) was prepared by sol-gel method. Phase composition and morphology of the thin films were characterized by XRD, SEM and AFM. The effect of annealing temperature on film crystallinity, surface morphology, dielectric properties and ferromagnetism were investigated. When the annealing temperature was 700 °C, the BTO film and the NZFO film got the better dielectric properties and ferromagnetic properties. Then the BTO thin film was spin-coated on the substrate, and the NZFO thin film was in-situ sintered on the BTO thin film. The composite film possessed both ferromagnetism and dielectric properties. Finally, an inductive coil was fabricated on the BTO/NZFO composite film to produce a capacitance and inductance integrated device.

Effect of growth temperature on the microstructural properties of 0.95Na0.5Bi0.5TiO3–0.05BaTiO3 films prepared on MgO (0 0 1) substrates

Lead-free 0.95(Na0.5Bi0.5)TiO3–0.05BaTiO3 (NBT-BT) piezoelectric films have been successfully fabricated by high-pressure magnetron sputtering deposition technique on (0 0 1)-oriented MgO substrates at 800 °C and 900 °C, respectively. By advanced electron microscopy techniques, the orientation relationship of (0 0 1)[1 1 0]film//(0 0 1)[1 0 0]MgO and (0 0 1)[1 0 0]film//(0 0 1)[1 0 0]MgO is determined for the NBT-BT/MgO heterostructures prepared at 800 °C and 900 °C, respectively. In comparison, a high density of zigzag-typed planar defects appear in the film prepared at 900 °C. At the semi-coherent interfaces, periodic dislocation arrays form to relax the film-substrate misfit strain. In particular, the formation of both (a/2) 〈0 1 0〉 -type and (a/2) 〈011-〉 -type interfacial dislocations facilitates the growth of NBT-BT films on rough MgO substrates at 900 °C. Our findings indicate that the mode of film growth and microstructure for NBT-BT films prepared on MgO substrates can be tuned by the growth temperature.

Crystallographic orientation-dependent piezoelectric response in BaTiO3 thin films and the domain evolution under different temperatures

The effects of crystallographic orientation on the domain structures and piezoelectric response of BaTiO3 (BTO) thin films were investigated by piezoresponse force microscopy (PFM) systematically. It is found that the domain structures of BTO films are obviously orientation dependent, and the (111) oriented BTO film shows the best piezoelectric properties. Therefore, the nanoscale polydomain switchings within valid single grains of the BTO(111) thin film were observed by PFM under different temperatures. According to the switching process, the a1/a2c, r/a2c, and a1c/r polydomain states were specially introduced into the theoretical model to describe the temperature-induced polydomain switchings of the BTO(111) thin film. The misfit strain-temperature phase diagram was simulated to present the a1/a2c-r/a2c-a1c/r-p domain switching, which corresponds with the threshold temperature of domain switchings obtained from the experimental results of the BTO(111) thin film.

Structural studies of epitaxial BaTiO3 thin film on silicon

BaTiO3 thin films (60 nm-thick) grown on SrTiO3/Si templates have been characterized for their structural and electrical properties. The epitaxy of the BaTiO3 film on silicon was confirmed by X-ray diffraction with good crystallinity. The temperature-dependent structural properties were checked by infrared spectroscopy in absorption mode. The films were found to remain in a single ferroelectric phase over a temperature range from 5 to 385 K. Low-temperature orthorhombic-rhombohedral phase transitions characteristic of bulk BaTiO3 are absent in the films due to the clamping effect from the Si substrate.

Investigation of structural, optical dielectrical and optical conductivity properties of BaTiO3, Al0.01Ba0.99TiO3 and La0.01Ba0.99TiO3 thin films prepared by pulsed laser deposition

The pulsed laser deposition technique was used to prepare BaTiO3 (BTO), Al0.01Ba0.99TiO3 (ABTO) and La0.01Ba0.99TiO3 (LBTO) thin films. The structures of these films were determined using x-ray diffraction, while the surface topography was examined by scanning electron microscopy. This study shows that these films have a nanopolycrystalline structure. The optical properties of these samples were studied. The optical parameters such as optical energy gap, refractive index, extinction coefficient, dielectric loss and dielectric tangent loss were determined for these films. The values of oscillating energy (Eo) and dispersion energy (Ed) increase for the BTO, ABTO and LBTO thin films, respectively. While the values of both effective mass/carrier concentration (N/m*) and infinite permittivity (ε∞) decrease for the BTO, ABTO and LBTO films, respectively. On the other hand, both terms of optical conductivity (the real part σ1 and the imaginary part σ2) and the ratio of the surface energy loss function to the volume energy loss function were determined optically for these films.

Novel fractal analysis of nanograin growth in BaTiO3 thin film

The grain size and the ferroelectric morphology are the two most important factors in the research and development of advanced dielectric devices. It is important to synthesize nanostructures in order to achieve optimal grain size and inhibit grain growth while controlling the sintering parameters. It is also important to find new methods to study the grain growth during densification. BaTiO3 films were successfully obtained via the sol-gel spin coating method.In this paper, we report the deposition of nanostructured BaTiO3 thin film by spin coating of sol-gel precursors. The densification, grain growth and microstructure evolution have been studied. Moreover, a novel physical and mathematical fractal analysis have been applied successfully to the densification and nano grain growth of BaTiO3 thin film. The discrepancy between the fractal dimension and the grain growth with increasing temperatures and soaking time are presented and discussed.

Charge Coupling Enhanced Photocatalytic Activity of BaTiO3/MoO3 Heterostructures.

In this work, we proposed an efficient heterostructure photocatalyst by integrating the ferroelectric BaTiO3 (BTO) layer with the semiconductor MoO3 layer, availing the ferroelectric polarization of BaTiO3 and high generation of photoinduced charge carriers in the MoO3 layer. The effect of MoO3 layer thickness (tMoO3) on the photocatalytic efficiency of the BTO/MoO3 heterostructures is found to be optimum at tMoO3 = 67 nm as tMoO3 varies from 40 to 800 nm. The BTO/MoO3 heterostructure with tMoO3 = 67 nm exhibits a high efficiency of 86% for the degradation of rhodamine B (RhB) under the exposure of UV-visible light for 60 min. The photocatalysis rate kinetics analysis reveals that the rate constant in the heterostructure is 1.7 times of pure BTO and 3.2 times of pure MoO3 films. The enhanced photocatalytic activity in the heterostructures is attributed to the electric field-driven carrier separation due to the ferroelectric polarization and the heterojunction band bending. The charge coupling effect between BaTiO3 and MoO3 is evident from the current-voltage characteristics. The maximum lattice strain in the heterostructure with tMoO3 = 67 nm as evident from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) analysis further confirms the charge transfer between the layers. The degradation as well as decolorization efficiency of the BTO/MoO3 heterostructure is higher than that of pure BTO and MoO3 films. Radical trapping experiments reveal that electrons are the major contributors to the photocatalytic activity of the BTO/MoO3 heterostructure. The reusability test shows only a reduction of 5% in the efficiency of the heterostructure after five photocatalysis cycles. The heterostructure can also efficiently decompose the other dyes such as rose bengal and methyl violet. Thus, our findings prove that an efficient and reusable photocatalyst can be designed through the integration of the ferroelectrics with the semiconductor layers.

Piezoelectric inverse opal BaTiO3 films using one-drop spin-coated polystyrene-polydimethylsiloxane particle array templates

In this study, as an effective piezoelectric network structure, barium titanate (BaTiO3) inverse opal films were developed using well-ordered polystyrene-polydimethylsiloxane (PS-PDMS) particle array templates. In order to develop the particle array templates, colloidal solution concentration and solvent drying temperature were simultaneously investigated to achieve an optimal condition during post thermal treatment after one-drop spin-coating. The PS-PDMS particle array templates exhibited a maximum hexagonal pattern of 3475 μm2 and a thickness of 75 ± 10 μm owing to sufficient colloidal particle movement (by Brownian motion) and capillary force (by solvent evaporation) induced during the post thermal treatment process. The piezoelectric inverse opal BaTiO3 films were obtained via sol-gel synthesis of BaTiO3 precursors in the PS-PDMS particle array templates. After calcination at 600 °C, clear perovskite crystal structure (ABO3) was confirmed from the inverse opal films, which can provide a sufficient piezoelectric property from the sponge-like three-dimensional network structure. Further, the one-drop spin-coating method with post thermal treatment could be a feasible approach for the facile preparation of thick particle array templates for various applications such as solar cells, piezoelectric energy harvesters, and chemical sensors.

Electron transition and electron-hole recombination processes in epitaxial BaTiO3 films with embedded Co nanocrystals

An epitaxial BaTiO3 (BTO) film with embedded Co nanocrystals (NCs) was prepared according to interfacial engineering. Compared with the polycrystalline matrix in previous NCs-matrix systems, the current single-crystal BTO matrix possessed no grains and grain boundaries. The NCs and interface between the NCs and BTO could be regard as the grains and grain boundaries in the NCs-matrix system, respectively. By modulating the size (D) of Co NCs and spacing (R) between the NCs, we achieved the tuneable band gap, Schottky barrier height, the width of potential barrier and well of the nanocomposites. The electron transition and electron-hole recombination processes was well clarified for the NCs-matrix system. An ideal model was provided for explaining the effects of the interaction for NCs, grains and grain boundaries on the photoelectricity nature of materials.

Orientation and electrode configuration dependence on ferroelectric, dielectric properties of BaTiO3 thin films

BaTiO3 (BTO) thin films with an SrRuO3 buffer layer have been deposited on a range of lattice mismatched substrates, including single crystalline (111)-oriented LaAlO3 and (100)-, (110)-, and (111)- oriented SrTiO3 substrates by pulse laser deposition. The results show that the crystal structure of BTO film is affected by the type and orientation of the substrates. The BTO films exhibits strong ferroelectric and dielectric anisotropy. Different electrode configurations affect the voltage required for polarization, but do not affect the final polarization state. The (111)-oriented film exhibits a large polarization Ps=92.43μC/cm2, Pr=51.74μC/cm2, the (100) orientation has a smaller coercive field EC=19.52 kV/cm and a leakage current, and the (110) orientation has a larger dielectric constant.

Area-Selective Atomic Layer Deposition of Crystalline BaTiO3

Patterned, crystalline BaTiO3 (BTO) films were formed directly on STO(001) surfaces using atomic layer deposition and restricting Ba and Ti precursor adsorption to STO(001) by passivating regions of the substrate with a polystyrene blocking layer. Patterns were prepared by spin-coating polystyrene onto STO(001), UV-crosslinking the polystyrene, and rinsing away uncrosslinked polystyrene with toluene. Amorphous 9–12 nm thick BTO films were deposited at 225 °C on polystyrene-patterned STO(001) surfaces. These films were crystallized upon annealing at elevated temperatures. Atomic force microscopy, scanning electron microscopy, and time of flight secondary ion mass spectroscopy were used after growth of BTO and removal of polystyrene resist and reveal BTO features with dimensions similar to the shadow mask. Reflection high-energy electron diffraction and X-ray diffraction show that BTO epitaxially crystallizes to the substrate, forming BTO(001), after annealing under vacuum at ≥770 °C with an oxygen partial ...

Segregation particles induced ultrahigh energy storage performances in BiMnO3 modified BaTiO3 films

Lead-free BiMnO3 modified BaTiO3 solid solution films are prepared by Sol-gel methods. An ultrahigh energy storage density of 94.1 J/cm3 and an efficiency of 84.51% are obtained, together with excellent frequency and thermal stability, in 0.92BaTiO3-0.08BiMnO3 solid solution films. The Jujube-Cake structure of the segregation particles in the films is suggested to improve the electric insulation, breakdown strength, and the maximum polarization, which are the key factors for energy storage performances in relaxor ferroelectrics. This work opens a route to improve the energy storage performances in solid solution films.