Barium Strontium Titanate Films Research Articles

ГЕНЕРАЦИЯ ПОВЕРХНОСТНЫХ АКУСТИЧЕСКИХ ВОЛН СЕГНЕТОЭЛЕКТРИЧЕСКОЙ ПЛЕНКОЙ BST ПРИ ДЕЙСТВИИ ОДНООСНОЙ НАГРУЗКИ

The electro-mechanical properties of a ferroelectric film of barium strontium titanate (BST) film located on a silicon substrate depend on applied external strain. A significant dependence is observed for concentrations close to values, where a phase transition for the ferroelectric film occurs. A model of single-crystal BST film near the phase transition under uniaxial strain is studied by the thermodynamic theory of phase transitions. The material properties of the film obtained by the model are used for numerical study of the excitation of Rayleigh’ acoustic waves on the surface of the film-substrate heterostructure. Shifting the extrema of S-parameters, characterizing the efficiency of excitation of surface acoustic waves, is shown under the applied strain. The change of S-parameters for the first three resonances determined principally by the geometry of the interdigital electrodes is presented. The largest shift of resonant frequency is observed in a case of the second resonance that corresponds to Sezava wave.

30 GHz ferroelectric phase shifter on silicon carbide

Thin ferroelectric barium-strontium titanate (BST) films of high structure quality have been grown on semi-insulating silicon carbide substrates. The crystal structure and elemental composition of the obtained films were studied by the X-ray diffraction and Medium Energy Ions Scattering. Planar capacitors based on these BST films reveal the combination of high tunability and low losses at microwaves. 30 GHz ferroelectric phase shifter demonstrating a figure of merit of 22 deg/dB with a phase shift of Δϕ = 220 deg is implemented based on BST films on silicon carbide substrate.

Comparative study of the dielectric properties of the bulk and film of perovskite Ba0.6Sr0.4TiO3

This effort aimed to investigate the differences between raw materials and thin films to enhance the film performance and get encouraging results. Barium strontium titanate (BST) is a solid solution consisting of titanate barium (BT) and titanate strontium (ST). BST powder was synthesized using the sol–gel process, and BST film was deposited using pulsed laser deposition (PLD). Barium, strontium acetate, and Ti-isopropoxide were utilized as raw material sources. XRD was used to characterize the BST perovskite crystal structure. The SEM and LCR meters revealed morphology surface and dielectric properties. XRD pattern shows a cubic structure phase. The particle size of the bulk exhibited 122.88[Formula: see text]nm while the film particle size was 84[Formula: see text]nm. The dielectric constant of the bulk shape exhibited was greater than the form of the films, which was attributed to different thicknesses, densities, defects, and porosity.

Enhancement of antibacterial and cytocompatibility of Ti by Zn-doped BST coatings

Titanium (Ti) is a material commonly used in orthopedic implants. However, the lack of antimicrobial properties limits its application in implants. Herein, we constructed zinc (Zn)-doped barium strontium titanate (BST) films on Ti. The results show that the Zn-doped BST films can effectively improve the antibacterial ability of Ti substrates, which presents potential applications in bone repair.

Effect of Ba/Sr ratio on the nonlinear optical properties of Ba1-xSrxTiO3 (x = 0.1–0.9) thin films

Perovskite-structured barium strontium titanate (Ba1-xSrxTiO3, x = 0.1–0.9) films have been epitaxially fabricated by using a pulsed-laser deposition technique. The third-order nonlinear optical properties were studied through a z-scan method, allowing the resolution of the nonlinear refractive and absorptive contributions to the responses. Although all the samples show almost the same value of nonlinear absorption coefficient, the extracted nonlinear refractive index of the sample of x = 0.3 is apparently larger than that of other samples. Dependency of the nonlinear optical properties on the Ba/Sr ratio is discussed in terms of the crystal phase transformation and metal-oxygen bond length of the selected materials.

Ferroelectric sensor BaxSr1-xTiO3 integrated with android smartphone for controlling and monitoring smart street lighting

In this report, we demonstrated an application of a thin film Barium Strontium Titanate (BST) as a light sensor integrated with an Android smartphone as a model of smart street lighting. BST thin films were fabricated using chemical solution deposition methods followed by spin coating with a variety of mole fractions. We assumed that changes in the lattice parameters of its tetragonal crystal structure caused by variations in the mole fraction result in different ions displacement characteristics that induce charges polarization in the crystal structure. We have confirmed that the BST thin film with mole fraction x = 0.500 was the best thin film for the light sensor in this prototype. Furthermore, it has been found that the smart street lighting gives ∼69.23 % power saving and lower power usage than a conventional street lighting. Additionally, this developed system has successfully reported the lamp status that is to be maintained to an Android phone of the maintainer by using a short message system. This self-reporting makes it easy for maintainer to identify broken lamps and to do repairs. Moreover, implementation of such features to the street lighting can reduce the operating cost.

Local piezoelectric properties of perforated ferroelectric barium–strontium titanate films

Objectives. Focused ion beam etching remains one of the most common methods for fabricating 2D photonic crystals and structures based on functional materials. This technique is quite well developed for semiconductors. But at the same time, the change in the properties of ferroelectric materials under the action of a focused ion beam, including parameters of distribution and switching of the polarization state under the action of an electric field, remains poorly studied. The purpose of this work is to determine the local piezoelectric parameters in perforated ferroelectric films of barium strontium titanate (Ba0.8Sr0.2TiO3) with ordered vertical air channels fabricated by focused ion beam etching.Methods. Experimental studies were conducted using piezoresponse force microscopy under applied electric field in planar geometry.Results. It is shown that the perforation of a ferroelectric film leads not only to the formation of significant inhomogeneities in the piezoelectric response distribution in the structure, but also to the noticeable increase in the magnitude of both the vertical and lateral components of the piezoresponse near the perforation holes. The calculation results showed that the greatest enhancement is observed for the lateral component of the piezoresponse: from 5 pm/V for a nonperforated film to 65 pm/V in the perforated area.Conclusions. The most probable mechanism for such a change in properties is the influence of a disturbed layer that occurs at the boundary and the inner surface of vertical air channels. The properties of this layer are due to two factors: amorphization of the structure as a result of the focused ion beam etching and the appearance of pinned domain states near the hole, leading to the formation of the complex piezoresponse distribution both at the hole boundary and in the gap between the perforations. The information obtained is important for understanding the peculiarities of the formation of local piezoelectric and ferroelectric responses in photonic crystals fabricated by focused ion beam etching, as well as for finding ways to control their state when an external electric field is applied.

Stability and optical tunability of flexible BST membrane observed in terahertz band

Ferroelectric materials are generally inflexible in their normal state, and our synthesized barium strontium titanate (BaxSr1-xTiO3, X = 0.6, BST) films are so elastic and flexible that they can be bent at about 140°. The flexibility of the BST film prevents the material from fracturing due to mismatching forces. We demonstrate by THz-TDS (Terahertz time domain spectroscopy) system that the fabricated flexible BST film maintains a stable transmittance under different bending conditions. In addition, under an external optical pump, the transmittance amplitude can be modulated by about 90%. This property can be used in the design of tunable terahertz devices in the case of additional pumps. The film's flexibility and the possibility of further tuning will expand the range of applications for wearable terahertz devices to be developed in the near future.

Study of the Layer-Type BST Thin Film with X-ray Diffraction and X-ray Photoelectron Spectroscopy

In the present paper, results of X-ray photoelectron studies of electroceramic thin films of barium strontium titanate, Ba1−xSrxTiO3 (BST), composition deposited on stainless-steel substrates are presented. The thin films were prepared by the sol-gel method. A spin-coating deposition of BST layers with different chemical compositions was utilized so the layer-type structure of (0-2) connectivity was formed. After the deposition, the thin-film samples were heated in air atmosphere at temperature T = 700 °C for 1 h. The surfaces of BST thin films subjected to thermal treatment were studied by X-ray diffraction. X-ray diffraction measurements confirmed the perovskite-type phase for all grown thin-film samples. The oxidation states of the elements were examined by the X-ray photoelectron spectroscopy method. X-ray photoelectron spectroscopy survey spectra as well as high-resolution spectra (photo-peaks) of the main metallic elements, such as Ti, Ba, and Sr, were compared for the layer-type structures, differing in the deposition sequence of the barium strontium titanate layers constituting the BST thin film.

ANNEALING TEMPERATURES’ EFFECTS ON MICROSTRUCTURE AND OPTICAL PROPERTIES OF Ba0.95Sr0.05TiO3 FILMS

ANNEALING TEMPERATURES’ EFFECTS ON MICROSTRUCTURE AND OPTICAL PROPERTIES OF Ba0.95Sr0.05TiO3 FILMS. Ferroelectric materials, one of which is Barium Strontium Titanate (BST), can be applied for photovoltaic. Ferroelectric films function as the P-type semiconductor in the P-N junction. BST (Ba0.95Sr0.05TiO3) films have been deposited on Pt/Si (111) and quartz substrates via the CSD method prepared by spin coater. The films were annealed at various temperatures of 800 °C, 900 °C, and 1000 °C to observe the annealing temperatures' effects on the microstructure and optical properties of the BST films. From the XRD results, the intensity of diffraction peaks gets higher along with the higher annealing temperature. It thus causes the level of crystallization and the crystal size of the Ba0.95Sr0.05TiO3 films to increase. The morphology results reveal that the grains size of the Ba0.95Sr0.05TiO3 films is getting larger with the higher annealing temperature. The optical properties examined in the Ba0.95Sr0.05TiO3 films include absorbance and bandgap energy values. Values of bandgap energy show a decrease with increasing sintering temperature. The smallest bandgap energy of the Ba0.95Sr0.05TiO3 film is achieved at 1000 °C of 3.20 eV. BST films were annealed at temperature 1000 °C attained from this study can be considered as candidate for a photovoltaic ferroelectric material.

Effects of thermal misfit strains on dielectric features of sandwich barium strontium titanate multilayer thin films on metal plates

Effects of thermal misfit strains on dielectric features for sandwich structural barium strontium titanate (BST) thin films on metal plates were investigated via a modified thermodynamic model. When TEC of substrates is closer to that of BST, larger permittivity and tunability can be received. The tendency of permittivities and tunabilities of such films as a function of TEC of substrates agrees with that of single compositional BST films and compositionally graded BST multilayer films. The highest tunability reaches 60% at the biasing field of 300 kV/cm when the films are onto Ti metal. Moreover, Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3 structure can obtain higher tunability than Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3 structure, while Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3/Ba[Formula: see text]Sr[Formula: see text]TiO3 films show better compatible composition range for relatively larger tunability. Dielectric properties of sandwich-like BST films in some references can also be analyzed based on our calculated results.

Sol–gel derived barium strontium titanate thin films using a highly diluted precursor solution

Among lead-free ferroelectric materials, Barium Strontium Titanate (BST) has interesting ferroelectric, pyroelectric, piezoelectric, and energy-harvesting properties. This material can be advantageously solution-deposited. There is a need for homogeneous and dense films with optimized electrical properties. BST thin films are elaborated with a highly diluted precursor solution of less than 0.05 M. The electric properties are correlated with the morphology and structure of the films as a function of precursor solution dilution. The film growth is columnar with a tetragonal perovskite structure. As the dilution increases, the roughness of the top surface and of the columns decreases, facilitating grain coalescence. In addition, the permittivity of the grains and of the grain boundaries decreases. The highest dielectric strength (400 kV/cm) is obtained for the sample elaborated with the most diluted precursor solution of 0.008 M. For a given polarization, the necessary poling electric field decreases by a factor 2.3 as dilution increases by a factor 4. Finally, hysteresis loops are obtained with increasing saturation and remnant polarizations as the dilution increases. The saturation polarization is approximately doubled as the solution dilution is multiplied by four. To conclude, BST films elaborated with highly diluted solutions have enhanced ferroelectric properties.

Investigation of the barium strontium titanate films on the silicon substrate

A study of the electrical and photoelectric properties of the heterostructure of barium strontium titanate film on a silicon substrate was performed. The conductivity of the heterostructure significantly increased and the capacitance decreased with frequency. The photoconductivity significantly increased for the sample modified by Cr+ ion implantation. The temperature dependence of the resistance under green laser irradiation demonstrated maxima at 150 K.

Comprehensive dielectric performance of alternately doped BST multilayer films coated with strontium titanate thin layers

Abstract It is a huge difficulty to improve the comprehensive dielectric performance of barium strontium titanate (BST) films for applications in energy storage, microwave, etc. Herein, on Pt/Ti/SiO2/Si substrate strontium titanate (ST), manganese (Mn) doped BST and yttrium (Y) doped BST layers were attempted to be designed as ST/MnBST/YBST/ … /MnBST/YBST/ST films and prepared by a modified sol–gel method, and structures and performances of the films were studied. X-ray diffraction shows that the films are ABO3 perovskite polycrystalline with Ti4+ at B sites replaced by some Mn2+ and exhibit dense nodular microstructures observed by a scanning electron microscope. The films exhibit optimized comprehensive performance with leakage current density of less than 1E-10 A/cm2 at 20 V and dielectric losses of 0.3%–0.4% at 100 kHz and about 1.8% at 1 GHz, meeting the needs of some applications.

Sandwich-type composite multilayer films of strontium titanate and barium strontium titanate and their controllable dielectric properties

It is a challenge to reduce the dielectric loss and increase the tunability of pure barium strontium titanate (BST) films for microwave tunable application because these two properties change simultaneously. Herein, a novel composite of strontium titanate (ST) and potassium-doped BST (KBST) has been designed as ST/KBST/ST sandwich-type film with various ST and KBST layers. X-ray diffraction patterns show that the film exhibits cubic perovskite polycrystalline structure composed of BST and ST phase, mainly grow along (110) crystal plane with average grain size of less than 20 nm and decreasing BST phase/ST phase ratio with increasing film thickness. Scanning electron microscope shows that no interfacial layer can be observed, indicating that ST and KBST are fully compounded. Low dielectric loss and high tunability at -10 – 10 V and stable and excellent dielectric properties at 1 GHz are achieved, meeting the needs of microwave tunable application at high frequency. The surface structures are also studied by other analysis methods, and ST/MgBST/ST sandwich-type film is compared.

Ultra-high extinction-ratio light modulation by electrically tunable metasurface using dual epsilon-near-zero resonances

The lossy nature of indium tin oxide (ITO) at epsilon-near-zero (ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprising two ITO discs and a high dielectric constant perovskite barium strontium titanate (BST) film. The ENZ wavelength in the accumulation and depletion layers of ITO discs is controlled by applying a single bias voltage. The coupling of magnetic dipole resonance with the ENZ wavelength inside the accumulation layer of ITO film causes total absorption of reflected light. The reflection amplitude can achieve ~84 dB or ~99.99% modulation depth in the operation wavelength of 820 nm at a bias voltage of −2.5 V. Moreover, the metasurface is insensitive to the polarization of the incident light due to the circular design of resonators and the symmetrical design of bias connections.

Конечно-элементное моделирование характеристик ПАВ-фильтров на основе тонких пленок титаната бария стронция

Конечно-элементное моделирование характеристик ПАВ-фильтров на основе тонких пленок титаната бария стронция

Ultrafast Modulation of Ferroelectric Polarization in a Ba0.8Sr0.2TiO3 Film with an Intensive Subperiodic Terahertz Pulse

The results of an experimental and theoretical study of the effect of an intense, single-period terahertz pulse on the ferroelectric polarization in a barium–strontium titanate film are presented. Modulation of the ferroelectric polarization in the field of a terahertz pulse with a strength of up to 23.2 MV/cm is demonstrated via generation of the second optical harmonic. The presence of a nonlinear dependence of the intensity of the second optical harmonic on the electric field strength of the THz pulse is shown.

"Synthesis and characterization of Ba0.8Sr0.2TiO3 perovskite thin films prepared by Sol Gel Technique "

"Barium strontium Titanate (BST) is a solid solution consist of BaTiO3 and SrTiO3 that mixed with suitable ratio. Barium strontium Titanate oxide (Ba0.8Sr0.2TiO3) thin films prepared by sol gel technique. Barium strontium Titanate thin films deposited on Si substrate and annealed at [400,500, 600 and 700] ºC. The characterization of BST films investigated by a different technique, the X-Ray Diffraction (XRD) and Scanning Electron Macroscopy (SEM) revealed the phases, crystal structure and surface topography of the films. XRD pattern shows tetragonal phase for Ba0.8Sr0.2TiO3 perovskite structure with many peaks for different plans. The films annealed at the different temperature that indicated intermediate phases on perovskite structure of Ba0.8Sr0.2TiO3.

Study of Sputtered Barium Strontium Titanate Films for Energy Harvesting Applications

Study of Sputtered Barium Strontium Titanate Films for Energy Harvesting Applications