Barium Strontium Titanate Thin Films Research Articles

Design of Enhanced Wide Band Microstrip Patch Antenna Based on Defected Ground Structures (DGS) for Sub-6 GHz Applications

In this paper a comprehensive comparative study of three distinct microstrip patch antenna (MPA) designs, each optimized for the sub-6 GHz applications, is presented. The initial design phase utilized a Rogers RT 5880 substrate with a permittivity (εr1) of 2.2 and a thickness(H1) of 1.42 mm. The proposed model achieved a resonance band ranging from 4.8 to 7 GHz, with a bandwidth of 2.2 GHz and a return loss (S11) of -20 dB. Subsequent enhancements involved integrating a Barium Strontium Titanate (BST) thin film (εr2 = 250, thickness(H2) = 0.005 mm), effectively shifting the operational band to 3.5-5.3 GHz. The final design iteration, which incorporated both BST and a Defective Ground Structure (DGS), represented a substantial advancement, achieving wideband operation from 1.8 to 6 GHz, expanding the bandwidth to 4.2 GHz, and improving the S11 to -25 dB. This integration also resulted in a compact antenna size of 30 x 26.5 x 1.42 mm³. These findings underscore the synergistic impact of BST and DGS in enhancing MPA design, marking a significant progression in antenna technology, vital for a range of wireless communication.

Manipulation of phase transitions and electrical properties of Ba1-xSrxTiO3 thin films through orientation engineering

This study investigates the influence of epitaxial orientation on the phase structures and electrical properties of Barium Strontium Titanate (Ba1-xSrxTiO3, BST) thin films by employing a thermodynamic model. A comprehensive analysis is conducted, including the construction of strain-concentration and temperature-strain phase diagrams for (001)-, (110)-, and (111)-oriented BST thin films. The results demonstrate that BST thin films with high-index (110) and (111) orientations have a greater tendency to stabilize the low-symmetry ferroelectric phase compared to the low-index (001) orientation. Subsequently, the impact of epitaxial orientation on the piezoelectric and electrocaloric properties is explored based on the constructed phase diagrams. Significantly, enhanced piezoelectric and electrocaloric effects closely related to the epitaxial orientation are observed at the different phase boundaries for BST thin films. These findings have profound implications for future experimental investigations and the design of devices incorporating BST thin films with precise epitaxial orientations and innovative functionalities.

The Effect of Deposition Temperature on Ba<sub>0.8</sub>Sr<sub>0.2</sub>TiO<sub>3</sub> Films Prepared by Pulsed Laser Deposition Technique

Barium strontium titanate (Ba0.8Sr0.2TiO3) thin films have been prepared by pulsed laser deposition (PLD). The thin film of (Ba0.8Sr0.2TiO3) was deposited on a silicon (Si) substrate with different deposition temperatures. The XRD pattern identifies these specimens as being of the tetragonal phase. As the deposition substrate temperature varied from 200 °C to 400 °C, the average crystal size of BST increased from 34 nm to 68 nm calculated by the XDR pattern. Field (FESEM) images have estimated the particle size of the film. The dielectric constant increased with increasing substrate temperature.

Optical Properties of Sol-Gel Deposited Barium Strontium Titanate (BaxSr1-xTiO3) Films

Optical properties of sol-gel deposited Barium Strontium Titanate (BaxSr1-xTiO3, BST) thin films were studied to determine their suitability as light sensors. Crystallized BST films were formed by annealing in air at 700 °C for 1 h. Lattice parameters and grain sizes were determined for all the compositions. The band gap and refractive index values of the samples were determined from the optical transmission spectra for different compositions. Band gap of all the compositions were in the semiconductor range that would allow them to be used for photodiode and light sensor applications. Refractive index is reported for all the compositions. HIGHLIGHTS Different compositions of BaxSr1-xTiO3 with x = 0.0, .... 1.0 were deposited by sol-gel method Band gap variation with compositions is reported for both amorphous and crystalline films Refractive index variation with composition is reported for both amorphous and crystalline films Suitability of different compositions for light sensor applications are suggested from band gap and refractive index values GRAPHICAL ABSTRACT

Optimized Tunability of Barium Strontium Titanate Thin Films onto Different Plates with Proper Buffer Layers

Misfit strain, polarization, permittivity, and tunability of Ba x Sr1−x TiO3 (BST) thin films on various substrates with varied buffer layers are calculated by a modified thermodynamic model. The lattice parameters of the LaAlO3 (LAO), CaTiO3 (CT), BaZr0.25Ti0.75O3 (BZT), and MgO buffer layers grow consecutively as does the thermal expansion coefficient (TEC) of the Si, Ti, Ni, and stainless steel (SS) substrates. When the TEC of substrates is bigger (such as Ni, SS) than that of the films, introducing buffer layers with larger lattice parameters (such as BZT, MgO) can improve the permittivity and tunability. Conversely, inserting buffer layers with smaller lattice parameters (such as LAO, CT) can enhance the dielectric response when the TEC of substrates is smaller (such as Si, Ti) than that of the films. The relationship between the TEC of substrate and the lattice parameter of buffer layer is primarily linear for achieving high tunability. According to several references, introducing LaNiO3 buffer layers can significantly increase the tunability of BST solid solutions prepared on Si‐based substrates, which is in line with the estimated rule. This law offers a guide for choosing the best substrate and buffer layer when producing BST films with strong dielectric response.

Evaluating the impact of substrate deposition on optical properties of perovskite barium strontium titanate (Ba0.5Sr0.5TiO3) thin films prepared by pulsed laser deposition technique

Evaluating the impact of substrate deposition on optical properties of perovskite barium strontium titanate (Ba0.5Sr0.5TiO3) thin films prepared by pulsed laser deposition technique

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.

Efficiency of Generation of Surface Acoustic Waves in Barium Strontium Titanate Thin Films.

The excitation of surface acoustic waves (SAWs) on the surface of the ferroelectric film [barium strontium titanate (BST)] located on the dielectric substrate (silicon) was studied theoretically. We found that the most effective SAW excitation takes place when spontaneous polarization occurs in the film plane and the wave propagates along the direction adjacent to the direction of the spontaneous polarization vector. Based on a nonlinear model of phase transitions in solid BST solutions, the dependency of the material constants of piezo-effect equations on the misfit strain with a fixed concentration was obtained numerically. The effect of various misfit strains on SAW characteristics was studied for the film located on single-crystal silicon. It was shown that the effectiveness of SAW excitation increases as the misfit strain nears the boundary of phase transition.

Structural and optical parameters of sol-gel derived Barium Strontium Titanate (BST) thin film

Barium Strontium Titanate thin film was fabricated successfully on a corning glass substrate via sol-gel process technique. The as-prepared film was found to be amorphous, which crystallizes after annealing at different temperatures (500 °C, 550 °C). The influence of annealing temperature on the structural and optical properties of the fabricated thin films was analyzed. The XRD data reveals that the samples have a cubic structure with preferred orientation along (110) plane. Ultraviolet–Visible spectroscopy technique was used to determine various optical parameters such as transmittance, extinction coefficient (k), optical band gap, refractive index (n), and Urbach energy of the fabricated thin films. The optical bandgap of the crystalline sample decreased from 3.52 eV to 3.41 eV with the increase in annealing temperature. Optical transmittance spectra in the wavelength range 300 ∼ 1100 nm show good optical transparency of the BST thin film. The variation of the extinction coefficient and refractive index as a function of frequency has been discussed and reported. Optical parameters of the prepared thin film suggest its potential application in optoelectronic devices.

Reconfigurable Three Functional Dimension Single and Dual-Band SDR Front-Ends Using Thin Film BST-Based Varactors

This paper presents a performance evaluation of single and dual-band software-defined radio (SDR) front-ends using commercially available barium strontium titanate (BST) thin film to control SDR receivers dynamic range and mitigate interference. Firstly, an SDR front-end solution using a BST-based single-band bandpass filter (BPF) is developed to manage in-band attenuation according to the input power. Secondly, a dual-band SDR front-end to avoid high power interference with its spectral content on the below side of the second band is designed. This device is performed with a BST-based dual-band BPF providing independent control of the power limiting capabilities of the first and second bands. The BST component introduces a dependence on bias voltage, frequency, and input power. Consequently, by applying a 0 V bias, it is possible to target interferers between 700 MHz up to 1 GHz and attenuate them more than 7 dB at 40 dBm. The frequency dependence is defined by the second band, which retains its filtering performance while performing interference cancellation in the first band. This SDR solution implements a three functional dimension device in the upper MHz with a power-dependent insertion loss, high threshold power level, and frequency selectivity.

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.

The Effect of Photoconductive Mole Fraction Based on Thin Film BaxSr1-xTiO3 (x = 0.000; 0.125; 0.250; 0.375; 0.500) on Electrical Properties and Diffusivity Coefficient

Barium Strontium Titanate (BaxSr1-xTiO3) thin films have been fabricated for mole fraction (x= 0.000; 0.125; 0.250; 0.375; 0.500) on p-type silicon (100) substrate using Chemical Solution Deposition (CSD) method and spin coating technique. The film annealed at 850 ∘C for 8 hours with an increasing rate of 1.67 ∘C/minute. The BST thin film was characterized using an LCR meter that the film is given a different light intensity (0 lux, 4000 lux, 8000 lux). Data obtained from the LCR meter is conductance, capacitance, and impedance. Different mole fractions on Barium produce different electrical properties that show the value of electric conductivity, dielectric constant, impedance, and diffusion coefficient.

The Comparison of Optical Properties Between Ba0.25Sr0.75TiO3 and Ba0.75Sr0.25TiO3 Thin Films As The Light Sensors Application

An investigation has been carried out to determine the optical properties of Barium Strontium Titanate (BST) thin films, with different chemical composition, namely Ba0.25Sr0.75TiO3 and Ba0.75Sr0.25TiO3. BST thin films that were prepared by the Chemical Solution Deposition (CSD) method and was coated on an Indium Tin Oxide (ITO) substrate using the Spin Coating method at a speed of 3000 rpm for 30 seconds. BST thin films have been characterized using optical microscopy, UV-vis spectrophotometer and X-Ray Diffraction (XRD). The results obtained that the thickness of BST thin films with the composition of Ba0.25Sr0.75TiO3 and Ba0.75Sr0.25TiO3 were 42.7 μm and 28.152 μm respectively, the refractive index value of 2.31 and 2.30 respectively, and they had the gap energy of 3.4 eV and 3.3 eV respectively. From the data obtained data with notes using the same method and treatment, thin film with the chemical structure composition of Ba0.75Sr0.25TiO3 was declared superior for the usageas photodiode sensors.

A facile control of epitaxial-like barium strontium titanate thin films with various Ba/Sr ratios synthesized by a hydrothermal-galvanic couple method

Barium strontium titanate (BaxSr1-xTiO3; BST) thin films exhibiting superior dielectric tunability have many technological applications. BST thin films with various Ba/Sr ratios were facilely produced on TiN-coated Si substrates by a hydrothermal-galvanic couple (HT-GC) method in mixed Ba(CH3COO)2 and Sr(CH3COO)2 alkaline solutions. A cubic single phase of BST films with the perovskite structure was obtained. Epitaxial-like growth in that strongly preferred (111) BST films grew over (111)-oriented TiN underlayer was observed for all the obtained films. When increasing the mole fraction of Ba2+ in the reaction solutions, the (111) diffraction peak of BST films shifted toward lower Bragg's angles, indicating a transition from Sr-rich to Ba-rich BST. From the X-ray photoelectron spectroscopy and electron probe for microanalysis, BST films with a full range of Ba/Sr ratios were obtained. The Sr ions were more readily incorporated into the films than Ba ions, which is associated with the lower formation energy of SrTiO3. Field-emission scanning electron microscopy revealed a spherical-particulate microstructure of the BST films. The formation mechanisms of the films by such a method were also discussed. The obtained BST films exhibited a promising dielectric tunability that could reach as high as 92%.

Nanostructured Cobalt Doped Barium Strontium Titanate Thin Films with Potential in CO2 Detection.

In this work, (Ba0.75Sr0.25) (Ti0.95Co0.05) O3 perovskite nanostructured material, denoted subsequently as Co-doped BaSrTiO3, was synthesized in a one-step process in hydrothermal conditions. The obtained powder was heat-treated at 800 °C and 1000 °C, respectively, in order to study nanostructured powder behavior during thermal treatment. The Co-doped BaSrTiO3 powder was pressed into pellets of 5.08 cm (2 inches) then used for thin film deposition onto commercial Al2O3 substrates by RF sputtering method. The microstructural, thermal, and gas sensing properties were investigated. The electrical and thermodynamic characterization allowed the evaluation of thermodynamic stability and the correlation of structural features with the sensing properties revealed under real operating conditions. The sensing behavior with respect to the temperature range between 23 and 400 °C, for a fixed CO2 concentration of 3000 ppm, highlighted specific differences between Co-doped BaSrTiO3 treated at 800 °C compared to that treated at 1000 °C. The influence of the relative humidity level on the CO2 concentrations and the other potential interfering gases was also analyzed. Two possible mechanisms for CO2 interaction were then proposed. The simple and low-cost technology, together with the high sensitivity when operating at room temperature corresponding to low power consumption, suggests that Co-doped BaSrTiO3 has a good potential for use in developing portable CO2 detectors.

"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.

Predicting dielectric tunability of compositionally-graded barium strontium titanate thin films on metal substrates by thermodynamic modeling

Dielectric properties of compositionally-graded barium strontium titanate (BST) thin films respectively on Ti and stainless steel (SS) plates were computed using a modified thermodynamic model. Calculated results predict that higher dielectric constant and tunability can be obtained when the films are onto Ti substrates, which have smaller thermal expansion coefficient (TEC). For Ti substrates, “up-graded” films (Ba/Sr ratio increases from substrate to surface) exhibit higher tunability than “down-graded” films; whereas “up-graded” films on SS plates have relatively lower tunability. The received larger dielectric constant and tunability are because of smaller total out-of-plane polarization, which is resulting from smaller total compressive strain. The calculated dielectric constant and tunability of such graded films are in accordance with those of the films fabricated via sol-gel approaches, indicating that the dielectric behavior of ferroelectric films can be adjusted by designing compositional gradient.

Origin of improved tunability and loss in N2 annealed barium strontium titanate films

Barium strontium titanate (BSTO) thin films were deposited on Pt(111) by high throughput evaporative physical vapor deposition and then annealed at 650 \ifmmode^\circ\else\textdegree\fi{}C for 30 min under ${\mathrm{N}}_{2}$ atmosphere. Using advanced transmission electron microscopy, energy-dispersive x-ray spectroscopy and electron energy-loss spectroscopy, we directly show that not only does N substitute for O in the BSTO lattice but that it also compensates for $\mathrm{T}{\mathrm{i}}^{3+}$ ions, suppressing conductivity, thereby reducing dielectric loss and enhancing dielectric tunability. However, this effect is negated near the film edge where we speculate that exposed Pt acts as a reservoir of adsorbed/absorbed O and alters the local ${\mathrm{N}}_{2}$ concentration during annealing.

Structure and dielectric properties of barium strontium titanate ferroelectric thin film prepared by DC micro-arc oxidation

Barium–strontium titanate (BST) ferroelectric thin film was fabricated on Ti substrates by micro-arc oxidation (MAO) in an aqueous solution consisting of 0.6 mol/L Ba(OH)2·8H2O and 0.4 mol/L Sr(OH)2·8H2O. The phase composition, elements distribution, dielectric and ferroelectric properties of the BST thin film were characterized. The results show that the BST film is mainly composed of BaxSr(1−x)TiO3 phase. The Ba, Sr, Ti and O elements are generally uniformly distributed across the film, and the local fluctuation of elements distribution may be caused by MAO holes in the membrane. The BST film is mainly deposited through an electrophoretic process. The dielectric constant of the BST thin film is about 283 measured at 1 kHz, and the film has ferroelectric property at room temperature because of the misfit strain in the film.