Barium Films Research Articles

An active straight waveguide polarization rotator in single crystal thin film barium titanate-on-insulator

Electro-optic materials play an essential role in telecommunications. In active devices like Mach–Zehnder modulators, typically the diagonal Pockels coefficients are employed to induce an optical phase shift through electrical tuning of the refractive index along an optic axis. On the other hand, waveguide polarization rotators are usually passive devices where asymmetric structures or specially designed couplers are used. In this Letter, we exploit off diagonal Pockels coefficients to demonstrate an active straight waveguide polarization rotator using a c-axis single crystal thin film barium titanate (BTO)-on-insulator, with a maximum power conversion of ∼30% from the input TE (or TM) mode into its orthogonal mode observed. The device is switched on or off through an applied voltage and is demonstrated in a simple straight waveguide. A TM output extinction ratio of 26.1 dB is achieved in the device with a TE input. The r51 value in the BTO thin film is estimated to be around 600 pm/V. This work adds a different polarization rotation scheme to the active photonics family.

The optical and electrical properties of Ba thin films for junction diode application by jet nebulizer spray pyrolysis method

• Ag/Ba/n-Si/Ag structured junction diode were successfully fabricated using JNSP method. • Surface morphology of films exhibited nanoplate-like structures. • I-V characteristics of the Ag/Ba/n-Si/Ag diode a superior performance light condition. • In particular, substrate temperature 550°C diode is apt for the optoelectronic applications. In this research work, we have fabricated junction diode based on barium thin films. The film was coated on a glass plate and silicon substrate by low-cost spray pyrolysis coating technique via different substrate temperature as 400°C, 450°C, 500°C and 550°C. Structure, surface morphology, optical and electrical characteristics of barium films were investigated. In particular, the I-V characteristic diode parameters of Ag/Ba/n-Si/Ag diodes in different temperature were analysed. The maximum barrier height (Φ b ) for the diode fabricated substrate at temperature 550°C was observed as 0.78eV. Also, from minimum ideality factor (n) of the diode parameters, the maximum substrate temperature was found. From I to V analysis it was revealed that the fabricated diodes were more suitable for the growth of high-quality optoelectronic applications.

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.

WITHDRAWN: Development of polymeric films of metha acrylate, barium and titanium based compounds and thermal characterizations

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Correlation of Auger electron spectroscopy and microsynchrotron radiation x-ray photoelectron spectroscopy investigations of Ba-Sc-O desorption on W(100)

Thin films of barium and scandium metal were deposited onto W(100) from metal evaporation sources in ultrahigh vacuum. The Ba-Sc-W(100) surface was then exposed to oxygen and heated in stages to several temperatures up to 1400 °C to examine the desorption behavior of these adsorbates. In one case, microsynchrotron radiation x-ray photoelectron spectroscopy (micro-SRXPS) was performed on this surface using a low energy electron microscope. In another experiment, reported here, Auger electron spectroscopy data were collected from the Ba-Sc-O-W(100) surface as a function of heating to temperatures corresponding to the same temperatures used for the micro-SRXPS. Both measurements show that barium desorbs with scandium and oxygen at or below 800 °C.

Application of thin film barium strontium titanate (BST) in a microcontroller based tool to measure oxygen saturation in blood

Tools to measure pulse and blood SpO2 have been made using thin-film barium strontium titanate (BST) as the sensor. There are three phases in designing a prototype for measuring the pulse and SpO2. The first is constructing and profiling the optical and electrical characteristics of thin-film BST. From the optical characteristic profiling, it was discovered that there are three wave peaks that are absorbed the most by the film: 450, 600–640, and 900 nm. From the electrical characteristic profiling, it was discovered that the film produced is classified as a photodiode with two sensitivities: exp(–0.0018)/lux when illuminated by white light and exp(–0.0429)/lux when illuminated by infrared light. The second is designing the electronic circuit which consists of an amplifier circuit, filter, and a minimum Atmega328P-PU microcontroller system. From the tests that had been conducted, each circuit succeeded in processing the signal as expected. The third, testing the SpO2 on 20 patients using the prototype and a standard model Elitech Fox-1 oximeter as the reference tool. The results that were recorded demonstrated that the accuracy of the prototype in measuring the SpO2 reached 98% in comparison to the reference tool.

Strain-dependence of χ(2) in thin film barium strontium titanate

Optical second-harmonic generation (SHG) in reflection characterized variations in the second-order nonlinear optical susceptibility χ(2) of Ba1−xSrxTiO3 (BSTO) alloy films grown epitaxially on SrTiO3(001) (STO) as Sr molar ratio x changed from 0 to 1 and thickness from 10 to 50 nm. X-ray diffraction showed that BSTO films with x ≳ 0.1 were highly crystalline and compressively strained with out-of-plane (in-plane) lattice constant 4.09 > c > 3.97 (3.903 < a < 3.907 Å, pinned to substrate) for 0 < x < 1. Spectroscopic ellipsometry showed that the BSTO dielectric function was nearly x-invariant in the range of fundamental (780 nm) and SH (390 nm) wavelengths. SHG intensity peaked at x ∼ 0.3 for a given film thickness, suggesting that composition control can optimize ferroelectric and electro-optic properties of BSTO films grown on STO buffer layers.

Thickness-dependent thermal conductivity of ultrathin (< 100 nm) barium titanate films

Thin film barium titanate (BaTiO3) is a promising material in the electronics and ceramics industry owing to its compelling dielectric properties. A number of works have investigated its dielectric and structural properties, but less studied are its thermal properties particularly at sub-100 nm thicknesses. Here, we measure the room-temperature thermal conductivity of ultrathin (< 100 nm), pulsed laser deposited BaTiO3 films. The measured thermal conductivities are thickness-dependent, and this trend is consistent with the thickness-dependent crystallinity of the films. Transmission electron microscopy analysis of the films reveals the presence of an initial amorphous layer ~ 60 nm thick from the growth interface and the subsequent formation of columnar grains of width ~ 12 nm that are embedded within an amorphous matrix. For a region that incorporates grains with columnar morphology, we find that cross-plane heat conduction may be favored by 30–40% over in-plane heat conduction due to the columnar morphology of grains.

Properties of Thin Films of Barium–Strontium Titanate Solid Solutions by Induced Piezoelectric Effect

Piezoelectric effect equations have been derived by linearizing the nonlinear equations of state of a thin film existing in a paraelectric phase in the presence of an external electrical field (induced piezoelectric effect). The behavior of the piezoelectric and elastic constants of thin films of a solid barium–strontium titanate solution BST065 (x = 0.65) in a planar field at different misfit strain values has been studied numerically.

Effect of the stresses caused by substrate on the electrical conductivity of ferromagnetic manganite lanthanum–barium films

This is a complex study of the electrophysical and magnetic characteristics of epitaxial manganite La0.7Ba0.3MnO3 (LBMO) films under conditions of crystal structure stresses caused by misfit in the lattice parameters of the LBMO crystal and a substrate. The substrate used had the lattice parameter smaller than that in the LBMO crystal. It is shown that the temperature dependence of the electrical resistance of the films at low temperatures is not dependent on the existence of stresses in the film and agrees well with the calculation with allowance made for the interaction of carriers with magnetic excitations in the presence of strongly correlated electronic states. The study of the ferromagnetic resonance line indicates an inhomogeneity of the ferromagnetic phase in the LBMO films and the increase in the ferromagnetic resonance line width with decreasing temperature.

Ferroelectric properties in thin film barium titanate grown using pulsed laser deposition

The characteristics of polycrystalline BaTiO3 metal-insulator-metal capacitors, fabricated using pulsed laser deposition, are investigated from room temperature to 420 K. The capacitance–voltage characteristics show ferroelectric behaviour at room temperature, with a phase transition to paraelectric at higher temperature. However, the permittivity response shows paraelectric behaviour across all measured temperatures. So BaTiO3 exists here in a mixture of cubic and tetragonal phases. The BaTiO3 films have a columnar structure, with grain size increasing with film thickness due to their increasing height but not diameter. This correlates with an increase in remnant polarization. The results support a size driven phase transition in thin films of polycrystalline BaTiO3.

Spectral phonon scattering effects on the thermal conductivity of nano-grained barium titanate

We study the effect of grain size on thermal conductivity of thin film barium titanate over temperatures ranging from 200 to 500 K. We show that the thermal conductivity of Barium Titanate (BaTiO3) decreases with decreasing grain size as a result of increased phonon scattering from grain boundaries. We analyze our results with a model for thermal conductivity that incorporates a spectrum of mean free paths in BaTiO3. In contrast to the common gray mean free path assumption, our findings suggest that the thermal conductivity of complex oxide perovskites is driven by a spectrum of phonons with varying mean free paths.

Fabrication of Titanate Barium Films by Electrophoretic Deposition Technique

Fabrication of Titanate Barium Films by Electrophoretic Deposition Technique

Tunable Patch Antenna with BST Capacitors

Recently there is increasing interest in developing tunable circuits to implement multiband communication systems. These include tunable filters, tunable amplifiers and antennas. Tunable ferroelectric capacitor fabricated with thin film barium strontium titanate (BST) gives the opportunity to fabricate these tunable circuit modules. In this paper, we present the results of tunable patch antenna with tunable ferroelectric capacitors. The patch antenna in the frequency range of 2–3 GHz was fabricated on FR-4 substrate. The parallel plate ferroelectric capacitors were fabricated on sapphire substrates. The performance of the patch antenna was studied with ferroelectric capacitors attached to the coplanar wave guide as well as radiating edge. The performance of the antenna was simulated using ADS and compared with experimental results the radiation pattern of the antennas is studied in an anechoic chamber.

Broad band absorbance of barium hexaferrite thick films in the 8-12 GHz frequency spectrum

Screen printed barium hexaferrite thick films on alumina with broad band absorbance in the X band were fabricated. BaFe12O19 was synthesized using a cost effective low temperature co-precipitation method with varying Fe/Ba molar ratio and pH. The thick film showed increased grain size for higher Fe/Ba molar ratio. The complex permittivity and permeability of these thick films showed wavelike behavior in a range of 9.5 GHz to 10.5 GHz. Synthesis conditions of hexaferrite powder and the dependency of the complex permittivity and the permeability of BaFe12O19 thick films on thickness in the 8 to 12 and the permeability of BaFe12O19 thick films in the 8 GHz to 12 GHz frequency spectrum are discussed in this paper. The high frequency (8 GHz to 12 GHz) reflection loss of thick film barium hexaferrite was investigated and was found to be dependent on the synthesis parameters and the thickness of the thick films. The absorption measured was more than 80% over the entire X band.

Electrical Reliability of Solgel Barium Titanate Films on Copper Foils for Organic Package Integration

AbstractThere is an increasing need for integrating high dielectric constant ceramic thin film components in organic and 3D IC packages to lower the power-supply impedance at high frequencies and supply noise-free power to the ICs. Sol-gel approach is very attractive for high density capacitors because of its ability to precisely control the composition of the films and the ease of introducing dopants to engineer the dielectric properties such as breakdown voltages and DC leakage characteristics. Thin films on copper foils lend themselves to organic package integration with standard foil lamination techniques used in package build-up processes. However, fabrication of thin film barium titanate on copper foils is generally affected by process incompatibility during crystallization in reducing atmospheres, leading to poor crystallization, oxygen vacancies and copper diffusion through the film that degrades the electrical properties.This paper focuses on the dielectric properties and electrical reliability of thin films on copper foils. Thin film (300-400 nm) embedded capacitors with capacitance density of 2 μF/cm2, low leakage current and high breakdown voltage were fabricated via sol-gel technology and foil lamination. To lower the leakage current, the chemical composition was altered by incorporating – 1.) Excess barium 2.) Acceptor dopants such as Mn. Both approaches lowered the leakage current compared to that of pure barium titanate. SEM analysis showed enhanced densification and refined grain structure with chemistry modification. The films showed good stability in leakage currents at 150 C with an applied field strength of 100 kV/cm, demonstrating the electrical reliability of these films.

Photoluminescence of Tb3+ ions in barium–strontium–calcium titanate xerogels

Terbium-doped films of barium–strontium–calcium titanate with the perovskite phase were fabricated using the sol-gel method. Photoluminescence of trivalent terbium ions with a strong band at 543 nm was observed at 4.2 and 300 K for films fabricated by spin-on deposition on porous anodic alumina and annealed at 500 and 750°C. The possibility of using sol-gel synthesis of perovskites to investigate spontaneous emission of terbium and other lanthanides in photonic crystals with a tunable photonic band gap is discussed.

RESIDUAL STRESS IN VERY THIN BARIUM STRONTIUM TITANATE FILMS

ABSTRACT Residual stress in thin film barium strontium titanate is thought to be preferentially distributed within the thickness of the film, such that a high degree of residual stress is manifested at the film-substrate interface, and the level of residual stress gradually decreases towards the free surface. To investigate this phenomena, a series of very thin films of barium strontium titanate with both cubic (30-70 Ba-Sr ratio) and tetragonal (80-20 Ba-Sr ratio) lattice structures were fabricated on platinized silicon and magnesium oxide. The thickness of these films was varied from 4–25 nm and the level of residual stress was investigated. The results highlighted within this paper, indicate that the cubic and tetragonal films manifest stress via different mechanisms, and that the substrate affected the magnitude of the residual stress but not the mechanism of stress relief.

Evolution of gettering technologies for vacuum tubes to getters for MEMS

Getter materials are technically proven and industrially accepted practical ways to maintain vacuum inside hermetically sealed tubes or devices to assure high reliability and long lifetime of the operating devices.The most industrially proven vacuum tube is the cathode rays tubes (CRTs), where large surfaces are available for the deposition of an evaporated barium film by a radio frequency inductive heating of a stainless steel container filled with a BaAl4 powder mixed to Ni powder. The evolution of the CRTs manufacturing technologies required also new types of barium getters able to withstand some thermal process in air without any deterioration of the evaporation characteristics.In other vacuum tubes such as traveling waves tubes, the space available for the evaporation of a barium film and the sorption capacity required to assure the vacuum for the lifetime of the devices did not allow the use of the barium film, prompting the development of sintered non evaporable getter pills that can be activated during the manufacturing process or by flowing current through an embedded resistance. The same sintered non evaporable getter pills could find usage also in evacuated parts to thermally isolate the infrared sensors for different final applications.In high energy physics particle accelerators, the getter technology moved from localized vacuum getter pumps or getter strips to a getter coating over the surface of vacuum chambers in order to guarantee a more uniform pumping speed.With the advent of solid state electronics, new challenges faced the getter technology to assure long life to vacuum or inert gas filled hermetical packages containing microelectronic devices, especially in the telecommunication and military applications. A well known problem of GaAs devices with Pd or Pt metalization is the H2 poisoning of the metal gate: to prevent this degradation a two layer getter film has been develop to absorb a large quantity of H2 per unit of getter surface.The development of Micro Electro Mechanical Systems (MEMS) with moving parts in a vacuum environment required the development of a new generation of getter film, few microns thick, that can be selectively patterned onto a silicon or glass wafer (usually 4″ or 8″). This wafer with patterned getter film can be used directly as the cap wafer of a wafer to wafer bonded MEMS structure, assuring long life and reliability to the moving MEMS structure especially in automotive applications where thermal cycles are required for qualification.

In situ transmission Fourier transform infrared (FT-IR) spectroscopy investigations of the surface chemistry of gettering common gases in vacuum systems with a common commercial flashed getter alloy as a function of temperature

Studies of gettering reactions of a commercial flashed metal alloy commonly used in vacuum electronics with common gases found in vacuum electronic systems (CO, CO 2, CH 4, and O 2) have been carried out in situ using Fourier transform infrared spectroscopy (FT-IR) to better understand the nature of these reactions as a function of temperature. Flashed alloy was found to adsorb CO at temperatures greater than −5 ± 5 °C across a pressure range from 3 to 50 Torr of CO. Multivariate curve resolution (MCR) was needed to extract the pure component spectra and temperature profiles for signals having intensities 10–200 times less than the background. No spectral evidence for adsorbed CO 2 or CH 4 was observed but both CO and CO 2 were found to react with the barium film at temperatures above 77 ± 5 °C forming what is likely a combination of Ba(OH) 2, Sr(OH) 2, and other trace metal oxides and hydroxides. Again MCR was needed to resolve the pure spectral components and temperature profiles of these highly overlapped components. The production of metal hydroxides is likely caused by the presence of H 2 sorbed to the getter during the flash as low temperature, <−50 °C, experiments with O 2 showed similar reaction products. In the case of CH 4 no reaction is seen with the flashed alloy surface up to 120 °C. However, in the presence of what is NiO (Ni is a trace impurity in the getter) and potentially BaO, CH 4 does react at temperatures greater than 55 °C to produce CO 2 which in turn reacts with the alloy film as outlined above.