Barium Titanate Thin Films Research Articles

Enhanced photoelectrochemical properties of 100 MeV Si8+ ion irradiated barium titanate thin films

Effects of high electronic energy deposition on the structure, surface topography, optical property and photoelectrochemical behavior of barium titanate (BaTiO3) thin films were investigated by irradiating films with 100MeV Si8+ ions at different ion fluences in the range of 1×1011–2×1013ionscm−2. BaTiO3 thin films were deposited on indium tin oxide coated glass substrate by sol gel spin coating method. Irradiation induced modifications in the films were analyzed using the results from XRD, SEM, cross sectional SEM, AFM and UV–Vis spectrometry. Maximum photocurrent density of 0.7mAcm−2 at 0.4V/SCE and applied bias hydrogen conversion efficiency (ABPE) of 0.73% was observed for BaTiO3 film irradiated at 5×1011 ionscm−2, which can be attributed to maximum negative value of the flatband potential and donor density and lowest resistivity.

Preferentially oriented BaTiO3 thin films deposited on silicon with thin intermediate buffer layers

Barium titanate (BaTiO3) thin films are prepared by conventional 2-methoxy ethanol-based chemical solution deposition. We report highly c-axis-oriented BaTiO3 thin films grown on silicon substrates, coated with a lanthanum oxynitrate buffer layer of 8.9 nm. The influence of the intermediate buffer layer on the crystallization of BaTiO3 film is investigated. The annealing temperature and buffer layer sintering conditions are optimized to obtain good crystal growth. X-ray diffraction measurements show the growth of highly oriented BaTiO3 thin films having a single perovskite phase with tetragonal geometry. The scanning electron microscopy and atomic force microscopy studies indicate the presence of smooth, crack-free, uniform layers, with densely packed crystal grains on the silicon surface. A BaTiO3 film of 150-nm thickness, deposited on a buffer layer of 7.2 nm, shows a dielectric constant of 270, remnant polarization (2Pr) of 5 μC/cm2, and coercive field (Ec) of 60 kV/cm.

Structure and dielectric properties of barium titanate thin films for capacitor applications

Abstract BaTiO 3 is a typical ferroelectric material with high relative permittivity and has been used for various applications, such as multilayer ceramic capacitors (MLCCs). With the tendency of miniaturization of MLCCs, the thin films of BaTiO 3 have been required. In this work, BaTiO 3 thin films have been deposited on Pt-coated Si substrates by RF magnetron sputtering under different deposition conditions. The films deposited at the substrate temperature from 550 °C–750 °C show a pure tetragonal perovskite structure. The films deposited at 550 °C–625 °C exhibit (111) preferential orientation, and change to (110) preferential orientation when deposited above 650 °C. The film morphologies vary with working pressure and substrate temperature. The film deposited at 625 °C and 4.5 Pa has the relative permittivity of 630 and the loss tangent of 2% at 10 kHz.

Study of the structure and mechanical properties of hexagonal BaTiO3 thin films prepared by sol–gel processing

Hexagonal barium titanate (HBT) thin films were prepared on borosilicate plate substrates via sol–gel method using the dip-coating process. The structure, texture and morphology of the thin film were analyzed by X-ray diffraction, atomic force microscopy, nanoindentation technique, and transmission electron microscopy. The results showed that the thin film annealed at 700 °C crystallized with BaTiO3 hexagonal phase and traces of Ba2TiO4 (secondary phase). The nanoparticles and the RMS roughness of the sample treated at 700 °C presented high values when compared with those thermally treated at lower temperatures. The hardness and Youngs’ modulus of the thin films increased with increasing in grain size, and the thin film annealed at 700 °C with crystallite size about 10 nm presented multiple “pop-in” events during nano-indentation loading curves. The annealing temperature, growth size and surface roughness were discussed in connection with the HBT mechanical properties.

Synthesis and Properties of Highly Oriented Lead Barium Titanate Thin Film on MgO(100) by a Nonaqueous Sol-Gel Process

This study investigated the structure, microstructure and optical properties of the highly-oriented lead barium titanate (Pb1-xBaxTiO3, PBT) thin films prepared on MgO (100) substrate by a nonaqueous sol-gel process. The film precursor was synthesized by the modified sol-gel processing from lead acetate, barium acetate, and titanium isopropoxide, acetylacetone as chelating agent, and ethylene glycol as solvent. This stable precursor was formed by acetylacetone chelating with titanium isopropoxide and then mixing the solution of the acetates. The spin-coating technique was used to deposit the PBT films on MgO (100) substrate with different barium contents and various spin-coating numbers, respectively. X-ray diffraction was employed to study the crystal structure of the thin film and field emission scanning electron microscopy was used to characterize the microstructure of the films. Optical properties of the thin films were investigated by Ultraviolet-visible spectrophotometer. All films exhibited a (100) preferred orientation, especially the PB0.5T (3-coating layers) thin film. In the optical properties, the adsorption wavelength shifted to the ultraviolet region with increasing barium.

Modified structural, morphological and photoelectrochemical properties of 120 MeV Ag9+ ion irradiated BaTiO3 thin films

The effects of high electronic energy deposition on the structure, surface topography, optical property and photoelectrochemical behavior of barium titanate thin (BaTiO3) films have been investigated by irradiating films with 120 MeV Ag9+ ions at different ion fluences in the range of 1 × 1011–3 × 1012 ions cm−2. Barium titanate thin films were deposited on indium tin oxide-coated glass substrate by sol–gel spin coating method. The structure of the film was crystalline with tetragonal phase. Surface topography was studied by atomic force microscopy detailing the values of roughness of the films. Maximum photocurrent density of 1.78 mA cm−2 at 0.4 V/SCE and applied bias photon-to-current efficiency (ABPE) of 0.91% was observed for BaTiO3 film irradiated at 1 × 1011 ions cm−2.

Experimental investigations on barium titanate nanocomposite thin films as an opto-electronic humidity sensor

This article reports the synthesis and characterisation of Barium titanate (BaTiO3) nanocomposite and its application as opto-electronic humidity sensor. Titanium tetrachloride and barium hydroxide were mixed in molar ratio 1 : 1 in deionised water under continuous stirring at room temperature. Later, sodium hydroxide solution was added to above solution with continuous stirring. Finally, BaTiO3 gel was obtained. The synthesised nano-composite material was characterised using a scanning electron microscope, X-ray diffraction (XRD) and UV-Visible spectrophotometer. SEM image of the composite film shows that the film is porous having uniform grains. From XRD the minimum crystallite size of BaTiO3 was found to be 8 nm using Debye–Scherer formula. UV-Visible absorption spectroscopy was used for optical characterisation of the film. It was found that the optical band gap of the composite material was 3.50 eV. Barium titanate thin film was deposited on the base of an equilateral prism using sol–gel spin coating process at 4000 rpm. The humidity sensing properties of the film was investigated at different angles of incidence. It was observed that the intensity of reflected light increased with an increase in relative humidity (%RH) in the range 5–95% at a particular angle of incidence. Sensing element has maximum sensitivity ∼6 µW/%RH, which is quite significant for sensor fabrication purposes.

Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate (BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition (PAD) technique. The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion. Crystal structures, surface morphologies, and dielectric performance were examined and compared for BTO thin films annealed under different temperatures. Correlations between the fabrication conditions, microstructures, and dielectric properties were discussed. BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with ∊r ∼ 400 and tan δ < 0.025 at 100 kHz. The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

Sputtered Modified Barium Titanate for Thin-Film Capacitor Applications.

New apparatus and a new process for the sputter deposition of modified barium titanate thin-films were developed. Films were deposited at temperatures up to 900 °C from a Ba0.96Ca0.04Ti0.82Zr0.18O3 (BCZTO) target directly onto Si, Ni and Pt surfaces and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Film texture and crystallinity were found to depend on both deposition temperature and substrate: above 600 °C, the as-deposited films consisted of well-facetted crystallites with the cubic perovskite structure. A strongly textured Pt (111) underlayer enhanced the (001) orientation of BCZTO films deposited at 900 °C, 10 mtorr pressure and 10% oxygen in argon. Similar films deposited onto a Pt (111) textured film at 700 °C and directly onto (100) Si wafers showed relatively larger (011) and diminished intensity (00ℓ) diffraction peaks. Sputter ambients containing oxygen caused the Ni underlayers to oxidize even at 700 °C: Raising the process temperature produced more diffraction peaks of NiO with increased intensities. Thin-film capacitors were fabricated using ~500 nm thick BCZTO dielectrics and both Pt and Ni top and bottom electrodes. Small signal capacitance measurements were carried out to determine capacitance and parallel resistance at low frequencies and from these data, the relative permittivity (εr) and resistivity (ρ) of the dielectric films were calculated; values ranged from ~50 to >2,000, and from ~104 to ~1010 Ω∙cm, respectively.

Microstructural and optical investigations of Ce-doped barium titanate thin films by FTIR and spectroscopic ellipsometry

(BaTiO3)1− x (CeO2) x (with x = 0, 1, 3, 5.7 and 16 at.%) thin films were prepared by electron beam evaporation method. According to X-ray diffraction, nanosized and amorphous Ce-doped barium titanate thin films were obtained. The crystallinity diminished as Ce content increased. The increase in the Ce slightly shifts the absorption peaks at 433–450 and 416–424 cm−1 to higher wavenumbers. A two-layer model was used to describe the experimental ellipsometric data. The Bruggeman effective medium approximation (BEMA) was used to describe the surface roughness layer and the Cauchy dispersion relation was used to describe the main Ce-doped barium titanate layer. The refractive index and the extinction coefficient were found to increase with increasing Ce content; however, the optical band gap decreased with increasing Ce content. The accurate determination of the optical constants of Ce-doped barium titanate thin films may favor them in the applications of optical thin film devices.

Influence of high temperature processing of sol–gel derived barium titanate thin films deposited on platinum and strontium ruthenate coated silicon wafers

Thin films of barium titanate (BTO) of 200nm thickness, derived from an alkoxide–carboxylate sol–gel process, were deposited on Pt/Ti and SrRuO3/ZrO2–8%Y2O3 coated Si wafers. Films with a dense columnar microstructure were obtained by repeated deposition of thin amorphous layers from low-concentrated sols, and crystallization at 800°C. This method added 10nm thickness to the crystalline BTO film in each deposition step. The harsh processing conditions had a negative impact on the platinized silicon wafers, where Pt–Si silicides were formed. This led to diffusion of Si into BTO and interfacial silicate formation. The interfacial silicate layer was the cause of deteriorated dielectric and ferroelectric properties of the BTO layer. Use of SrRuO3/ZrO2–8%Y2O3/Si substrates solved the problem. No diffusion of Si was observed, and BTO films with good dielectric and ferroelectric properties were obtained.

Barium Titanate Thin Films Deposited by Electrophoresis on &lt;I&gt;p&lt;/I&gt;-Doped Si(001) Substrates

Barium titanate (BaTiO3) thin films have been prepared by electrophoretic deposition on p-doped and platinum covered silicon (Si) substrates. Their structure, nanostructure and dielectric properties were characterized. The as-deposited films were polycrystalline and composed by barium titanate nanograins with an average grain size approximately 9 nm. Annealing at high temperatures promoted grain growth, so that the samples annealed at 600 degrees C presented average grain sizes approximately 24 nm. From Raman spectroscopy measurements it was found that the tetragonal (ferroelectric) BaTiO3 phase was stabilized on the films. Also, at higher annealing temperatures, cation disorder was reduced on the films. From measurements of the temperature dependence of the dielectric permittivity the corresponding paraelectric-ferroelectric phase transition was determined. The observed transition temperature (approximately 100 degrees C) was found to be below the BaTiO3 bulk or thick film values, due to the small nanosized grains composing the films.

Preparation and optical properties of barium titanate thin films

Barium titanate (BTO) films were prepared by sol–gel spin-coating technique. The crystal structure and optical properties of BTO films have been investigated. The results indicate that the BTO films are single perovskite phase having tetragonal symmetry. The band gap of the BTO films increases with the increasing of layer number and decreasing of solution concentration. The transmittance and band gap of the BTO films annealed at 900 °C is more than that of the BTO films annealed at 700 °C when wavelength is 200–1000 nm. When wavelength is 400–1000 nm, the absorption coefficient α obtained by experiment is higher than that obtained by calculation (close to zero).

MISFET structures with barium titanate as a dielectric layer for application in memory cells

This work shows investigations of La 2O 3 containing BaTiO 3 thin films deposited on Si substrates by Radio Frequency Plasma Sputtering (RF PS) of sintered BaTiO 3 + La 2O 3 (2 wt.%) target. Round, aluminum (Al) electrodes were evaporated on top of the deposited layers. Thus, metal–insulator–semiconductor (MIS) structures were created with barium titanate thin films playing the role of an insulator. The MIS structures enabled a subsequent electrical characterization of the studied film by means of current–voltage (I–V) and capacitance–voltage (C–V) measurements. Several electronic parameters, i.e., ε ri , ρ, V FB , Δ V H were extracted from the obtained characteristics. Moreover, the paper describes technology process of MISFETs fabrication and possibility of their application as memory cells. The influence of voltage stress on transfer and output I–V characteristics of the transistors are presented and discussed.

Permittivity scaling in Ba1−xSrxTiO3 thin films and ceramics

A dramatic enhancement in the electromechanical response of barium titanate thin films is demonstrated by understanding and optimizing the relationship between organic removal, crystallization, and microstructure, which therefore results in pore elimination, larger grain sizes, and superior densification. The combination enables one to produce bulk-like dielectric properties in a thin film with a room temperature permittivity value above 3000. This advancement in complex oxide thin film processing science creates a new perspective from which to compare, parameterize, and better understand a collection of literature data concerning the manner in which the dielectric response of BaTiO3 depends upon physical dimensions. We are consequently able to apply a single physical model to bulk ceramic and thin film systems, and so demonstrate that the existence of parasitic interfacial layers are not needed to explain dielectric scaling. This work is instrumental in illustrating that extrinsic contributions to scaling are predominant, and that a fundamental understanding of material synthesis provides important opportunities to broaden the spectrum of nonlinear electromechanical properties that can be achieved in ferroelectric thin films.

Synthesis and Characterization of BaTiO3/CoFe2O4 thin films

ABSTRACTNanocomposites formed by ferrimagnetic and ferroelectric materials are multiferroic material in which magnetoelectric coupling occurs via piezoelectricity and magnetostriction phenomena. These nanocomposites have a variety of applications in tunable microwave devices using electric control of spin wave propagation or new magnetic memories in which the magnetic response is controlled by electric field.In this work, transparent and homogeneous thin films of barium titanate interleaved with cobalt ferrite were prepared by sol–gel method using dip-coating process. Films of pure barium titanate and cobalt ferrite were also prepared for comparison. The nanocomposite films were deposited onto clean quartz substrates, where a coating of each material was deposited interleaved, where the cobalt ferrite film formed the last layer. The films were dried in air after each dipping and heated at 900 oC for 1 hour to convert the amorphous films into crystalline ones. The samples were characterized by low angle X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) and UV-Vis spectroscopy.

High-Mobility Pentacene-Based Thin-Film Transistors With a Solution-Processed Barium Titanate Insulator

Pentacene-based organic thin-film transistors (OTFTs) with solution-processed barium titanate (Ba1.2Ti0.8O3) as a gate insulator are demonstrated. The electrical properties of pentacene-based TFTs show a high field-effect mobility of 8.85 cm2 · V-1 · s-1, a low threshold voltage of -1.89 V, and a low subthreshold slope swing of 310 mV/decade. The chemical composition and binding energy of solution-processed barium titanate thin films are analyzed through X-ray photoelectron spectroscopy. The matching surface energy on the surface of the barium titanate thin film is 43.12 mJ · m-2, which leads to Stranski-Krastanov mode growth, and thus, high mobility is exhibited in pentacene-based TFTs.

High-pressure hydrogen materials compatibility of piezoelectric films

Hydrogen is well known for materials compatibility issues, including blistering and embrittlement in metals, which are challenges for its use as the next-generation “green” fuel. Beyond metals, hydrogen also degrades piezoelectric materials used as actuators used in direct injection hydrogen internal combustion engines. We present the materials compatibility studies of piezoelectric films in high-pressure hydrogen environments. Absorption of high-pressure hydrogen and composition changes were studied with an elastic recoil detection analysis and Rutherford back-scattering spectrometry in lead zirconate titanate and barium titanate thin films. Hydrogen surface degradation in the form of blistering and Pb mixing was also observed.

Pulsed laser deposition of semiconducting crystalline double-doped barium titanate thin films on nickel substrates

We synthesized by pulsed laser deposition (Ba,Sr,Y)TiO3 and (Ba,Pb,Y)TiO3 thin films on mechanically polished nickel substrates.The synthesized thin films were analyzed for: crystalline structure by X-ray diffractometry, morphology and surface topography by atomic force microscopy, optical and scanning electron microscopy, and elemental composition by energy dispersive X-ray spectroscopy and electrical properties by electrical measurements.We have shown that film properties were determined by the dopants, target composition, and deposition parameters (oxygen pressure, substrate temperature and incident laser fluence). All films exhibited a semiconducting behavior, as proved by the decrease of electrical resistance with heating temperature.

Preparation of Barium Titanate Thin Films by MOCVD Using Ultrasonic Nebulization

Barium titanate thin films were deposited on Pt/Ti/SiO2/Si and Si substrates by the MOCVD using ultrasonic nebulization and their deposition characteristics were investigated. The co-solution of barium tetramethyl-heptanedionate and titanium di-isopropoxy bis-tetramethyl-heptanedionate in a solvent was used as the starting source material. The composition of thin films was controlled by changing the molar ratio of Ba/Ti source in the solution and the deposition temperature. The stoichiometric and BaTiO3 single phase films could be made at the deposition temperature of 350∼375°C using the soutions with the Ba/Ti source ratio of 6:1∼3.5:1. The dielectric constant of BaTiO3 film was about 115. And the BaTiO3 thin film had the remanent polarization of 0.268 μC/cm2 and the coercive force of 37.501 kV/cm.