Pt-coated Si Substrates Research Articles

Magnetic and self-biased properties of highly oriented M-type barium ferrite films on Pt-coated Si substrate by magnetron sputtering

Highly oriented M-type barium ferrite (BaM) thin films were deposited by sputtering on Pt-coated Si Substrate with different substrate temperatures. X-ray diffraction and atomic force microscopy results show that BaM films have crystal texture of c-axis grains perpendicular to film plane with apparent hexagonal morphology. On the other hand, it is clearly observed that the remanent magnetization (Mr) in out-plane is higher than those in in-plane, and the Mr in out-plane increases with increasing the substrate temperature, reaching maximum when substrate temperature (Ts) is 600 °C. The hysteresis curves also indicate that the BaM thin film exhibits nice self-biased property with 4πMr of 3803.04 Gs, squareness ratio (Mr/Ms) of 0.96, and coercivity of 1767.3 Oe. These results make sure that these BaM films have potential for use in self-biasing microwave/millimeter wave magnetic devices such as circulators and isolators.

Li loss during the growth of (Li,La)TiO3 thin films by pulsed laser deposition

The structure and composition of pulsed laser deposited films of (Li,La)TiO3 was related to the initial target composition and the deposition conditions. Loss of Li during both the target sintering and film growth led to films being poor in Li compared to the target. A target made from powders of composition Li1.57La0.56TiO3 produced a single phase perovskite structured film of composition Li0.64La0.49TiO3. Films on Pt-coated Si substrates were polycrystalline and showed cracks due to thermal mismatch, while an epitaxial film on (001) SrTiO3 was tetragonally distorted withc/a=0.99 due to lattice mismatch.

Synthesis and Electrical Properties of Garnet-type Solid Oxide Electrolyte Thin Films from Solution Route

ABSTRACTDevelopment of Al-stabilized Li7La3Zr2O12 (LLZO) fast Li ion conducting thin films was attempted by chemical solution deposition (CSD) method with the nominal composition of Li5.95Al0.35La3Zr2O12. The films were crystallized at 600°C on Pt-coated Si substrates in almost single phase without a preferred orientation to any crystallographic axis. Subsequent thermal annealing at 760°C improved packing of LLZO grains with the film thickness of 1.1μm. AC impedance measurements were conducted both with Li reversible and Au blocking microelectrodes deposited on the films annealed at 760°C. Total Li ion conductivity σtotal comprised of bulk and grain boundary contribution was studied. The temperature dependence of σtotal was described with single thermal activation process and σtotal∼2x10-5 S/cm and activation energy of Ea=0.58eV were estimated. These values may be attributed to tetragonal modification of LLZO crystal.

Synthesis and field-emission properties of oriented GaN nanowires

Oriented gallium nitride (GaN) nanowires grown on Pt-coated Si (1 1 1) substrates, were synthesised using the chemical vapour deposition method under different Ga sources. The characteristics of the grown GaN nanowires were investigated using scanning electron microscopy and X-ray diffraction, which found that the as-synthesised GaN nanowires of the three samples are of different orientation, and all displayed hexagonal wurtzite structures of GaN crystals. The electron field-emission properties of the three samples of GaN nanowires showed a low turn-on field of 4.5, 5.5 and 6.2 V/µm, respectively, and field enhancement factors of 1337, 2948 and 2599, respectively.

Growth of undoped and Fe doped TiO2 nanostructures and their optical and photocatalytic properties

Undoped and Fe-doped TiO2 nanostructures have been successfully grown on Pt-coated quartz and Si (100) substrates using vapor-liquid-solid (VLS) growth method. The scanning electron microscopy (SEM) image showed that TiO2 grew in nanowires (NWs) with diameters of 200–400 nm and lengths greater than 12 μm. However, the morphology of Fe-doped TiO2 consists of chunk shaped nanoparticles (NPs). The X-ray diffraction analysis for undoped TiO2 NWs clearly showed the formation of tetragonal rutile TiO2, whereas for the Fe-doped TiO2 NPs it showed orthorhombic TiO2 phase and there are no crystalline peaks for iron or iron oxide. The refractive index and extinction coefficient values of undoped and Fe-doped TiO2 nanostructures were derived from the ellipsometric measurements. Enhanced photocatalytic activities were obtained for undoped and Fe-doped TiO2 nanostructures. The obtained results may find potential applications in optical devices and degradation of organic wastes.

Structural and dielectric properties of Ba(X1/3Ta2/3)O3 thin films grown by RF-PLD

Ba(X1/3Ta2/3)O3 (X=Mg, Zn) thin films were grown on commercial Pt-coated Si substrates by radiofrequency plasma beam assisted pulsed laser deposition (RF-PLD) method. Single phase Ba(Mg1/3Ta2/3)O3 and Ba(Zn1/3Ta2/3)O3 ceramic targets having an ordered hexagonal structure (with P3¯m1 space group) were used for deposition. Structural, morphological and surface characterizations of the Ba(X1/3Ta2/3)O3 (BXT) films were performed using X-ray diffraction, scanning electron microscopy and atomic force microscopy. X-ray diffraction studies evidenced a cubic (disordered) perovskite structure, with unit cell typical for Pm3m space group. Scanning electron microscopy investigations showed that BXT films have a columnar microstructure, which is oriented perpendicular to the substrate. The temperature dependence of the dielectric permittivity of the films was recorded at 100kHz. Unlike targets, the BXT films exhibit positive values of the temperature coefficient of the dielectric permittivity. BaMg1/3Ta2/3O3 and BaZn1/3Ta2/3O3 thin films with dielectric constant of about 22.5 and 25, respectively have been obtained.

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.

Fabricating ordered functional nanostructures onto polycrystalline substrates from the bottom-up

Microemulsion-mediated synthesis has emerged as a powerful bottom-up procedure for the preparation of ferroelectric nanostructures onto substrates. However, periodical order has yet to be achieved onto polycrystalline Pt-coated Si substrates. Here, we report a new methodology that involves microemulsion-mediated synthesis and the controlled modification of the surface of the substrate by coating it with a template-layer of water-micelles. This layer modifies the surface tension of the substrate and yields a periodic arrangement of ferroelectric crystalline nanostructures. The size of the nanostructures is decreased to the sub-50 nm range and they show a hexagonal order up to the third neighbors, which corresponds to a density of 275 Gb in−2. The structural analysis of the nanostructures by synchrotron X-ray diffraction confirms that the nanostructures have a PbTiO3 perovskite structure, with lattice parameters of a = b = 3.890(0) A and c = 4.056(7) A. Piezoresponse force microscopy confirmed the ferro-piezoelectric character of the nanostructures. This simple methodology is valid for the self-assembly of other functional oxides onto polycrystalline substrates, enabling their reliable integration into micro/nano devices.

Dielectric properties of Ba(Zn1/3Ta2/3)O3 thin films on Pt-coated Si substrates

Ba(Zn1/3Ta2/3)O3 (BZT) thin films were grown on Pt-coated Si substrates at 500°C substrate temperatures by pulsed electron beam deposition method and post-annealed at 600 and 650°C for 1h. The X-ray diffraction patterns indicate that the as-grown films are partially crystallized but single-phase cubic perovskite structure was formed in annealed films. The temperature dependence of the dielectric constant of the BZT films was recorded in the −100 to +100°C range. The annealing treatment induces a decrease of the temperature coefficient of the dielectric permittivity with an order of magnitude, from 2000 to 100ppm/°C. The influence of the annealing treatments on the temperature behavior of the BZT films was evidenced; a dielectric constant of about 21 at room temperature was obtained for the films annealed at 650°C.

Fabrication and Characterization of Dielectric Nanocube Self-Assembled Structures

Orderly assemblies of BaTiO3 (BT) cube-shaped nanocrystals (nanocubes) and BT–SrTiO3 (ST) mixture nanocubes were fabricated on Pt-coated Si substrates directly by capillary-force-assisted solution self-assembly and heat treatment. These dielectric nanocubes aligned face to face in quite a wide region of 10×50 µm2 on the average with a height of 1 µm. The local microstructure of the nanocube assembly was observed by high-resolution transmission electron microscopy. It was revealed that the lattice strain at the interface of the neighboring nanocubes was locally induced. The piezoresponse of the BT–ST mixture nanocube assembly showed a nonlinear curve and a stepwise behavior at a high poling field, which differed from the ferroelectric BT and paraelectric ST assemblies investigated by scanning probe microscopy. The characteristic behavior might be attributed to the interfacial lattice strain in mixture assemblies.

Piezoresponse properties of orderly assemblies of BaTiO3 and SrTiO3 nanocube single crystals

Orderly assemblies of BaTiO3 (BT) nanocubes, SrTiO3 (ST) nanocubes and BT-ST mixture nanocubes were fabricated on Pt-coated Si substrate directly by solution self-assembly and heated at 850 °C. The dielectric nanocubes aligned face to face in a quite wide region of several tens of square-micrometers with a height of one micrometer, and even inside of the structures was ordered. The piezoresponse of BT-ST mixture assembly showed non-linear curve and stepwise behavior at high poling field, which differed from ferroelectric BT and paraelectric ST nanocube assemblies.

Effects of Ambient Pressure on the Structural and Magnetic Properties of Bismuth Ferrite Nanoparticles Prepared by Pulsed Laser Deposition (PLD)

Nanoparticles of bismuth ferrite (BiFeO3) were fabricated by high-pressure pulsed laser deposition method (PLD) on Pt-coated Si substrates. Effects of the ambient oxygen pressure during deposition (from 1 Torr to 15 Torr) were studied with respect to the microstructures and magnetic properties of the samples. It was found that as the pressure is higher than 5 Torr isolated nanoparticles are formed and the size of these nanoparticles decreases with the deposition pressure. All the nanoparticles exhibit ferromagnetic behavior and the magnetic coercive filed decreases with the particle size.

Fabrication of Dielectric Nanocubes in Ordered Structure by Capillary Force Assisted Self-Assembly Method and Their Piezoresponse Properties

Ordered structures of barium titanate (BT) nanocubes, strontium titanate (ST) nanocubes and BT/ST nanocubes mixture were directly fabricated on Si and Pt-coated Si substrates using a capillary force assisted assembly method. The morphology of self-assembled structures was observed using field emission scanning electron microscopy (FE-SEM) and scanning probe microscopy (SPM). It was revealed that nanocubes were arranged with various degrees of ordering to develop multilayer and monolayer regions at the surface of substrates. The elemental mapping of the structure consisting of the nanocubes mixture was also investigated by transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX). It was revealed that BT and ST nanocubes coexisted homogeneously in the structure and had possibility to be arranged in order to each other. The piezoresponse properties obtained by scanning probe microscopy (SPM) indicated that the hetero-interface between BT and ST nanocubes would introduce anomaly in piezoelectric properties.

Preparation of (020)-oriented BaTi2O5 thick films and their dielectric responses

Abstract Barium dititanate (BaTi2O5) thick films were prepared on a Pt-coated Si substrate by laser chemical vapor deposition, and ac electric responses of (0 2 0)-oriented BaTi2O5 films were investigated using several equivalent electric circuit models. BaTi2O5 films in a single phase were obtained at a Ti/Ba molar ratio (mTi/Ba) of 1.72–1.74 and deposition temperature (Tdep) of 908–1065 K as well as mTi/Ba = 1.95 and Tdep = 914–953 K. (0 2 0)-oriented BaTi2O5 films were obtained at mTi/Ba = 1.72–1.74 and Tdep = 989–1051 K. BaTi2O5 films had columnar grains, and the deposition rate reached 93 μm h−1. The maximum relative permittivity of the (0 2 0)-oriented BaTi2O5 film prepared at Tdep = 989 K was 653 at 759 K. The model of an equivalent circuit involving a parallel combination of a resistor, a capacitor, and a constant phase element well fitted the frequency dependence of the interrelated ac electrical responses of the impedance, electric modulus, and admittance of (0 2 0)-oriented BaTi2O5 films.

Bulk-like dielectric properties from metallo-organic solution–deposited SrTiO3 films on Pt-coated Si substrates

SrTiO3 (STO) thin films were grown onto Pt/Ti/TiO2/SiO2/Si and bare Si substrates via metallo-organic solution deposition (MOSD). X ray diffraction, scanning electron microscopy, atomic force microscopy, spectroscopic ellipsometry (SE), and dielectric/insulating measurements were utilized to characterize the STO thin films. By optimizing the solution molarity, it is shown that it is possible to obtain low-frequency dielectric properties in STO thin films on Si substrates that approach those of bulk STO: a dielectric permittivity of 325 at 100 kHz with a tunability of ∼28% at ∼650 kV/cm, a low loss (<2%), and a leakage current density of 1.0 × 10−6 A/cm2 at 100 kV/cm. The bulk-like dielectric response of these films is attributed to the elimination of the relatively large in-plane tensile thermal stresses, which arise due to the thermal expansion mismatch between the STO film and the Si substrate. These tensile thermal stresses may be relaxed or completely eliminated through modification of the post-coalescence compressive growth stresses by precursor solution optimization. The SE data indicates that the STO thin films have a refractive index of ∼2.04 at 633 nm wavelength, which is lower than that of bulk STO. The dielectric, physical, and optical characterization results above the bandgap are consistent, but below the bandgap, the optical-frequency results demonstrate a ∼25% reduced dielectric response as compared to the bulk, which may be due to the different polarization mechanisms at work at high frequencies. These findings demonstrate that high-quality, electronic-grade, thin film STO films can be grown on Si substrates via the affordable, simple, and industry-standard MOSD technique by carefully adjusting the deposition parameters.

Preparation of Ba–Ti–O films by laser chemical vapor deposition

Ba–Ti–O films were prepared on Pt-coated Si substrate by laser chemical vapor deposition, and their orientations and microstructures were compared. Ba2TiO4, BaTiO3, BaTi2O5, Ba4Ti13O30 and BaTi4O9 single-phase films were prepared at Ti to Ba molar ratio from 0.41 to 3.49. The α′-Ba2TiO4 film showed (010) and (091) co-orientation with elongated, truncated columnar grains. The BaTiO3 film was composed of triangular and hexagonal grains with slight (111) orientation. The BaTi2O5 film had (010) orientation and faceted columnar grains. The Ba4Ti13O40 film showed (100) and (012) co-orientation with shellfish-like grains. The BaTi4O9 film showed (010) orientation with slightly rounded faceted columnar grains. The deposition rates of Ba–Ti–O films ranged from 30 to 144μmh−1.

Characterization of Dielectric Nanocubes Ordered Structures Fabricated by Solution Self-Assembly Process

Ordered structures of barium titanate (BT) nanocubes, strontium titanate (ST) nanocubes and BT–ST nanocube mixture were directly fabricated on Si and Pt-coated Si substrates using a colloidal solution assembly method inspired by convection self-assembly. BT/ST alternating layered structure was also fabricated by repeating the self-assembly process several times. The microstructure of the self-assembled structures was observed using field emission scanning electron microscopy (FE-SEM) and scanning probe microscopy (SPM). It was revealed that nanocubes were arranged with various degrees of ordering to develop monolayer regions at the surface of the substrates. The crystallographic phase and orientation of the assembly consisting of BT and ST nanocubes were evaluated by X-ray diffraction analysis. The (100) and (200) diffractions of BT and ST were observed and no other diffractions were observed. The BT and ST nanocubes had a 100 face and were arrayed orderly with their faces parallel to the surface of the substrates. The piezoresponse properties obtained by scanning probe microscopy (SPM) indicated that the heterointerface between BT and ST nanocubes would introduce an anomaly in piezoelectric properties.

Ion beam-assisted pulsed laser deposition of (Ba,Sr)(Ti,Zr)O3 films on Pt-Si substrates

Ion beam-assisted pulsed laser deposition with an Ar–oxygen ion mixture was used to prepare Ba0.6Sr0.4Ti0.7Zr0.3O3 (BSTZ) thin films on Pt-coated Si substrates. The ion beam with an anode voltage of 600 V was effective to reduce the thermal budget, i.e., to achieve similar crystallinity with approximately 100 °C lower deposition temperature compared to the cases without ionization. It was revealed that the dielectric properties (relative dielectric constant ɛr and its electric field tunability), out-of-plane lattice parameter of (001)-oriented grains (a001), and the existence of (110)-oriented grains are correlated with one another. Elongation of a001 was suppressed, resulting in large ɛr values comparable with that of a ceramic bulk of the same composition, in the BSTZ films that contain (110)-oriented grains. Less volume of amorphous BSTZ region is supposed to be playing an important role for the bulklike properties of these BSTZ films.

3-7 圧電薄膜を用いた振動エナジーハーベスターの特性評価(OS3 電池レス・デバイスのためのエネルギーハーベストの展開)

We fabricated piezoelectric vibration energy harvesters composed of PZT and lead-free KNN thin films on Si cantilevers and characterized the output voltage and power of those piezoelectric films. Both of the PZT and KNN films were deposited on Pt-coated Si substrates by rf-magnetron sputtering. The harvesters had a simple unimorph cantilever structure with the almost same dimensions, and the characteristics of power generation were examined. When we applied the acceleration of 10m/s^2 on the PZT and KNN energy harvesters, they generated the output power of 1.11 and 1.01μW at the resonant frequency under 10m/s^2, indicating lead-free KNN films are comparable to PZT films for the performance for power generation.

10.2478/s11814-009-0293-5

The possibility of the formation of PbTiO3 from a multilayer structure of PbO and TiO2 layers on Pt-coated Si substrates prepared by rapid thermal metal organic chemical vapor deposition (RTMOCVD) followed by an appropriate annealing process was examined. The metal organic precursors of PbO and TiO2 were Pb(C2H5)4 and Ti(Oi-C3H7)4, respectively. The composition of the PbTiO3 thin film was adjusted by control of the thickness of each binary oxide layer of PbO and TiO2. The multilayer structure was converted into crystalline PbTiO3 by rapid thermal annealing under O2 ambient at temperature greater than 550 °C. As the annealing temperature was increased from 550 to 750 °C, the peaks related to perovskite PbTiO3 in the XRD patterns became stronger and sharper. From this study, it was confirmed that the crystalline PbTiO3 thin films could be prepared from the interdiffusion reaction of multilayer structure composed of primitive binary oxides through the appropriate post annealing process.