Fabrication of conductive oxide polycrystalline BaPbO3 films by chemical solution deposition and their electrical resistivity

BaPbO₃ films were fabricated by a chemical solution deposition on the SiO₂/Si(100) and MgO(100) substrates followed by a post-deposition annealing at the temperatures between 673 and 1073 K under oxygen flow. Polycrystalline BaPbO₃ films were formed together with secondary phases such as PbO and Pb₃O₄ onto MgO(100) substrates at around 750 K, and the films were crystallized into single phase of BaPbO₃ above 823 K. Endothermic peak in differential thermal analysis due to crystallization of BaPbO₃ was observed at 750 K, which is consistent with crystallization temperature of BaPbO₃ estimated from X-ray diffraction. The electrical resistivity depended on the annealing temperature even in the single phase BaPbO₃ films, the lowest resistivity of 3?×?10^?6 μΩ·m which was comparable to that of bulk BaPbO₃ was achieved at the annealing temperature of 873 K.     

化学水浴法制备ZnS薄膜

采用了化学水浴法制备异质结薄膜太阳电池中的窗口层ZnS薄膜.尝试了酸性溶液制备ZnS薄膜,讨论了溶液成分、水浴时间和温度对薄膜成分和形貌的影响.研究结果表明在75℃,6 h条件下沉积得到的薄膜最平整,成分最符合化学计量比,退火后薄膜主要为纤锌矿结构的ZnS相.     

PZT thick films by diol chemical solution deposition

Process optimization and properties of lead zirconate titanate (PZT) films for piezoelectric micromachined ultrasonic transducers (pMUTs) for scanning probe devices will be presented. The goal of the work was a replacement of the tetragenic and mutagenic solvent and a decrease of time-consuming PZT 2–methoxy ethanol (2MOE) route. An alternative diol-based solution synthesis process was developed and “Design Of Experiment” (DOE) was used to achieve processing optimization for thick and crack free films. Tight parameter control allowed to develop a highly reproducible PZT diol process. The crystallization behaviour of crack-free PbZr_0.53Ti_0.47O₃ films (1–5 μm) with oriented perovskite structure was examined by X-ray diffraction and surface analysis using scanning electron microscopy. Piezoelectric and dielectric properties were examined. The effective transverse piezoelectric coefficient e _31,f of sol–gel processed films was investigated for 4 μm thick layers. Best properties were achieved with {1 0 0}-textured films, where a remanent e _31,f value of −7.3 C/m² was measured for 4.1 μm thick films.     

Nb3Sn single-phase targets for fiber-reinforced-superconductors and technique of preparing superconducting films without post annealing

A new type of superconductor is being developed for the application of high-field pulsed superconducting magnets, which are called fiber-reinforced-superconductors (FRS). A filament of FRS consists of a reinforcement fiber with high elastic modulus and a superconducting layer around it. The strain can be reduced against electromagnetic force because of highelastic modulus fibers. If Nb₃Sn target is utilized, the preparation process of FRSs is shortened and there is the possibility to produce Nb₃Sn layer which leads to high current density because of its uniform stoichiometric Nb₃Sn layer. This paper presents first a technique of preparing a single-phase target of Nb₃Sn to produce superconducting layers on reinforcement fibers of FRSs. Mixture of niobium and tin powder was reacted in a furnace filled with argon gas to be Nb₃Sn, and then it was broken and cast into a stoichiometric target with a diameter of 77 mm. The critical temperature of the target itself was 17.5 K. The thin film deposited with the target showed no superconductivity without post annealing, but it had critical temperature from 14.5 K to 12.5 K after heat treatment. Second, a new target containing rich tin was prepared and the film deposited with it had superconductivity without post annealing.     

Heterogeneously doped nanocrystalline ceria films by grain boundary diffusion: Impact on transport properties

Heterogeneous doping of nanocrystalline ceria films, by controlled in-diffusion along grain boundaries, is explored as a means for modifying the space charge potential and the inhomogeneous distribution of defects in the space charge layer known to control the electrical properties of nanocrystalline electroceramics. Nanocrystalline cerium oxide thin films were grown by pulsed laser deposition and modified by a novel doping technique. Thin diffusion sources were deposited and cations such as Ni²⁺ and Gd³⁺ were in-diffused at temperatures of 700–800 °C along columnar grain boundaries normal to the surface; the resulting diffusion profiles were examined by Time-of-Flight SIMS. The properties of these modified films were compared with as-deposited samples, with in-diffusion resulting in decreased electrical conductivity. It is proposed that the variation in conductivity results from a redistribution of charge carriers in the space charge layers due to a change in the space charge potential.     

Fabrication of yttrium aluminum garnet transparent ceramics from yttria nanopowders synthesized by carbonate precipitation

Nanocrystalline yttria powders have been successfully synthesized by using yttrium nitrate as starting salt and ammonium hydrogen carbonate as precipitant. It was found that a small amount of ammonia sulfate in the yttrium nitrate solution can effectively reduce the agglomeration and the resultant powders display good dispersion. Pure cubic phase yttria powders were prepared by calcining the precipitate at 1100 °C for 4 h. The size of the as-prepared yttria powders was about 60 nm in diameter and showed excellent sintering activity. The as-prepared yttria nanopowders and commercial ultrafine alumina powders were used to fabricate YAG ceramics by solid-state reaction method and transparent YAG ceramics have been obtained by vacuum sintering at 1760 °C for 6 h.     

用超声喷雾热分解法制备SnO2:F薄膜

采用超声喷雾热分解法沉积高性能掺氟二氧化锡(SnO2:F)透明导电膜(TCO),其最小方块电阻为9 Ω(400 nm厚),可见光透过率大于80%。X射线衍射(XRD)分析表明,SnO2:F薄膜为多晶结构;原子力显微镜(AFM)观察表明,SnO2:F薄膜平均粒径约为100 nm。此外对石墨导热体和置于其上的玻璃基片两者之间的温度差别做了初步研究。     

Sputter deposition of ferroelectric thin films

Ferroelectric films are typically deposited by a variety of techniques, the two most common being chemical methods (sol-gel, metalorganic decomposition) and sputtering. In this paper we briefly review the sputtering techniques, and then discuss ion beam sputter deposition in greater detail. In particular, ion beam sputter deposition of epitaxial lead zirconate titanate (PZT) films is described. It is shown that the films with compositions close to the morphotropic boundary typically show well-developed ferroelectric hysteresis loops, Pmax around 45 μC/cm2, and Pr around 20 μC/cm2. In comparison with typical polycrystalline sol-gel PZT films, however, coercive fields of thin epitaxial films are large (120-200 kV/cm for 95 nm films). The pulsed fatigue behavior is remarkably similar to a polycrystalline non-oriented sol-gel PZT film investigated for comparison. The similarities suggest that the aging behavior may be dominated by the electrodes, which were Pt in both systems.     

PLZT films prepared by aerosol deposition and their birefringence evaluation

Pb_0.91La_0.09(Zr_0.65Ti_0.35)O₃ (PLZT) films were prepared by the aerosol deposition method (ADM) and their optical and electro‐optic (EO) properties investigated for application to hologram optical switch. We found that a higher transmittance of the films was obtained with smaller particles. The transmittance of the PLZT film deposited with particles of 0.2 µm average diameter, the smallest size in this experiment, was nearly 100%, showing that the PLZT film deposited by aerosol deposition can be applied to practical optical devices. We evaluated the birefringence shift of the film to make the EO performance clear. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fabrication of polyurea thin films for optical second-harmonicgeneration by vapor deposition polymerization. Effects of poling fieldand monomer structure on reactivity and SHG performance

Aromatic PU (polyurea) thin films were fabricated for second-order nonlinear optical application by vapor deposition polymerization using MDI (4,4-diphenylmethane diisocyanate) and DDM (4,4-diaminodiphenylmethane) or DNB (p-diamino nitro benzene). The former was abbreviated to PU (DDM) and the latter to PU (DNB). In PU (DDM) fabricated by VDP (vapor deposition polymerization), the SH (second-harmonic) intensity showed orientation stability up to 200°C due to polymerization and simultaneous orientation under the dc field (the poling process). In PU (DNB) fabricated by VDP, although the enhanced optical nonlinearity due to the introduction of the NO₂ group was achieved, a drastic decay of SH intensity was observed at 200°C. The decay was attributed to hindrance of the polymerization by the dc field, suggesting that the strong poling field reduces reactivity of some monomers. In PU (DNB) fabricated by EVDP (VDP under electric field), SHG (second-harmonic generation) was observed. Applying a higher electric field was effective in improving the optical nonlinearity. Film fabrication at higher temperature was also effective in improving the orientation stability and the optical nonlinearity, due to further polymerization during fabrication. We attributed this to the increase in the number of urea groups. The use of appropriate monomers that polymerize under high electric fields would result in improvement of SHG characteristics     

Low-temperature synthesis of barium titanate thin films by nanoparticles electrophoretic deposition

The nanoparticles electrophoretic deposition (EPD) of barium titanate (BaTiO₃ or BTO) thin films was investigated. BTO nanocrystallites in a pseudocubic perovskite phase with an average particle size of about 10 nm were synthesized at a low temperature of 90°C by a high-concentration sol–gel process. By using a mixed solvent of 2-methoxyethanol and acetylacetone as dispersing medium, transparent and well-dispersed BTO nanocrystallites suspensions within the concentration range of 0.0125 to 0.20 mol/l was successfully prepared for nanoparticles EPD. A uniform microstructure and a smooth surface were observed on the deposited films. The film thickness of the deposited films increased rapidly with increasing EPD time in the initial period of EPD, and thereafter gradually increased to a limited thickness. With increasing applied EPD voltage, the limited film thickness increased. A near linear relation between the film thickness of films and the concentration of suspensions was observed under the same EPD conditions. The microstructures of the deposited BTO thin films were investigated.     

Ferroelectric films of lead germanate prepared by modified chemical deposition techniques

Abstract

The high adhesive, single crystal lead germanate films of 5–105 μm in thick were fabricated on platinum substrates by in situ sol-gel technique. The stoichiometry of the films was closed to 5:3:11 without any oxygen deficiency. The microstructure of better films consisted of closed packed hexagonal crystals of 200–300 μm in size. Ferroelectric transition was sharp with Curie point 170–180°C, ε₂₀=30–40, tgδ₂₀?0.02, ε_max?200, P_s=3.2 μC/cm², E_c=16 kV/cm, ρ=10⁸–10⁹ Ωcm. All these parameters (with the exception of ε_max) were in a good agreement with bulk single crystals ones.     

Low‐resistive and transparent AZO films prepared by PLD in magnetic field

Al₂O₃‐doped ZnO (AZO) thin films have been deposited onto glass substrates using a split target consisting of AZO (1 wt%) and AZO (2 wt%) by pulsed laser deposition with an ArF excimer laser (λ = 193 nm, 15 mJ, 10 Hz, 0.75 J/cm²). By applying a magnetic field perpendicular to the plume, the lowest resistivity of 8.54 × 10^?5Ω·cm and an average transmittance exceeding 91% over the visible range were obtained at a target‐to‐substrate distance of 25 mm for approximately 279‐nm‐thick AZO film (1.8 wt%) grown at a substrate temperature of 230 °C in vacuum. From cross‐sectional TEM observations and the XRD spectrum, a reason why the low resistivity (54 × 10^?5Ω·cm) was reproducibly obtained was considered to be due to the fact that a disorder of crystal growth originating in the vicinity of the interface between the substrate and the film was suppressed by application of the magnetic field and the c‐axis orientation took preference, giving rise to the increase of mobility. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(2): 40–45, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20026     

Characterization of conduction in PZT thin films produced by laser ablation deposition

Abstract

Both direct current (d.c.) and alternating current (a.c.) conductivity measurements were undertaken on lead zirconate titanate (PZT) films synthesized by laser ablation deposition. Direct current (I) displayed an initial time dependence of the form I ∝ t^?γ (γ ∝ 0.5–1.0). The possible reasons for this time dependence are discussed. At lower temperatures, the a.c. electrical conductivity shows a frequency dependence of the form σ ∝ ω′ which is explained as electrical charge hopping. At higher temperatures, the d.c. component of electrical conductivity becomes dominant, and is accompanied by a strong low frequency dispersion of the dielectric constant. The results are compared to published data on conductivity in SrTiO₃, and discussed in terms of the latest theories for dielectric response of materials.     

Crystalline and optical properties of PLZT films prepared by pulsed laser deposition

Abstract

The PLZT (3/66/34), PLZT (3/46/54), PLZT (9/65/35) and PLZT (28/0/100) thin films were deposited on MgO (100), Sapphire (0001) and fused silica substrates by using pulsed KrF excimer laser deposition technique. The conventional in-situ and 2-step heating processes were utilized to facilitate the synthesis of a large area of uniform PLZT thin film. Pure perovskite phase can be obtained only under very narrow process conditions, the highly textured PLZT films can be easily obtained by in-situ heating process. For PLZT (28/0/100) material, epitaxial films were successfully coated on MgO (100) substrates by 600°C in-situ and RTA 650°C 2-step heating processes. The latter was found to possess higher refractive index and lower extinction coefficient.     

On-site fabrication of ceramics films from solution precursors by ink-jet and spray assisted processes

Solution processing based on Ink-jet and spray technologies is one of low cost on-site ceramic patterns/films fabrication methods at moderate temperatures from precursor solutions. In the present study, we have used ink-jet and spray technologies to fabricate ceramic films of titania directly on glass substrates at 300–400^∘C. The precursor solution was prepared by dissolving Titanium tetraisopropoxide in appropriate solvents (water/ethanol and acetylacetone). A cleaned glass substrate was kept on a hot plate and heated it up to a predetermined temperature. Droplets of the precursor solution produced through a spray gun were traveled towards heated substrate with a atmospheric pressure. When the droplets hit on the heated substrate, precursor started to decompose, nucleate and grow into the TiO₂ film. The anatase pattern was directly obtained by ink-jet method at moderate temperatures.     

Electromechanical properties of PMN-PT thin films prepared by pulsed laser deposition technique

Abstract

Ferroelectric relaxor thin films of the composition 0.9Pb(Mg_1/3Nb_2/3)O₃-0.1PbTiO₃ (PMN-PT) were fabricated by pulsed laser deposition technique on Pt/Ti/SiO₂/Si(100) substrates using a La_0.5Sr_0.5CoO₃ film as a template layer. The films were polycrystalline with random orientation of the grains. Electromechanical properties of the films were evaluated by a sensitive interferometric technique as a function of the dc and ac electric fields and frequency. Experimental results show that the effective piezoelectric coefficient d₃₃ can be tuned over a wide range of magnitudes by varying dc bias fields. A small hysteresis and a low remanent d₃₃ were observed, which favor the use of PMN-PT films in electric field-controlled micromechanical devices. The maximum d₃₃ ranged from 50 to 100 pm/V, depending on the thickness of the films and frequency. The piezoelectric properties are explained based on the expression for the electrostriction biased by polarization. At low electric field, strain is proportional to the square of electric field, while at higher fields it can be better described as the polarization squared. The asymmetry of the strain response in PMN-PT films is attributed to the polarization offset appearing due to the different electrode materials.     

HTc superconducting films of bismuth-strontium cuprate prepared by modified chemical deposition techniques

Abstract

The homogeneous solutions of meta-acrylates of Bi, Pb, Sr, Ca, Cu were synthesized, and by spray-pyrolysis of the solutions and following annealing the high temperature superconducting Bi₂Sr₂CaCu₂O_x+Bi₂Sr₂Ca₂Cu₃O_x films were prepared on LaAlO₃ substrates. The connection was observed between annealing temperature, film thickness and type, quantity, and forms of impurity phases, such as strontium and calcium cuprates, calcium oxides, strontium oxides. The properties of these films (T_s ? 81 K, ΔT_s ? 1 K) were shown to take place in case if their microstructure consisted of scale-like plates forming [001] texture. Also, it was concluded that under optimum conditions the T_scould be raised to > 100 K in Bi–containing films