Preparation and Optical Properties of Gold-Dispersed BaTiO3, PGO (Pb5Ge3O11) and PLT (Pb1-1.5xLaxTiO3) Thin Films by Sol-Gel Process

Gold-dispersed BaTiO₃, PGO and PLT thin films, which will be used for third-order nonlinear optical devices, were prepared by sol-gel process with spin-coating using HAuCl₄4H₂O, Ba(CH₃COO)₂, Ti[O(CH₂)₃CH₃]₄, Pb(CH₃COO)₂3H₂O, Ge[O-n-C₄H₉]₄, La(CH₃COO)₃1.5 H₂O as starting materials. The thin films were heat-treated in air at temperatures ranging from 400 to 800 for 1 h. The nonlinear optical property of these thin films was measured by the degenerate four-wave mixing (DFWM) method using a frequency-doubled Nd: YAG laser with 20 ps pulse duration. Third-order nonlinear susceptibility χ⁽³⁾ of gold-dispersed BaTiO₃, PGO and PLT thin films with 5 vol% of gold were 1.410⁻⁶ esu, 3.510⁻⁷ esu respectively. The large χ⁽³⁾ may be ascribed to the high dielectric constant of the films.     

Nonlinear Current-Voltage Curves for Thin-Film Gas-Sensitive Structures

Current-voltage curves for sensor structures based on thin tin oxide films are examined in various gases. Conditions favoring symmetrical nonlinear curves in the voltage range −30 to 30 V are found.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 735–737.Original Russian Text Copyright © 2005 by Simakov.Published on the basis of a report delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004).     

Molecular origins of the remarkable chiral sensitivity of second-order nonlinear optics.

Recent observations of remarkably large chiroptical effects in second-harmonic generation (SHG) and sum-frequency generation (SFG) measurements suggest exciting possibilities for the development of new chiral-specific spectroscopies and novel chiral materials for nonlinear optics. Several fundamental studies designed to elucidate the molecular and macromolecular origins of the chiral responses are reviewed to provide a framework for development of this emerging field. In general, the chiral activity in SHG and SFG has the potential to arise from complex interactions between hosts of different competing effects. Fortunately, relatively simple electric dipole-allowed mechanisms routinely dominate the nonlinear optical chiral activities of most practical systemsexpressions can often be generated to link the. This substantial reduction in complexity allows for the development of simple models connecting the macroscopic nonlinear optical response to intuitive molecular and supramolecular properties.     

Characteristics of Ag/Bi<Subscript>3.25</Subscript>La<Subscript>0.75</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript>/p-Si heterostructure prepared by sol-gel processing

The metal-ferroelectric-semiconductor (MFS) heterostructure has been fabricated using Bi_3.25La_0.75Ti₃O₁₂ (BLT) as a ferroelectric layer by sol-gel processing. The effect of annealing temperature on phase formation and electrical characteristics of Ag/BLT/p-Si heterostructure were investigated. The BLT thin films annealed at from 500°C to 650°C are polycrystalline, with no pyrochlore or other second phases. The C-V curves of Ag/BLT/p-Si heterostructure annealed at 600°C show a clockwise C-V ferroelectric hysteresis loops and obtain good electrical properties with low current density of below 2×10⁻⁸ A/cm² within ±4 V, a memory window of over 0.7 V for a thickness of 400 nm BLT films. The memory window enlarges and the current density reduces with the increase of annealing temperature, but a annealing temperature over 600°C is disadvantageous for good electrical properties.     

Synthesis of highly textured superconducting NdBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7-<Emphasis Type="Italic">y</Emphasis></Subscript> thin films by two aqueous sol-gel dip coating techniques

Today, the deposition of coated conductors on a variety of substrates is often performed using a vacuum or low pressure technique. However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and attaining independence of geometric constraints of the substrates are areas in which vacuum techniques will need sustained development in order to answer industrial demands. The development of the next generation of deposition methods, based on deposition under atmospheric environment and from aqueous precursor solutions is a real challenge. This work describes the deposition of thin NdBa₂Cu₃O_7-y layers on SrTiO₃ single crystals based on a new sol-gel dip coating process using aqueous precursor solutions. Two inorganic aqueous sol-gel routes were investigated, a metal nitrate–citric acid based and a metal acetate–triethanol amine based solution. Using detailed thermal analysis, it is shown that adjusting the different parameters during thermal treatment can be used to control the morphology of the films. Also special attention is given to the microstructure of the thin film because of its relevance to the superconducting transport properties of the coated conductor system.     

聚(ε-己内酯)薄膜结晶形貌及分子取向研究

用匀胶机通过溶液铸膜方法在硅片和铝箔基板上分别制备具有不同厚度的聚(ε-己内酯)(PCL)薄膜. 通过原子力显微镜(AFM)和偏光衰减全反射傅里叶红外光谱(ATR-FTIR)对薄膜中PCL的结晶形貌、 片晶生长方式及分子链取向进行了研究. AFM结果表明, 在200 nm或更厚的薄膜中, PCL主要以侧立(edge-on)片晶的方式生长; 对于厚度小于200 nm的薄膜, PCL片晶更倾向于以平躺(flat-on)的方式生长. 这种片晶生长方式的改变在硅片和铝箔基板上都表现出同样的倾向. 此外, 在15 nm或更薄的薄膜中, PCL结晶由通常的球晶结构变为树枝状晶体. 偏光ATR-FTIR结果表明, 当膜厚小于200 nm时, 薄膜结晶中PCL分子链沿垂直于基板表面方向取向, 并且膜越薄, 取向程度越高, 与AFM的观测结果一致.     

Microstructure and ferroelectric properties of r.f. magnetron sputtering derived PZT thin films deposited on interlayer (PbO/TiO2)

Lead zirconate titanate (PZT) thin films were deposited on Pt/Ti/SiO₂/Si and interlayer/Pt/Ti/SiO₂/Si substrate by radio frequency (r.f.) magnetron sputtering with a Pb_1.1Zr_0.53Ti_0.47O₃ target. The crystallization of the PZT thin films was formed only by substrate temperature. When interlayer (PbO/TiO₂) was inserted between the PZT thin film and the Pt electrode, the grain growth and processing temperature of the PZT thin films were considerably improved. Compared to PZT/Pt structure, the dielectric constant and polarization properties of the PZT/interlayer/Pt structure were fairly improved. In particular, PZT/interlayer/Pt at the substrate temperature of 400 °C showed prevalent ferroelectric properties (_r=475.97, tanδ=0.0591, P_r=23 μC/cm²). As a result of an X-ray photoelectron spectroscopy (XPS) depth-profile analysis, it was found that PZT/interlayer/Pt deposited only by substrate temperature without the post-annealing process via r.f. magnetron sputtering method remained independent of each other regardless of substrate temperatures.     

Evaluation of phenyldimethylethoxysilane treated high-performance thin-layer chromatographic plates. Application to analysis of flavonoids inScutellariae radix

Summary The retention and selectivity of flavonoids (baicalin, baicalein, wogonin, oroxylin A) inScutellariae radix have been studies by high-performance thin-layer chromatography on phenyldimethylethoxysilane-treated silica plates. The silica plates treated with phenyl groups were used for physical and chemical analysis. From elemental carbon analysis, the maximum number of bonded phenyl surface groups per gram was calculated to be 0.467×10²¹ (Oginal silica plate: Merck Art. 15109, Silica gel 100 F₂₅₄). With methanol-1/15 M phosphate buffer (pH 6.2) mixtures as mobile phase, baicalin, baicalein, wogonin, and oroxylin A inScutellariae radix were separated. It has been shown that phenyl-treated plates are more suitable for selective separation of baicalin, baicalein, wogonin, and oroxylin A than octadecyl-treated plates.     

Aqueous Titanate Sols from Ti Alkoxide-α-Hydroxycarboxylic Acid System and Preparation of Titania Films from the Sols

Aqueous titanate sols were prepared by reactions of titanium tetraisopropoxide (TIP) with -hydroxycarboxylic acids in water. IR and Raman spectra, and elemental analyses of the precipitates obtained from the sols revealed that the carboxylates were chelated to titanium but the Ti species were polymerized to form a cluster that had a colloidal nature. Spin-coating of titania (TiO₂) thin films from these sols was also examined. Interestingly, it was found that (004) preferentially oriented anatase films with refractive index of 2.54 were obtained from TIP-lactic acid-NH₃ (1:1:1, molar ratio) aqueous sol. This crystallographic orientation was characteristic of the TIP-lactic acid-NH₃ (1:1:1) system, and was not affected by the kinds of substrates used and the heating rate of the film. TEM observation indicated that small anatase grains had already formed at 200°C. Therefore, the crystallographic orientation might depend strongly on the structure of the chemical species of the precursor solutions.     

NiOxHy薄膜的电致变色特性和机理

运用循环伏安和阶跃电位方法研究了Ni（OH）2粉末靶直流溅射沉积的NiOxHy薄膜电致变色特性．结合实时的光透射-时间变化，发现着色后的薄膜在零外电势下有一自发的消色过程，该过程可能对应着Li 的自发注入。着色没有自发过程，获取了着消色状态Ni2p3／2和O1s的XPS谱，表明在着色态镍被氧化，消色态镍被还原，相应地氧的化学环境发生改变．