{（Eu（PW11）2）m/PEI}多层纳米复合膜的制备和光谱表征

在科技竞争日益激烈的今天,功能性分子材料的设计和获得是科学界面临的主要挑战之一.多金属氧酸盐因其具有特定的结构和优越的光、电和磁等物理化学性质,已经成为构造新型功能材料的重要无机构筑块.借助于分子间弱的相互作用将多金属氧酸盐引入到纳米复合薄膜材料中,利用无机和有机组分的协同作用来诱导和产生新的功能特性,必定会给这种无机构筑块在材料科学中的应用创造更多的机会.静电沉积技术是制备有机一无机超薄膜的一种有效方法,人们已经成功地实现了各种无机材料的组装,它们在非线形光学、导电膜、电致发光器件和传感器等方面有着潜在的应用前景.利用层层自组装法(layer bylayer self assembly,LBL),制备出有序且稳定的多金属氧酸盐Eu(PW111)2的多层膜.应用紫外光谱研究其层层组装过程,观察到层层组装是一个均一过程.荧光光谱研究表明所制备的含稀土多金属氧酸盐阴离子的多层膜,通过调节膜的厚度、组成和结构,多层膜具有Eu3 的特征发射.这一结果为发光器件的发展提供了丰富的数据.     

The effect of nature of polyions and treatment after deposition on wetting characteristics of polyelectrolyte multilayers

The sequential adsorption of oppositely charged polyelectrolytes (PE) occurs to be a powerful tool for obtaining various materials of precisely defined properties. The interfacial features of PE multilayer films are governed by the choice of polycation/polyanion pairs and the conditions of film formation. Additionally, the long time exposure to the conditions different than that encountered during formation usually affects polyelectrolyte multilayer structure.The wettability of heterogeneous surfaces produced by ‘layer-by-layer’ (LbL) adsorption of polyelectrolytes was investigated in this work. We focused on the influence of film treatment after deposition on wetting properties of obtained multilayers. The effect of the nature of the first layer was also studied. Apart from simple arrangements: (polyallylamine hydrochloride)/(polysodium 4-styrenesulfonate) (PAH/PSS) and (poly-l-lysine hydrobromide)/(poly-l-glutamic acid sodium salt) (PLL/PGA) more complicated structures were considered having as a first layer two types of polyethylene imines (PEI) of different molecular weight.Wetting properties of such polyelectrolyte films were determined experimentally by contact angle measurements using technique of direct image analysis of the shape of sessile drop.     

Shrinking of ultrathin polyelectrolyte multilayer capsules upon annealing: A confocal laser scanning microscopy and scanning force microscopy study

Heating-induced morphological changes of micrometer size capsules prepared by step-wise deposition of oppositely charged polyelectrolytes onto melamine formaldehyde (MF) latex particles and biological cells with subsequent dissolution of the core have been investigated by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). For poly(styrenesulfonate-Na salt)/poly(allylamine hydrochloride) polyelectrolyte capsules a remarkable heating-induced shrinking is observed. An increase of the wall thickness corresponding to the capsule diameter decrease is found. The morphology of these microcapsules after temperature treatment is characterized. The thickening of the polyelectrolyte multilayer is interpreted in terms of a configurational entropy increase via polyanion-polycation bond rearrangement. Received 20 January 2000     

Polyelectrolyte multilayer formation: Electrostatics and short-range interactions

We investigate the phenomenon of multilayer formation via layer-by-layer deposition of alternating charged polyelectrolytes. Using mean-field theory, we find that a strong short-range attraction between the two types of polymer chains is essential for the formation of multilayers. For strong enough short-range attraction, the adsorbed amount per layer increases (after an initial decrease), and finally it stabilizes in the form of a polyelectrolyte multilayer that can be repeated hundreds of times. For weak short-range attraction between any two adjacent layers, the adsorbed amount (per added layer) decays as the distance from the surface increases, until the chains stop adsorbing altogether. The dependence of the threshold value of the short-range attraction as function of the polymer charge fraction and salt concentration is calculated.     

Tribological behavior of in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films

Multilayer polyelectrolyte films containing silver ions were obtained by molecular deposition method on a glass plate or a quartz substrate. The in situ Ag nanoparticles were synthesized in the multilayer polyelectrolyte films which were put into fresh NaBH₄ aqueous solution. The structure and surface morphology of composite molecular deposition films were observed by UV-vis spectrophotometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tribological characteristic was investigated by AFM and micro-tribometer. It was found that the in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films have lower coefficient of friction and higher anti-wear life than pure polyelectrolyte molecular deposition films.     

Multilayering of a pseudo polyelectrolyte (PVPh) with a strong polyelectrolyte (PDMAC) from aqueous media

The introduction of pseudo polyelectrolytes (pPE) into the field of multilayer thin films has recently been achieved with the successful combination of poly(4-vinylphenol) (PVPh) with the weak polyelectrolyte (WPE), polyallylamine hydrochloride (PAH). This paper examines the stretching of this limit by exploring the extremes of using the pPE with the strong polyelectrolyte (SPE), poly(diallyldimethylammonium chloride) (PDMAC). UV-Vis absorbance and atomic force microscopy (AFM) topography data reveal a linear growth trend in film thickness that depends critically upon the assembly pH. At an assembly pH of 11.0 the multilayer was five times thicker compared to that assembled at pH 12.0. AFM topography images also show that the surface roughness of the films increases as the assembly pH decreases.     

Growth and structure of Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 thin films prepared by pulsed laser deposition technique

Bi_0.5(Na_0.7K_0.2Li_0.1)_0.5TiO₃ (BNKLT) thin films were prepared on Pt/Ti/SiO₂/Si substrates by pulsed laser deposition (PLD) technique. The films prepared were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effects of the processing parameters, such as oxygen pressure, substrate temperature and laser power, on the crystal structure, surface morphology, roughness and deposition rates of the thin films were investigated. It was found that the substrate temperature of 600 °C and oxygen pressure of 30 Pa are the optimized technical parameters for the growth of textured film, and all the thin films prepared have granular structure, homogeneous grain size and smooth surfaces.     

Picosecond nonlinear optical response of Ba0.5Sr0.5TiO3 thin films fabricated by pulsed laser deposition

Well-crystallized Ba_0.5Sr_0.5TiO₃ thin films with good surface morphology were prepared on MgO(1 0 0) substrates by pulsed laser deposition technique at a deposition temperature of 800 °C under the oxygen pressure of 2 × 10⁻³ Pa. X-ray diffraction and atomic force microscopy were used to characterize the films. The full width at half maximum of the (0 0 2) Ba_0.5Sr_0.5TiO₃ rocking curve and the root-mean-square surface roughness within the 5 μm × 5 μm area were 0.542° and 0.555 nm, respectively. The nonlinear optical properties of the films were determined by a single beam Z-scan method at a wavelength of 532 nm with laser duration of 55 ps. The results show that Ba_0.5Sr_0.5TiO₃ thin films exhibit a fast third-order nonlinear optical response with the nonlinear refractive index and nonlinear absorption coefficient being n₂ = 5.04 × 10⁻⁶ cm²/kW and β = 3.59 × 10⁻⁶ (m/W), respectively.     

Deposition of ZnO multilayer on LiNbO3 single crystals by DC-magnetron sputtering

Zinc oxide (ZnO) thin films were deposited on LiNbO₃ (LN) single crystals with 200 nm thicknesses by three different ways, where coating of zinc (Zn) film was followed by thermal oxidation for four, two, and one steps with 50, 100, and 200 nm thicknesses repeatedly. Sample, which was produced at 4-step of deposition and oxidation of Zn layer, showed high transmittance and low structural defect due to a lower photoluminescence intensity and Urbach energy. Average grain size in X-ray diffraction (XRD), scanning electron microscopy (SEM) micrograph, and atomic force microscopy (AFM) images for multilayer of ZnO was lower than monolayer of ZnO thin films. Applying multilayer coating technique leads to decrease of surface roughness and scattering on light on surface and fabrication of LiNbO₃ waveguides with lower optical loss.     

La0.5Sr0.5CoO3薄膜的外延生长及其机理研究

利用脉冲激光制膜法,在多种衬底和温度条件下,系统研究了La_0.5Sr_0.5CoO₃(LSCO)薄膜的结构和外延生长特性,在LaAlO₃,SrTiO₃和MgO衬底上实现了LSCO薄膜的外延生长.外延生长的薄膜具有低的电阻率和金属性导电特征.研究表明,外延生长的最佳温度范围为700—800℃,最佳衬底为LaAlO₃.并着重探讨了衬底材料和淀积温度等多种因素对LSCO薄膜的生长与性 关键词：     

Multilayer Bi1.5Zn1.0Nb1.5O7/Ba0.6Sr0.4TiO3/Bi1.5Zn1.0Nb1.5O7 thin films for tunable microwave applications

Bi_1.5Zn_1.0Nb_1.5O₇/Ba_0.6Sr_0.4TiO₃/Bi_1.5Zn_1.0Nb_1.5O₇ tunable multilayer thin film has been fabricated by pulsed laser ablation and characterized. Phase composition and microstructure of multilayer films were characterized by X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film has very smooth surface with RMS roughness of 1.5-2 nm and grain size of 100-150 nm. Total film thickness has been measure to be 375 nm. The BZN thin films at 300 K, on Pt(1 1 1)/SiO₂/Si substrate showed zero-field dielectric constant of 105 and dielectric loss tangent of 0.002 at frequency of 0.1 MHz. Thin films annealed at 700 °C shows the dielectric tunability of 18% with biasing field 500 kV/cm at 0.1 MHz. The multilayer thin film shows nonferroelectric behavior at room temperature. The good physical and electrical properties of multilayer thin films make them promising candidate for tunable microwave device applications.     

Lead-free ferroelectric BaTiO3 doped-(Na0.5Bi0.5)TiO3 thin films processed by pulsed laser deposition technique

The difficulties in synthesizing phase pure BaTiO₃ doped-(Na_0.5Bi_0.5)TiO₃ are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na_0.5Bi_0.5)TiO₃-0.08BaTiO₃, (BNT-BT_0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT_0.08, thin films deposited by PLD on Pt/TiO₂/SiO₂/Si substrates are investigated in this paper. Perovskite structure of BNT-BT_0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 °C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT_0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 μC/cm² and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT_0.08 thin film is ferroelectric at the nanoscale level and piezoelectric.     

利用［Fe/Pt］n多层膜降低L10-FePt有序化温度

采用直流磁控溅射方法制备了Fe/Pt多层膜和FePt单层薄膜，再经不同温度真空热处理得到 了有序相L10₀-FePt薄膜.通过x射线衍射谱和磁性研究表明，FePt单层薄膜需 要在500℃ 以上热处理，才能开始有序化转变，而Fe/Pt多层膜可以降低FePt薄膜有序化温度.［Fe(1 5nm)/Pt(15nm)］13₁₃薄膜在350℃热处理后，有序度已经增加到 06，相应矫 顽力达到了501kA/m.多层膜化促进有序化在较低的温度下进行，这是由于热处理过程中多 关键词： 0-FePt有序相')" href="#">L10₀-FePt有序相 磁控溅射 有序度 Fe/Pt多层膜     

Multi-layer structures including zigzag sculptured thin films for corrosion protection of AISI 304 stainless steel

To increase corrosion resistance of the sample,its electrical impedance must be increased.Due to the fact that electrical impedance depends on elements such as electrical resistance,capacitance,and inductance,by increasing the electrical resistance,reducing the capacitance and inductance,electrical impedance and corrosion resistance can be increased.Based on the fact that these elements depend on the type of material and the geometry of the material,multilayer structures with different geometries are proposed.For this purpose,conventional multilayer thin films,multilayer thin film including zigzag structure(zigzag 1)and multilayer thin film including double zigzag structure(zigzag 2)of manganese nitride are considered to protect AISI 304 stainless steel against corrosion in salt solution.These multilayer coatings including zigzag structures are prepared by alternately using the conventional deposition of thin film and glancing angle deposition method.After deposition,the samples are placed in a furnace under nitrogen flux for nitriding.The cross sections of the structures are observed by field emission scanning electron microscopy(FESEM).Atomic force microscope(AFM)is used to make surface analyses of the samples.The results show that the multilayer thin films including zigzag structures have smaller grains than conventional multilayer thin films,and the zigzag 2 structure has the smaller grain than the other two samples,which is attributed to the effect of shadowing and porosity on the oblique angle deposition method.Crystallography structures of the samples are studied by using x-ray diffraction(XRD)pattern and the results show that nitride phase formation in zigzag 2 structure is better than that in zigzag 1 structure and conventional multilayer thin film.To investigate the corrosion resistances of the structures,electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization tests are performed.The results reveal that the multilayer thin films with zigzag structures have better corrosion protection than the conventional multilayer thin films,and the zigzag structure 2 has the smallest corrosion current and the highest corrosion resistance.The electrical impedances of the samples are investigated by simulating equivalent circuits.The high corrosion resistance of zigzag 2 structure as compared with conventional multilayer structure and zigzag 1 structure,is attributed to the high electrical impedance of the structure due to its small capacitance and high electrical resistance.Finally,the surfaces of corroded samples are observed by scanning electron microscope(SEM).     

Polyelectrolyte adsorption

The problem of charged polymer chains (polyelectrolytes) as they adsorb on a planar surface is addressed theoretically. We review the basic mechanisms and theory underlying polyelectrolyte adsorption on a single surface in two situations: adsorption of a single charged chain, and adsorption from a bulk solution in θ solvent conditions. The behavior of flexible and semi-rigid chains is discussed separately and is expressed as function of the polymer and surface charges, ionic strength of the solution and polymer bulk concentration. We mainly review mean-field results and briefly comment about fluctuation effects. The phenomenon of polyelectrolyte adsorption on a planar surface as presented here is of relevance to the stabilization of colloidal suspensions. In this respect we also mention calculations of the inter-plate force between two planar surfaces in presence of polyelectrolyte. Finally, we comment on the problem of charge overcompensation and its implication to multi-layers formation of alternating positive and negative polyelectrolytes on planar surfaces and colloidal particles.     

Chemical bath deposition of hausmannite Mn3O4 thin films

A low-temperature chemical bath deposition (CBD) technique has been used for the preparation of Mn₃O₄ thin films onto glass substrates. The kinetic behavior and the formation mechanism of the solid thin films from the aqueous solution have been investigated. Structure (X-ray diffraction and Raman), morphological (atom force microscope), and optical (UV-vis-NIR) characterizations of the deposited films are presented. The results indicated that the deposited Mn₃O₄ thin films of smooth surface with nanosized grains were well crystalline and the optical bandgap of the film was estimated to be 2.54 eV.     

Preliminary investigations on the antibacterial activity of zinc oxide nanostructures

We have fabricated electroactive multilayer thin films containing ferritin protein cages. The multilayer thin films were prepared on a solid substrate by the alternate electrostatic adsorption of (apo)ferritin and poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) (NIPAAm-co-CIPAAm) in pH 3.5 acetate buffer solution. The assembly process was monitored using a quartz crystal microbalance. The (apo)ferritin/poly(NIPAAm-co-CIPAAm) multilayer thin films were then cross-linked using a water-soluble carbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide. The cross-linked films were stable under a variety of conditions. The surface morphology and thickness of the multilayer thin films were characterized by atomic force microscopy, and the ferritin iron cores were observed by scanning electron microscopy to confirm the assembly mechanism. Cyclic voltammetry measurements showed different electrochemical properties for the cross-linked ferritin and apoferritin multilayer thin films, and the effect of stability of the multilayer film on its electrochemical properties was also examined. Our method for constructing multilayer films containing protein cages is expected to be useful in building more complex functional inorganic nanostructures.     

Sensing charged macromolecules with nanocrystalline diamond-based field-effect capacitive sensors

The possibility of a label-free electrical detection of layer-by-layer adsorbed polyelectrolyte (PE) multilayers using a field-effect capacitive electrolyte-diamond-insulator-semiconductor (EDIS) structure is investigated. Positively charged synthetic polyelectrolyte PAH (Poly (allylamine hydrochloride)) and negatively charged PSS (Poly (sodium 4-styrene sulfonate)) have been used as a model system. Nanocrystalline diamond films were grown on p-Si-SiO₂ substrates by a microwave plasma-enhanced chemical vapor deposition from a mixture of methane and hydrogen. The EDIS sensors functionalized with charged macromolecules have been characterized by means of capacitance-voltage and constant-capacitance methods. Alternating shifts in the capacitance-voltage and constant-capacitance curves have been observed after the adsorption of each polyanion and polycation layer, respectively. The effect of the number of the adsorbed PE layers and polarity of the outermost layer on the sensor response is discussed.     

Multilayer films of cationic graphene-polyelectrolytes and anionic graphene-polyelectrolytes fabricated using layer-by-layer self-assembly

Extremely thin sheets of carbon atoms called graphene have been predicted to possess excellent thermal properties, electrical conductivity, and mechanical stiffness. To harness such properties in composite materials for multifunctional applications, one would require the incorporation of graphene. In this study, new thin film composites were created using layer-by-layer (LBL) assembly of polymer-coated graphitic nanoplatelets. The positive and negative polyelectrolytes used to cover graphene sheets were poly allylamine hydrochloride (PAH) and poly sodium 4-styrenesulfonate (PSS). The synthesized poly allylamine hydrochloride-graphene (PAH-G) and poly sodium 4-styrenesulfonate-gaphene (PSS-G) were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and thermo gravimetric analysis (TGA). The multilayer films created by spontaneous sequential adsorption of PAH-G and PSS-G were characterized by ultra violet spectroscopy (UV-vis), scanning electron microscopy (SEM), and AFM. The electrical conductivity of the graphene/polyelectrolyte multilayer film composites measured by the four-point probe method was 0.2 S cm⁻¹, which was sufficient for the construction of advanced electro-optical devices and sensors.     

Effect of deposition temperature on orientation and electrical properties of (K0.5Na0.5)NbO3 thin films by pulsed laser deposition

Lead-free ferroelectric K_0.5Na_0.5NbO₃ (KNN) thin films have been prepared on Pt/TiO₂/SiO₂/Si substrates by pulsed laser deposition process. The structures, crystal orientations and electrical properties of thin films have been investigated as a function of deposition temperature from 680 °C to 760 °C. It is found that the deposition temperature plays an important role in the structures, crystal orientations and electrical properties of thin films. The crystallization of thin films improves with increasing deposition temperature. The thin film deposited at 760 °C exhibits strong (0 0 1) preferential orientation, large dielectric constant of 930 and the remnant polarization of 8.54 μC/cm².