Multilayer Composite Films Research Articles

Characteristics of Sn/Li 2O multilayer composite anode for thin film microbattery

Sputtering growth of a Sn/Li 2O multilayer composite thin film is conducted to produce an anode thin film with less capacity fading than that of a pure SnO 2 film for a thin-film battery. The structural properties of the Sn/Li 2O multilayer are examined. In addition, the electrochemical characteristics of the Sn/Li 2O and pure SnO 2 thin films are compared. X-ray diffraction and transmission electron microscopy measurements reveal a Sn crystalline peak only and a Sn–Li 2O multilayer structure, respectively, in the Sn/Li 2O thin film. A SnO 2 thin film with a polycrystalline phase shows an irreversible side-reaction at 0.8 V versus Li/Li +, an initial charge retention of about 29%, and poor cycleability in the cut-off voltage range from 1.2 to 0 V versus Li/Li +. By contrast, no irreversible side-reaction is found in the Sn/Li 2O multilayer composite thin film while there is an initial charge retention of 49% and better cycleability (more than twice) than that of pure SnO 2 film after about 150 cycles. These results indicate that the Sn/Li 2O multilayer composite thin film can be used for tin-based, thin-film, microbatteries and provide motivation to pursue fabrication of Sn–Li 2O anode powder for bulk type batteries.

Preparation and tribological studies of nanocomposite films fabricated using spin-assisted layer-by-layer assembly

Uniform and smooth composite multilayer films composed of gold nanoparticles and polyelectrolytes ([Au/(PAH-PSS) n PAH] m ) multilayers were fabricated on a silicon substrate using a time-and cost-efficient spin-assisted layer-by-layer (SA-LbL) self-assembly technique. The microstructure and morphology of the multilayer films were characterized by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The tribological behavior of the composite multilayer films was evaluated using a ball-on-plate tribometer. It was found that the density of the monolayer of gold nanoparticles on the silicon substrate was dependent on the deposition time, but the coverage of the Si substrate by the gold nanoparticle kept almost unchanged at a deposition duration above 30 min. The antiwear life and load-carrying capacity of the [Au/(PAH-PSS) n PAH] m composite film substantially increased with increasing number of the polymer bilayers and gold nanoparticles monolayer, which could be attributed to the robust organic–inorganic nanocomposite structure and PAH and PSS fragments transferred onto the counterpart surface.

Microstructure and magnetic properties of (001) oriented FePt∕B4C composite films

FePt ∕ B 4 C multilayer composite films have been prepared by magnetron sputtering and subsequent annealing in vacuum. It was found that the B4C layers effectively serve as spacers to separate the FePt layers, enhancing (001) orientation of FePt alloy. Our results show that highly (001) oriented [Fe45Pt55(8 nm)∕B4C (4 nm)]3 film with satisfactory perpendicular coercivity (4.75 kOe) has significant potential as a perpendicular recording medium.

Electrochemical and photoelectrochemical study on exfoliated Nb 3O 8 nanosheet

Transition metal oxide nanosheet of Nb 3O 8 was synthesized by delaminating a layered host compound of KNb 3O 8. Ultrathin two-dimensional morphology, about 1 nm thickness vs. submicrometer lateral size, was revealed by atomic force microscopy. The colloidal nanosheets were assembled layer-by-layer with polycation onto an indium-tin-oxide (ITO)-coated glass electrode via sequential adsorption technique. UV–vis absorption spectra in the assembly process showed the linear enhancement of absorbance at 270 nm per deposition cycle, indicating the successful formation of multilayer composite films, which can be converted into polymer free films upon exposure to UV light. The cyclic voltammogram of resulting Nb 3O 8 nanosheet film electrodes exhibited reduction/oxidation (Nb 4+/Nb 5+) peaks at −1.2 V (vs. Ag/Ag +) attributable to insertion and deintercalation of Li + ions into and from the nanosheet galleries. The reaction (reduction/oxidation) ratio of the electroactive Nb atom in Nb 3O 8 nanosheet was calculated to be 6.3% by integrating a charge transfer in a sweep range of +1.0 to −1.9 V. The Nb 3O 8 nanosheet electrode generated anodic photocurrent in response to UV illumination. Analysis on the photocurrent action spectrum indicated that Nb 3O 8 nanosheet is an indirect transition-type semiconductor with bandgap energy of 3.58 eV. The flat-band potential was estimated to be −1.32 V vs. Ag/Ag + from the applied potential dependence.

Microstructure evolution, magnetic and mechanical properties of FePt/B4C multifunctional multilayer composite films

FePt/B4C multilayer composite films with a Fe/Pt two-layer structure and a Fe/Pt/Fe sandwich structure were prepared by magnetron sputtering and subsequent annealing in vacuum. When the B4C interlayer thickness of the FePt/B4C films is bigger than 3 nm, a stable value of grain size, coercivity and hardness is observed. The characterizations of the microstructure demonstrate that the diffusion of B and C atoms in the FePt layer is so finite that the multilayer structure of the FePt/B4C films is maintained after annealing at 500 °C for 30 min. The finite diffusion of B and C atoms is responsible for the FePt grain growth confinement, grain and layer separation and eventually induces the stable value mentioned above. The single composite films may find application in substituting the traditional three-layer structure commonly used in the present data storage technology.

Effect of interfacial diffusion on microstructure and properties of FePt/B 4C multifunctional multilayer composite films

FePt/B 4C multilayer composite films were prepared by magnetron sputtering and subsequent annealing in vacuum. By changing Fe layer thickness of [Fe/Pt] 6/B 4C films, optimal magnetic property (8.8 kOe and remanence squareness is about 1.0) is got in [Fe(5.25 nm)/Pt(3.75 nm)] 6/B 4C sample whose composition is Fe rich and near stoichiometric ratio. The characterizations of microstructure demonstrate that the diffusion of B and C atoms into FePt layer depends strongly on B 4C interlayer thickness. When B 4C interlayer thickness of [Fe(2.625 nm)/Pt(3.75 nm)/Fe(2.625 nm)/B 4C] 6 films is bigger than 3 nm, stable value of grain size (6–6.5 nm), coercivity (6–7 kOe) and hardness (16–20 GPa) is observed. Finally, the multifunctional single FePt/B 4C composite film may find its way to substitute traditional three-layer structure commonly used in present data storage technology.

Layer-by-layer composite films of polyaniline and vanadium pentoxide sol gels studied by electrochemical surface plasmon spectroscopy

Electroactive multilayer films of polyaniline (PAni) and vanadium pentoxide (V2O5) sol-gels were prepared on gold surfaces by means of the layer-by-layer (LBL) method. The stepwise buildup and the optoelectrochemical behaviour of the composite films were investigated in-situ by electrochemical surface plasmon spectroscopy (ESPS). A thickness increment of 2.3 nm per deposited bilayer was obtained by modelling the surface plasmon spectra. The composite multilayer films display charging-discharging characteristics similar to a bare vanadium pentoxide xerogel network along with an optoelectrochemical response which is dominated by the conducting polymer component. Electrochemical impedance spectroscopy (EIS) experiments confirm the findings from ESPS with regard to the presence of different conductive states of the composite.

Preparation and characterization of conducting poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) Langmuir–Blodgett film

The self-assembly of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) nanoparticles at an air/water interface was achieved by means of the electrostatic force between an octadecylamine (ODA) monolayer and PEDOT-PSS nanoparticles. A surface pressure ( π)–area ( A) isotherm and X-ray photoelectron spectroscopy of the composite film were used to confirm the electrostatic force between the SO 3 − group of PSS and the NH 4 + group of aliphatic amines. Monolayer and multilayer composite films of ODA/PEDOT-PSS and ODA-stearic acid (SA)/PEDOT-PSS were fabricated. These solid Langmuir–Blodgett films were investigated by the UV–Vis spectrum, atomic force microscopy, and X-ray diffraction method. It is observed that ODA-SA/PEDOT-PSS films had a higher film-forming capability than ODA/PEDOT-PSS films and an ordered multilayer structure was developed. The conductive properties of ODA-SA/PEDOT-PSS LB films were investigated in detail. Factors influencing the film conductivity such as the layer number and surface pressure were discussed and the conductive mechanism was also studied.

Surface plasmon resonance and electrochemistry characterization of layer-by-layer self-assembled DNA and Zr 4+ thin films, and their interaction with cytochrome c

Through electrostatic layer-by-layer (LbL) assembly, negatively charged calf thymus double stranded DNA (CTds-DNA), and positively charged Zr 4+ ions were alternately deposited on gold substrate modified with chemisorbed cysteamine. Thus-prepared three-dimensional DNA networks were characterized by surface plasmon resonance (SPR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and infrared reflection–absorption spectroscopy (IR-RAS). SPR spectroscopy indicates that the effective thickness of DNA monolayer in the (DNA/Zr 4+) 1 bilayer was 1.5 ± 0.1 nm, which corresponds to the surface coverage of 79% of its full packed monolayer. At the same time, a linear increase of film thickness with increasing number of layers was also confirmed by SPR characterizations. The data of XPS and IR-RAS show that Zr 4+ ions interact with both the phosphate groups and nitrogenous bases of DNA and load into the framework of DNA. Furthermore, the interactions between this composite film and heme protein cytochrome c (Cyt c) were investigated by SPR spectroscopy and electrochemistry. Compared with the adsorption of Cyt c on DNA monolayer, this composite multilayer film can obviously enhance the amount of immobilized Cyt c confirmed by SPR reflectivity-incident angle (R- θ) curves. Cyclic voltammetry (CV) indicates the Cyt c adsorbed on the composite film is electroactive, and the enhancement of peak current in CV indirectly verifies the increase of the amount of immobilized Cyt c.

Nacre-like TiO2 - and ZnO- Based Organic / Inorganic Hybrid Systems

ABSTRACTA bioinspired approach combining chemical bath deposition (CVD) of oxides with layer-by-layer (LBL) assembly of organic polymers has been used to prepare two different types of organic/inorganic multilayer composite films, whose morphology resembles that of naturally occurring nacre. Both process steps allow for a precise control of the layer thickness, thus enabling to tailor the architecture of the multilayer composites. The first type of composite films comprised of TiO2 layers, separated by organic interlayer composed of several oppositely charged polyelectrolytes, while the second type of composite films contained ZnO as the inorganic and poly (amino acids) as the organic component. AFM investigations revealed a granular structure of the inorganic layers which originates from the oxide particles. TEM investigation disclosed that the TiO2 particles are amorphous, while the ZnO particles are crystalline. Moreover, TEM cross-sectional analysis of the composite films confirmed the presence of inorganic layers that are well-separated by organic layers, although signatures of partial interpenetration have been observed at the interfaces. The hardness and Young's modulus of both types of composite films, as determined by nanoindentation testing, increased in comparison to the monolithic oxide films. The enhanced mechanical performance underlines the effectiveness of combining layers of different shear moduli into an alternate architecture.

Photoluminescence from Au nanoparticles embedded in Au:oxide composite films

Au:oxide composite multilayer films with Au nanoparticles sandwiched by oxide layers (such as SiO2, ZnO, and TiO2) were prepared in a magnetron sputtering system. Their photoluminescence (PL) spectra were investigated by employing a micro-Raman system in which an Argon laser with a wavelength of 514 nm was used as the pumping light. Distinct PL peaks located at a wavelength range between 590 and 680 nm were observed in most of our samples, with Au particle size varying from several to hundreds of nanometers. It was found that the surface plasmon resonance (SPR) in these composites exerted a strong influence on the position of the PL peaks but had little effect on the PL intensity.

Nanosized multilayer films with concurrent photochromism and electrochromism based on Dawson-type polyoxometalate

An inorganic–organic composite multilayer film constructed of poly(vinyl alcohol) (PVA) with Dawson-type phosphotungstate anion [P 2W 18O 62] 6− (P 2W 18) and poly(allylamine hydrochloride) (PAH) were fabricated on quartz, ITO, silicon and CaF 2 substrates by a layer-by-layer self-assembly method. The film was provided with concurrent photochromism and electrochromism. IR spectra showed that the structure of the PVA was fully maintained in the multilayer film. And their photochromic and electrochromic properties were investigated by UV–vis spectra, cyclic voltammetry (CV), chronoamperometry (CA) measurement and X-ray photoelectron spectra (XPS). Atomic force microscopy (AFM) was used to investigate the surface topography. This study provides a new route to explore the possibility of application to polyoxometalate-based hybrid inorganic–organic materials.

Layer-by-Layer assembly and humidity sensitive behavior of poly(ethyleneimine)/multiwall carbon nanotube composite films

Raw CVD grown multiwall carbon nanotubes (MWCNTs) were oxidized in a mixture of concentrated sulfuric acid and nitric acid to obtain water soluble MWCNTs. Composite multilayer films of the oxidized MWCNTs and poly(ethyleneimine) (PEI) were fabricated through the layer-by-layer (LbL) assembly approach. The oxidized MWCNTs were characterized with Fourier transform infrared spectroscopy. The LbL assembly process of the multilayer films was monitored with a UV–vis spectrophotometer. The surface and sectional morphology of the films were observed under a Schottky field emission scanning electron microscope. On the assembled thin films, two parallel metal electrodes were vapor deposited. The resistance between the two electrodes was measured at different relative humidity levels at room temperature. The data show that the resistance increases with increasing the relative humidity over the range of 5–97% RH and that, in the range of 5–85% RH, the resistance increases almost linearly. The experimental data also show that the humidity sensitive multilayer films have response and recovery times of about 2 and 30 s, respectively.

Composite Thin Film by Hydrogen-Bonding Assembly of Polymer Brush and Poly(vinylpyrrolidone)

Based on hydrogen-bonding layer-by-layer (LBL) assembly in aqueous solution, poly(vinylpyrrolidone) (PVPON) and a spherical polymer brush with a poly(methylsilsesquioxane) (PSQ) core and poly(acrylic acid) (PAA) hair chains were used to fabricate composite multilayer thin films. Hydrogen bonding as the driving force was confirmed by FT-IR spectrometry. A simple method (Filmetric F20) was introduced to determine the thickness and refractive index of the films. The film thickness was found to be a linear function of the number of bilayers. The average increase in thickness per bilayer is 28.3 nm. The film morphology was characterized with scanning electron microscopy and atomic force microscopy. The images obtained from the two instruments show a great resemblance. The films were further calcined to get an inorganic film by removing the organic components, or treated with tetrabutylammonium fluoride (TBAF) to remove the PSQ core and get an organic film. The optical properties and morphological changes induced by these treatments were also studied.

Layer-by-layer assembly of polyelectrolyte/TiO2 thin films with reflection-enhancing function

Abstract Colloidal TiO 2 was prepared by hydrolyzing tetra- n -butyl titanate. Composite multilayer films of poly(sodium 4-styrenesulfonate) (PSS) and colloidal TiO 2 particles were layer-by-layer assembled onto optic fibers and microscope glass slides. As the PSS/TiO 2 film was deposited onto the end face of a glass fiber, the reflected optic intensity periodically oscillated as the bilayer number of the film increased. After a 24-bilayer film was coated onto the both sides of a glass slide, the transmittance at 850 nm decreased more than 20%, which means that the film could serve the function as a reflection-enhancing coating. X-ray diffraction analysis and data of TEM electron diffraction analysis show that the colloidal TiO 2 particles are mainly brookite nanocrystals and that the PSS/TiO 2 films are polycrystalline films. Scratching experiments indicate that the composite films are of relatively high hardness.

Multicomponent Patterning of Layer‐by‐Layer Assembled Polyelectrolyte/Nanoparticle Composite Thin Films with Controlled Alignment

Composite thin films of polyelectrolytes and fluorescent nanoparticles can be directly transfer-printed onto various substrates including indium tin oxide coated poly(ethylene terephthalate). The sequential transfer printing of thin films with controlled alignment introduces multicomponent patterns onto substrates, demonstrating possible practical device fabrication using functional polyelectrolyte multilayer composite thin films (see Figure).

NONLINEAR OPTICAL PROPERTIES OF AU:TiO2 MULTILAYER COMPOSITE FILMS

Au:TiO 2 multilayer composite films were prepared by the method of alternating multitarget magnetron sputtering technique. Samples were annealed afterwards. The surface plasmon resonances of the annealed films are around 700nm. TEM pictures showed the remained layered structure with grown gold particles between the layers. The values of χ(3) measured by degenerated four wave mixing (DFWM) are in the order of 10-7 esu which are one order larger than the previous work. The figure of merit (FOM), χ(3)/α, is in the order of 10-12 esu cm. The great improvement of χ(3) is assumed to be the result from the enhancement of field localization caused by the metallic/dielectric host multilayer structure.

Preparation and characterization of Au/SiO2 multilayer composite films with nonspherical Au particles

Au/SiO2 multilayer composite films containing nonspherical Au particles were prepared by a magnetron sputtering method. Uniform size and shape distributions of Au particles were obtained in these films. Au particles embedded in these films can be shaped into spheres or ellipsoids by controlling the thickness of the Au layer, and the thermal annealing temperature and time duration. Their linear optical properties were characterized in the wavelength range between 300–1000 nm. Their effective nonlinear optical susceptibility, χ(3), was found to be much larger than that prepared by the cosputtering method at low Au volume fraction. We attributed the enhancement of the value of χ(3) to the more uniform size and shape distribution, as well as the higher two-dimensional metal particle density in the multilayer films.

Electrostatically self-assembled multilayer film formed by a novel ruthenium(II) complex and [Nd(SiW 9Mo 2O 39) 2] 13−

A new ultrathin composite multilayer film was prepared by alternating adsorption of [Nd(SiW 9Mo 2O 39) 2] 13− and a novel Ru(II) complex cation of [Ru(bpy) 2(BPBH)] 2+ (in which BPBH = 1,6-bis-((2-(2-pyridyl)benzimidazoyl))hexane, bpy = 2,2′-bipyridine) by electrostatic layer-by-layer self-assembly technique. The multilayer film was characterized by UV–vis spectroscopy and cyclic voltammetry. The results showed that the film was grown regularly and was of good electrochemical activity.

Improving multilayer films endurance by photoinduced interaction between Dawson-type polyoxometalate and diazo resin

A composite multilayer film constructed of Dawson anion [P 2Mo 18O 62] 6− and diazo resin (DR) was prepared by the electrostatic layer-by-layer (LbL) self-assembly method. The film could be stabilized by the photoinduced interaction between Dawson anion and diazo resin. IR spectra and X-ray photoelectron spectra revealed the possible occurrence of partial transformation from electrostatic interaction to covalent interaction between layers of the film after irradiation by UV light. Such transformation evidently increases the endurance of the film, which was demonstrated by AFM images and etching experiments with organic solvent. This study provides a new route to stabilze the polyoxometalate-based multilayer film by virtue of the photoinduced reaction with photosensitive polymer.