Thin film net metal-polymer composites

On the basis of carboxylated nitrocellulose were formed ordered micronets containing nanoparticles of nickel in their surface layer. The optimal conditions for a uniform coating with nickel of the polymer net film are as follows: activating the surface with solutions of tin(II) and palladium chlorides for 30–60 s and the action of the nickel developer for at least 3 min at 20°C.     

Thin film characterisation using backscattering spectrometry

The use of proton resonance backscattering spectrometry for the estimation of carbon as thin films formed on a target material is discussed. Conventional He backscattering experiments were also carried out on TiVN films formed on beryllium backing but the determination of stoichiometry of these films were difficult using conventional software for depth resolution.     

Thin films of coordination polymer magnets

Many applications of molecule based magnets, whether they are in information storage, displays, or as components in electronic or spintronic devices, will require putting the active materials on a surface or interfacing them with other components. Although there are many examples of molecule-based magnets, the families of tetracyanoethylene (TCNE) based magnets and Prussian-blue analogs possess materials properties that are close to those required for practical applications, and are the most advanced with respect to studies as thin films. This critical review focuses on fabrication and characterization of thin films of TCNE and Prussian-blue analog coordination polymer magnets. Emphasis is on current developments in thin film heterostructures and potential spintronics applications (135 references).     

The influence of polymer morphology on polymer film electrochemistry

The electrochemical behavior of functionalized polystyrene-coated electrodes shows a marked dependence on the nature of the electrolyte ions. Scanning electron microscope and surface profile measurements are presented which show that changes in polymer film volume and morphology accompany electrochemical oxidation. Changing polymer morphology by doping the films with soluble monomers during preparation is shown to produce large changes in electrochemical response. Diffusion coefficients were determined for a neutral organic dye dopant in each of the polymer films investigated, and these correlate very well with the oxidation overpotentials observed electrochemically. The nature of polymer film/solvent interactions and the mechanism by which counter ions penetrate the polymer phase is discussed and is related to other physical properties of amorphous polymers in terms of free volume concepts.     

Thin film analysis in the nanometer scale

A survey is presented on the present state of the art in analytical transmission electron microscopy (ATEM). An essential advantage of this method is the simultaneous use of imaging, analytical and microdiffraction techniques with a lateral resolution in the 1...5 nm range. Two different analytical techniques are frequently used as ATEM attachments, energy dispersive X-ray spectrometry (EDXS) and electron energy loss spectrometry (EELS). Microscopic images with nanometer resolution may be also produced by energy selected imaging (ESI) with characteristic energy loss electrons. Advantages and limitations of all these methods will be discussed using actual material problems in the field of thin film research.     

Thin film analysis in the nanometer scale

A survey is presented on the present state of the art in analytical transmission electron microscopy (ATEM). An essential advantage of this method is the simultaneous use of imaging, analytical and microdiffraction techniques with a lateral resolution in the 1.5 nm range. Two different analytical techniques are frequently used as ATEM attachments, energy dispersive X-ray spectrometry (EDXS) and electron energy loss spectrometry (EELS). Microscopic images with nanometer resolution may be also produced by energy selected imaging (ESI) with characteristic energy loss electrons. Advantages and limitations of all these methods will be discussed using actual material problems in the field of thin film research.     

Thin film order of symmetric diblock copolymers

The ordering in thin films of symmetric diblock copolymers of polystyrene and poly(methyl methacrylate) has been investigated by neutron reflectivity as a function of film thickness and temperature. The order-disorder transition in the thin films was found to lose its first order character in that the transition occurs in a continuous manner without the correlation length becoming infinite. In addition, a transition from a partially to fully ordered state was observed which was fully reversible. This transition depended in a power law manner on the film thickness and extrapolates to the bulk order-disorder transition temperature for thick films.     

Thin film interference of colloidal thin films

A stairlike colloidal crystal thin film composed of poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) monodispersed colloids was fabricated on an inclined silicon substrate. Different bright colors were observed on the various parts of the film with different layers as white light irradiated perpendicularly on it. The relationship between the colors and layers of the film was investigated and discussed according to the principle of thin film interference. On the basis of the phenomenon of thin film interference, a one-layer colloidal film having uniform color was researched and it would display diverse colors before and after swollen by styrene (St). A circular stairlike colloidal film was achieved to mimic the colors of the peacock tail feather.     

Two-dimensional self-healing hydrogen-bond-based supramolecular polymer film

A monolayer hydrogen-bond-based supramolecular polymer (HSP) film has self-healing properties at the two-dimensional limit after destroyed by tip of atomic force microscopy and it can also modify the SiO₂ dielectric for copper phthalocyanine field effect transistor with improved mobility.     

Thin film fabrication of PMMA/MEH-PPV immiscible blends by corona discharge coating and its application to polymer light emitting diodes

We introduce a new and facile process, corona discharge coating (CDC), to fabricate thin polymer films of the immiscible poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) and poly(methyl methacrylate) (PMMA) blends. The method is based on utilizing directional electric flow, known as electric wind, of the charged unipolar particles generated by corona discharge between a metallic needle and a bottom plate under high electric field (5-10 kV/cm). The electric flow rapidly spreads out the polymer solution on the bottom plate and subsequently forms a smooth and flat thin film over a large area within a few seconds. The method is found to be effective for fabricating uniform thin polymer films with areas larger than approximately 30 mm2. The thin films obtained by CDC exhibit unique microstructures where well-defined spherical and cylindrical domains of approximately 50 nm in diameter coexist. These nanosized domains are found to be much smaller than those in films made by conventional spin coating, which suggests that CDC is beneficial for fabricating phase-separated thin film structures with significantly increased interfacial areas. The effects of the applied voltage, tip-to-plate distance, and substrates on the film formation as well as the resulting microstructure are investigated. Furthermore, the light emitting performance of a device prepared by CDC is compared with one made by spin coating.     

Switching of the helical polymer conformation in a solid polymer film

A chiral photochromic polyisocyanate was incorporated into a solid polymer matrix of poly(methyl methacrylate) (PMMA), yielding an isotropic polymer film. Isomerization of the chiral photochromic azo side groups (cis‐trans) triggers a reversible conformational change of the helical polyisocyanate backbone. Thus the chirooptical properties of the film can be switched photochemically. The isomerization of the helix is much slower than the isomerization of the azo side groups. Below T_g , the photochemically modified helix conformation is thus stable, despite thermal relaxation of the azo chromophores.     

Thin film assembly of spider silk-like block copolymers

We report the self-assembly of monolayers of spider silk-like block copolymers. Langmuir isotherms were obtained for a series of bioengineered variants of the spider silks, and stable monolayers were generated. Langmuir-Blodgett films were prepared by transferring the monolayers onto silica substrates and were subsequently analyzed by atomic force microscopy (AFM). Static contact angle measurements were performed to characterize interactions across the interface (thin film, water, air), and molecular modeling was used to predict 3D conformation of spider silk-like block copolymers. The influence of molecular architecture and volume fraction of the proteins on the self-assembly process was assessed. At high surface pressure, spider silk-like block copolymers with minimal hydrophobic block (f(A) = 12%) formed oblate structures, whereas block copolymer with a 6-fold larger hydrophobic domain (f(A) = 46%) formed prolate structures. The varied morphologies obtained with increased hydrophobicity offer new options for biomaterials for coatings and related options. The design and use of bioengineered protein block copolymers assembled at air-water interfaces provides a promising approach to compare 2D microstructures and molecular architectures of these amphiphiles, leading to more rationale designs for a range of nanoengineered biomaterial needs as well as providing a basis of comparison to more traditional synthetic block copolymer systems.     

Thin film processing of axially modified phthalocyanine derivatives

A new class of hydroxyl terminated silicon phthalocyanine (SiPc) derivatives was prepared by capping dihydroxy SiPc with a variety of compounds containing two or more hydroxyl groups. The unique feature of these polyhydroxy SiPc derivatives is their function as crosslinkers that allows their processability into polyurethane films on reacting with isophorone diisocyanate. The films possess high impact resistance, thermostability at 125°C for over 10 h, and low absorption in the visible region. Solid polymeric films incorporating over 20% (w/w) of Pc rings were prepared without phase segregation. The kinetic parameters of polymerization, such as reaction conversion versus time and temperature, heat of reaction (ΔH), activation energy (ΔE), and reaction order (n) were investigated. Some of the polyhydroxy SiPc derivatives exhibit very high solubility in common organic solvents and possess adequate optical transparency for use as nonlinear optical materials in vision protection against laser light. © 1996 John Wiley & Sons, Inc.     

Thin film characterization by total reflection x-ray fluorescence

Sensitive and accurate characterization of films thinner than a few nm used in nanoelectronics represents a challenge for many conventional production metrology tools. With capabilities in the 10¹⁰ at/cm², methods usually dedicated to contamination analysis appear promising, especially Total-reflection X-Ray Fluorescence (TXRF). This study shows that under usual configuration for contamination analysis, with incident angle smaller than the critical angle of the substrate, TXRF signal saturation occurs very rapidly for dense films (below 0.5 nm for HfO₂ films on Si wafers using a 9.67 keV excitation at 0.5°). Increasing the incident angle, the range of linear results can be extended, but on the other hand, the TXRF sensitivity is degraded because of a strong increase of the measurement dead time. On HfO₂ films grown on Si wafers, an incident angle of 0.32° corresponding to a dead time of 95% was used to achieve linear analysis up to 2 nm. Composition analysis by TXRF, and especially the detection of minor elements into thin films, requires the use of a specific incident angle to optimize sensitivity. Although quantitative analyses might require specific calibration, this work shows on Co–based films that the ratio between minor elements (W, P, Mo) and Co taking into account their relative sensitivity factors is a good direct reading of the composition.     

Thin film deposition from hexamethyldisiloxane fed glow discharges

Hexamethildisiloxane-oxygen fed radiofrequency discharges have been studied under high power density and 0.05÷0.1 torr pressure, i.e., experimental conditions of high monomer fragmentation. Actinometric Optical Emission Spectroscopy of plasma phase, X-Ray Photoelectron Spectroscopy and Infrared Spectroscopy analyses of the deposited films allowed to set the basis of the first “semi-quantitative” mechanism of deposition of siloxane films which can reasonably account for both deposition rates and film compositions. A by-product of the research is the use of CH-to-Ar emission ratio as a probe of carbon content in the film, an important practical parameter for process control.     

Spontaneous film formation from a polymer solution

An unusual continuous film formation process of lateral pentyloxy substituted poly(p-phenylene terephthalate)s (s-PPPT) and poly(carbonate) (PC) is observed. A liquid film of polymer solution creeps over the surface of water dropped into the polymer solution. By vaporization of the solvent a solid polymer film is formed on the water surface and can be removed. The driving force for the film formation mechanism is assumed by the reduction of the surface tension of water. Experiments verify this mechanism by increasing the film formation speed using a gas stream, by reducing the formation speed through lowering the surface tension by rinsing agents, and by lowering the solubility of the polymer. As expected, no effects are found by variation of the pH-value of water. Necessary conditions for the film formation process are: good solubility of the polar polymers in organic solvents having a high vapor pressure, complete phase separation, solution density higher than water density, and a surrounding gas phase unsaturated with solvent vapor.The thickness of the mechanically stable films is less than 0.5 m. The films are amorphous by microscopical, FT-IR, x-ray, and DTA investigations.     

Effect of precipitants on polymer film porosity

IR spectroscopy and electron microscopy have been employed to study the effect of precipitants on the formation of porous structures in poly(vinyl alcohol)-based and modified polyacrylonitrile-based polymer films prepared by the wet casting method. Conditions for formation of porous structures in the polymer films are established as depending on parameters of solubility and pH of precipitants. The spectral method is tested for studying porosity of polymer materials in near and medium IR regions.