Structure Formation In Thin Films Research Articles

Vehicle transmission lubrication technology using surface-active films

The process of polarization of a lubricant when exposed to an electric potential is considered. A model is presented for the formation of thin film structures on friction surfaces that realize the effect of selective transfer during electrochemical processes with electric field control. The results of experimental studies of the wear resistance of prototypes under various physical and mechanical conditions using electric fields are presented. A comparative analysis of the wear resistance of materials showed a greater protective ability of polarized lubricants. Keywords transmission, lubrication, process, polarization, wear resistance, experimental, research, analysis

Investigation of structure formation in thin films by means of optical pyrometry

The paper presents an approach to the identification of structural and phase changes in high-speed processes of spraying coatings and high-temperature synthesis of three-dimensional products from metal and ceramics. A method for evaluating the spectral degree of blackness of materials by means of optical pyrometry is described. An experimental complex was developed to study the degree of blackness of the surface of molybdenum, tantalum and tungsten foils in the process of stationary heating by electric current. The results of complex experimental studies are presented, showing that a jump in emissivity makes it possible to detect a change in the aggregate state of matter (liquid - solid), phase transitions, exo- and endothermic reactions in thin films, and also to determine characteristic temperatures with an error of 0.1–1.5%.

Correlation study of nanocrystalline carbon doped thin films prepared by a thermionic vacuum arc deposition technique

The synthesis of Ag, Mg and Si nanocrystalline, embedded in a hydrogen-free amorphous carbon (a-C) matrix, deposited by a high vacuum and free buffer gas technique, were investigated. The films with compact structures and extremely smooth surfaces were prepared using the thermionic vacuum arc method in one electron gun configuration, on glass and silicon substrates. The surface morphology and wettability of the obtained multifunctional thin films were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and free surface energy (FSE) by See System. The results from the TEM measurements show how the Ag, Mg and Si interacted with carbon and the influence these materials have on the thin film structure formation and the grain size distribution. SEM correlated with EDX results reveal a very precise comparative study, regarding the quantity of the elements that morphed into carbides nanostructures. Also, the FSE results prove how different materials in combination with carbon can make changes to the surface properties.

Insights into poly(3‐hexylthiophene)‐b‐poly(ethylene oxide) block copolymer: Synthesis and solvent‐induced structure formation in thin films

AbstractWe report the synthesis, characterization, and solvent‐induced structure formation in thin films of an amphiphilic rod‐coil conjugated block copolymer, poly(3‐hexylthiophene)‐b‐poly(ethylene oxide). The diblock copolymers were prepared by a facile click reaction and their characterizations as well as thermal, crystalline, optical properties, and self‐assembly behavior have been investigated in detail. A series of morphologies including two‐phase separated nanostructure, nanofibrils, and their mixed morphology could be obtained depending on the selectivity of solvents to different blocks. Structural analyses demonstrate there is a subtle balance between microphase separation of copolymer and the π‐π stacking of the conjugated P3HT and such balance can be controlled by changing the solvents of different selectivity in solution and the length of P3HT block. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Impact of nanoparticle size and shape on selective surface segregation in polymer nanocomposites

A study of the impact of the size and shape of a nanoparticle on the evolution of structure and surface segregation in polymer nanocomposite thin films is presented. This is realized by monitoring the evolution of structure with thermal annealing and equilibrium depth profile of a deuterated polystyrene/protonated polystyrene bilayer in the presence and absence of various nanoparticles. For the three shapes examined, sheet-like graphene, cylindrical carbon nanotubes, and spherical soft nanoparticles, the presence of the nanoparticles slowed the inter-diffusion of the polymers in the thin film. The larger nanoparticles slowed the polymer motion the most, while the smaller spherical nanoparticles also significantly inhibited polymer chain diffusion. At equilibrium, the soft spherical nanoparticles, which are highly branched, segregate to the air surface, resulting in a decrease in the excess deuterated PS at the surface. The graphene sheets and single walled carbon nanotubes, on the other hand, enhanced the dPS segregation to the air surface. The graphene sheets were found to segregate to the silicon surface, due to their higher surface energy. Interpretation of these results indicates that entropic factors drive the structural development in the nanocomposite thin films containing the spherical nanoparticles, while a balance of the surface energies of the various components (i.e. enthalpy) controls the thin film structure formation in the polymer-carbon nanoparticle nanocomposites.

Photoinduced formation of thin-film structures in titanium alkoxides via direct deposition from solution and from spin-coated solid-state precursor films

Abstract

Methods of parallel integration of carbon nanotubes during the formation of functional devices for microelectronics and sensor technologies

Methods of formation of thin film structures and sensor elements based on carbon nanotubes have been developed. Methods of integration using deposition from solutions, probe micromechanics and the electrokinetic positioning of nanotubes providing compatibility with traditional microelectronic technology, are suggested. Peculiarities of the parallel integration of carbon nanotubes in the process of formation of thin films, networks, and individual conduction channels are revealed.

Field-induced layering of confined ferromagnetic nanoparticles: the role of attractive interactions

We present Molecular Dynamics simulation results for confined ferromagnetic nanoparticles (film geometry) under the influence of strong, homogeneous magnetic fields. We focus on the role of short-ranged attractive interactions between the particles for the structure formation in thin films consisting of four to five monolayers. To this end we compare simulation results for Stockmayer particles (Lennard-Jones plus dipolar interactions) with corresponding results for dipolar soft spheres, where the short-ranged potential is purely repulsive. At moderate and large average densities, both systems exhibit pronounced layering. Based on the corresponding normal pressure oscillations we show that the field-induced effects on the layer formation in this density range are essentially independent of the short-range interactions. The dipolar soft sphere system merely has a stronger tendency to form a crystal-like lateral structure upon application of a parallel field. More pronounced differences occur at lower densities and not too high dipolar coupling strengths within the vapour–liquid region of the confined, zero-field Stockmayer system. Applying a perpendicular field, the Stockmayer system develops a blob structure absent in the corresponding repulsive system. Finally, for very large values of both, dipolar coupling parameter and field strength of a perpendicular field, we find evidence for a field-induced in-plane crystallisation of the layered systems.

Characterization of the dynamics of block copolymer microdomains with local morphological measures

We investigate the structure formation in thin films of cylinder forming block copolymers. With in situ scanning probe microscopy image sequences can be recorded with high temporal (2 min per frame) and spatial (10 nm) resolution. We compare different image processing methods for quantitative analysis of the large amount of data. Computing local Minkowski functionals yields local geometrical and morphological information about the observed structures and enables us to track their evolution with time. An alternative characterization method is to reduce the gray scale images to their skeleton and to classify and count the branching points of the skeletonized structure. We tracked the temporal evolution of these measures and computed correlation functions.

Effect of fluorescent labeling of β-lactoglobulin on film and interfacial properties in relation to confocal fluorescence microscopy

When using fluorescence microscopy for the investigation of β-lactoglobulin (BLG) stabilized thin liquid films and monolayers, it is necessary to label the protein sample with a fluorescent dye. In the present study, we discuss the effect of labeling β-lactoglobulin with either Rhodamine iso-thiocyanate (RITC) or Fluorescein iso-thiocyanate (FITC) on the BLG properties at the air–water interface and in thin films. RITC and FITC are the two most frequently used dyes in fluorescence microscopy. Two different Rhodamine concentrations were used, namely the concentration conventionally used in fluorescence microscopy, and a two times higher Rhodamine concentration. Interfacial tension and rheology measurements, and thin film investigations using X-ray reflectivity or the diminishing bubble method showed that the labeling procedure of the β-lactoglobulin using Rhodamine at the lowest concentration does not change the viscoelastic properties of the air–water interface, as well as the film thickness and gas permeability. However, when taking the higher Rhodamine concentration the films are thicker and more permeable for gas. Similarly, Fluorescein at a concentration equivalent to the highest concentration of Rhodamine induced also a modification of the protein film properties. However, the labeling did not influence the BLG monolayer viscoelastic characteristics. Labeling β-lactoglobulin with Rhodamine allows now using confocal fluorescence microscopy (CSLM) for the elucidation of structure formation in thin films and at water–air surfaces. As an example, images from thin films as formed in the diminishing bubble experiment and stabilized with labeled BLG show that the formed BLG aggregates are highly surface active, i.e., enriched at the water–air interface. The obtained images reveal that the aggregates are also present in the film. In general, CSLM combined with the diminishing bubble method seems to be an excellent experimental set-up to visualize the distribution of labeled components throughout a thin film and its adjacent monolayers. This is not possible using the diminishing bubble method in combination with conventional microscopy.

Fourier transform infrared spectroscopy study of molecular structure formation in thin films during hexamethyldisiloxane decomposition in low pressure rf discharge

The growth of plasma deposited organic films in general is non-homogeneous, i.e. the films can consist of several layers: substrate–film interface and cross-linked bulk plasma polymer. The fourier transform infrared spectroscopy study shows evidence for a substrate–film interface layer that appears to be formed during a gas conversion in a discharge. The reflection–absorption spectroscopy and evanescent wave spectroscopy techniques have been used to analyse the evolution of molecular structure of the films growing in hexamethyldisiloxane (HMDSO) plasmas of a low pressure capacitive rf (13.56 MHz) discharge. The pulsed operation mode of the rf discharge was used in order to provide successive steps of the HMDSO plasma–chemical conversion into stable neutral products, which were monitored by mass spectrometry. The HMDSO conversion exerts influences on the film deposition resulting in a gradient in the molecular structure of the growing films. The comparison of the film growth on substrates at floating and rf self-bias potentials shows that ions control the deposition kinetics and influence the molecular structure of films.

Nanostructured Thin Films via Self-Assembly of Block Copolymers

Thin films of incompatible block copolymers self-assemble into highly regular supramolecular structures with characteristic dimensions in the 10-100 nm regime. There is increasing interest in controlling the resulting structures and utilizing them, for instance in the area of nanotechnology. So far, research has concentrated mainly on exploiting the melt structure of diblock copolymers. Recent work on block copolymer solutions and more complex co- and terpolymer architectures has revealed a rich variety of novel thin-film structures, some of which exhibit high complexity and order. In addition, by use of mean field dynamic density functional theory along with well-controlled experiments, the fundamentals of thin film structure formation have been elucidated. We highlight some aspects of these studies and point to future directions in this lively field of materials science.

Quasi-crystalline structure formation in thin films

Experimental techniques used for preparing quasi-crystalline (QC) thin filmsare reviewed. Results of experiments in which the QC phase formation was produced by high temperature (575 K) successive deposition (HTSD) of aluminium and a transition metal are discussed in detail. It is shown that HTSD-prepared thin films are suitable model systems for studying the elementary processes and kinetics of QC phase formation. A model consisting of nucleation, growth and coalescence of QC grains as well as perpendicular growth of the continuous film is proposed for the description of QC film growth. Auger depth profiling and energy-dispersive X-ray analysis of cross-sectional transmission electron microscopy samples of the Al/QC layer system proved the homogeneity o( a thick (approximately 0.5 μm) QC film and gave a composition of 80 at.%A1-20 at.% Mn for the OC phase. It has been determined that the reaction producing the QC phase takes place at the free surface of the QC phase in the case of HTSD, and aluminium is transported through the QC layer to the reaction sites. The formation of voids in the host aluminium films indicates that there exist specific sites in these films, possibly resulting from defects, which are the sources of aluminium diffusion.