Initial Film Research Articles

Influence of Low-Temperature Annealing on the Electrical Conductivity of SiOx Films

In this paper, the results on the conductivity of silicon enriched SiOx films and the influence of low temperature annealing at 450 °C in the H2 and vacuum are presented. SiOx films were prepared on Si substrate by low pressure chemical vapor deposition (LP CVD) with using SiH4, N2O as the precursor gases and H2 as a carrier gas. The measurements of current-voltage characteristics were carried out in the wide temperature range 95-334 K. It was revealed that the influence of atmosphere of the low temperature annealing is significant. In general case it was established that after the annealing of the initial film in the hydrogen the conductivity increases and after annealing in the vacuum decreases. Characteristic feature of all films (without and with annealing) is the conductivity according to the Mott’s law at low voltages (U < 1 V) in temperature range 295 < T < 345 K. The calculated densities of electron states (traps) in bandgap near the Fermi level from slope of curves in Mott’s coordinate are equal to N = 2.12 × 1017 eV−1 × cm−3 (initial film), N = 4.14 × 1019 eV−1 × cm−3, (H2), N = 6.62 × 1016 eV−1 × cm−3 (vacuum). At higher voltages and lower temperature another transport mechanisms have been revealed. Among them are space-charge limited current (SCLC), Poole-Frenkel mechanism and Fowler-Nordheim tunneling.

Energy conversion during the crown evolution of the drop impact upon films

The energy conversion is proposed to analyze the effects of inertial force, surface tension, gravitational force and viscous force during the crown evolution of the drop impact phenomena. The incompressible laminar Navier–Stokes equations coupled with the volume of fluid model are solved numerically in the axisymmetric frame to simulate the impact process. The influences of both the ratio of the initial kinetic energy to the surface tension energy of the drop as well as the initial film thickness on the energy conversion during the impact process are studied in detail. The ratio of the initial kinetic energy to the surface tension energy of the drop can affect the energy conversion at a very early stage of the impact process, thus it can affect the occurrence of prompt splash significantly; while the initial film thickness can affect the energy conversion process during the whole impact process, and it is related to the occurrence of delayed splash. The energy conversion process corresponds to the type of impact phenomena, which is affected by the film depth significantly. according to the differences in energy curves and flow characteristics, the impact phenomenon is divided into three types: the drop impacts on shallow, medium and deep films. A typical impact process of the medium film is analyzed in detail. The impact process is divided into five stages, namely, crown formation, crown growth, crown stabilization, crown collapse and central jet formation. In the crown formation and growth stages, inertial force promotes the deformation of the liquid-gas interface and surface tension prevents the deformation; while in the crown collapse stage, inertial force prevents the deformation and surface tension does the opposite effect. During the whole process, the viscous force plays a prevention effect.

Enhanced piezoelectricity of a PVDF-based nanocomposite utilizing high-yield dispersions of exfoliated few-layer MoS2

Abstract Piezoelectric polymer composite films have attracted extensive attention due to their comprehensive characteristics such as low cost, good flexibility, mechanical property and excellent processability. Among the known polymers, poly (vinylidene fluoride) (PVDF) is an ideal piezoelectric polymer because the β-crystalline form of PVDF has the highest polarization per unit cell. However, initial PVDF mostly suffers from the lack of a β phase, restricting its potential applications. Few-layer MoS2 is predicted to be strongly piezoelectric owing to the opposite orientations of adjacent atomic layers. In this work, we report an efficient approach to enhance the piezoelectric property of PVDF-based nanocomposites by combining few-layer MoS2 with PVDF. The product yield for few-layer MoS2 reached a value as high as 83.3% via a unique liquid-exfoliation technique. For a few-layer MoS2/PVDF composite film with 1 wt.% few-layer MoS2, a high piezoelectric performance enhancement of 360% was achieved compared with the initial PVDF film. In addition, due to the intrinsic lubrication of MoS2, the highest elongation of the piezoelectric composite film was found to be four times higher than that of the pure PVDF film.

Metal Insulator Transition in Vanadium Dioxide Hydrated by Means of the Plasma-Immersion Ion Implantation Method

In the work, we explore the modification of the structure of vanadium dioxide films, as well as the metal-semiconductor phase transition in them, when hydrated by the method of plasma-immersion ion implantation. Based on a detailed X-ray analysis and the Raman spectra of the initial and hydrated films, it is shown that the plasma-ion modification of the transition and the metallization of vanadium dioxide (at a hydrogen concentration above 10at. %) are most likely associated with electron-correlation effects amplified by hydrogen implantation and an increase in the free charge carrier density in the material.

Effect of soluble surfactants on vertical liquid film drainage

A mathematical model is established to investigate the gravity-driven drainage of vertical films containing a soluble surfactant by considering the coupling effect of surface elasticity, adsorption coefficient, and surfactant solubility. The lubrication theory is applied to derive the four coupled nonlinear partial differential equations describing the film thickness, surface velocity, and surfactant concentration on the surface and in the bulk. Simulated results showed that the surface elasticity, adsorption coefficient, and surfactant solubility are indispensable factors in the drainage process of a liquid film containing a soluble surfactant. In the initial stage of the drainage, the initial film thickness increases with increasing surface elasticity and the film surface tends to be more rigid. With further drainage, the liquid film exhibits different notable features for high and low elasticity. For low surface elasticity, the surfactant distribution produces a positive Marangoni effect, which counteracts gravity. However, for high surface elasticity, the film surface exhibits a reverse Marangoni effect, which accelerates the drainage and leads to an unstable film. As the solubility decreases, both the film stability and initial surface elasticity enhance. The surface elasticity gradually approaches a limiting dilational elasticity modulus owing to the film thinning. For a large Ks, the film surface is insufficient to produce a strong Marangoni effect and then the liquid film tends to easily destabilize. For a small Ks, the soluble surfactant is similar to an insoluble surfactant, and the film is much thicker in the later stage of the drainage.

Intrasurgical Protein Layer on Titanium Arthroplasty Explants: From the Big Twelve to the Implant Proteome.

Aseptic loosening in total joint replacement due to insufficient osteointegration is an unsolved problem in orthopaedics. The purpose of the study is to obtain a picture of the initial protein adsorption layer on femoral endoprosthetic surfaces as the key to the initiation of osseointegration. The paper describes the first study of femoral stem explants from patients for proteome analysis of the primary protein layer. After 2 min in situ, the stems are explanted and frozen in liquid nitrogen. Proteins are eluted under reducing conditions and analyzed by LC-MS/MS. After exclusion of proteins identified by a single peptide, the implant proteome is found to consist of 2802 unique proteins. Of these, 77% are of intracellular origin, 9% are derived from the plasma proteome, 8% from the bone proteome, and four proteins with highest specificity score could be assigned to the bone marrow proteome (transcriptome). The most abundant protein in the adsorbed total protein layer is hemoglobin (8-11%) followed by serum albumin (3.6-6%). A detailed knowledge of the initial protein film deposited onto the implants, as demonstrated here for the first time, may help to understand and predict the response of the osseous microenvironment to implant surfaces.

Direct formation of continuous multilayer graphene films with controllable thickness on dielectric substrates

Direct formation of graphene films on dielectric substrates is investigated by the “etching-precipitation” method which converts metal-carbon mixed films to graphene films by etching metal away by Cl2 at 600–650 °C. Here we report a new approach for improved control of the layer number and continuity of the graphene films. Reactive sputtering of Fe in C2H4/Ar enabled fine control of the carbon concentrations and thicknesses of the initial Fe-C films, which yielded continuous multilayer graphene films of controllable average layer numbers of ~10–40, low resistivity down to ~240 μΩ cm, and high Raman G-band to D-band intensity ratio up to 16 directly on SiO2 substrates. We also show that the carbon concentration of the initial Fe-C films determines the film continuity and crystallinity of the graphene.

Facile synthesis of petal-like nanocrystalline Co3O4 film using direct high-temperature oxidation

A novel petal-like cobalt oxide (PCO) structure has been fabricated by electrodeposition of the nanostructured Co film followed by elevated-temperature oxidation. The structure exhibits monodisperse petal-like cobalt oxide nanosheets and core–shell structure with oxide as shell and metal as core. The morphology was studied by changing the surface structure of the initial Co film and oxidation temperature, finding that the PCO could only be obtained by calcining the arched Co film at 500 °C. The growth mechanism is briefly discussed based on the Caberra–Mott theory. The electrochemical behaviour analysis indicates the prepared material’s potential as electrode materials in supercapacitors.

Study of Structure and Optical Density of Track Membranes

This work presents research results of surface, including optical characteristics of poly (ethylene terephthalate) film under the influence of heavy ion radiation and following chemical etching for use as light filter. The optical density of the films and track membranes was determined in the wavelength range of 310-990 nm. Optical density measurements were carried out with gap of 50 nm. Track membrane was researched with the track diameters of 300 nm and concentration of 4·108см-1. It is determined, that the optical density of the initial film and irradiated are comparatively low in the entire researched wavelength range and does not exceed the value of 0.1. It is shown that for the track membrane in the ultraviolet region there is a sharp rise in the optical density values, at the wavelength of 650 nm to the maximum value, and the values gradually decrease in visible color and continue to decrease in the IR region.

Elastohydrodynamics of a pre-stretched finite elastic sheet lubricated by a thin viscous film with application to microfluidic soft actuators

The interaction of a thin viscous film with an elastic sheet results in coupling of pressure and deformation, which can be utilized as an actuation mechanism for surface deformations in a wide range of applications, including microfluidics, optics and soft robotics. Implementation of such configurations inherently takes place over finite domains and often requires some pre-stretching of the sheet. Under the assumptions of strong pre-stretching and small deformations of the lubricated elastic sheet, we use the linearized Reynolds and Föppl–von Kármán equations to derive closed-form analytical solutions describing the deformation in a finite domain due to external forces, accounting for both bending and tension effects. We provide a closed-form solution for the case of a square-shaped actuation region and present the effect of pre-stretching on the dynamics of the deformation. We further present the dependence of the deformation magnitude and time scale on the spatial wavenumber, as well as the transition between stretching- and bending-dominant regimes. We also demonstrate the effect of spatial discretization of the forcing (representing practical actuation elements) on the achievable resolution of the deformation. Extending the problem to an axisymmetric domain, we investigate the effects arising from nonlinearity of the Reynolds and Föppl–von Kármán equations and present the deformation behaviour as it becomes comparable to the initial film thickness and dependent on the induced tension. These results set the theoretical foundation for implementation of microfluidic soft actuators based on elastohydrodynanmics.

Stability of a twisted Plateau border with line tension and bending stiffness

The stability of a Plateau border between three soap films is considered, taking into account the effects of line tension and bending stiffness in the border. A simple geometry is considered, in which the border initially lies in equilibrium along the axis of a circular cylinder, with three equally-spaced films radiating outwards to meet the inside wall of the cylinder. The films are pinned at the two ends of the cylinder with a fixed relative twist, so the initial film surfaces are helicoids. The stability of this system to small perturbations, involving both the films and the border, is investigated as a function of the cylinder aspect ratio, twist angle, film surface tension, border line tension, and border bending stiffness. Analytically, the stability problem is reduced to finding the first occurrence of a zero eigenvalue of an infinite matrix, which is then estimated numerically. The results from this calculation are in good agreement with full numerical simulations.

SiGe films and graded buffers grown by liquid phase epitaxy from different growth solution compositions

SiGe films were grown on Si (0 0 1) by liquid phase epitaxy from short growths (950–940 °C) with different solution compositions (2% Ge, 4% Ge, 5% Ge). The initial growth transitions from the characteristic crosshatch morphology into a more three-dimensional morphology with increasing Ge content in the solution. We found that the highest Ge film that maintains two-dimensional film growth is 3.1% Ge. The initial film changes from fully strained to 30% partially relaxed and back to fully strained as the composition increases from 1.4% Ge to 3.1% Ge. In addition, SiGe graded buffers were grown with different solution compositions (2% Ge, 4% Ge, 5% Ge) from 950 to 750 °C. The initial film of each graded buffer (the first film to form on the substrate) is fully relaxed at high temperature but experiences tensile strain after cooling to room temperature while the part of the graded buffer further from the substrate experiences increasing compressive strain as the film thickness increases and becomes richer in Ge. The threading dislocation density of graded buffers (i.e. thicker films) grown with the 4% Ge- and 5% Ge-content-solutions is ∼106 cm−2, one order of magnitude lower than their own initial films (the film grown in the first ∼10 °C growth interval) while the threading dislocation density of the graded buffers grown with 2% Ge-content-solution is similar to its initial film’s threading dislocation density, ∼106 cm−2.

From Aggregates to Porous Three-Dimensional Scaffolds through a Mechanochemical Approach to Design Photosensitive Chitosan Derivatives.

The crustacean processing industry produces large quantities of waste by-products (up to 70%). Such wastes could be used as raw materials for producing chitosan, a polysaccharide with a unique set of biochemical properties. However, the preparation methods and the long-term stability of chitosan-based products limit their application in biomedicine. In this study, different scale structures, such as aggregates, photo-crosslinked films, and 3D scaffolds based on mechanochemically-modified chitosan derivatives, were successfully formed. Dynamic light scattering revealed that aggregation of chitosan derivatives becomes more pronounced with an increase in the number of hydrophobic substituents. Although the results of the mechanical testing revealed that the plasticity of photo-crosslinked films was 5–8% higher than that for the initial chitosan films, their tensile strength remained unchanged. Different types of polymer scaffolds, such as flexible and porous ones, were developed by laser stereolithography. In vivo studies of the formed structures showed no dystrophic and necrobiotic changes, which proves their biocompatibility. Moreover, the wavelet analysis was used to show that the areas of chitosan film degradation were periodic. Comparing the results of the wavelet analysis and X-ray diffraction data, we have concluded that degradation occurs within less ordered amorphous regions in the polymer bulk.

Convective Drying Kinetics of Polymer Strip Films Loaded with a BCS Class II Drug.

Polymer strip film is a promising dosage form for oral delivery of poorly water-soluble drugs. Drying is an important step in the production of polymer strip films with significant effects on critical quality attributes (CQAs). In this study, a custom-made batch drying setup was used to study convective drying kinetics of wet polymer strip films loaded with dry-coated micronized griseofulvin (GF) at various drying conditions. A rate-based semi-empirical model was formulated and parameters were estimated by integral method of analysis using a coupled optimizer-ordinary differential equation solver. Despite its simplicity with three parameters, the model could fit the experimental data very well for all drying conditions, which enabled us to examine the effects of air velocity, temperature, and initial wet film thickness on drying kinetics quantitatively. The modeling results clearly delineate a drying mechanism with constant-rate and falling-rate periods. One set of kinetic parameter estimates reasonably predicted the drying kinetics for two different wet film thicknesses in the selected process conditions, which demonstrates the predictive capability of the model. After reporting the limitations of the semi-empirical model, upon future modification and refinement, its potential use in drying process development and process control was highlighted.

Self Formed Anisotropic Proton Conductive Polymer Film by Nanophase Separation

An anisotropic proton conductive polymer film was prepared from poly(decylacrylamide-co-12-acrylamidododecanoic acid). The polymer film was prepared on a solid substrate by spin coating and the structure was analyzed by X-ray diffraction measurement. The initial polymer film exhibited featureless diffraction, which indicates that the film was amorphous. On the other hand, when the film was annealed at 60°C under 98% RH, the film structure was converted from amorphous to highly oriented lamellar structure. The proton conductivities of the film parallel and perpendicular to the substrate surface were studied by impedance measurement. The conductivity at the parallel direction increase whereas that at the perpendicular direction decrease with measurement time. This is because the film formed a lamellar structure in-situ during the proton conductivity measurement. In other words, the anisotropic conduction state can be reached as long as the proton conductivity measurements were carried out.

Correlation between conjunctival scraping cytology and other clinical dry eye metrics in determination of dry eye related inflammation

Background/Aim. New and improved definition of dry eye disease (DED) emphasized that hiperosmolarity and inflammation with initial tear film instability play etiological role. The aim of this study was to explore relation of some commonly used clinical tests to dry eye disease (DED) related inflammation measured by conjunctival scraping cytology. Methods. We examined 100 subjects, 80 of them having DED. We performed Schirmer without anesthesia (Schirmer I), Fluorescein Tear Break Up Time (FTBUT), Rose Bengal (RB), Lid Parallel Conjunctival Folds (LIPCOF), Tear Meniscus Height (TMH) and Tear Ferning (TF) and compared the values to scraping scores of tarsal conjunctiva. Results. FTBUT had the best sensitivity (93.6%). The highest specificity was found with RB (93.2%), but it was also high with Schirmer I, TF and FTBUT (respectively 89.8%, 84.5%, 78.0%). RB and FTBUT had the highest correlation with conjunctival scraping score (r = 0.707, p &lt; 0.001; r = -0.507, p &lt; 0.001). Conclusion. In our study, FTBUT, though often used in many combinations of the DED tests, showed a remarkably high sensitivity and specificity on its own, as well as good correlation with DED related inflammation detected with conjunctival scraping cytology.

Electrochemical Oxidation of Fe–Ni Alloys in Cryolite–Alumina Molten Salts at High Temperature

The anodic oxidation process of Fe–Ni alloys containing various components as anodes in 48.2NaF–43.8AlF3–8.0Al2O3 (wt%) molten salts at 980°C was characterized using linear sweep voltammetry. The anodic polarization curves of all of the Fe–Ni alloys, which displayed a typical active–passive–transpassive feature, are similar to that of Fe. Based on the dissolution–precipitation mechanism, an initial passivation film comprised of FeO was formed at a passivation potential. Subsequently, FeO was oxidized to Fe2O3, resulting in the formation of an outer film overlying the FeO film, which corresponded with the scanning electron microscopy and energy-dispersive X-ray spectrometry results, showing that the main components of the passivation film were iron oxides. Because of the chemical dissolution of oxides, oxides are continuously formed to resist chemical dissolution and protect the alloy matrix. The passivation film was broken down during oxygen evolution because of a lack of alumina. No passive behavior was observed on Ni. In addition, the preoxidized alloys possessed superior corrosion resistance to that of the nonoxidized alloys. The preoxidized 43Fe–57Ni alloy was observed to be stable during constant-current electrolysis based on a chronopotentiometric study, indicating that the preoxidized 43Fe–57Ni alloy had a good corrosion resistance to the cryolite–alumina molten salts.

Effect of Millisecond Annealing Temperature of Ni1-&lt;italic&gt;x&lt;/italic&gt;Pt&lt;italic&gt;x&lt;/italic&gt; Si Formation on Leakage Current Characteristics of Static Random- Access Memory Cells

The importance of optimizing the millisecond annealing (MSA) temperature for Pt-doped NiSi ( ${\mathrm {Ni}}_{{1}-{x}}$ Pt x Si) contact formation was highlighted by implementing and characterizing the ${\mathrm {Ni}}_{{1}-{x}}$ Pt x Si films in the static random-access memory (SRAM) cells fabricated with a 28-nm design rule. MSA at 750 °C–900 °C effectively reduced the junction leakage current compared to that with the conventional rapid thermal annealing, because of its efficient suppression of Ni diffusion in the junction region. Moreover, with an increase in the MSA temperature, the beneficial effects of maintaining a low junction leakage, such as interface flattening and grain size increase, were observed. However, the increase in the MSA temperature deteriorated the statistical distribution of the standby leakage current of the SRAM cells by producing more encroachment and spiking defects; this was attributed to the build-up of a high initial film stress and large stress relaxation during the subsequent back-end processes.

Рентгенолюминесценция толстых пленок оксида цинка

Studies of thick films (approximately 30 μm) of undoped zinc oxide on sapphire substrate obtained by magnetron sputtering method with the use of an uncooled target were conducted. The structural and luminescent properties of the initial films and films that underwent additional recrystallization annealing in the air were investigated. The time and temperature dependent characteristics of the samples were considered. It was shown that annealing in air leads to an improvement in the structural, optical, and luminescent properties of the obtained film.

Kompozitni filmovi na bazi pogače uljane tikve golice dobijeni različitim postupkom filtracije

Packaging is inseparable retainer of almost all food products. However, most of produced packaging ends as packaging waste after consumption of the product. Increasing amounts of packaging waste that should be managed represents serious challenge of every modern society. There are many different approaches to address this subject, amongst which biodegradable, natural biopolymer-based or even edible packaging holds considerable potential. In this paper, a by-product of edible oil industry, left after completed extraction by cold pressing of oil from hulls of pumpkin seeds, was used to produce biopolymer packaging films. Pumpkin oil cake was used to produce composite bio-based films. Different filtration of film forming suspension was applied in order to test composite film production using different filtration fractions, leading to higher process yield and minimizing waste. In addition, films were casted on surface, about ten times larger comparing to the cast surface typically reported for these types of films in the literature, in order to test the possibility for commercial production and scale up process. Also, casted mass of film forming suspension was varied in order to define minimal casting mass per unit area. Presented results showed that biopolymer films based on the pumpkin oil cake can be successfully produced in sheets (50x35 cm), compared to films earlier produced in the form of discs with diameter 12 cm. Different filtration fractions from initial film forming suspension can be used for film formation, leading to increased production yield. Different filtration fractions lead to different film properties that should be adjusted according to selected application. Casted mass of film forming suspension was successfully decreased (comparing to earlier literature data) without compromising film functional properties and minimal casting mass was defined as 26 g/m2.