Reduction Of Film Thickness Research Articles

Ways to improve conditions in mineral oil lubrication of the internal combustion engines

AbstractThe paper analyses some phenomena affecting the cam-follower contact conditions, highlights some detrimental influences over the lubrication regime in this contact. The analysis of the theoretical model revealed the significant influence of thermal and starvation effects on the reduction of film thickness. To avoid these negative phenomena and in order to improve the lubrication regime we propose an original technical solution by using additional oil feed with oil jets, directed over the contact area.

Topological and electronic transitions in a Sb(111) nanofilm: The interplay between quantum confinement and surface effect

When the dimension of a solid structure is reduced, there will be two emerging effects, quantum confinement and surface effect, which dominate at nanoscale. Based on first-principles calculations, we demonstrate that due to an intriguing interplay between these two dominating effects, the topological and electronic (topoelectronic) properties of Sb (111) nanofilms undergo a series of transitions as a function of the reducing film thickness: transforming from a topological semimetal to a topological insulator at 7.8 nm (22 bilayer), then to a quantum spin Hall (QSH) phase at 2.7 nm (8 bilayer), and finally, to a normal (topological trivial) semiconductor at 1.0 nm (3 bilayer). Our theoretical findings identify the existence of the QSH in the Sb (111) nanofilms within a narrow range of thickness and suggest that the Sb (111) nanofilms provide an ideal test bed for experimental study of topoelectronic phase transitions.

Melting of solid nanoscale films with free surfaces

In the framework of the mean-field Landau theory and the Lindemann melting criterion, a novel method has been applied to study the properties of thin solid films. A novel profile of the order parameter in thin solid films of nanoscale thicknesses has been obtained. In terms of this method, it was shown that surface ordering of thin solid films affects their physical properties. A dependence of the order parameter on the reduced film thickness was obtained. It was shown that the melting temperature of a thin film with free surfaces decreases with decreasing film thickness. Nevertheless, it was found that there was no depression of the melting point due to the reduced thickness of films at least down to 15 nm. The results are in good agreement with available experimental data.

Edge loading in metal-on-metal hips: low clearance is a new risk factor

The revision rate of large head metal-on-metal and resurfacing hips are significantly higher than conventional total hip replacements. The revision of these components has been linked to high wear caused by edge loading; which occurs when the head–cup contact patch extends over the cup rim. There are two current explanations for this; first, there is loss of entrainment of synovial fluid resulting in breakdown of the lubricating film and second, edge loading results in a large local increase in contact pressure and consequent film thickness reduction at the cup rim, which causes an increase in wear.This paper develops a method to calculate the distance between the joint reaction force vector and the cup rim – the contact patch centre to rim (CPCR) distance. However, the critical distance for the risk of edge loading is the distance from the contact patch edge to rim (CPER) distance. An analysis of explanted hip components, divided into edge worn and non-edge-worn components showed that there was no statistical difference in CPCR values, but the CPER value was significantly lower for edge worn hips.Low clearance hips, which have a more conformal contact, have a larger diameter contact patch and thus are more at risk of edge loading for similarly positioned hips.

Inhomogeneities in YBa2Cu3O7 thin films with reduced thickness

Morphology and physical properties of mono- (YBa2Cu3O7) and multilayered (YBa2Cu3O7/SmBa2Cu3O7/ YBa2Cu3O7) superconducting thin films with thickness ranging from 90nm to 28nm have been investigated. For both types of samples, the superconducting properties degraded with reduction of film thickness. Structural and electromagnetic properties were visualized through scanning electron microscopy and magneto-optical imaging, respectively, and revealed high level of inhomogeneity for thinner (<58nm) samples. However, samples with thickness above 58nm showed enhanced homogeneity, which explains better superconducting characteristics observed in these films. Results of this work demonstrate that multilayering approach performed by conventional laser ablation results in degradation of superconducting properties in films with thickness below 90nm, although has positive impact on morphology of these films, which is crucial for device fabrication process.

S116051 原子間力顕微鏡を用いた繰り返ししゅう動における単分子吸着膜の変形破壊挙動の観察

Island-shaped self-assembled monolayer (SAM) of octadecyl-trichlorosilane was repeatedly slid with the atomic force microscope (AFM) to clarify the deformation and fracture behavior, employed as model for localized adsorption films in practical boundary frictional conditions. There were two types of the island-shaped adsorption film; one is well-assembled monomolecular film with 2.2nm in thickness, another is less-assembled monomolecular film with about 0.8nm in thickness. The well-assembled monomolecular film can respond like as solid film with large rigidity, and then, has Coulomb frictional property. On the other hand, the less-assembled film can respond like as elastic material if relatively low normal load is applied. In this case, friction coefficient also linearly depends on the applied normal load. Moreover, if the normal load increases by certain level, kinetic response of the film indicates plastic behavior. That is, there is irreversible reduction of film thickness due to the applied load and its associated increase in friction coefficient.

Caracterização físico-química de filmes comestíveis de amido adicionado de acerola (Malphigia emarginata D.C.)

Edibles films are an alternative to synthetic materials used for packing food products. Barbados cherry is rich in vitamin C and carotenoids. The aim of this study was to characterize and develop films by casting from cassava starch, lyophilized Barbados cherry pulp and glycerol. The films were characterized with respect to thickness, water vapor permeability (WVP), water solubility, vitamin C, carotene and mechanical properties. The interaction of pulp and glycerol reduced film thickness. An increase in pulp concentration up to 60% increased WVP but beyond this concentration reduced both WVP and solubility leading to an increased level of vitamin C and β carotene in the films.

From Flat to Nanostructured Photovoltaics: Balance between Thickness of the Absorber and Charge Screening in Sensitized Solar Cells

Nanoporous metal oxide electrodes provide a high internal area for dye anchoring in dye-sensitized solar cells, but the thickness required to extinguish the solar photons also enhances recombination at the TiO(2)/electrolyte interface. The high extinction coefficient of inorganic semiconductor absorber should allow the reduction of the film thickness, improving the photovoltage. Here we study all-solid semiconductor sensitized solar cells, in the promising TiO(2)/Sb(2)S(3)/P3HT configuration. Flat and nanostructured cells have been prepared and analyzed, developing a cell performance model, based on impedance spectroscopy results, that allows us to determine the impact of the reduction of metal oxide film thickness on the operation of the solar cell. Decreasing the effective surface area toward the limit of flat samples produces a reduction in the recombination rate, increasing the open circuit potential, V(oc), while providing a significant photocurrent. However, charge compensation problems as a consequence of inefficient charge screening in flat cells increase the hole transport resistance, lowering severely the cell fill factor. The use of novel structures balancing recombination and hole transport will enhance solid sensitized cell performance.

Impact of film thickness of organic semiconductor on off-state current of organic thin film transistors

Impact of film thickness on off-state current of bottom contact organic thin film transistor has been investigated using two dimensional numerical simulations and analytical model. Off-state current of the device reduces by six orders of magnitude as film thickness is scaled from 45 nm to 10 nm, with rate of reduction in off-state current being slow first and then significantly higher. An analytical model for off-state current has been developed to offer an insight into above results of off-state current, and the model predictions are found in good agreement with reported experimental results. The developed model is especially important for the device with smaller film thickness as at such film thicknesses, space charge limited current model is inadequate to explain off-state current of such devices. A horizon for scaling device channel length through a reduction in film thickness only has been explored using an analytical model and simulation results. Off-state current of a shorter channel length (L) device can be comparable to a relatively longer channel length (i.e., L + δL) device if the fractional reduction in film thickness becomes equal to square of the fractional reduction in channel length. Following such reduction in film thickness successively for a number of steps, an expression for film thickness corresponding to the device with a desired value of channel length has been developed and verified with simulation results. Although the device with larger film thickness has a problem of poor subthreshold performance, it, in general, has advantage of better mobility. To alleviate this problem of the device with larger film thickness, a stack contact device has been proposed. An investigation of its subthreshold performance shows that its off-state current can be significantly lower as compared to conventional contact device.

Crystallization, Mechanical Properties, and Controlled Enzymatic Degradation of Biodegradable Poly(&lt;I&gt;ε&lt;/I&gt;-caprolactone)/Multi-Walled Carbon Nanotubes Nanocomposites

Biodegradable poly(epsilon-caprolactone) (PCL)/multi-walled carbon nanotubes containing carboxylic groups (f-MWNTs) nanocomposites were prepared via simple melt compounding at low f-MWNTs loading in this work. Scanning and transmission electron microscopy observations indicate a homogeneous and fine distribution of f-MWNTs throughout the PCL matrix. The effect of low f-MWNTs loading on the crystallization, mechanical properties, and controlled enzymatic degradation of PCL in the nanocomposites were studied in detail with various techniques. The experimental results indicate that the incorporation of f-MWNTs enhances both the nonisothermal crystallization peak temperature and the overall isothermal crystallization rate of PCL in the PCL/f-MWNTs nanocomposites relative to neat PCL; moreover, the incorporation of a small quantity of f-MWNTs has improved apparently the mechanical properties of the PCL/MWNTs nanocomposites compared to neat PCL. The enzymatic degradation of neat PCL and the PCL/f-MWNTs nanocomposites at low f-MWNTs loading was studied in detail. The variation of weight loss with enzymatic degradation time, the surface morphology change, the reduced film thickness, the appearance of f-MWNTs on the surface of the films, and the almost unchanged molecular weight after enzymatic degradation suggest that the enzymatic degradation of neat PCL and the PCL/f-MWNTs nanocomposites may proceed via surface erosion mechanism. The presence of f-MWNTs reduces the enzymatic degradation rate of the PCL matrix in the nanocomposites compared with that of the pure PCL film.

The Solar Sail Materials (SSM) project – Status of activities

SSM (Solar Sail Materials) is an on-going project for the European Space Agency (ESA) relying on past and recent European solar sail design projects. It aims at developing and testing future technologies suitable for large, operational solar sailcrafts. SSM investigates three main areas: 1. Sail film and coating materials, including film thickness reduction and large scale assembly processes. 2. Sail-to-Structure Interfaces (SSIF) including sail container and attachments. 3. Correlation of ground sail tensioning strategies with 3D imaging and Finite Elements Model (FEM) simulations. Concerning sail films and coatings, a survey of promising materials has been completed, pre-trials of Kapton® 50HN plasma etching have been performed with an “easy” thickness reduction of about 2.5 μm and, a method for large scale sail manufacturing has been proposed. Concerning SSIFs, a survey on boom technologies has been updated, sail corner attachment concepts have been defined and investigated and a concept for a lightweight sail container with an opening mechanism has been proposed. Concerning correlated FEM simulations, on-ground (1 g) optimal tensioning strategies have been investigated on a 2 m hypotenuse sail mock-up and first FEM simulations have been carried out which show promising results. The main objective of these integrated tasks is ultimately to allow future scalability of prediction of optimal tensioning strategies in-orbit.

Evolution of magnetic bubble domains in manganite films

We report a thickness-dependent evolution of magnetic domains from long stripe-like to bubble-like entities in La1−xSrxMnO3 (x ∼ 0.3) (LSMO) films grown on LaAlO3 substrates. By using 2-D fast Fourier transformation of magnetic force microscopy images and power spectral density function, we accurately determine the domain width in LSMO films with a wide range of thickness (50–325 nm). We find that the domain size scales with the Kittel’s square root law [C. Kittel, Phys. Rev. 70, 965 (1946).] only when reduced film thicknesses are used, which suggests the critical role of substrate-film interaction in domain formation.

Combinatorial study of WInZnO films deposited by rf magnetron co-sputtering

The compositional dependence of co-sputtered tungsten indium zinc oxide (WInZnO) film properties was first investigated by means of a combinatorial technique. Indium zinc oxide (IZO) and WO 3 targets were used with different target power. W composition ratio [W/(In+Zn+W)] was varied between 3 and 30 at% and film thickness was reduced as the sample position moved toward WO 3 target. Furthermore, the optical bandgap energy increased gradually, which might be affected by the reduction in film thickness. All the WInZnO films showed an amorphous phase regardless of the W/(In+Zn+W) ratio. As the W/(In+Zn+W) ratio in WInZnO films increased, the carrier concentration was restricted, causing the increase in electrical resistivity. W cations worked as oxygen binders in determining the electronic properties, resulting in suppressing the formation of oxygen vacancies. Consequentially, W metal cations were effectively incorporated into the WInZnO films as a suppressor against the oxygen vacancies and the carrier generation by employing the combinatorial technique.

Isothermal Physical Aging of Poly(&lt;i&gt;ethyl methacrylate&lt;/i&gt;)/Polyhedral Oligomeric Silsequioxanes Nanocomposite Thin Films

The effects of the polyhedral oligomeric silsequioxanes (POSS) in stacked poly(methyl methacrylate) (PMMA) film samples were investigated in two different film thicknesses, ~50 and ~660 nm. The types of the POSS include methacryl-, octaisobutyl-, and octasilane-POSS. The glass transition temperature (Tg) and isothermal physical aging was depressed by the reduction of film thickness. Among POSS molecules used in this work, methacryl-POSS was the greatest effect in both Tg and relaxation enthalpy (DHRelax) due to the physical aging. The Kohlrausch-Williams-Watts (KWW) relaxation function was used to further understand the effect of POSS and film thickness on the physical aging.

Quantitative Assessment of the Enzymatic Degradation of Amorphous Cellulose by Using a Quartz Crystal Microbalance with Dissipation Monitoring

The systematic evaluation of the degradation of an amorphous cellulose film by a monocomponent endoglucanase (EG I) by using a quartz crystal microbalance with dissipation monitoring (QCM-D) identified several important aspects relevant to the study the kinetics of cellulose degradation by enzymes. It was demonstrated that, to properly evaluate the mechanism of action, steady state conditions in the experimental set up need to be reached. Rinsing or diluting the enzyme, as well as concentration of the enzyme, can have a pronounced effect on the hydrolysis. Quantification of the actual hydrolysis was carried out by measuring the film thickness reduction by atomic force microscopy after the enzymatic treatment. The values correlated well with the frequency data obtained by QCM-D measurement for corresponding films. This demonstrated that the evaluation of hydrolysis by QCM-D can be done quantitatively. Tuning of the initial thickness of films enabled variation of the volume of substrate available for hydrolysis which was then utilized in establishing a correlation between substrate volume and hydrolytic activity of EG I as measured by QCM-D. It was shown that, although the amount of substrate affects the absolute rate of hydrolysis, the relative rate of hydrolysis does not depend on the initial amount of substrate in steady state system. With this experimental setup it was also possible to demonstrate the impact of concentration on crowding of enzyme and subsequent hydrolysis efficiency. This effort also shows the action of EG I on a fully amorphous substrate as observed by QCM-D. The enzyme was shown to work uniformly within the whole volume of swollen film, however being unable to fully degrade the amorphous film.

Ferroelectricity and strain effects in orthorhombic YMnO3 thin films

We report on the dielectric properties of epitaxial [0 0 1]- and [1 0 0]-textured thin films of antiferromagnetic orthorhombic YMnO3 and their variation under compressive epitaxial strain. It is found that weakly strained YMnO3 films are ferroelectric with a polarization along the c-axis switchable by 90° by an external magnetic field. With reducing film thickness and increasing epitaxial strain, the ferroelectric order is progressively suppressed. Analysis of structural, dielectric and magnetic data indicates that suppression of ferroelectricity with reducing thickness is accompanied by an enlarged ratio a/b of the in-plane cell parameters of the orthorhombic structure and the appearance of a net magnetization. All results can be well-described by considering the multiferroic phase diagram of orthorhombic manganites.

Grain boundary mediated leakage current in polycrystalline HfO 2 films

In this work, we combine conductive atomic force microscopy (CAFM) and first principles calculations to investigate leakage current in thin polycrystalline HfO 2 films. A clear correlation between the presence of grain boundaries and increased leakage current through the film is demonstrated. The effect is a result of a number of related factors, including local reduction in the oxide film thickness near grain boundaries, the intrinsic electronic properties of grain boundaries which enhance direct tunnelling relative to the bulk, and segregation of oxygen vacancy defects which increase trap assisted tunnelling currents. These results highlight the important role of grain boundaries in determining the electrical properties of polycrystalline HfO 2 films with relevance to applications in advanced logic and memory devices.

Effect of Film Thickness on Resistance Switching Characteristics for Cu/NiO/Pt Structure

The effect of NiO film thickness on resistance switching characteristics of a Cu/NiO/Pt structure is investigated. I-V results show that forming voltage decreases with the reduction of film thickness, and finally drops down to the set voltage. NiO film thickness should be controlled under a typical thickness in order to implement lower power consumption device design. The underlying mechanism of the phenomenon is attributed to the important role that Cu atoms play in the structure. Due to redox existing in the interface between Cu and NiO film, Cu atoms are ionized and pushed to the opposite electrode when the positive voltage is applied to Cu electrode, Cu conductive filaments are formed. In opposite, Cu atoms lost their electrons and are pushed off from Pt electrode when the positive voltage is applied to the Pt electrode, resulting in the rupture of Cu filaments.

Fabrication of double- and multi-walled carbon nanotube transparent conductive films by filtration-transfer process and their property improvement by acid treatment

Double-walled carbon nanotubes (DWCNTs) and two kinds of vertically aligned multi-walled carbon nanotubes were employed as raw materials to fabricate transparent conductive films (TCFs). DWCNTs constructed the densest conductive network at the same transmittance, and the corresponding TCFs showed the best performance (320 Ω/□ at 75.0% T). The ratio of dc conductivity to optical conductivity (σdc/σop) of the as-dispersed DWCNTs was 3.88. The as-obtained TCFs were dipped in HNO3 solution to improve their performances. Attributed to the removal of sodium dodecyl sulfate molecules, reduction of film thickness, and doping with electron acceptors (such as oxygen), the surface resistance after HNO3 treatment decreased. The σdc/σop ratio of the DWCNTs was further increased to 5.24.

Peculiarity of a CO2-philic block copolymer confined in thin films with constrained thickness: “a super membrane for CO2-capture”

CO2-philic block copolymer thin films with constrained thickness, comparable to the polymer radius of gyration (Rg), were examined due to their strange behaviour. The experimental CO2 permeances for example are almost two-fold higher than those theoretically calculated by the relation between permeance, thickness and permeability. We suggest that the reduction of film thickness towards Rg and the re-organization of the block-copolymer (by using an appropriate substrate) in a constrained nanospace result in a super permeable membrane. This finding may have great implications for the design of smart materials, especially for applications as selective membranes for CO2-capture.