Effect Of Film Structure Research Articles

1D/2D Co3O4/NiO composite film for high electrochromic performance

As an electrochromic material, Co3O4 has limited applications due to its low optical modulation range and short cycle life. In order to improve the electrochromic properties, a 1D/2D Co3O4/NiO composite film was prepared by simple two-step hydrothermal process and discontinuous annealing. The electrochromic properties of the composite structure are significantly improved compared with the nanostructures using two oxides alone. The effect of film structure on electrochromic properties was studied in detail. The results show that the 1D/2D Co3O4/NiO composite film have remarkable optical modulation (16–73% in the 350–800 nm range) and high Li+ diffusion rate (5.15 × 10−12 cm2/s). The improvement of electrochromic properties is mainly due to the porous structure, which increase the two active materials to leak fully in the electrolyte, thus enhancing the diffusion of ions and electrons. NiO nanosheets grow well and distribute uniformly on the surface of Co3O4 nanowires, allowing the two parts to fully contact the electrolyte. Cyclic voltammetry (CV) analysis shows that the peak current of the composite film is much higher than that of the single film, indicating that the nanoarray has high electrochemical reactivity. Results of electrochemical impedance spectroscopy show that the composite film has the lower charge transfer resistance and ion diffusion resistance, which are conducive to rate capacity. This work provides a strategy for improving the electrochromic properties of cobaltosic oxide.

Influence of film structure on the microstructure and properties of TiAlN coatings on Al-Si alloys

Due to the disadvantages of poor friction and low wear resistance, the application of Al-Si alloys with unique properties in pistons is limited. In this work, TiAlN ceramic coatings were prepared by filtered cathode vacuum arc technique to improve the surface properties of Al-Si alloys. To overcome the high residual stress of hard coatings growth on soft substrate surfaces due to interfacial mismatch and defect accumulation, gradient and multilayer film structures were adopted to improve adhesion strength. The effects of film structure on the microstructure, mechanical and tribological properties of coatings were systematically investigated. The results showed that the coatings with different film structures showed a multiphase microstructure with the dominated phase of TiAlN and a small amount of AlTi and TiN phases. Monolayer and multilayer coatings exhibited TiAlN (111) orientation, while the gradient coating showed (220) orientation due to the growth of columnar to equiaxed crystals. Compared with the monolayer coating, TiAlN coatings with gradient and multilayer structures had significantly reduced compressive stress and improved adhesion and scratch propagation resistance. Among them, the multilayer coating showed the lowest friction coefficient (~0.44) and wear rate (~5.14 × 10 −5 mm 3 /Nm), which were attributed to the high hardness (~31.01 GPa), toughness (H/E = 0.135, H 3 /E 2 = 0.563 GPa), critical load L C3 (~26.58 N). Interfacial effects in the multilayer structure could enhance synergy of the coating, thereby preventing crack initiation and propagation and adhesion failure. • TiAlN coatings with different structures were prepared on Al-Si alloys by FCVA. • Coatings were dominated by fcc TiAlN phase with less AlTi and TiN phases. • Adhesion of gradient and multilayer coatings were effectively improved. • Multilayer coatings showed the best mechanical and tribological properties.

Ultrahigh energy storage density at low operating field strength achieved in multicomponent polymer dielectrics with hierarchical structure

Dielectric composites with excellent capacitive energy storage capabilities have great potential applications in energy storage capacitors operating efficiently at relatively low field strengths. Herein, unlike the traditional methods via the introduction of fillers including randomly distributed ceramic nanofibers and aligned nanowires arrays into the monolayer films are simply to increase the energy storage density (Ue), both Ue and charge–discharge efficiency (η) at low electric field strengths have been improved in tri-layered all-polymer films owing to the synergistic effect of multiple interbedded interfaces and deliberately modulation of linear dielectric poly(methyl methacrylate) (PMMA) contents. The effects of film structure on the energy storage capabilities have been comparatively discussed. Consequently, an ultrahigh Ue of 15 J cm−3 accompanied with great η of 76.5% has been delivered in the resulting tri-layered film via optimizing the PMMA content (30 wt%) of out layers at 350 MV m−1, surpassing the energy storage upper limits of the reported polymer dielectrics that show the Ue of ~12 J cm−3 and η of ~70% at comparable electric fields of 310–380 MV m−1. Along with high pulsed power density, multicomponent polymer dielectrics with hierarchically structure provide an effective paradigm for achieving the low operating field strength applications of capacitive energy storage devices with excellent energy storage capability.

Structural sensitivity of MoS2-based films in solid space lubrication

ABSTRACTThe Ti/MoS2 films with nano-composite and nano-multilayer structures are synthesised as well as the pristine MoS2 film by unbalanced magnetron sputtering. The effects of film structure on the solid lubrication performance in vacuum have been investigated. The microstructural analysis by scanning electron microscope and transmission electron microscope displays that the addition of Ti in MoS2 films with both nanostructures hinders the growth of columnar grains, leading to the improved compactness of films and mechanical properties. Through the analysis, it is found that the metallic titanium in the form of nanocrystals can transform into fine and uniform wear debris which benefits the preserve of transfer film, while the large and non-uniform debris resulted from the layer form can lead to localised severe damage and unstable friction.

Effect of film structure and morphology on the dielectric breakdown characteristics of cast and biaxially oriented polypropylene films

Effects of cast film extrusion and biaxial orientation on morphological development and DC dielectric breakdown performance of non-oriented and biaxially oriented polypropylene (BOPP) films were studied. Cast films, based on two capacitor-grade isotactic polypropylene (iPP) homopolymers, were manufactured using three different extruders under different crystallization conditions and subsequently biaxially oriented using a laboratory stretching machine. Analysis of polymorphic composition and microstructural features was carried out in conjunction with large-area multi-breakdown performance assessment under progressive DC voltage ramp conditions. Polymorphic α/β-form crystalline composition and spherulitic/trans-crystalline morphology formed during cast film extrusion were found to directly affect the biaxially oriented film morphology and breakdown characteristics. For the BOPP films, decrease in dielectric strength was traced back to β→α crystal transformation and subsequent microvoid/porosity formation upon biaxial stretching. Topographical features and increasing surface roughness were also found to correlate with lower BOPP film dielectric strength. Dependence of breakdown strength on the biaxial stretch ratio was demonstrated, with higher biaxial stretch ratio resulting in improved BOPP film breakdown performance. As an extreme case, the biaxially oriented films were compared against non-oriented cast films in similar thickness range, highlighting the essential role of biaxial orientation in the high-dielectric-performance of thin films in capacitor applications. Control of polymer design as well as optimization of film processing and morphological development was found to be necessary to avoid formation of structural defects and loss of electrical insulation integrity.

Crystallization and Reconstructive Layer Transformation of a-Si/Au Multilayer Thin Films under a Strong Gravitational Field

There were still unclear questions in the new method that fabricate the high quality poly crystalline Si thin film from amorphous Si thin film with lower annealing temperature than conventional Si recrystallization temperature. In that recrystallization process, the recrystallization mechanism was generally explained by the MIC (Metal Induced Crystallization) of Au. In this paper, we have discussed the effects of film structure and strong gravity on recrystallization, by using conventional furnace and high-temperature ultracentrifuge furnace system. The five kinds of samples (two bilayered Si/Au thin films, two multilayered Si/Au thin films and trilayered Si/Au/Si thin film) and found the effects of structure and strong gravity. The best for crystallization was Au/Si multilayered thin film, which is almost finished to crystallize even at 673 K annealing. The strong gravity advanced and retreated the crystallization, depending to thin film structure.

Effect of film structure on the electrochemical properties of gold electrodes for neural implants

The development of interfaces with low impedance is a prerequisite for long-term neural devices. A broad range of new materials has been developed for this purpose. Here we show how the performance of traditional gold electrodes can be improved by controlling the deposition parameters of the gold film. The morphology of the film was tuned from granular to columnar structure as shown by scanning electron microscopy of film cross sections. Electrochemical characterisation with impedance spectroscopy, chronoamperometry and cyclic voltammetry demonstrates that the dense columnar structure of the films effectively lowers the impedance of the interface and increases charge injection properties. The samples produced are also compared to titanium nitride films, a well-established electrode material with a columnar structure.

Effect of film structure on field emission properties of nitrogen doped hydrogenated amorphous carbon films

In this study, we investigated the effect of bonding structure of nitrogen doped a-C:H ( a-C:N:H) film on the electrical and field emission properties. The bonding structure in nitrogen doped a-C:H films were controlled via growth using an acetonitrile methane mixture. Nitrogen atoms in the a-C:N:H films were incorporated in termination structure such as C≡N and N–H. Current–voltage measurements for a-C:N:H films showed that the electrical conductivity was high for the lightly nitrogen doped films. The lightly doped a-C:N:H film exhibited lower threshold field emission voltage than heavy nitrogen doped films. The behavior observed in this research suggests that nitrogen atoms do not act as electron donors. The results can be interpreted as that incorporated nitrogen atoms do not acts as electron donor because they are involved in the C≡N and N–H termination structures. Characterizations of the doping system, not only doping species, is necessary to design the electronic structures of a film to obtain high efficiency field emission.

Effects of film structure on electrochromic properties of the multilayer films containing polyoxometalates

Multilayer films of tungstophosphate anion (P 2W 18) and poly(allylamine hydrochloride) (PAH) were fabricated on quartz and ITO substrates by layer-by-layer self-assembly method. These films were characterized by UV–vis spectroscopy, cyclic voltammetry (CV), chronoamperometric (CA), chronocoulometry (CC) and atomic force microscopy (AFM). The effects of film structure on multilayer electrochromic properties were investigated. The electrochromic responses of the composite films were related to the surface coverage of anion and multilayer thickness. It was found that higher concentration of polycation and anion, or adding salt to the polycation solution used for multilayer film preparation led to thicker and denser film structure which improved optical contrast and coloration efficiency whereas prolonged response time.

Thermal bonding of polypropylene films and fibers

AbstractThe thermal bonding behavior of different grades of polypropylene was studied in this research. Initial bonding studies were done with polypropylene films of different grades of polymer with varying morphology, and the studies were extended to polypropylene fibers. Polypropylene fibers manufactured with different cross‐sections, deniers, polymer melt‐flow rates, and different processing conditions were bonded under various conditions. The effect of film structure, properties, and bonding conditions on the bonding efficiency was studied by comparing the tensile strength of bonded films. Thermal bonding was carried for a range of temperatures covering poor, optimum, and over bonding. Changes taking place to the polymer in bond point and the original surface were analyzed using the SEM. Higher bond strength was observed in the vicinity of melting temperature and the strength reduced with a further increase in bonding temperature. The frequent failure point was observed at the bond edge crossover points where film undergoes maximum thickness transition. Lower pressure and shorter time were found to be appropriate for bonding. Films with lower orientation formed better bonds. The optimum bond strength and the optimum bonding temperature observed were different for different polymers. Fiber bond strength results were similar to the results observed in the case of films with respect to the bonding temperatures studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Application of the discrete dipole approximation for dipoles embedded in film

An implementation of the discrete dipole approximation for dipoles embedded in film on substrate is derived. It is capable of predicting the scattering response from various types of subsurface features such as trenches and contact-vias. An arbitrarily shaped subsurface feature is modeled with dipoles inside the film material on top of a substrate. Relative polarizability, direct interactions, and reflection interactions are derived and applied to construct a system of equations that are solved with an iterative method. The far-field scattering response is computed from the dipole moment solution of the system matrix with the help of the reciprocity theorem. The validity of the proposed method is compared with that of other existing theories, and the effect of film structure on far-field scattering is shown with high-aspect-ratio cylindrical contact-via models.

The Effects of Film Structure and Surface Hydrogen on the Properties of Amorphous Carbon Films

Molecular dynamics simulations were used to examine the mechanical and tribological properties of amorphous-carbon thin films with and without surface hydrogen. The simulations showed that the three-dimensional structure, not just the sp3-to-sp2 carbon ratio, is paramount in determining the mechanical properties of the films. Particular orientations of sp2 ringlike structures create films with both high sp2 content and large elastic constants. Films with graphite-like top layers parallel to the substrates have lower elastic constants than films with large amounts of sp3-hybridized carbon. The layered structure of the hydrogen-free films caused them to have novel mechanical behavior, which also influenced the shape of the friction versus load data. The atomic-scale structure of the film at the interface was of critical importance in determining the load at which tribochemical reactions (or wear) between the counterface and films were induced.

Effects of film structure on mechanical and adhesion properties of latex films

In order to investigate the effect of the particular structure of latex films on mechanical (stress-strain behaviour) and adhesion (measured by peeling) properties, this work compares these characteristics for latex films and corresponding “solution films”. Solution films were obtained by dissolving the latex film in an appropriate solvent and forming a new film by evaporating the solvent. In this way, the latex and solution films have exactly the same composition but different structures. Four different systems were studied, namely a homopolymer of 2-ethyl hexyl methacrylate, a copolymer of styrene and butyl acrylate, a copolymer of butyl acrylate with a zwitterionic monomer, and, finally, an ethyl acrylate-methyl methacrylate copolymer partially grafted onto a hydrophilic polyester. It was shown that latex films have Young's moduli systematically higher than the corresponding solution films. This is due to the fact that the hydrophilic shells of the latex particles form a continuous phase in the latex film which increases the modulus thanks to polar interactions. Modeling was possible using an appropriate equation (Palierne's Model) which allowed the determination of the modulus and volume fraction of the shell phase, without adjustable parameter. On the other hand, adhesion energy for latex films is always smaller than for solution films. This is interpreted in terms of structure of the film-support interface and interface and dissipative processes within the bulk of the film.

Dielectric Properties of (BaxSr1-x)TiO3 Thin Films Prepared by RF Sputtering for Dynamic Random Access Memory Application

Dielectric properties of (Ba0.5Sr0.5)TiO3 and (Ba0.75Sr0.25)TiO3 thin films have been investigated, focusing on the effects of film structure and Ba/Sr compositions on the dielectric properties. Dielectric constant of the films increased with increasing grain size and with improvement in film crystallinity. For the 50-nm-thick films deposited at 660° C, the dielectric constant of 400 for the (Ba0.5Sr0.5)TiO3 film is larger than that of 320 for the (Ba0.75Sr0.25)TiO3 film. This indicated that dielectric constant is affected by the ratio of Ba/Sr composition. Leakage current density of less than 1×10-7 A/cm2 at 1 V and SiO2 equivalent thickness of 0.38 nm are measured at 120° C for 660° C-deposited (Ba0.5Sr0.5)TiO3 film of 30 nm in thickness. The (Ba0.5Sr0.5)TiO3 film has the possibility for application to generations beyond 256 Mbit dynamic random access memories.

The cathodic polarization of aluminum covered with anodic oxide films in a neutral borate solution—II. Film breakdown and pit formation

Porous and barrier type oxide films were formed anodically on pure aluminum and dissolved chemically. The specimens were then cathodically polarized by the potential sweep method in a neutral borate solution. It was found that the cathodic current starts to increase at about −2 to −3 V(Ag/AgCl) and that at more negative potentials increases almost linearly, accompanied by hydrogen evolution. The cathodic polarization curve shifts in the anodic direction with decreasing film formation potential and increasing chemical dissolution time. During cathodic polarization, cubic-shaped pits are formed by local corrosion of the metal substrate. The number of pits formed by cathodic polarization is larger for porous than for barrier type oxide films, while the pit number is independent of the film formation potential, it increases considerably with increasing chemical dissolution time. The ratio of the local corrosion rate to the electrochemical reaction rate during cathodic polarization is about 0.03 on specimens without chemical dissolution, and about 0.10 with chemical dissolution. The effect of film structure on the pit formation during cathodic polarization is discussed in terms of imperfections in the oxide.

Magnetic texture in films with perpendicular anistropy

The notion of magnetic texture in films for perpendicular magnetic recording is introduced. The characteristics of magnetic texture dispersion ( δϑ 50) in CoCr films are also defined. The method of determination of material constants from the curves of film magnetization, including the first and second anisotropy constants K 1 and K 2, as well as ° ϑ 50 is proposed. The effects of film structure have been studied on the basis of a magnetostatic model of a columnar structure. The shape anisotropy constants is estimated to have the value ≈5×10 5 erg/cm 3, when M s in the volume of column is 400 G. The criteria for the applicability of films as perpendicular magnetic recording media are also formulated.

A Measurement of Induced Charge in CnTCNQ Langmuir-Blodgett Films Sandwiched between Aluminum Electrodes

Electrical properties of CnTCNQ Langmuir-Blodgett films sandwiched between aluminum electrodes are studied using thermally stimulated electrical measurements, and both the effect of film structure and the influence of native aluminum oxide are stressed. A change in induced charges on an electrode (Δq2) is measured while heating a sample. The relation between Δq2 and the number of deposited layers is in good agreement with a simple model based on a double-layered dielectric system. The direction of polarization in a film as deposited is also investigated using a photo-induced current measurement.

Structure and mechanical properties of ion-plated thick films

Copper and other metallic films deposited onto a vacuum-heat-treated tungsten substrate are prepared by ion plating for film thicknesses from 5 to 30 μ. The fracture cross section and surface morphology of films are examined by means of a scanning electron microscope. The structure of ion-plated films formed under usual plating conditions is, in general, a columnlike (or spongelike) structure containing a number of microporosities. In some cases, the layered structure of dense–porous is observed. When the ionization of metallic atoms is enhanced during the ion plating using three auxiliary cathodes with hot filaments, the film consists of dense and equiaxed structure. Further, the effect of film structure on mechanical properties of films (Knoop hardness, friction, and wear) is also examined.

Effect of Film Structure on Photoelectric Emission from Thin Films of Aluminium

Films of aluminium were evaporated on to quartz substrates at pressures of less than 2 × 10−9 Torr. The photoelectric emission current for vacuum-side illumination by monochromatic light of photon energy in the range 4.3–5.0 eV was determined as a function of the thickness of the film. The curve of photocurrent vs film thickness rises to a maximum at a thickness of about 50 A, and then falls to a constant value of about 0.2 of the maximum. The photoelectric work function increases to a value of 4.27 ± 0.02 eV at a thickness of 50 A, and remains approximately constant as the thickness of the film is increased. The maximum in the yield curve is due to a maximum in the number of photons absorbed, probably due to scattering of the incident light between the irregular islands making up the film and to the relatively high surface-to-volume ratio of the islands.

The effect of film structure on magnetoelastic properties of thin permalloy films

It has been observed that the magnetoelastic coefficient of thin permalloy films does not only depend on the Ni: Fe ratio but also on the film structure, which was varied by varying the deposition parameters and by annealing the films. By annealing the magnetoelastic coefficient may be shifted to more positive as well as to more negative values, depending on the annealing temperature, the gas atmosphere, and the deposition parameters, especially the crucible material. Typical thin-film effects, e.g., oxidation of the film surface and the grain boundaries, impurities enclosed within the film lattice during deposition and lattice imperfections are believed to be responsible for different magnetoelastic properties at the same film composition.