Intermediate Film Research Articles

Enhanced drainage and thinning of liquid films between bubbles and solids that support surface waves.

We study the thinning and drainage of the intermediate liquid film between a bubble and a solid surface at close proximity in the presence of a surface acoustic wave (SAW) in the solid. Specifically, we employ the diffraction of light to observe a long air bubble confined in a solid rectangular channel filled with silicone oil. This setup, constituting a two-dimensional physical model of thin film drainage, allows us to analyze the influence of a SAW on the rate of thinning of the micron-thick liquid film separating the bubble and the solid substrate. The viscous penetration of the SAW into the liquid imposes a convective drift of mass, redistributing the fluid in the film against capillary resistance and producing a net drift of liquid out of the film. The rate of drainage of liquid from the film increases by one to several orders of magnitude in comparison to the rate of drainage due to the Laplace pressure of the bubble alone. The experimental findings agree well with a newly developed theory describing the SAW-enhanced drainage as a competition between the capillary flow and SAW-induced streaming.

High-Performance Formamidinium-Based Perovskite Solar Cells via Microstructure-Mediated δ-to-α Phase Transformation

The δ → α phase transformation is a crucial step in the solution-growth process of formamidinium-based lead triiodide (FAPbI3) hybrid organic–inorganic perovskite (HOIP) thin films for perovskite solar cells (PSCs). Because the addition of cesium (Cs) stabilizes the α phase of FAPbI3-based HOIPs, here our research focuses on FAPbI3(Cs) thin films. We show that having a large grain size in the δ-FAPbI3(Cs) non-perovskite intermediate films is essential for the growth of high-quality α-FAPbI3(Cs) HOIP thin films. Here grain coarsening and phase transformation occur simultaneously during the thermal annealing step. A large starting grain size in the δ-FAPbI3(Cs) thin films suppresses grain coarsening, precluding the formation of voids at the final α-FAPbI3(Cs)–substrate interfaces. PSCs based on the interface void-free α-FAPbI3(Cs) HOIP thin films are much more efficient and stable in the ambient atmosphere. This interesting finding inspired us to develop a simple room-temperature aging method for preparing ...

Enhancement of the Opto-Electrical Properties of Ag Intermediate ZTO Films by Vacuum Annealing

Sn-doped ZnO (ZTO)/Ag/ZTO tri-layer films were deposited on glass substrates by radio frequency (RF) and direct current (DC) magnetron sputtering and then vacuum annealed at 100, 200 and 300 ℃ for 30 min with a proportions of H2/N2 gas flow of 6/6 sccm, to investigate the effects of annealing temperature on their electrical, and optical properties. After annealing at a temperature of 300 ℃, the optical transmittance in the visible wavelength region increased from 82.0 to 83.8% and their electrical resistivity decreased to as low as 5.38×10-5 Ω cm at an annealing temperature of 300 ℃. The figure of merit revealed that ZTO/Ag/ZTO films annealed at 300 ℃ have higher optical and electrical performance than the other TCO films prepared under different conditions. (Received June 7, 2016; Accepted August 30, 2016)

A pure and stable intermediate phase is key to growing aligned and vertically monolithic perovskite crystals for efficient PIN planar perovskite solar cells with high processibility and stability

Solvent engineering has been extensively used to control the growth of a high-quality perovskite layer for solar cells by forming intermediate phases. However, the intermediate phase formation is often poorly understood and its effects on the perovskite layer growth are still elusive. Here, we have conducted a systematic and in-depth study on the above two issues through a strict control over the DMSO/DMF ratio in CH3NH3PbI3 perovskite solutions, and thus an effective control over the compositions of intermediate films. The films thus obtained, including perovskite, perovskite/MA2Pb3I8(DMSO)2 and MA2Pb3I8(DMSO)2, afford perovskite crystals via down-growth, down-and up-growth, and up-growth mechanisms, respectively. Significantly, the up-growth perovskite crystals from the pure MA2Pb3I8(DMSO)2 exhibits the best interface contact with NiO substrate, optimal alignment without horizontal grain boundaries and a relatively large grain size, which facilitate charge transfer and reduce charge recombination in PSCs. As a result, the PIN planar PSCs based on NiO have achieved a PCE of 18.4%, a value which is among the highest for NiO-based PSCs, with the highest stability among the tested sample cells. Furthermore, the pure MA2Pb3I8(DMSO)2 intermediate phase presents a high long-term stability, which enlarges the operating window for perovskite deposition and thus considerably improves the device processibility.

Laser welding of fused silica glass with sapphire using a non- stoichiometric, fresnoitic Ba2TiSi2O8·3 SiO2 thin film as an absorber

Laser welding of dissimilar materials is challenging, due to their difference in coefficients of thermal expansion (CTE). In this work, fused silica-to-sapphire joints were achieved by employment of a ns laser focused in the intermediate Si-enriched fresnoitic glass thin film sealant. The microstructure of the bonded interphase was analyzed down to the nanometer scale and related to the laser parameters used. The crystallization of fresnoite in the glass sealant upon laser process leads to an intense blue emission intensity under UV excitation. This crystallization is favored in the interphase with the silica glass substrate, rather than in the border with the sapphire. The formation of SiO2 particles was confirmed, as well. The bond quality was evaluated by scanning acoustic microscopy (SAM). The substrates remain bonded even after heat treatment at 100°C for 30min, despite the large CTE difference between both substrates.

<em>In Situ</em> Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films.

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

The Effect of Anodic Oxide Films on the Nickel-Aluminum Reaction in Aluminum Braze Sheet

The influence of an anodic oxide surface film on the nickel-aluminum reaction at the surface of aluminum brazing sheet has been investigated. Samples were anodized in a barrier-type solution and subsequently sputtered with nickel. Differential scanning calorimetry (DSC) and metallography were used as the main investigative techniques. The thickness of the anodic film was found to control the reaction between the aluminum substrate and nickel coating. Solid-state formation of nickel-aluminum intermetallic phases occurred readily when a relatively thin oxide film (13 to 25 nm) was present, whereas intermetallic formation was suppressed in the presence of thicker oxides (~60 nm). At an intermediate oxide film thickness of ~35 nm, the Al3Ni phase formed shortly after the initiation of melting in the aluminum substrate. Analysis of DSC traces showed that formation of nickel-aluminum intermetallic phases changed the melting characteristics of the aluminum substrate, and that the extent of this change can be used as an indirect measure of the amount of nickel incorporated into the intermetallic phases.

Influence of Heat Transfer on Anode Reactions When Electrowinning Metal from Its Oxides Dissolved in Molten Fluorides

Detection of CF4 coevolution during commercial electrowinning from oxide fluoride melts at anode potentials below those required for direct electrochemical formation raise doubts about published mechanisms of the cause of anode effects (AE). By linking anode-electrolyte potential gradients with anode carbon structure, cell design, and the composition of gases emitted we have obtained a better understanding of all product formation reactions. Interfacial heat transfer to satisfy the entropic energy deficit is found to be the common link between electrode potential, operating conditions and gas composition for all reactions occurring in the fluoride-oxide melts studied. Concurrent thermodynamic analysis suggests that formation of an intermediate such as a fluorinated carbon surface or COF2 would lower the required potential for the overall reactionAl2O3+2Na3AlF6l+9/2C=4Al+3COg+3/2CF4g+6NaFlThis is supported by experimental verification of the intermediate. The entropic energy deficit is linked to the buildup of the resistive or passivating intermediate fluoride film on the carbon anode surface which is capable of generating Joule heat enabling the various parallel reactions to occur with or without an anode effect.

Enhancement of the absorbance figure of merit in amorphous-silicon p-i-n solar cell by using optimized intermediate metallic layers

In this paper, a new approach based on optimized intermediate metallic thin film engineering aspect is proposed to improve the absorption behavior for amorphous-Silicon (a-Si:H) p-i-n Solar Cell. The overall solar cell optical performance comparison between the conventional design and a proposed design including three different intermediate metallic layers (Au, Ag and Ti) is carried out numerically using accurate solutions of Maxwell’s equations. It is found that the proposed design with intermediate metallic sub-layers’ engineering provides superior integral absorption in comparison to that offered by the conventional structure. Therefore, the introduced intermediate metallic layers play a paramount role in increasing the light absorbance and modulate the electric field in the intrinsic region, where more light can be absorbed again by a-Si in the near infrared and infrared-regions using titanium as intermediate metallic layers. Furthermore, a hybrid computation based on combined numerical- metaheuristic modeling approach is proposed to boost the solar cell performance by optimizing the intermediate metallic layers. The obtained results indicate the advantage of the proposed design methodology in improving the amorphous solar cell performances.

Ni 층간박막에 따른 SnO2박막의 전기적, 광학적 물성 변화

<TEX>$SnO_2$</TEX> single layer films (100 nm thick) and 2 nm thick Ni intermediated <TEX>$SnO_2$</TEX> films were deposited on glass substrate by RF and DC magnetron sputtering without intentional substrate heating and then the influence of the Ni interlayer on the electrical and optical properties of the films were investigated. As deposited <TEX>$SnO_2$</TEX> single layer films show the optical transmittance of 82.6% in the visible wavelength region and a resistivity of <TEX>$6.6{ \times}10^{-3}{\Omega}cm$</TEX>, while <TEX>$SnO_2/Ni/SnO_2$</TEX> trilayer films show a lower resistivity of <TEX>$2.7{ \times}10^{-3}{\Omega}cm$</TEX> and an optical transmittance of 76.3% in this study. Based on the figure of merit, it can be concluded that the intermediate Ni thin film effectively enhances the opto-electrical performance of <TEX>$SnO_2$</TEX> films for use as transparent conducting oxides in flexible display applications.

Thickness and temperature dependence of the magnetodynamic damping of pulsed laser deposited La0.7Sr0.3MnO3 on (111)-oriented SrTiO3

We have investigated the magnetodynamic properties of La0.7Sr0.3MnO3 (LSMO) films of thickness 10, 15 and 30nm grown on (111)-oriented SrTiO3 (STO) substrates by pulsed laser deposition. Ferromagnetic resonance (FMR) experiments were performed in the temperature range 100–300K, and the magnetodynamic damping parameter α was extracted as a function of both film thickness and temperature. We found that the damping is lowest for the intermediate film thickness of 15nm with α≈2·10−3, where α is relatively constant as a function of temperature well below the Curie temperature of the respective films.

Platinum/yttrium iron garnet inverted structures for spin current transport

30-80 nm thick yttrium iron garnet (YIG) films are grown by pulsed laser deposition on a 5 nm thick sputtered Pt atop gadolinium gallium garnet substrate (GGG) (110). Upon post-growth rapid thermal annealing, single crystal YIG(110) emerges as if it were epitaxially grown on GGG(110) despite the presence of the intermediate Pt film. The YIG surface shows atomic steps with the root-mean-square roughness of 0.12 nm on flat terraces. Both Pt/YIG and GGG/Pt interfaces are atomically sharp. The resulting YIG(110) films show clear in-plane uniaxial magnetic anisotropy with a well-defined easy axis along 〈001〉 and a peak-to-peak ferromagnetic resonance linewidth of 7.5 Oe at 9.32 GHz, similar to YIG epitaxially grown on GGG. Both spin Hall magnetoresistance and longitudinal spin Seebeck effects in the inverted bilayers indicate excellent Pt/YIG interface quality.

Decorating wood flour/HDPE composites with wood veneers

The low surface free energy makes wood plastic composites difficult to bond with traditional adhesives, such as urea formaldehyde resin (UF). This study investigates the decoration of wood flour/high‐density‐polyethylene composite (WF/HDPE) board with poplar wood veneers. High‐density polyethylene (HDPE) or maleic anhydride grafted polyethylene (MAPE) film was introduced between the veneer and the WF/HDPE composite board as an intermediate component to strengthen the bond. Surface bonding strength, hot water resistance, and bending performance of the composites were then evaluated. Contact angle, Attenuated total reflection‐Fourier transform infrared (ATR‐FTIR) spectroscopy, and scanning electron microscopy (SEM) were used to analyze the interface of the wood veneer and the WF/HDPE composites. The addition of MAPE film enhanced the polar characteristic of the WF/HDPE composite surface and increased the number of functional groups reacting with the –OH groups present in the wood veneer. A MAPE intermediate film increased the surface bonding strength of the wood veneer to WF/HDPE composite surface, and also endured boiling water without delimitation failure. After being covered with the wood veneer, the flexural strength and modulus of WF/HDPE composite panels increased four times comparing to that of the uncovered composites. POLYM. COMPOS., 39:1144–1151, 2018. © 2016 Society of Plastics Engineers

Plasmonic behaviour of sputtered Au nanoisland arrays

The specificity of the formation of Au sputtered nanoisland arrays (NIA) on a glass substrate or on a ZnO thin film doped by Ga is demonstrated. Statistical analysis of morphology images (SEM, AFM) exhibited the Log-normal distribution of the size (area) of nanoislands—their modus AM varied from 8 to 328nm2 depending on the sputtering power density, which determined the nominal thicknesses in the range of 2–8nm. Preferential polycrystalline texture (111) of Au NIA increased with the power density and after annealing. Transverse localised surface plasmonic resonance (LSPR; evaluated by transmission UV–vis spectroscopy) showed the red shift of the extinction peaks (Δl≤100nm) with an increase of the nominal thickness, and the blue shift (Δλ≤−65nm) after annealing of Au NIA. The plasmonic behaviour of Au NIA was described by modification of a size-scaling universal model using the nominal thin film thickness as a technological scaling parameter. Sputtering of a Ti intermediate adhesive ultrathin film between the glass substrate and gold improves the adhesion of Au nanoislands as well as supporting the formation of more defined Au NIA structures of smaller dimensions.

Possibility of the use of intermediate carbidsiliconoxide nanolayers on polydiamond substrates for gallium nitride layers epitaxy

The results of using carbidsiliconoxide (a-C:SiO1.5) films with a thickness of 30–60 nm, produced by the pyrolysis annealing of oligomethylsilseskvioksana (CH3–SiO1.5)n with cyclolinear (staircased) molecular structure, as intermediate films in the hydride vapor phase epitaxy of gallium nitride on polycrystalline CVD-diamond substrates are presented. In the pyrolysis annealing of (CH3–SiO1.5)n films in an atmosphere of nitrogen at a temperature of 1060°C, methyl radicals are carbonized to yield carbon atoms chemically bound to silicon. In turn, these atoms form a SiC monolayer on the surface of a-C:SiO1.5 films via covalent bonding with silicon. It is shown that GaN islands grow on such an intermediate layer on CVD-polydiamond substrates in the process of hydride vapor phase epitaxy in a vertical reactor from the GaCl–NH3–N2 gas mixture.

Atomic Scale Imaging of Nucleation and Growth Trajectories of an Interfacial Bismuth Nanodroplet

Because of the lack of experimental evidence, much confusion still exists on the nucleation and growth dynamics of a nanostructure, particularly of metal. The situation is even worse for nanodroplets because it is more difficult to induce the formation of a nanodroplet while imaging the dynamic process with atomic resolution. Here, taking advantage of an electron beam to induce the growth of Bi nanodroplets on a SrBi2Ta2O9 platelet under a high resolution transmission electron microscope (HRTEM), we directly observed the detailed growth pathways of Bi nanodroplets from the earliest stage of nucleation that were previously inaccessible. Atomic scale imaging reveals that the dynamics of nucleation involves a much more complex trajectory than previously predicted based on classical nucleation theory (CNT). The monatomic Bi layer was first formed in the nucleation process, which induced the formation of the prenucleated clusters. Following that, critical nuclei for the nanodroplets formed both directly from the addition of atoms to the prenucleated clusters by the classical growth process and indirectly through transformation of an intermediate liquid film based on the Stranski-Krastanov growth mode, in which the liquid film was induced by the self-assembly of the prenucleated clusters. Finally, the growth of the Bi nanodroplets advanced through the classical pathway and sudden droplet coalescence. This study allows us to visualize the critical steps in the nucleation process of an interfacial nanodroplet, which suggests a revision of the perspective of CNT.

Electrical Conductive Surface Functionalization of Polycarbonate Parts with CNT Composite Films during Injection Molding

This study describes a reactive process to transfer an electrical conductive polycarbonate (PC) film onto the surface of bulk polycarbonate by an injection molding process using hyper branched poly (ethylenimine) (PEI). Due to a nucleophilic substitution reaction between the amino groups of the poly (ethylenimine) and the carbonate groups of the PC, a stable covalent crosslinking is established. The resulting conductive layer has an average thickness of about 3 -7 µ m and a surface roughness that depends on the roughness of the cavity. The lowest resulting electrical surface resistivity of the final injection molded part of 5.58 ∙ 104 Ω per square is measured for a composites film loaded with 5 wt.% CNT . The crosslinking PEI layer has a thickness of about 50 nm, which equates with the hydrodynamic radius of a random PEI molecule with molecular weight of about 750.000 g∙mol-1. As a consequence, all PEI intermediate surface films remain completely on the PC parts.

Shielding Superconductors with Thin Films as Applied to rf Cavities for Particle Accelerators

Determining the optimal arrangement of superconducting layers to withstand large amplitude AC magnetic fields is important for certain applications such as superconducting radiofrequency cavities. In this paper, we evaluate the shielding potential of the superconducting film/insulating film/superconductor (SIS') structure, a configuration that could provide benefits in screening large AC magnetic fields. After establishing that for high frequency magnetic fields, flux penetration must be avoided, the superheating field of the structure is calculated in the London limit both numerically and, for thin films, analytically. For intermediate film thicknesses and realistic material parameters we also solve numerically the Ginzburg-Landau equations. It is shown that a small enhancement of the superheating field is possible, on the order of a few percent, for the SIS' structure relative to a bulk superconductor of the film material, if the materials and thicknesses are chosen appropriately.

Study of the mechanical behavior and corrosion resistance of hydroxyapatite sol–gel thin coatings on 316 L stainless steel pre-coated with titania film

In order to reinforce the clinical applications of hydroxyapatite (HAP) sol–gel coatings deposited onto 316 L stainless steel, we suggest the introduction of an intermediate thin layer of titania (TiO2) on the substrate. The titania sub-layer is introduced in order to improve both the corrosion resistance and the mechanical properties of the HAP/316 L stainless steel coated system. The two coatings, HAP and TiO2, were studied separately and afterwards, compared with the bi-layered coating. A film without any cracks is obtained under the optimum conditions in terms of annealing temperature, dipping rate and aging effect. Microstructural, morphological and profilometry analysis revealed the non-stoichiometric carbonated porous nature of the hydroxyapatite coatings, which were obtained after annealing at 500°C during 60min in the atmosphere. The obtained TiO2 coatings exhibit a dense and uniform surface. Addition of TiO2 as sub-layer of the HAP coating tends to increase the homogeneity and the crystallinity rate as compared to the HAP one.The mechanical properties, i.e. hardness and elastic modulus, are determined by means of nanoindentation experiments and the adhesion between the coating and substrate is estimated by scratch tests. The corrosion behavior is evaluated by potentiodynamic cyclic voltammetry tests. As a main result, the values of the elastic modulus and hardness, respectively of 30GPa and 2.5GPa, are relatively high for the HAP–TiO2 bilayer coating. This result allows the use of such coated material as a replacement material for hard tissues. The adhesion strength increased from 2925mN up to 6430mN after the addition of the TiO2 intermediate film. According to the Tafel's analysis, the 316 L stainless steel specimens coated with both HAP and titania layers (ECorr=−234mV, lCorr=0.089μAcm−2) present a better resistance than the HAP-coated specimens (ECorr=−460mV, lCorr=0.860μAcm−2).