Preparation of the nickel foam/Ni-Ce-Co-O film electrode by thermal decomposition for oxygen evolution reaction

The Ni-Ce-Co-O film on nickel foam was prepared by thermal decomposition of acetates. The electrochemical activity of the film was affected by the temperature of thermal decomposition. Cerium ions introduced into the oxide film could increase the surface area and improve the oxygen evolution reaction (OER) activity of the electrode. Compared with thermal decomposition of nitrates, the OER activity of the film prepared with acetates was higher. When the nickel foam/Ni-Ce-Co-O film electrode prepared with acetates was used as the anode, in 30% KOH solution (88 ± 2 °C) at the current density of 4000 A/m², the cell voltage was 250 mV lower than that of the nickel foam anode. Furthermore, the film electrode exhibited good stability.     

Preparation of indium sulfide thin films by spray pyrolysis using a new precursor indium nitrate

Indium nitrate and thiourea were used as the precursor solutions for preparing indium sulfide thin films using Chemical Spray Pyrolysis (CSP) technique. Films having various In/S ratios were characterized using X-Ray Diffraction (XRD), Energy Dispersive X-ray Analysis (EDX), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), optical absorption, transmission and photosensitivity measurements. Sample having In/S ratio 2/3 showed better crystallinity with band gap 2.66 eV. Depth profile of the sample also indicated the formation of indium sulfide. It was also observed that In/S ratio in the initial precursor solution determined the composition as well as electrical properties of the films. Maximum photosensitivity was observed for the sample prepared using solution having In/S ratio 2/4.     

Electrodeposition of n-type Bi2Te3−ySey thermoelectric thin films on stainless steel and gold substrates

Thermoelectric films of n-Bi₂Te_3−ySe_y were prepared by potentiostatic electrodeposition technique onto stainless steel and gold substrates at room temperature. These films were used for morphological, compositional and structural analysis by environment scanning electron microscope (ESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The effect of different substrates on the structure and morphology of Bi₂Te_3−ySe_y films and relation between Se content in the electrodepositing solutions and in the films were also investigated. These studies revealed that Bi, Te and Se could be co-deposited to form Bi₂Te_3−ySe_y semiconductor compound in the solution containing Bi³⁺, HTeO₂⁺ and H₂SeO₃. The morphology and structure of the films are sensitive to the substrate material. The doped content of Se element in the Bi₂Te_3−ySe_y compound can be controlled by adjusting the Se⁴⁺ concentration in the electrodepositing solution. X-ray diffraction analysis indicates that the films prepared at −40 mV versus saturated calomel electrode (SCE) exhibit strong (1 1 0) orientation with rhombohedral structure.     

Effect of the Pd-Au thin film thickness uniformity on the performance of an optical fiber hydrogen sensor

Thin alloy film of Pd and Au, formed by simultaneous electron-beam and thermal evaporation techniques, respectively, is used in the design of an optical fiber hydrogen sensor. The sensor consists of a multimode fiber (MMF) in which a short section of single mode fiber (SMF), coated with the Pd-Au thin film, is inserted. Due to core diameter mismatch, the SMF cladding guides light, allowing the interaction between the sensing layer and the guided light. When the sensor is exposed to hydrogen, the Pd-Au layer refractive index diminishes and causes attenuation changes on the transmitted light. Several samples with different layer thickness uniformity were fabricated and tested in a very simple experimental set-up. We have observed that the sensor signal change is dependant on layer thickness uniformity, since the effective interaction length between the evanescent field and the sensing layer is increased. By contrast, such uniformity practically has no influence on the time response of the sensor. The resulting Pd-Au film can detect 4% hydrogen with a response time of 15 s.     

Interfacial and adhesional aspects in polyurethane (PUR) membrane coating on Si3N4 surface of ISFET gate for REFET fabrication

Polyurethane membrane coatings on: (i) packaged ISFET (ion-sensitive field-effect transistor) devices and (ii) those in the form of chips have been investigated. The study has revealed that for reliable membrane deposition, proper film adhesion at polyurethane-silicon nitride and polyurethane-cured epoxy interfaces of ISFET was necessary. Membranes formed on packaged ISFETs were found to lift off after a short time period (<1 h) when immersed in pH 6.86 buffer solution. This was because the adhesion between polyurethane and surrounding cured epoxy was insufficient. If the membrane coating was performed on the chip, and the chip was subsequently packaged (protecting the coating on the sides with epoxy and curing the epoxy to fasten the membrane), the coating was not attacked in buffer solution. Based on these studies, a process for depositing reliable, long-lasting polyurethane membranes on ISFET gate surfaces has been proposed. Membrane reliability has been confirmed by storing the membrane-coated ISFET in buffer solution over seven days and periodically observing it microscopically. Membranes have been characterized through pH sensitivity and gate-source impedance measurements. pH sensitivities of ISFETs with polyurethane membranes were measured to be ≤4.2 mV/pH.     

Adhesive-free bonding of Zerodur glass to silicon

This work demonstrates anodic bonding of Zerodur glass having very low co-efficient of thermal expansion (CTE) to Si, Zerodur glass to thermally grown silicon dioxide on silicon and Pyrex glass to Ge. Bonding results, using point cathode contact and plate cathode contact configurations, are discussed. Bonding parameters, i.e. applied dc voltage, temperature and bonding time were determined. Heating and cooling rates for crack-free bonding of Zerodur glass were also determined.     

SbOx Thin Films Used for Write-Once Blue Laser Recording

SbOx thin films are deposited by reactive dc-magnetron sputtering from an antimony metal target in Ar＋O2 with the relative O2 content 7%. It is found that the as-deposited films can represent a two-component system comprising amorphous Sb and amorphous Sb2 O3. The crystallization of Sb is responsible for the changes of optical properties of the films. The results of the static test show that the SbOx thin films have good writing sensitivity for blue laser beams and the recording marks are very clear and circular. High reflectivity contrast of about 41% is obtained at a writing power 6mW and writing pulse width 300ns. In addition, the films show a good stability after reading 10000 times.     

Write-Once Medium with Fe-Doped BiOx Thin Films for Blue Laser Recording

Fe：BiOx films are fabricated on K9 glass substrates by rf-magnetron sputtering of a BiFeO target under argon atmosphere with increasing sputtering power from 80 to 200 W at room temperature. It is found that the thin films grown at the sputtering power of 160 W can be formed at an appropriate deposition rate and have an improved surface morphology. The XPS result reveals that the films investigated are comprised of Bi, Fe and O elements. A typical XRD pattern shows that no phase transition occurs in the films up to 400℃. The results of the blue laser recording test demonstrate that the Fe：BiOx films have good writing sensitivity for blue laser beam （406.7nm） and good stability after reading 10000 times. The recording marks of 200nm or less are obtained. These results indicate that the introduction of Fe into BiOx films can reduce the mark size and improve the stability of the films.     

Effect of organic additives on characterization of electrodeposited Co-W thin films

Co-W thin films were electrodeposited from aqueous bath with different organic additives. Electrochemical analysis showed that the transient state was limited and polarization behaviors were more evident during Co-W electrodeposition in the presence of organic additives. SEM measurement indicated that the surface morphology was affected by the nature of the organic additives to a large extent. Homogeneous Co-W thin films were obtained from the solutions containing ethyl methacrylate. Moreover, it was obvious that the presence of organic additives, in the electroplating bath, modified the structure and magnetic properties of the Co-W thin films according to the XRD and VSM measurements.     

Modeling of chemical-mechanical polishing with soft pads

Received: 8 Dezember 1997/Accepted: 5 January 1998     

Influence of complexing agent on the electrodeposited Co-Pt-W magnetic thin films

Complexing agents are often used to improve the quality of electrodeposited alloys. Influence of different complexing agents with hydroxycarboxylic acid group on the electrodeposited Co-Pt-W thin films has been investigated. Cathodic polarization curves show that the polarization behaviors of electroplating bath with different complexing agents are very different. Surface morphology, phase composition and magnetic properties are observed by means of FESEM, XRD and vibrating sample magnetometer (VSM), respectively. It has been found out that, if citrate was used as complexing agent, the Co-Pt-W thin films were homogeneous and the granular crystals with the average grain size of 2 μm have been observed. Co-Pt-W thin films exhibited hexagonal close packed (hcp) lattice and strong perpendicular anisotropic magnetic behavior (H_c⊥ = 215.5 kA/m; H_c∥ = 55.4 kA/m). In the presence of gluconate, needle-like deposits were obtained and a strong face centered cubic (fcc(1 1 1)) texture was measured. The Co-Pt-W thin films showed isotropic magnetic behavior. In the case of tartate and malate, the coexistence of needle-like deposits and cellular deposits appeared. The XRD patterns showed that the mixed fcc and hcp phase formed. Perpendicular anisotropic magnetic behaviors of thin films, from malate or tartate baths, were not obvious.     

Molecular imprinting and adsorption of metallothionein on nanocrystalline titania membranes

Metallothionein (MT) imprinted TiO₂ membrane was synthesized via surface sol-gel process, using MT as template and TiO₂ sol as imprinted matrix. Appropriate template cavities in the TiO₂ sol-gel membrane were formed after the template molecules were removed on treatment with 1% NaOH solution. In situ technique of quartz crystal microbalance (QCM) was employed to study the molecular imprinting behavior of MT on nanocrystalline titania membranes. The imprinted membrane showed selectivity recognition for MT as compared to the other proteins. The amount of adsorption increased with the increasing of MT concentration both on imprinted membrane and non-imprinted membrane. The adsorption amount increased with the increasing of pH on imprinted membrane.     

Surface wave effect on light scattering from one-dimensional photonic crystals

Light scattering and reflection measurements using attenuated total reflection technique for s polarization of the incident light on a finite one-dimensional photonic crystal are reported. Angular specular reflection was measured experimentally to determine, the optimum thickness, the angular position of the surface mode, and the number of bi-layers of the system. It was demonstrated that the position of the surface mode inside the last film is close to the asymptotic value when the number of periods is increased. Spectral reflection measurements were made to determine experimentally the band gap width and measure the dispersion relation of the surface mode inside this band. The corresponding field amplitude was calculated (∣E∣²) showing that in resonant conditions it has a maximum near the surface. The angular dependence of the scattered light measured displays a peak caused by singles cattering and located approximately at the excitation angle of the surface electromagnetic mode. When the incident light is in resonance with the surface electromagnetic wave, it is found experimentally that the scattering of light is enhanced overall by approximately one order of magnitude in comparison with the off-resonance case.     

Intensity-Dependent Optical Nonlinear Absorption and Refraction of Gold Nanorods

Au nanorods dispersed in aqueous solution were prepared with the electrochemical method. The absorption spectrum shows two absorption peaks corresponding to the perpendicular and transverse surface plasma resonance absorption of the nanorods. The third-order optical nonlinear properties are investigated by Z-scans. The signs of the nonlinear absorption coemcient and refractive index are reversed as the intensity of incident laser increases, which is due to the shape change of the gold nanoparticles melted by the intense laser pulses.     

Ice adhesion on super-hydrophobic surfaces

In this study, ice adhesion strength on flat hydrophobic and rough super-hydrophobic coatings with similar surface chemistry (based on same fluoropolymer) is compared. Glaze ice, similar to naturally accreted, was prepared on the surfaces by spraying super-cooled water microdroplets at subzero temperature. Ice adhesion was evaluated by spinning the samples at constantly increasing speed until ice delamination occurred. Super-hydrophobic surfaces with different contact angle hysteresis were tested, clearly showing that the latter, along with the contact angle, also influences the ice-solid adhesion strength.     

Preparation and study of complex self-assembled film as a super-thin barrier on silver

A self-assembled monolayers (SAMs) of (3-mercaptopropy) trimethoxysilane (3-MPT) chemisorbed on silver surface was chemically modified by 1-octadecanethiol (C₁₈H₃₇SH) (to form self-assembled mixed-monolayer (SAMM)) and the co-polymer of N-vinylcarbazole and methyl methacrylate ester to form complex self-assemblied film (CSAF). The combinative state of interface between SAMs (or SAMM) and co-polymer were characterized by dynamic mechanical thermal analysis (DMTA). The thickness of film on Ag was characterized by X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) measurements in 10% NaOH aqueous solution with the silver surface and covered with film indicated that 3-MPT SAMs modified with C₁₈H₃₇SH and then with co-polymer have higher capability against oxidation.     

Anti-icing performance of superhydrophobic surfaces

This article studies the anti-ice performance of several micro/nano-rough hydrophobic coatings with different surface chemistry and topography. The coatings were prepared by spin-coating or dip coating and used organosilane, fluoropolymer or silicone rubber as a top layer. Artificially created glaze ice, similar to the naturally accreted one, was deposited on the nanostructured surfaces by spraying supercooled water microdroplets (average size ∼80 μm) in a wind tunnel at subzero temperature (−10 °C). The ice adhesion strength was evaluated by spinning the samples in a centrifuge at constantly increasing speed until ice delamination occurred. The results show that the anti-icing properties of the tested materials deteriorate, as their surface asperities seem to be gradually broken during icing/de-icing cycles. Therefore, the durability of anti-icing properties appears to be an important point for further research. It is also shown that the anti-icing efficiency of the tested superhydrophobic surfaces is significantly lower in a humid atmosphere, as water condensation both on top and between surface asperities takes place, leading to high values of ice adhesion strength. This implies that superhydrophobic surfaces may not always be ice-phobic in the presence of humidity, which can limit their wide use as anti-icing materials.     

Effect of surface fluorination on the photocatalytic and photo-induced hydrophilic properties of porous TiO2 films

Porous surface-fluorinated TiO₂ (F-TiO₂) films were prepared through PEG modified sol-gel method and surface fluorination. The as-prepared films were characterized with XRD, FTIR, AFM, XPS and UV-vis DRS. The effects of surface fluorination on the photocatalytic activity and hydrophilicity of porous TiO₂ film were studied by photocatalytic degradation of rhodamine B (RhB) as well as water contact angle (CA) on porous TiO₂ film. The results showed that the surface fluorination increased the adsorption of RhB on the porous TiO₂ film and enhanced the photocatalytic degradation of RhB. The concentration and pH of NaF solutions affected much the photocatalytic activity of porous TiO₂ film. Porous F-TiO₂ film prepared in 40 mM NaF solution at pH 4.0 showed the highest photocatalytic activity. Because of its porous structure, the porous F-TiO₂ film had original water CA of 22.7°, which is much smaller than that of normal F-TiO₂ film. Under UV light irradiation, the water CA of porous F-TiO₂ film decreased to 5.1° in 90 min.     

Local enrichment and its nonlocal consequences for victim-exploiter metapopulations

The stabilizing effects of local enrichment are revisited. Diffusively coupled host-parasitoid and predator-prey metapopulations are shown to admit a stable fixed point, limit cycle or stable torus with a rich bifurcation structure. A linear toy model that yields many of the basic qualitative features of this system is presented. The further nonlinear complications are analyzed in the framework of the marginally stable Lotka-Volterra model, and the continuous time analog of the unstable, host-parasitoid Nicholson-Bailey model. The dependence of the results on the migration rate and level of spatial variations is examined, and the possibility of “nonlocal” effect of enrichment, where local enrichment induces stable oscillations at a distance, is studied. A simple method for basic estimation of the relative importance of this effect in experimental systems is presented and exemplified.