Homogeneous Metal Films Research Articles

Measurement of the Conductivity of Screen Printing Films at Microwave Frequency Employing Resonant Method

The conductivity of screen printing films at microwave frequency is one of the most important properties of conductive ink when applied in printed electronics. However, the existing methods of conductivity characterization at microwave frequency focus on homogeneous metal films or semiconductors, which are not suitable for conductive composite materials with poor thickness uniformity, like screen printing films. In this research, by applying a classic stripline ring resonator, a rigorous electromagnetic model was set up, and the conductivity of the screen printing film was able to be deduced by comparison between the measurement and simulation results. As a result, the equivalent conductivity of the film is 2 × 106 S/m at 1–3 GHz, which is a little higher than its average direct current conductivity of 1.82 × 106 S/m. This method has been proved to be feasible in measuring the conductivity of screen printing films at microwave frequency. Furthermore, it has great potential in the characterization of other printed conductive composite materials on rough surfaces, like textiles.

Ultra-low-voltage electrophoretic assembly of extremely water-repellent functional nano-Al films with long lifespan

It is still a bottleneck to design anti-wetting homogeneous metal films or coatings with great stability via by a high-efficiency and low-cost technique with applications in fields of battery, sensors, and electronics, etc. This paper proposed an environment-friendly ultra-low-voltage electrophoretic deposition (EPD) with facile modification post-processing method to fabricate a novel extremely water-repellent functional nano-Al films with evenly loose net-like structures and high purity. The optimized stable suspension consists of water–ethanol with trace nitric acid and polyethyleneimine. Product with an ultra-high contact angle of ~ 171° and extreme low sliding angle of 3 years) with great potential applications. These results provide a novel approach with low-cost and less energy consumption for preparing other functional ant-wetting metal coatings with wide potential applications.

Nanoporous platinum electrode grown on anodic aluminum oxide membrane: Fabrication, characterization, electrocatalytic activity toward reactive oxygen and nitrogen species

A new type of nanoelectrode, nanoporous platinum (NPt) electrode was prepared on aluminum oxide membrane by thermal evaporation deposition. The morphology, conductivity and electrocatalytic activity of NPt electrode were characterized and compared with those of nanofilm-Pt electrode through scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques, respectively. SEM images showed that “nanocavities” observed in NPt electrode were actually 2-dimensional enclosures by linked nanoparticles. It was different from the conventional arrays of “nanocavities” formed on homogeneous metal films. EIS data indicated that NPt electrode possesses higher conductivity. Compared with that on nanofilm-Pt electrode (14.05 Ω·cm2), the impedance spectrum on NPt electrode exhibits a semicircle portion with much smaller diameters (1.24 Ω·cm2 for NPt-100, 1.48 Ω·cm2 for NPt-200). Meanwhile, the response sensitivity of NPt electrode to O2 is 0.85 mA cm−2, which is larger than that of nanofilm-Pt electrode (0.54 mA cm−2). The largest catalytic current for nitric oxide (NO) was obtained in buffer with pH value of 9.4 while for Angeli's salt (AS) was obtained in buffer with pH value of 5.4. Additionally, electrocatalytic mechanisms of NPt electrode toward NO and AS were proposed, which indicating it depended on pH value of buffer solution.

Magneto-Optical Kerr Effect Enhancement in Co-Ti-O Nanocomposite Films

Co-Ti-O nanogranular films with different volume concentrations of a magnetic phase and Co/Ti-O layered structures with different numbers of layer pairs are studied by the magneto-optical Kerr effect. It is shown that, unlike the case of homogeneous metal films, the magneto-optical spectra of the nanogranular films exhibit resonance with a significant increase in the Kerr rotation angle in the wavelength range 500-700 nm. It is found that the Kerr rotation angle of the Co/Ti-O layer structures in the wavelength range 500-600 nm grows by an order of magnitude as compared to its value for ordinary Co films.

Effect of catalyst for nickel films for NiSi formation with improved interface roughness

Iodine is an effective catalyst to obtain homogeneous and smooth metal films with good interface properties. We adopted an iodine catalyst during the nickel film deposition by using atomic layer deposition (ALD) with bis(1-dimethylamino-2-methyl-2-butoxide)nickel [Ni(dmamb) 2] precursor and hydrogen reactant gas. The effect of iodine catalyst to nickel nucleation process was studied. The deposited films were silicided by rapid thermal process (RTP) which was performed by varying temperature from 400 °C to 900 °C in nitrogen ambient. The crystalline properties of nickel and nickel silicide films were examined by X-ray diffractometer (XRD) with various deposition temperatures. The interface properties and the surface morphology of nickel silicide films were studied by using Auger electron spectroscopy (AES) depth profile analyses and scanning electron microscopy (SEM). The experimental results showed that the iodine-catalyzed silicide film, which have a clean and smooth interface, exhibit lower resistivity, and lower leakage current density compared to that of non iodine-catalyzed films in implemented n +/p junction diode.

Cherenkov-like mechanism of surface waves excitation

The theory of the excitation of surface waves by a fast charged particle moving though a thin homogeneous metal film surrounded by a dielectric medium is proposed. The Vavilov-Cherenkov effect is shown to occur for surface waves at the particle velocity one or two orders of magnitude lower than the corresponding velocities in a homogeneous medium.

Tuning the optical transmission through a homogeneous doped semiconductor film by applying an external magnetic field

We theoretically and numerically studied the transmission of light through a homogeneous doped semiconductor film with a Drude tensor in the presence of an external magnetic field. The magneto-induced homogeneous metal films are found to exhibit a magneto-induced light transparency due to cyclotron resonance. In particular, the surface plasmon (SP) resonance mode of the magneto-induced metal film move to higher frequencies with increasing magnetic field, bringing about large changes in the extraordinary light transmission peaks predicted to occur in such a magneto-induced semiconductor film.

Cherenkov excitation of surface waves

A theory of the excitation of surface waves by a fast charged particle moving in a thin homogeneous metal film surrounded by a dielectric medium has been proposed. The Cherenkov effect for the surface waves has been shown to occur at the velocity of particles one or two orders of magnitude lower than the respective velocity in a homogeneous medium.

Transmittance and transparency of subwavelength-perforated conducting films in the presence of a magnetic field

We theoretically and numerically studied the transmission of light through a subwavelength-perforated metal film, as well as through a homogeneous metal film with a Drude ac conductivity tensor, in the presence of a static magnetic field. Both the perforated and the homogeneous metal films are found to exhibit a magnetoinduced light transparency and a decreasing reflectivity due to cyclotron resonance. In particular, the cyclotron resonance and the surface plasmon resonance of the perforated metal film move to higher frequencies with increasing magnetic field, bringing about large changes in the extraordinary light transmission peaks predicted to occur in such a film. The practical possibility of changing the sample transparency by application of a static magnetic field is discussed.

High-optical-throughput individual nanoscale aperture in a multilayered metallic film

The optical transmission of an individual subwavelength aperture in a multilayered metal film is shown to be enhanced compared with that of a homogeneous metal film. The enhancement effect is due to the light coupling to surface plasmon excitation facilitated by a film periodicity. The sensitivity of the transmission to the dielectric filling of the aperture is also shown. The latter effect can be used to switch and control the transmittance. Devices based on enhanced transmission through nanosized apertures can find applications in high-density optical and magneto-optical data storage, high-resolution microscopy, and photolithography, where nanoscale light sources with high-optical-power throughput are required, as well as in sensor applications.

On the optical properties of gadolinium hydride systems

Thin Pd-capped rare-earth metallic films switch reversibly from their initial reflecting state (metal phase) to visually transparent state (insulator or semiconductor phase) when exposed to gaseous hydrogen. Palladium-capped Gadolinium films were prepared by rf-sputtering technique to produce very homogeneous and high-quality metal films as indicated by X-ray and scanning electron microscope analysis. After preparation, a separate cell and experimental setup are used that allow both optical and electrical measurements of the films during hydrogen loading simultaneously. The thickness dependence of the switching properties of Gadolinium hydride system is presented. The complex refractive index, the thickness, as well as the energy gap, of GdH 3 films (transparent phase) were calculated from transmission data by use of a new technique based on “Forouhi–Bloomer” model, and by a recent “pointwise unconstrained minimization approach” method.

Site‐specific deposition of colloidal Pd nanoparticles on self‐assembled microtubules from biolipid

AbstractLipid microtubules with wound ribbon features were fabricated by self‐assembling method, and the deposition patterns of colloidal Pd particles on tubular template were investigated. The result indicates that colloidal Pd nanoparticles are preferentially decorated on the helical markings in the interior and on the exterior of preformed tubule and to the edge of loosely helical ribbons to obtain helical deposition features. The multi‐bilayer microstructure of tubules can be marked by fine Pd nanoparticles deposited at the edge of helical ribbon. There are the site‐specific interactions between lipid tubular template and colloidal Pd particles at the helical edge. A new route was illustrated that colloidal Pd particles firmly attach at the edge of thin flat membranes, and then thin membranes roll up and reassemble into tubule together with particles to form helical deposition patterns. The site‐specific deposition of Pd is unbeneficial to obtain the homogeneous metal film on tubules, but it can be utilized to reveal the different chemical nature of lipid molecular assembly.

Preparation and characterization of Pd–Cu composite membranes for hydrogen separation

Pd–Cu composite membranes were made by successive electroless deposition of Pd and then Cu onto various tubular porous ceramic supports. Ceramic filters used as supports included symmetric α-alumina (nominal 200 nm in pore size), asymmetric zirconia on α-alumina (nominal 50 nm pore size), and asymmetric γ-alumina on α-alumina (nominal 5 nm pore size). The resulting metal/ceramic composite membranes were heat-treated between 350 and 700 °C for times ranging from 6 to 25 days to induce intermetallic diffusion and obtain homogeneous metal films. Pure gas permeability tests were conducted using hydrogen and nitrogen. For an 11 μm thick, 10 wt.% Cu film on a nominal 50 nm pore size asymmetric ultrafilter with zirconia top layer, the flux at 450 °C and 345 kPa H 2 feed pressure was 0.8 mol/m 2 s. The ideal hydrogen/nitrogen separation factor was 1150 at the same conditions. The thickness of the metallic film was progressively decreased from 28 μm down to 1–2 μm and the alloy concentration was increased to 30 wt.% Cu. Structural factors related to the ceramic support and the metallic film chemical composition are shown to be responsible for the differences in membrane performance. Among the former are the support pore size, which controls the required metal film thickness to insure a leak-free membrane and the internal structure of the support (symmetric or asymmetric) which changes the mass transfer resistance. The support with the 200 nm pores required more Pd to plug the pores than the asymmetric membranes with smaller pore sizes, as was expected. However, leak-free films could not be deposited on the support with the smallest pore size (5 nm γ-alumina), presumably due to surface defects and/or a lack of adhesion between the metal film and the membrane surface.

Thin metal and metal oxide films deposited by the anodic vacuum arc technique

Thin metal (e.g., Al, Cu, Ag) and metal oxide films (e.g., SiO x , Al y O x , Sn y O x ) were deposited on synthetic materials using a vacuum arc with a consumable anode. In constrast to a cathodic vacuum arc, the anodic vacuum arc generates a droplet free, only the evaporated anode material consisting of plasma in the entire volume. The degree of ionization can easily be influenced by the geometrical position of the anode with respect to the cathode. The ion energy on the surface can be adjusted by biasing the substrates. With this technology it is possible to deposit thin homogeneous metal films with an extremely high rate of growth. The films are distinguished by their high purity and bulk character. The temperature of the substrates during deposition is well below 100°C and ignition takes place below 10 −2 Pa. In order to deposit metal oxide films on synthetic materials we evaporated metals or metal oxides (e.g., SiO) in an oxygen atmosphere with an oxygen partial pressure ranging between 10 −1 and 5 Pa (reactive anodic arc deposition). The metal films and metal layer systems were deposited to improve the electrical performance of the synthetic materials. The quality of the films was characterized by measuring the adhesion, and additionally the portion of scattered light of the transmission for the metal oxide films were measured after a sand trickling test according to DIN 52 348.

Thin metal and SiO x films deposited by the anodic vacuum arc technique

Thin metal and SiO x films were deposited on synthetic materials using a vacuum arc with a consumable anode. In contrast to a cathodic vacuum arc, the anodic vacuum arc generates a droplet-free plasma that consists of only the evaporated anode material in the entire volume. The degree of ionization can easily be affected by the geometrical position of the anode with respect to the cathode, and the ion energy can be adjusted by a bipolar bias. With this technology, it is possible to deposit thin homogeneous metal films with an extremely high rate of growth. The films are distinguished by their high purity and bulk character. The temperature of the substrates during deposition is much below 100 °C and the ignition takes place below 10 −2 Pa. To deposit SiO x films on synthetic materials, we evaporated Si, SiO 2 in an oxygen atmosphere with a pressure ranging between 10 −1 and 5 Pa (reactive anodic arc deposition). The permeability of the deposited films for visible light is a function of the oxygen partial pressure p O 2 within the system. The permeability increases but the growth rate decreases with increasing p O 2 . Furthermore, we investigated the effect of a pretreatment of the synthetic material substrates by plasma etching with different gas composition (CF 4 and O 2) on the adhesion of the SiO x films.

Synthesis and evaluation of magnetic thin films

A simple, economic chemical vapor deposition (CVD) method for the coating of substrates with high quality homogeneous thin metal films is developed. The physical and magnetic properties of these magnetic films are evaluated. The results show that the film quality achieved is equivalent to that of other techniques. >

Tungsten metal film formed by spin-coating amorphous peroxopolytungstic acid

A homogeneous, amorphous peroxopolytungstic acid film can be formed easily with the spin-coating method. The film is found to provide a homogeneous tungsten metal film after reduction with hydrogen at ∼400 °C. Although the electric resistivity (∼450 μΩ cm) is higher than that for the bulk (5.65 μΩ cm), this method has an advantage in addition to spin coatability: tungsten metal films with fine patterns can be easily obtained because the starting material is photosensitive.

Superconducting Transition of Quench-Condensed Ultrathin Films

The condition of the onset of superconductivity in highly homogeneous ultrathin Bi and Pb films has been investigated by measuring the temperature dependence of the sheet resistance R□. The experimental results suggest that highly homogeneous metal films with R□ lower than ∼6 k Ω could be superconducting, while those with R□ greater than ∼6 k Ω are insulating at zero temperature, in agreement with the condition of the onset of global superconductivity in granular films. The superconducting transition temperature Tc shows a remarkable decrease with increasing the normal-state sheet resistance, unlike the results of granular films.

Application of emission electron microscopy to the surface examination and topography of glasses with thin surface (Al, Cu, Au, Ni, Pt) metal films

Results are reported of an examination of the surface structure and topography of silica glass plates, produced on an industrial scale. The successive stages whereby the surface structure is modified in mechanical and chemical processes are followed systematically. The kinetics were studied of processes occurring on the surface under the influence of chemical corroding agents and heating, during surface formation and evolution in the laboratory and glassworks. Surface analysis was performed with an electron emission microscope, yielding information on local structural details down to 30 and 15 nm, the resolving powers of the measuring systems. Recrystallisation processes of surface metals and thin homogeneous metal films, evaporation-deposited onto the glass surface in high vacuum, were also investigated. Direct information was obtained concerning the surface structure and topography, the grain distribution, and kinetic processes occurring in a series of silica glasses and in metallic surface films.

Adhesion of evaporated metal films

An abrasion-resistivity test was developed to study the adhesion of vacuum-deposited aluminum films on glass surfaces. The test consists of measuring the electrical resistance of the metal film during abrasion by a stream of fine silicon carbide particles. An analysis is given of the anticipated test results on homogeneous and nonhomogeneous metal films and on effects near the interface. Differences in the plating and annealing conditions of evaporated aluminum films were detected by the abrasion-resistivity test. Poorest adhesion was found on platings made on unclean surfaces and platings made at a slow rate of evaporation of the metal. The optimum substrate temperature for good adhesion was determined to be 175°C. Annealing of the aluminum film resulted in formation of a surface oxide layer and development of an interlayer compound at the interface.