Anodic Aluminum Oxide Substrate Research Articles

Atomic layer deposition of ultrathin blocking layer for low-temperature solid oxide fuel cell on nanoporous substrate

An ultrathin yttria-stabilized zirconia (YSZ) blocking layer deposited by atomic layer deposition (ALD) was utilized for improving the performance and reliability of low-temperature solid oxide fuel cells (SOFCs) supported by an anodic aluminum oxide substrate. Physical vapor-deposited YSZ and gadolinia-doped ceria (GDC) electrolyte layers were deposited by a sputtering method. The ultrathin ALD YSZ blocking layer was inserted between the YSZ and GDC sputtered layers. To investigate the effects of an inserted ultrathin ALD blocking layer, SOFCs with and without an ultrathin ALD blocking layer were electrochemically characterized. The open circuit voltage (1.14 V) of the ALD blocking-layered SOFC was visibly higher than that (1.05 V) of the other cell. Furthermore, the ALD blocking layer augmented the power density and improved the reproducibility.

Engineering of the electrode structure of thin film solid oxide fuel cells

Abstract In this study, we systematically examined the effects of anode structures in nanoporous template-based thin film solid oxide fuel cells on the electrochemical performance. The fuel cells were fabricated by sequential sputtering of the anode, the electrolyte and the cathode on an anodic aluminum oxide substrate without pinhole problems. Systematic investigation showed the substantial impacts of the porosity and the thickness of the Pt anodes on the reactivity at the anode/electrolyte interface and the mass transport in the electrode, which are closely related to the activation and the concentration overpotentials of fuel cells, respectively. Our results provide the fundamental insights into tailoring the anode structures for improved fuel cell performance.

Structural and optical characterization of nanostructured ZnO grown on alumina templates

The growth of nanostructured ZnO thin films on nanoporous anodic alumina substrates (NAAF) by dc reactive magnetron sputtering using a pure Zn metal target is reported. ZnO nanostructures reproduce the pore arrays of the NAAF substrates used as templates mimicking their hexagonal long range order. Stoichiometric nanostructured ZnO samples were grown with wurtzite type structure, highly textured and oriented in the (002) direction. The study of the NAAF pore size effect in the final morphology and optical properties of the nanostructured ZnO is presented for different ZnO thicknesses. The pore size of the nanostructured ZnO films was controlled in the range of 15–65 nm by choosing appropriate NAAF and the sputtering deposition conditions. The broad emission band observed in PL spectra of the samples should be associated with color centers transitions (F and H centers) appearing in the alumina templates.

Development of Titanium-Sputtered Anodized Aluminum Substrates for Dye-Sensitized Solar Cells

In this study, anodized aluminum coupons are sputtered with titanium and successfully demonstrated as dye-sensitized solar cell (DSC) electrode substrates in both anode [back-illumination (BI)] and cathode [front-illumination (FI)] configurations. The FI DSCs were found to be significantly more efficient than the BI devices registering an average efficiency of 5.7 vs 2.6 pct. By comparison, the efficiency of benchmark cells built with fluorine-tin oxide-glass was 6.7 and 4.6 pct, respectively. The thickness of the titanium-sputtered film was varied from 0.85 to 1.1 μm with the latter providing a better average efficiency when used as a counter electrode. According to preliminary stability testing, the Ti-sputtered anodized aluminum-based DSC devices exhibited a significant reduction of their efficiency over a period of 10 days that was partly attributed to triiodide redox electrolyte reaction with the aluminum substrate. This points to the need for optimization of the sputtered-titanium coating microstructure in order to completely isolate the aluminum substrate from the liquid electrolyte.

Two-Dimensional Ag Nanoparticle Tetramer Array for Surface-Enhanced Raman Scattering Measurements

A two-dimensional Ag nanoparticle tetramer array which served as a hotspot matrix for surface-enhanced Raman scattering detection of rhodamine 6G (R6G) molecules down to a concentration as low as 10–15 M was successfully fabricated by electrochemical deposition on an anodized aluminum substrate. The high detection sensitivity was attributed to both the electromagetic enhancement at the dense Ag nanoparticle tetramer hotspot matrix and chemical enhancement on the corrugated substrate. A single molecule dynamic adsorption behavior was experimentally sensed by the abrupt changes of the charateristic peak intensity and line shape in the spectroscopy when the R6G concentration was lowered to 10–15 M. Time-evolved spectroscopies revealed the adsorption behavior of either the single molecule in the nanogaps of 2–5 nm or multiple molecules in the nanogaps of 5–9 nm between the Ag nanoparticles.

High‐performance stacked‐coil transformers with thick metal layers

Miniaturised stacked-coil radio-frequency (RF) transformers were fabricated with thick metal layers using the low-cost anodised aluminium substrate process. The transformer consists of a 34 μm-thick substrate-buried copper lower coil and a 30 μm-thick copper/gold upper coil with a 3 μm-thick benzocyclobutene (BCB) interlayer between the coils. Owing to extremely low losses and tight coupling, the fabricated transformers achieved very low insertion losses as low as 0.28 dB and high maximum available gains of up to 0.96 at GHz frequencies. The results verify that the stacked-coil transformer with thick metal layers can be a promising component for high-performance miniaturised RF circuits.

Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source.

Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

Reformer-Integrated Thin-Film Solid Oxide Fuel Cell for Ethanol Fuel

Ethanol reformer and thin-film solid oxide fuel cell are integrated on single nano-porous anodic aluminum oxide(AAO) substrate. Manganese doped cobalt catalyst is utilized as fuel reformer which is deposited on one side of the substrate, and thin-film single cell is fabricated on another side of the AAO, which is made of Pt, Ru and YSZ thin films. Electrochemical performance is tested at 500℃, in the electrical heater, supplied by fuel-water bubbled inert gas stream. Fuel-water saturated inert gas flows into the reformer, and becomes hydrogen gas, COx, methane, etc. Reformed gas diffuses from reformer to single cell anode, passing through the nano-pores of AAO substrate. Although many carbon-containing substances such as COx or methane are chemically formed, the anode of single cell operates for considerably long time while maintaining high performance, because ruthenium in anode layer protects the catalyst particles from poisoning. This reformer-integrated cell structure acts as a direct-hydrocarbon fuel cell.

Fabrication and characterization of conductive anodic aluminum oxide substrates

Biomaterials that allow the utilization of electrical, chemical and topographic cues for improved neuron–material interaction and neural regeneration hold great promise for nerve tissue engineering applications. The nature of anodic aluminum oxide (AAO) membranes intrinsically provides delicate control over topographic and chemical cues for enhanced cell interaction; however their use in nerve regeneration is still very limited. Herein, we report the fabrication and characterization of conductive AAO (CAAO) surfaces for the ultimate goal of integrating electrical cues for improved nerve tissue behavior on the nanoporous substrate material. Parafilm was used as a protecting polymer film, for the first time, in order to obtain large area (50cm2) free-standing AAO membranes. Carbon (C) was then deposited on the AAO surface via sputtering. Morphological characterization of the CAAO surfaces revealed that the pores remain open after the deposition process. The presence of C on the material surface and inside the nanopores was confirmed by XPS and EDX studies. Furthermore, I–V curves of the surface were used to extract surface resistance values and conductive AFM demonstrated that current signals can only be achieved where conductive C layer is present. Finally, novel nanoporous C films with controllable pore diameters and one dimensional (1-D) C nanostructures were obtained by the dissolution of the template AAO substrate.

Immobilization of colloidal particles into sub-100 nm porous structures by electrophoretic methods in aqueous media

Conventional direct current (DC) and pulse-DC assisted electrophoretic depositions of colloidal particles, with average sizes of 10 and 50nm, into sub-100nm scaled pore arrays made from anodized aluminum substrate has been investigated. At the applied voltages lower than the decomposition voltage of water (∼1V), the number concentration of particle deposited on the surface by conventional DC was higher than that of pulse DC. The number of deposited particles increased with increasing pH. Deposition efficiency inside the pores can be enhanced by applying pulse DC. In the case of high (∼10V) applied voltage, no particles were observed inside pores even though pulse DC has been applied. The adhesion strength (removal behavior) of deposition was evaluated by applying a particle detachment simple system based on ultrasonic energy. The particles deposited inside the pores were not detached compared with those of the surface of the substrate.

Electrochemical impedance spectroscopy analysis of A-beta (1-42) peptide using a nanostructured biochip

A-beta (1-42) peptide (Aβ (1-42)) is a potential candidate for the prediction of Alzheimer's disease. In this study, we demonstrate a nanostructured biosensor based on electrochemical impedance spectroscopy (EIS) with uniformly deposited gold nanoparticles (GNPs) as the sensing electrode for effective detection of Aβ (1-42). An anodic aluminum oxide (AAO) layer with a nanohemisphere array was used as the substrate. A gold thin film was sputtered onto the AAO substrate to serve as the electrode for GNP deposition and the sensor for Aβ (1-42). Aβ (1-42) antibody was prepared, and its specificity with Aβ (1-42) was verified by Western blot. We observed aggregation of Aβ (1-42) at 1μgml−1. The morphology of Aβ (1-42) was in the form of round aggregates with diameter of around 1500–2000nm. EIS measurements for nanostructured biosensors were used to determine the concentration of Aβ (1-42). The plot for the dependence of EIS concentration measurement resulted in an equationΔRct=29098*log [Aβ (1-42)]+90150 with an R2 value of 0.9916. The linear detection range was between 1pgml−1 and 10ngml−1 of Aβ (1-42).

Significant room-temperature ferromagnetism in porous TiO2 thin films

Remarkable room-temperature ferromagnetism was found in porous TiO2 thin films deposited on porous anodic alumina substrates using DC-reactive magnetron sputtering. A physical property measurement system measurement indicates that the out-of-plane saturation magnetization is about 126emu/cm3. The magnetization depends on special porous structure and decreases rapidly after air-annealing. These suggest that the origin of ferromagnetism may be due to exchange interactions between singly ionized oxygen vacancies directly (F+–F+), or by mediation of conduction electrons (F+–conduction electrons–F+) in the porous TiO2 thin films. The results reveal that it is a promising candidate for spintronic devices.

Investigation of inkjet printing conditions for microdot pressure-sensitive sensor on anodized aluminum substrate

Investigation of inkjet printing conditions for microdot pressure-sensitive sensor on anodized aluminum substrate

Nanostructured Mesoporous Silica Wires with Intrawire Lamellae via Evaporation‐Induced Self‐Assembly in Space‐Confined Channels

Evaporation‐induced self‐assembly (EISA) of silica sol‐gel ethanol‐water solution mixtures with block‐copolymer were studied inside uniform micro/nano‐channels. Nanostructured mesoporous silica wires, with various intrawire self‐assembly structures including lamellae, were prepared via EISA process but in space‐confined channels with the diameter ranging from 50 nm to 200 nm. Membranes made of anodized aluminum oxide (AAO) and track‐etched polycarbonate (EPC) were utilized as the arrays of space‐confined channels (i.e., 50, 100, and 200 nm EPC and 200 nm AAO) for infiltration and drying of mixture solutions; these substrate membranes were submerged in mixture solutions consisting of a silica precursor, a structure‐directing agent, ethanol, and water. After the substrate channels were filled with the solution under vacuum impregnation, the membrane was removed from the solution and dried in air. The silica precursor used was tetraethyl othosilicate (TEOS), and the structure‐directing agent employed was triblock copolymer Pluronic‐123 (P123). It was found that the formation of the mesoporous nanostructures in silica wires within uniform channels were significantly affected by the synthesis conditions including (1) preassemble TEOS aging time, (2) the evaporation rate during the vacuum impregnation, and (3) the air‐dry temperature. The obtained intrawire structures, including 2D hexagonal rods and lamellae, were studied by scanning transmission electron microscopy (STEM). A steric hindrance effect seems to explain well the observed polymer‐silica mesophase formation tailored by TEOS aging time. The evaporation effect, air‐drying effect, and AAO versus EPC substrate effect on the mesoporous structure of the formed silica wires were also presented and discussed.

Magnetic Properties of NiFe Needles on Nanoporous Anodized Aluminum Oxides

In this study, a simple approach combining nanoporous templates with sputter deposition to obtain nano-sized permalloy structures is presented. The grain evolution and the corresponding magnetic anisotropy of permalloy films grown on the nanoporous anodized aluminum oxide (AAO) substrates with different deposition time were investigated. A grain evolution from a needle-like structure to a 2-D network was observed. As a consequence, the magnetization reversal of the permalloy films varied with the grain evolution. The magnetic domains of the permalloy films were pinned dominantly by the needle-like grain structure at the beginning; then, as the deposition time got longer, the domain sizes were constrained mainly by the underlying AAO network.

Optical absorption of amorphous silicon on anodized aluminum substrates for solar cell applications

The development of backside reflectors (BSRs) is crucial for the efficiency of future low cost thin-film silicon (Si) solar cells. In this work, nanostructured aluminum substrates intended as back reflectors are produced by anodization, and hydrogenated amorphous Si (a-Si:H) is deposited hereon. Substrates with periods of 320nm, 430nm and 700nm are investigated, with a-Si:H layers of 0–300nm, using optical spectroscopy and electron microscopy. It is shown from a theoretical model that the ratio of photons absorbed in the a-Si:H layer to the total number of photons absorbed is nearly independent of the substrate geometry, and general expressions for this ratio are derived for different layer thicknesses. The optical absorption in the a-Si:H layer is obtained from the total absorption spectra, and the integrated quantum efficiency (IQE) across the solar spectrum is found. The largest IQE is found for the 430nm structure, with 200nm and 300nm a-Si:H resulting in near equal IQEs. Thus, for actual cell production the 430nm structure with 200nm silicon is deemed the best choice.

Electrical characterization of anodic alumina substrate with via-in-pad structure

An anodic alumina substrate has been developed as a package substrate for dynamic random access memory devices. Unlike the conventional package substrates commonly made by laminating an epoxy-based core and cladding with copper, this substrate is fabricated using aluminum anodization technology. The anodization process produces a thick aluminum oxide layer on the aluminum substrate to be used as a dielectric layer. Placing copper patterns on the anodic aluminum oxide layer forms a new substrate structure that consists of a layered structure of aluminum, anodic aluminum oxide, and copper. Using selective anodization in the fabrication process, a via structure connecting the top copper layer and bottom aluminum layer is demonstrated. Additionally, by putting vias directly in the bond and ball pads in the substrate design, the via-in-pad structure is applied in this work. These two-layer metal structures and via-in-pad arrangements make routing easier and thus provide more design flexibility. Additionally, this new package substrate has improved the power distribution network impedance given the characteristics of these structures.

Multi-band emission in a wide wavelength range from tin oxide/Au nanocomposites grown on porous anodic alumina substrate (AAO)

The photoluminescence (PL) properties of tin oxide nanostructures are investigated. Three samples of different morphology, induced by deposition process and various geometrical features of nanoporous anodic aluminum oxide (AAO) substrate, are analyzed. X-ray photoelectronic spectroscopy (XPS) analysis reveals the presence of two forms of tin oxide on the surface of all studied samples: SnO and SnO2. The former form is typical for reduced surface with bridging oxygen atoms and every other row of in-plane oxygen atoms removed. The oxygen defects give rise to a strong emission in visible region. Two intense PL peaks are observed centered at about 540 (band I) and 620 (band II)nm. The origin of these bands was ascribed to the recombination of electrons from the conduction band (band I) and shallow traps levels (band II) to the surface oxygen vacancy levels. Upon deposition of Au nanoparticles on the top of tin oxide nanostructures the emission at 540 and 620nm disappears and a new band (band III) occurs in the range >760nm. The PL mechanism operating in the studied systems is discussed. The tin oxide/Au nanocomposites can be used as efficient multi-band light emitters in a wide (from visible to near infrared) wavelength range.

Preparation of an In Situ Crosslinked Polymer Coating and a Double-Layered Thermal CTP Plate

The research relates to a method for preparing an in-situ crosslinked polymer coating. It has excellent solubility in aqueous alkaline solution, but didnt dissolve in general organic solvents and water. The crosslinked polymer coating was made through the reaction of a copolymer derived from diacetone acrylamide (DAAM) and ethacryloyloxyethyl-carbazochrome-p-toluenesulfonamide (MCTS) with a crosslinking agent, isonicotinyl hydrazide. The two components were dissolved in 3-methoxypropanol to prepare the coating solution, which was then coated to a grained and anodized aluminum substrate and dried at 120 °C for 5 min to obtain the crosslinked coating. There exists intermolecular hydrogen bond between the pyridine ring of isonicotinyl hydrazide and the sulfonamide group of the MCTS unit of the copolymer. The reaction between the hydrazide group and the carbonyl group during the drying process generated the hydrazone bond, resulting in the crosslinked polymer coating. The intermolecular hydrogen bond and the covalent bond render the coating insoluble in most organic solvents. However, the hydrogen bond was readily broken down when the coating was exposed to aqueous alkaline solution due to the ionization of the sulfonamide group, causing rapid dissolution of the coating. The coating was also used as the under-layer for the preparation of a double-layed CTP plate. The performance of the double-layed CTP plate was preliminarily studied.

Electromechanical Properties of Vertically Aligned Carbon Nanotube

In this paper a simple method is used for fabrication of vertically aligned carbon nanotube (VACNT) within the cylindrical pores anodic aluminum oxide (AAO) substrate. Electronic and mechanical properties of VACNT have been obtained after removing AAO substrate. Vertically aligned carbon nanotube shows very interesting electromechanical properties which can be used in CNT-based sensors to detect chemical analytical or physical properties such as temperature orpressure.