• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.11-15
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• 2018

The parts of equipment for semiconductor are protected by anodic aluminum oxide film to prevent corrosion. This study investigated contamination particle and cracking behavior of anodic oxidation in sulfuric acid containing cerium salt. The insulating properties of the sample were evaluated by measuring the breakdown voltage. It was confirmed that the breakdown voltage was about 50% higher when the cerium salt was added, and that the breakdown voltage after the heat treatment was 55% and 35% higher at $300^{\circ}C$ and $400^{\circ}C$, respectively. After heating at $300^{\circ}C$ and $400^{\circ}C$, cracks were observed in non cerium and cerium 3mM, and more cracks occur at $400^{\circ}C$ than at $30^{\circ}C$. The amount of contamination particles generated in the plasma is about 45% less than that of non-cerium specimens.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.115.2-115.2
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• 2016

Al alloys are being used widely for automobile, aerospace and mechanical components because of their high strength ratio to weight. However, still they suffer from abrasion or corrosion owing to insufficient resistances to friction or mechanical impact and chemical attack. Plasma electrolytic oxidation (PEO) method is one of the promising surface treatment methods for Al alloys which can render better hardness than aluminum anodic oxide (AAO) films prepared by conventional anodizing method in acidic solutions. In this presentation, some basic nature of PEO film formation and growth process on Al alloys will be presented based on the experimental results obtained and discussed in view of dielectric breakdown and reformation and the role of various anions in film breakdown and reformation of PEO films.

• Journal of the Semiconductor & Display Technology
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• v.20 no.1
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• pp.37-41
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• 2021

We report on the formation of anodic aluminum oxide (AAO) film using sulfuric acid containing cerium salt. When the temperature of the sulfuric acid containing cerium salt changes from 5 ℃ to 20 ℃, the current density and the thickness growth rate increase. The surface morphology of the AAO film change according to the temperature of the electrolytes. And that affected the breakdown voltage and the plasma etch rate. The breakdown voltage per unit thickness was the highest at 15 ℃, and the plasma etch rate was the lowest at 10 ℃ at 2.80 ㎛/h.

• Corrosion Science and Technology
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• v.6 no.6
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• pp.275-281
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• 2007

The effect of annealing on the pitting corrosion resistance of anodized Al-Mg alloy (AA5052) processed by equal-channel angular pressing (ECAP) was investigated by electrochemical techniques in a solution containing 0.2 mol/L of $AlCl_3$ and also by surface analysis. The Al-Mg alloy was annealed at a fixed temperature between 473 and 573 K for 120 min in air after ECAP. Anodizing was conducted for 40 min at $100-400A/m^2$ at 293 K in a solution containing 1.53 mol/L of $H_2SO_4$ and 0.0185 mol/L of $Al_2(SO_4)_3$. The internal stress generated in anodic oxide films during anodization was measured with a strain gauge to clarify the effect of ECAP on the pitting corrosion resistance of anodized Al-Mg alloy. The time required to initiate the pitting corrosion of anodized Al-Mg alloy was shorter in samples subjected to ECAP, indicating that ECAP decreased the pitting corrosion resistance. However, the pitting corrosion resistance was greatly improved by annealing after ECAP. The time required to initiate pitting corrosion increased with increasing annealing temperature. The strain gauge attached to Al-Mg alloy revealed that the internal stress present in the anodic oxide films was compressive stress, and that the stress was larger with ECAP than without. The compressive internal stress gradually decreased with increasing annealing temperature. Scanning electron microscopy showed that cracks occurred in the anodic oxide film on Al-Mg alloy during initial corrosion and that the cracks were larger with ECAP than without. The ECAP process of severe plastic deformation produces large internal stresses in the Al-Mg alloy; the stresses remain in the anodic oxide films, increasingthe likelihood of cracks. It is assumed that the pitting corrosion is promoted by these cracks as a result of the higher internal stress resulting from ECAP. The improvement in the pitting corrosion resistance of anodized AlMg alloy as a result of annealing appears to be attributable to a decrease in the internal stresses in anodic oxide films

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.909-915
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• 2003

Anodic oxide films on aluminum play an important role as a dielectrics in aluminum electrolytic capacitor. In order to obtain the high capacitance, ZrO$_2$ films were coated on aluminum foils by sol-gel method and then, the properties of anodized films were studied. The coating and drying of the films were repeated 4-10 times and annealed at 300～$600^{\circ}C$ and the triple layer of ZrO$_2$/Al-ZrO$_{x}$ /Al$_2$O$_3$ was formed onto aluminum substrates after anodizing of ZrO$_2$/Al film. The thickness of $Al_2$O$_3$ layer was decreased with increasing the annealing temperature due to the densification of ZrO$_2$ film. The ZrO$_2$ films were crystallized even at 30$0^{\circ}C$ and showed nanocrystalline structure. The. capacitance of aluminum foil annealed at low temperature was higher than that at high temperature. The increase of capacitance was due to the high capacitance of ZrO$_2$ film annealed at low temperature. The capacitance of ZrO$_2$ coated aluminum increased about 3 times compared to that without a ZrO$_2$ layer after anodizing to 400 V. From these results, the aluminum foils with composite oxide layers are found to be applicable to the aluminum electrolytic capacitor.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.191-194
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• 2009

Porous alumina prepared by anodization has been widely studied since it shows very regular nanostructures at inexpensive prices. In this article, porous alumina is obtained by anodization of aluminum in the oxalic acid. After the first formed oxide is selectively removed from the aluminum substrate, the hexagonal nanostructures on the fresh aluminum are converted to nanodots by the second anodization in boric acid. Nanodots are arrayed in the convex of the hexagonal nanostructures. The optimization condition for the fabrication of nanodots with a height of 20 nm is investigated in detail. Subsequently, a gold film is deposited on the nanodots, resulting in the formation of gold nanodots arrays which are probably interesting substrate for biosensor applications.

• Journal of Surface Science and Engineering
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• v.51 no.2
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• pp.87-94
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• 2018

Various sealing techniques were applied to the anodized 5083 aluminum alloy for marine environment to reduce corrosion and cavitation erosion damage. Electrochemical experiments and cavitation erosion tests were conducted to evaluate the corrosion resistance and cavitation resistance of the anodic oxide film treated with sealing in natural seawater solution. Then, damaged surface morphology was analyzed by scanning electron microscope(SEM) and 3D microscope. As the results of the electrochemical experiments, it was observed that the surface damage of all the experimental conditions in the anodic polarization experiment was locally grown by the combination of crack and corrosion damage. In the Tafel analysis, the corrosion resistance of all sealing treatment conditions was improved compared to the anodizing. On the other hand, cavitation erosion tests showed that the anodizing and all the sealing treatment conditions generated local pit damage by cavitation erosion attack and grew to crater damage in the observation of damaged surface by SEM. Also, the weight loss and the surface damage depth measured with the experiment time presented that most of the sealing treatment conditions showed better cavitation erosion resistance than the anodizing, and they had an incubation period at the beginning of the experiment.

• Korean Journal of Materials Research
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• v.24 no.10
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• pp.532-537
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• 2014

In this study, highly sensitive hydrogen micro gas sensors of the multi-layer and micro-heater type were designed and fabricated using the micro electro mechanical system (MEMS) process and palladium catalytic metal. The dimensions of the fabricated hydrogen gas sensor were about $5mm{\times}4mm$ and the sensing layer of palladium metal was deposited in the middle of the device. The sensing palladium films were modified to be nano-honeycomb and nano-hemisphere structures using an anodic aluminum oxide (AAO) template and nano-sized polystyrene beads, respectively. The sensitivities (Rs), which are the ratio of the relative resistance were significantly improved and reached levels of 0.783% and 1.045 % with 2,000 ppm H2 at $70^{\circ}C$ for nano-honeycomb and nano-hemisphere structured Pd films, respectively, on the other hand, the sensitivity was 0.638% for the plain Pd thin film. The improvement of sensitivities for the nano-honeycomb and nano-hemisphere structured Pd films with respect to the plain Pd-thin film was thought to be due to the nanoporous surface topographies of AAO and nano-sized polystyrene beads.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.95-100
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• 2016

We suggest and simulate an optical filter that a red wavelength range cannot transmit to protect the psychological stress that originates from the cognition of red color in emergency medical technicians. When a nanohole hexagonal array is fabricated on gold film using Anodic Aluminum Oxide (AAO), the blocked wavelength can be tuned by the hole diameter and film thickness. The characteristic of the transmittance for normal incident white light is simulated with Finite Element Method (FEM) in the MATLAB platform. Although the transmittance of the overall wavelength is reduced by 50% by the gold film, the transmittance of the red wavelength range is decreased by over 87%.

• Korean Journal of Materials Research
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• v.17 no.2
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• pp.81-85
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• 2007

Embedded capacitor technology can improve electrical perfomance and reduce assembly cost compared with traditional discrete capacitor technology. To improve the capacitance density of the $Al_2O_3$ based embedded capacitor on Cu cladded fiber reinforced plastics (FR-4), the specific surface area of the $Al_2O_3$ thin films was enlarged and their surface morphologies were controlled by anodization process parameters. From I-V characteristics, it was found that breakdown voltage and leakage current were 23 V and $1{\times}10^{-6}A/cm^2$ at 3.3 V, respectively. We have also measured C-V characteristics of $Pt/Al_2O_3/Al/Ti$ structure on CU/FR4. The capacitance density was $300nF/cm^2$ and the dielectric loss was 0.04. This nano-porous $Al_2O_3$ is a good material candidate for the embedded capacitor application for electronic products.