• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.34 no.4
• /
• pp.242-245
• /
• 2021

In this work, we fabricated oxide on an n-type silicon substrate through local anodic oxidation (LAO) using atomic force microscopy (AFM). The resulting oxide thickness was measured and its correlation with load force, scan speed and applied voltage was analyzed. The surface oxide layer was stripped using a buffered oxide etch. Ohmic contacts were created by applying silver paste on the silicon substrate back face. LAO was performed at approximately 70% humidity. The oxide thickness increased with increasing the load force, the voltage, and reducing the scan speed. We confirmed that LAO/AFM can be used to create both lateral and, to some extent, vertical shapes and patterns, as previously shown in the literature.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2014.11a
• /
• pp.226-227
• /
• 2014

We demonstrate nanoscale local anodic oxidation (LAO) patterning on few layer graphene using atomic force microscope (AFM) at room temperature and normal atmosphere. We focus on the humidity dependency in nanoscale oxidation of graphene. The relationship between the oxidation size and the AFM setting values, such as set point, tip speed, and humidity are observed. By changing these values, proper parameters were found to produce features on demand size. This technique provides an easy way to form graphene oxide lithography without any chemical resists. We have obtained oxidation size down to 50-nm with 6-nm-height oxide barrier line with $0.1{\mu}m/s$ tip scanning speed and micrometer size symbols on a graphene flake. We attribute the bumps to local anodic oxidation on graphene surface and combination of oxygen ions into the graphene lattice.

• Journal of the Korean institute of surface engineering
• /
• v.56 no.2
• /
• pp.115-124
• /
• 2023

Anodization is an electrochemical process that electrochemically converts a metal surface into an oxide layer, resulting in enhanced corrosion resistance, wear resistance, and improved aesthetic appearance. Local anodization, also known as selective anodization, is a modified process that enables specific regions or patterns on the metal surface to undergo anodization instead of the entire surface. Several methods have been attempted to produce oxide layers via localized anodic oxidation, such as using a mask or pre-patterned substrate. However, these methods are often intricate, time-consuming, and costly. Conversely, the direct writing or patterning approach is a more straightforward and efficient way to fabricate the oxide layers. This review paper intends to enhance our comprehension of local anodization and its potential applications in various fields, including the development of nanotechnologies. The application of anodization is promising in surface engineering, where the anodic oxide layer serves as a protective coating for metals or modifies the surface properties of materials. Furthermore, anodic oxidation can create micro- and nano-scale patterns on metal surfaces. Overall, the development of efficient and cost-effective anodic oxidation methods is essential for the advancement of various industries and technologies.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.10a
• /
• pp.627-628
• /
• 2009

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.96.1-96.1
• /
• 2017

This presentation introduces anodizing science of typical valve metals of Al, Mg and Ti, based on the ionic transport through the andic oxide films in various electrolyte compositions. Depending on the electrolyte composition, metal ions and anions can migrate through the andic oxide film without its dielectric breakdown when point defects are present within the anodic oxide films under high applied electric field. On the other hand, if anodic oxide films are broken by local joule heating due to ionic migration, metal ions and anions can migrate through the broken sites and meet together to form new anodic films, known as plasma electrolytic oxidation (PEO) treatment. In this presentation, basics of conventional anodizing and PEO methods are introduced in detail, based on the ionic migration and movement mechanism through anodic oxide films by point defects and by local dielectric breakdown of anodic oxide films.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.1
• /
• pp.17-23
• /
• 2017

This work demonstrates arc generation and anodic film formation behaviors on Al1050 alloy during PEO (plasma electrolytic oxidation) treatment under a constant direct current in an alkaline electrolyte containing silicate, carbonate and borate ions. Only one big arc more than 2 mm diameter was generated first at the edges and it was moving on the fresh surface or staying occasionally at the edges, resulting in the local burning due to generation of an extremely big orange colored arc at the edges. Central region of the flat surface was not fully covered with PEO films even after sufficiently long treatment time because of the local burning problem. The anodic oxides formed on the flat surface by arcing once were found to consist of a number of small oxide nodules with spherical shape of $3{\sim}6{\mu}m$ size and irregular shapes of about $5{\sim}10{\mu}m$ width and $10{\sim}20{\mu}m$ length. The anodic oxide nodules showed uniform thickness of about $3{\mu}m$ and rounded edges. These experimental results suggest that one big arc observed on the specimen surface under the application of a constant direct current is composed of a number of small micro-arcs less than $20{\mu}m$ size.

• Journal of the Korean institute of surface engineering
• /
• v.17 no.2
• /
• pp.29-40
• /
• 1984

The structure of rapidly solidified Al-Si-based alloys and its relationship to subsequent anodic film growth in near neutral and acid solutions have been investigated. Solidification of the alloys proceeds via pre-dendritic nuclei, associated with rugosity of the casting surface, from which cellular-type growth, comprised of aluminium-rich material surrounded by silicon-containing material, emanates. Observation of ultramicrotomed sections of the alloys and their anodic films reveals the local oxidation of the silicon-rich phase and its incorporation into the anodic alumina film, formed in near neutral solutions. Such incorporation occurs but resultant isolation of the silicon-rich phase is not possible for anodizing in phosphoric acid, and a three-dimensional network of the oxidized silicon-containing phase, with continuing development of porous anodic alumina, is observed.

• Journal of the Korean Ceramic Society
• /
• v.28 no.6
• /
• pp.443-450
• /
• 1991

Microstructures of tantalum oxide, anodic-oxidized in oxalic acid, are shown to be related to voltage-time characteristics during formation reaction. It is observed that a crystalline phase transformed from an amorphous phase is recrystallized in the presence of the high electric field within the film, and this recrystallized film has a very porous microstructure. From the results of the XRD, the nonlinearity observed after the first spark voltage is recognized to be due to the local crystallization.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.14 no.4
• /
• pp.8-13
• /
• 2015

In this study, we fabricated and characterized a nanostructured surface based on a plastic injection molding with a local mold heating (LMH) system. A metal mold core with a closed packed nano convex array (CVA) was achieved by integrated engineering procedures: (1) master template fabrication by anodic aluminum oxidation (AAO), (2) nickel electroforming (NE) process, and (3) post-processing by precision machining. The nickel mold core was utilized to replicate a surface with a closed packed nano concave-array (CCA) based on injection molding using cyclic olefin copolymer (COC) as a plastic material. In particular, an LMH system was introduced to enhance transcription quality of the nano structures by delaying solidification of molten polymer near the surface of the mold core.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.5
• /
• pp.308-314
• /
• 2017

Anodic film formation behavior of AZ31 Mg alloy was studied as a function of NaOH concentration in 1 M $Na_2CO_3$ + 0.5 M $Na_2SiO_3$ solution under the application of a constant anodic current density, based on the analyses of voltage-time curves, surface appearances and morphologies of the anodically formed PEO (plasma electrolytic oxidation) films. The anodic film formation voltage and its fluctuations became largely lowered with increasing added NaOH concentration in the solution. Two different types of film defects, large size dark spots indented from the original surface and locally extruded white spots, were observed on the PEO-treated surface, depending on the concentration of added NaOH. The large size dark spots appeared only when added NaOH concentration is less than 0.2 M and they seem to result from the local detachments of porous PEO films. The white spots were observed to be very porous and locally extruded and their size became smaller with increasing added NaOH concentration. The white spot defects disappeared completely when more than 0.8 M NaOH is added in the solution. Concludingly it is suggested that the presence of enough concentration of $OH^-$ ions in the carbonate and silicate ion-containing electrolyte can prevent local thickening and/or detachment of the PEO films on the AZ31 Mg alloy surface and lower the PEO film formation voltage less than 70 V.