• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.8
• /
• pp.708-713
• /
• 2005

An alumina membrane with nano-sized pore array by anodic oxidation using the thin film aluminum deposited on silicon wafer was fabricated. It Is important that the sample prepared by metal deposition method has a flat aluminum surface and a good adhesion between the silicon wafer and the thin film aluminum. The oxidation time was controlled by observation of current variation. While the oxalic acid with 0.2 M was used for low voltage anodization under 100 V, the chromic acid with 0.1 M was used for high voltage anodization over 100 V. The nano-sized pores with diameter of $60\~120$ nm was obtained by low voltage anodization of $40\~80$ V and those of $200\~300$ nm was obtained by high voltage anodization of $140\~200$ V. The pore widening process was employed for obtaining the one-channel with flat surface because the pores of the alumina membrane prepared by the fixed voltage method shows the structure of two-channel with rough surface. Finally, the sample was immersed to the phosphoric acid with 0.1 M concentration to etching the barrier layer.

• Journal of the Korean Society of Mechanical Technology
• /
• v.20 no.6
• /
• pp.858-864
• /
• 2018

Graphene oxide (GO) laminate is a new promising material for water purification system, which has extraordinary permeability only for water molecule. It consists of numerous nano-channels, in which water molecules could be nano-confined, resulting in slip of the molecules for very fast transportation speed. In this study, water penetration rate via different thickness of GO membrane according to driven pressures are measured experimentally, so that speed of water molecules and permeability are evaluated. Generally, water penetration rate via a membrane with macroscopic-sized channel increases linearly with pressure difference between up and bottom side of the membrane, but that via GO membrane approaches asymptotic value (i.e. saturation) as like a log function. Moreover, the permeability of GO membrane was observed in inverse proportion to its thickness. Based on the experimental observations, a correlation for volume flux via GO membrane was suggested with respect to its thickness and external pressure difference.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.479-479
• /
• 2011

Flexible inverters based on complementary thin-film transistor (CTFTs) are important because they have low power consumption and other advantages over single type TFT inverters. In addition, integrated CTFTs in flexible electronic circuits on low-cost, large area and mechanically flexible substrates have potentials in various applications such as radio-frequency identification tags (RFIDs), sensors, and backplanes for flexible displays. In this work, we introduce flexible complementary inverters using pentacene and amorphous indium gallium zinc oxide (IGZO) for the p-channel and n-channel, respectively. The CTFTs were fabricated on polyimide (PI) substrate. Firstly, a thin poly-4-vinyl phenol (PVP) layer was spin coated on PI substrate to make a smooth surface with rms surface roughness of 0.3 nm, which was required to grow high quality IGZO layers. Then, Ni gate electrode was deposited on the PVP layer by e-beam evaporator. 400-nm-thick PVP and 20-nm-thick ALD Al2O3 dielectric was deposited in sequence as a double gate dielectric layer for high flexibility and low leakage current. Then, IGZO and pentacene semiconductor layers were deposited by rf sputter and thermal evaporator, respectively, using shadow masks. Finally, Al and Au source/drain electrodes of 70 nm were respectively deposited on each semiconductor layer using shadow masks by thermal evaporator. Basic electrical characteristics of individual transistors and the whole CTFTs were measured by a semiconductor parameter analyzer (HP4145B, Agilent Technologies) at room temperature in the dark. Performance of those devices then was measured under static and dynamic mechanical deformation. Effects of cyclic bending were also examined. The voltage transfer characteristics (Vout- Vin) and voltage gain (-dVout/dVin) of flexible inverter circuit were analyzed and the effects of mechanical bending will be discussed in detail.

• Korean Journal of Materials Research
• /
• v.21 no.6
• /
• pp.309-313
• /
• 2011

The power capacitors used as vehicle inverters must have a small size, high capacitance, high voltage, fast response and wide operating temperature. Our thin film capacitor was fabricated by alumina layers as a dielectric material and a metal electrode instead of a liquid electrolyte in an aluminum electrolytic capacitor. We analyzed the micro structures and the electrical properties of the thin film capacitors fabricated by nano-channel alumina and metal electrodes. The metal electrode was filled into the alumina nano-channel by electroless nickel plating with polyethylene glycol and a palladium catalyst. The spherical metals were formed inside the alumina nano pores. The breakdown voltage and leakage current increased by the chemical reaction of the alumina layer and $PdCl_2$ solution. The thickness of the electroless plated nickel layer was 300 nm. We observed the nano pores in the interface between the alumina layer and the metal electrode. The alumina capacitors with nickel electrodes had a capacitance density of 100 $nF/cm^2$, dielectric loss of 0.01, breakdown voltage of 0.7MV/cm and leakage current of $10^4{\mu}A$.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.5C no.2
• /
• pp.49-53
• /
• 2005

The current drive in a MOSFET is limited by the intrinsic channel resistance. All other parasitic elements in a device structure perform significant functions leading to degradation in the device performance. These other resistances must be less than 10$\%$-20$\%$ of the channel resistance. To meet the necessary requirements, the methodology of separation and quantification of those resistances should be investigated. In this paper, we developed an extraction method for the resistances using calibrated TCAD simulation. The resistance of the extension region is also partially determined by the formation of a surface accumulation region that gathers below the gate in the tail region of the extension profile. This resistance is strongly affected by the abruptness of the extension profile because the steeper the profile is, the shorter this accumulation region will be.

• Corrosion Science and Technology
• /
• v.5 no.1
• /
• pp.23-26
• /
• 2006

Recent development of ultrafine grained (UFG) low carbon steels by using equal channel angular pressing (ECAP) and their room temperature tensile properties are reviewed, focusing on the strategies overcoming their inherent mechanical drawbacks. In addition to ferrite grain refinement, when proper post heat treatments are imposed, carbon atom dissolution from pearlitic cementite during ECAP can be utilized for microstructural modification such as uniform distribution of nano-sized cementite particles or microalloying element carbides inside UFG ferrite grains and fabrication of UFG ferrite/martensite dual phase steel. The utilization of nano-sized particles is effective on improving thermal stability of UFG low carbon ferrite/pearlite steel but less effective on improving its tensile properties. By contrast, UFG ferrite/martensite dual phase steel exhibits an excellent combination of ultrahigh strength, large uniform elongation and extensive strain hardenability.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.2
• /
• pp.51-57
• /
• 2008

Recently, the manufacturer of microscopic structures along with the development of technology to produce electronics, communication and semiconductors allows various components to be smaller in size, with higher precision. Therefore, preoccupancy of micro/nano-level machining technology in order to product micro/nano-components and parts is key issue in the field of manufacturing. In this study, machinability of micro machining was studied through the machining of aluminum, brass and steel workpiece. Inspection of the cutting force variation patterns of large numbers of micro machining indicated that characteristics of the workpiece. Surface roughness prediction methods were developed by considering the variation of the static part of the feed direction cutting force. The accuracy of the proposed approaches were tested with experimental data and the agreement between the predictions and actual observations are addressed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.861-864
• /
• 2006

In this paper conduction phenomena have been considered for nano structure double gate MOSFET, using the analytical model. The Possion equation is used to obtain the analytical model. The conduction mechanisms to have an influence on current conduction are thermionic emission and tunneling current, and subthreshold swings of this paper is compared with those of two dimensional simulation to verify this model. The deviation of current path and the influence of current path on subthreshold swing have been considered according to the dimensional parameters of double gate MOSFET, i.e. gate length, gateoxide thickness, channel thickness. The optimum channel doping concentration is determined as the deviation of conduction path is considered according to channel doping concentration.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2013.12a
• /
• pp.41-41
• /
• 2013

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1686-1687
• /
• 2011

A microfabricated chip with in-channel electrochemical cell using interdigitated gold electrode was fabricated for sensitive electrochemical analysis. The gold electrodes were fabricated on glass wafer using thermal evaporator and were covered using PDMS mold containing microchannel for analyte and electrolyte. The active area of each electrode was $250\;{\mu}m{\times}200\;{\mu}m$ with a gap of 200 ${\mu}m$ between the electrodes. Microelectrodes results in maximum amplification of signal, since the signal enhancement effect due to cycling of the reduced and oxidized species strongly depends on the inter electrode distance. Analytes such as methylene blue and guanosine were characterized using the fabricated electrodes and their electrochemical characteristics were compared with conventional bulk electrodes. The device so developed shall find use as disposable electrochemical cell for rapid and sensitive analysis of electroactive species.