• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.411-411
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• 2012

Over the recent years, surface enhanced Raman spectroscopy (SERS) has dramatically grown as a label-free detecting technique with the high level of selectivity and sensitivity. Conventional SERS-active nanostructured layers have been deposited or patterned on rigid substrates such as silicon wafers and glass slides. Such devices fabricated on a flexible platform may offer additional functionalities and potential applications. For example, flexible SERS-active substrates can be integrated into microfluidic diagnostic devices with round-shaped micro-channel, which has large surface area compared to the area of flat SERS-active substrates so that we may anticipate high sensitivity in a conformable device form. We demonstrate fabrication of flexible SERS-active nanostructured substrates based on soft-lithography for simple, low-cost processing. The SERS-active nanostructured substrates are fabricated using conventional Si fabrication process and inkjet printing methods. A Si mold is patterned by photolithography with an average height of 700 nm and an average pitch of 200 nm. Polydimethylsiloxane (PDMS), a mixture of Sylgard 184 elastomer and curing agnet (wt/wt = 10:1), is poured onto the mold that is coated with trichlorosilane for separating the PDMS easily from the mold. Then, the nano-pattern is transferred to the thin PDMS substrates. The soft lithographic methods enable the SERS-active nanostructured substrates to be repeatedly replicated. Silver layer is physically deposited on the PDMS. Then, gold nanoparticle (AuNP) inks are applied on the nanostructured PDMS using inkjet printer (Dimatix DMP 2831) to deposit AuNPs on the substrates. The characteristics of SERS-active substrates are measured; topology is provided by atomic force microscope (AFM, Park Systems XE-100) and Raman spectra are collected by Raman spectroscopy (Horiba LabRAM ARAMIS Spectrometer). We anticipate that the results may open up various possibilities of applying flexible platform to highly sensitive Raman detection.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.74-74
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• 2000

낮은 유전상수(k$\leq$3)와 높은 열적안정성(>4$25^{\circ}C$)은 초고집적회로(ULSI)기술에서 RC 지연을 해결하기 위한 금속배선의 중간 절연층으로서의 2개의 가장 중요한 특성이다. 본 연구에서는 cyclohezane을 precursor로 사용하여 plasma enhanced chemical vapor deposition(PECVD)방법으로 유기박막을 성장시켰으며 낮은 유전상수와 높은 열적안정성을 동시에 확보하기 위하여 열적안정성은 좋지 않지만 유전상수가 낮은 박막(soft layer)위에 유전상수는 다소 높지만 열적안정성이 좋은 박막(hard layer)을 얇게 증착하여 hard layer/soft layer의 2층 구조를 형성하여서 구조적, 전기적 특성을 조사하였다. 유기박막은 5$0^{\circ}C$로 유지된 reactor 내부에서 argon(Ar) plasma에 의해 증착되었으며 platinum(Pt)기판과 silicon 기판위에 동시에 증착하였다. Pt 기판위에 증착한 시편으로 유전상수, I-V 등 전기적 특성을 측정하였고, silicon 기판위에 증착한 시편으로 열적안정성과 구조적 특성등을 분석하였다. 증착압력 0.2Torr에서 plasma power를 5W에서90W로 증가할 때 유전상수는 2.36에서 3.39로 증가하였으며 열적안정성은 90W에서 180W로 증가하였을 때 유전상수는 2.42에서 2.79로 증가하엿고 열적안정성은 모두30$0^{\circ}C$이하였다. 단일층 구조에서는 유전상수가 낮은 박막은 열적으로 불안정하고 열적 안정성이 좋은 박막은 유전상수가 다소 높은 문제가 나타났다. 이런 문제를 해결하기 위하여 2 Torr, 120W에서 증착한 유전상수가 2.55이고 열적으로 불안정한 박막을 soft layer로 5150 증착하고 그 위에 0.2Torr, 90W에서 증착한 유전상수가 3.39이고 열적으로 45$0^{\circ}C$까지 안정한 박막을 hard layer로 360 , 720 , 1440 증착하였다. 증착된 2층구조 박막의 유전상수는 각각 2.62, 2.68, 2.79이었으며 열적안정성 측정에서는 40$0^{\circ}C$까지 두께 감소가 보이지 않았다. 그러나 SEM 측정에서 열처리 후 표면이 거칠어지는 현상이 발견되었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.356-356
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• 2010

Tribological behaviors of the hard film on soft substrate system were explored using the hard thin film of diamond-like carbon (DLC) coated the soft polymer of polydimethysiloxane (PDMS). A DLC film with the Young's modulus of 100 GPa was coated on PDMS substrate with Young's modulus of 10 MPa using plasma enhanced chemical vapor deposition (PECVD) technique. The deposition time was varied from 10 sec to 10 min, resulting in nanoscale roughness of wrinkle patterns with the thickness of 20 nm to 510 nm, respectively, at a bias voltage of $400\;V_b$, working pressure 10 mTorr. Nanoscale wrinkle patterns with 20-100 nm in width and 10-30 nm height were formed on DLC coating due to the residual stress in compression and difference in Young's modulus. Nanoscale roughness effect on tribological behaviors was observed by performing a tribo-experiment using the ball-on-disk type tribometer with a steel ball of 6 mm in diameter at the sliding speed of 220 rpm, normal load of 1N and 25% humidity at ambient temperature of $25^{\circ}C$. Friction force were measured with respect to thickness change of coated DLC thin film on PDMS. It was found that with increases the thickness of DLC coating on PDMS, the coefficient of friction decreased by comparison to that of the uncoated PDMS. The wear tracks before and after tribo-test were analyzed using SEM and AFM.

• Journal of Physiology & Pathology in Korean Medicine
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• v.26 no.1
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• pp.35-39
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• 2012

Sweet potato soju(SPS) has been made by vacuum distillation because sweet potato contains much fibrous materials which give high density to sweet potato mash. Generally, the SPS made by vacuum distillation has soft flavors and tastes. If the viscosity of sweet potato mash could be decreased by degradation enzyme, the process and production of SPS making by the method of vacuum distillation may be simplified and easier to distil the fermented sweet potato. Because the fibrous materials of sweet potato contains pectin with methoxyl group, methanol can be produced by fibrous degradation enzyme. For appling the fiber degradation enzymes to sweet potato mash for making SPS, the enzyme should be needed to degrade fibrous material without producing methanol. Special two fibrolytic enzymes are selected from 26 kind of commercial enzymes for the simplified and easier production of sweet potato soju by vacuum distillation, The selected enzyme A and X can degrade the fibrous material pectin of sweet potato without producing methanol. Although the different companies have produced the enzymes, same cellulase has been prepared from Trichoderma. reesei. The viscosity of sweet potato mash treated by the enzymes is decreased by 3 times with comparison to the viscosity of sweet potato mash of control group. The methanol concentration in the vacuum distilled SPS treated with the enzymes is 0.16%. The concentration is similar to that of commercially distilled SPS(0.15%). The result may suggest that the selected cellulases, A and X, can be used to make SPS by vacuum distillation.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.65-74
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• 2012

In this paper, we present the results of our studies on optimal die design towards development of a vacuum die casting process to fabricate fuel cell bipolar plate with micro-channel array. Cavity and overflow shape is designed by computational filling analysis of MAGMA soft. Optimal die design consists of seven overflows at the end of cavity and three overflows at each side wall of cavity. The molten metal that passed the gate and reached the side wall flowed into the side overflow, no turbulent flow occurred, and the filling behavior and velocity distribution were uniform. In addition, partially solidified molten metal passing through the channel was perfectly eliminated by overflow without back-flow. When vacuum pressure, injection speed of low and high region was 300 mbar, 0.3 m/s and 2.5 m/s respectively with Silafont 36 die casting alloy, sound sample without casting defects was obtained. The experimental results are nearly consistent with simulation results.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.641-648
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• 2000

The horizontal drain method by installing drains horizontally in the ground is often used to expedite the dispersion of pore water and to increase the strength of dredged soft clay under the action of gravity or vacuum. In this study a numerical analysis method is developed to predict the consolidation process of soft ground with horizontal drains. One-dimensional self-weight consolidation theory is extended tn three-dimensions] theory with appropriate boundary conditions of horizontal drains. In the condition of pore water drainage by gravity, the behavior of the dredged clay with horizontal drains is compared with that of the clay without drains. The influence of design factors of drains on consolidation process is also analyzed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.705-708
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• 2003

To observe a hydrated biological specimen, an environmental chamber was necessary to keep the specimen in a wet state under vacuum surroundings. The specimen holder is as follows designed consequently. The specimen holder consisted of two Si wafers, the centers of which were Si$_3$N$_4$(100nm thickness) windows of a 0.3mm square. The windows were made by a photo-lithographic method. The transmission of a window at 400eV is about 70%. A hydrated biological specimen was put between the two windows. When the chamber was closed, two wafers were contact at the metal mesh by the pressure of O-rings, and the specimen holder moved by the three micrometers.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.795-796
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• 2006

본 논문은 청소기용 BLDC 전동기 모터에 기존의 전기강관이 아닌 SMC(Soft Magnetic Composite)를 적용하여 진공청소기용 BLDC 전동기 모터 설계를 하는데 있다. 본 논문에서 사용한 SMC는 순철 분말에 전기적 절연 코팅을 실시한 새로운 재질로 현재 많은 연구가 진행 되고 있는 분야이다. 그러나 재질의 특성에 적합한 모터 설계에 관한 연구는 미진 하였다. 따라서 본 연구는 진공청소기용으로 많이 사용되는 BLDC 모터에 SMC를 적용 하였을 때 BLDC 전동기의 특성을 알아 보고자 하였다. 본 연구에서 SMC재질을 사용 할 때는 어느 조건에서 사용함이 유리한지 알 수 있었다. 또한 고속 청소기에 적합한 설계를 실시한 결과 SMC 재질의 낮은 투자율로 말미암아 인덕턴스가 감소하고, 전류가 높아져, 출력 증대 되는 것으로 나타 났다. 향 후 본 연구는 SMC를 이용한 BLDC 모터 설계 시 설계 기준으로 이용 될 수 있을 것으로 사료된다.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.06c
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• pp.1.1-16
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• 1997

This lecture summarizes the progress of the development of the different ground improvement techniques in Bangkok Plain and is reviewed in relation to the extensive deep wen pumping and the resulting piezometric drawdown at deeper depths. Case records of test embankments with sand drains, sand wicks and PVD are presented to inustrate the effectiveness of different types of vertical drains with surcharge. The use of prefsbicated drain seems more superior than the other types of sand drain. Construction of test embaxlkment, criteria for PVD selection and relevant laboratory testing techniques are discussed for formulating the specif'ication. Alternative teckuuque, such in, the use of deep chemical mixing is reviewed in terms of the efficiency of cement, lime and flyash as additive. Vacuum pre-loading with surcharge and elctro- osmotic consolidation are also explored as possible tectmiques to improve the engineering properties of soft Bangkok clay.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.317-327
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• 2014

In order to develop nano-devices with much lower power consumption for beyond-CMOS applications, the fundamental understanding and precise control of the electronic properties of ultrathin transition metal oxide (TMO) films are strongly required. The metal-insulator transition (MIT) is not only an important issue in solid state physics, but also a useful phenomenon for device applications like switching or memory devices. For potential use in such application, the electronic structures of MIT, observed for TMO nano-structures, have been investigated using a synchrotron radiation angle-resolved photoelectron spectroscopy system combined with a laser molecular beam epitaxy chamber and a scanning photoelectron microscopy system with 70 nm spatial resolution. In this review article, electronic structures revealed by soft X-ray nano-spectroscopy are presented for i) polarity-dependent MIT and thickness-dependent MIT of TMO ultrathin films of $LaAlO_3/SrTiO_3$ and $SrVO_3/SrTiO_3$, respectively, and ii) electric field-induced MIT of TMO nano-structures showing resistance switching behaviors due to interfacial redox reactions and/or filamentary path formation. These electronic structures have been successfully correlated with the electrical properties of nano-structured films and nano-devices.