• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.335-335
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• 2011

Instability of a thin film attached to a compliant substrate often leads to emergence of exquisite wrinkle patterns with length scales that depend on the system geometry and applied stresses. However, the patterns that are created using the current techniques in polymer surface engineering, generally have low aspect ratio of undulation amplitude to wavelength, thus, limiting their application. Here, we present a novel and effective method that enables us to create wrinkles with a desired wavelength and high aspect ratio of amplitude over wavelength as large as to 2.5:1. First, we create buckle patterns with high aspect ratio of amplitude to wavelength by deposition of an amorphous carbon film on a surface of a soft polymer poly(dimethylsiloxane) (PDMS). Amorphous carbon films are used as a protective layer in structural systems and biomedical components, due to their low friction coefficient, strong wear resistance against, and high elastic modulus and hardness. The deposited carbon layer is generally under high residual compressive stresses (~1 GPa), making it susceptible to buckle delamination on a hard substrate (e.g. silicon or glass) and to wrinkle on a flexible or soft substrate. Then, we employ glancing angle deposition (GLAD) for deposition of a high aspect ratio patterns with amorphous carbon coating on a PDMS surface. Using this method, pattern amplitudes of several nm to submicron size can be achieved by varying the carbon deposition time, allowing us to harness patterned polymers substrates for variety of application. Specifically, we demonstrate a potential application of the high aspect wrinkles for changing the surface structures with low surface energy materials of amorphous carbon coatings, increasing the water wettability.

• Journal of the Korean Vacuum Society
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• v.21 no.2
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• pp.86-92
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• 2012

We have studied the effect of speed of deposited atom on morphology evolution during Glancing Angle Deposition (GLAD). Using Kinetic Monte Carlo simulation that incorporate molecular dynamics simulations, we have shown that the rough surface morphology became smoother as the speed of deposited atom is increased. The growth exponent ${\beta}$ change from 0.97 to 0.67 as the speed increase from ${\upsilon}_0$ to $10{\upsilon}_0$ in the case of GLAD. We also examined the effect of speed of deposited atom for the case of chemical vapor deposition (CVD) simulation. Compared to GLAD, the variation in scaling exponent ${\beta}$ is small but the speed of deposited atom also have considerable effect on growth morpholgy in the case of CVD.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.98-98
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• 2013

완전화 박막이란 사용자가 원하는 용도에 맞게 최적의 성능을 구현하도록 제조된 박막을 의미하며 금속이나 화합물 박막을 제조하되 각종 구조 제어 Tool이나 증착 공정을 변화시켜 나노화와 다층화 또는 치밀화를 통해 구현될 수 있다. 최근 고성능의 증착 및 제어 Tool이 개발되고 빗각증착(Oblique Angle Deposition)이나 스침각 증착(Glancing Angle Deposition) 방법 등의 기술이 개발되면서 사용자 목적에 최적인 박막 소재를 제공하여 User-friendly한 응용을 위한 연구개발이 활발히 진행되고 있다. 완전화 박막 제조에 대한 시도는 1990년대에 일본에서 시작되었다. 일본에서는 산학연이 공동으로 참여하는 NEDO 프로그램을 통해 경질코팅을 이용한 Protective Layer를 제조하여 차단 방식에 의한 내식성 구현 연구를 수행하였다. 유럽에서는 제 7차 European Framework Program (7th FT)을 통해 2007년부터 CORRAL (Corrosion Protection with Perfect Atomic Layer) 프로젝트를 만들어 완전화 박막 연구를 진행하고 있다. 상기 프로젝트는 얇은 자연 산화막이 Bulk의 부식을 방지해주는 것에 착안하여 HIPIMS나 Filtered Arc 또는 ALD 공정을 이용하여 자연 산화막과 유사한 Defect-free 산화막을 제조하여 Barrier형 내식성 박막을 구현하는 것을 목표로 하고 있다. 본 연구에서는 완전화 박막 구현을 위한 연구동향을 파악하고 완전화 박막 제조를 위한 기술적 과제와 몇 가지의 시도에 대한 기초 연구 자료를 소개한다.

• Proceedings of the Korea Crystallographic Association Conference
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• 2007.11a
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• pp.45-46
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• 2007

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.61-61
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• 2013

진공증착으로 제조된 박막은 주상정 조직으로 성장하여 박막 내에 기공을 포함하는 것이 일반적이다. 박막의 조직변화를 통한 특성 향상은 박막을 치밀하게 제조하거나 자연 산화막 등과 같이 원하는 형상의 조직을 형성하는 것이며 이를 위해 완전화 박막이라는 개념이 등장하였다. 본 논문에서는 완전화 박막의 제조를 위한 빗각 및 스침각 증착 기술을 소개하고 금속 및 화합물 박막의 빗각 증착 사례를 소개하고자 한다.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.217-218
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• 2008

In this paper, we investigate the optical and structural properties of linear and circular polarization-discriminatory inverters. Circular polarization-discriminatory handedness inverter is realized as a combination of half-wave plate and Bragg reflector and that of linear polarization in verter is realized as a combination of quarter-wave plate, Bragg reflector and quarter-wave plate.

• Journal of Sensor Science and Technology
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• v.25 no.6
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• pp.383-387
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• 2016

Well-ordered nanocolumnar indium oxide ($In_2O_3$) thin films have been successfully fabricated by glancing angle deposition (GAD) using an e-beam evaporator. Nanocolumnar structures have a porous and large surface area with a narrow neck between nanocolumns, which allows them to detect minute amounts of gases. The nanocolumnar $In_2O_3$ thin films were fabricated by the GAD process at five different positions, viz. top, bottom, center, left, and right in a four inch substrate holder. There was a divergence in the thickness and the base resistance of each sensor. However, all the sensors exhibited extremely high sensitivity that was greater than $10^3$ times the change in electrical resistance after being exposed to 50 ppm of acetone gas at $300^{\circ}C$. Furthermore, the nanocolumnar $In_2O_3$ sensors displayed an extremely low detection limit (1.2 ppb) in dry atmosphere as well as in high humidity (80%). We demonstrated that the GAD nanocolumnar $In_2O_3$ sensors have an enormous potential for many applications owing to their particularly simple and reliable fabrication process.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.407-411
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• 2020

In this study, we propose an array-type gas sensor with high selectivity and response using multiple oxide semiconductors. The sensor array was composed of SnO₂ and In₂O₃, and the detection characteristics were improved by using Pt, Au, and Pd catalysts. All samples were deposited directly on the Pt interdigitated electrode (IDE) through the e-beam evaporator glancing angle deposition (GAD) method. They grew in the form of well-aligned nanorods at off-axis angles. The prepared SnO₂ and In₂O₃ nanorod samples were exposed to CH₃COCH₃, C₇H₈, and NO₂ gases in a 300℃ dry condition. Au-decorated SnO₂, Au-decorated In₂O₃, and Pd-decorated In₂O₃ exhibited high selectivity for CH₃COCH₃, C₇H₈, and NO₂, respectively. They demonstrated a high detection limit of the sub ppb level computationally. In addition, measurements from each sensor were executed in the 40% relative humidity condition. Although there was a slight reduction in detection response, high selectivity and distinguishable detection characteristics were confirmed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.31-32
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• 2011

완전화 박막은 박막의 구조를 원하는 목적에 최적이 되도록 제어하는 방법을 이용하여 만들어진 박막을 의미하는 것으로 금속이나 화합물 박막을 제조하되 각종 구조 제어 Tool을 이용하여 나노화나 다층화 및 치밀화를 통해 구현될 수 있다. 최근 고성능의 증착 및 제어 Tool이 개발되고 스침각 증착 (Glancing Angle Deposition; GLAD) 방법 등의 기술이 개발되면서 User-defined 박막을 통해 User-friendly 응용을 위한 연구개발이 활발히 진행되고 있다. 본 연구에서는 완전화 박막 구현을 위한 연구동향을 파악하고 완전화 박막 제조를 위한 기술적 과제와 몇 가지의 시도에 대한 기초 연구 자료를 소개한다.

• Journal of Sensor Science and Technology
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• v.23 no.5
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• pp.291-294
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• 2014

In this study, a chemiresistive sensor based on one-dimensional $WO_3$ nanostructures is presented for application in non-invasive medical diagnostics. $WO_3$ nanostructures were used as an active gas sensing layer and were deposited onto a $SiO_2/Si$substrate using Pt interdigitated electrodes (IDEs). The IDE spacing was $5{\mu}m$ and deposition was performed using RF sputter with glancing angle deposition mode. Pt IDEs fabricated by photolithography and dry etching. In comparison with thin film sensor, sensing performance of nanostructure sensor showed an enhanced response of more than 20 times when exposed to 50 ppm acetone at $400^{\circ}C$. Such a remarkable faster response can pave the way for a new generation of exhaled breath analyzers based on chemiresistive sensors which are less expensive, more reliable, and less complicated to be manufactured. Moreover, presented sensor technology has the potential of being used as a personalized medical diagnostics tool in the near future.