• 한국진공학회지
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• 제15권4호
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• pp.410-420
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• 2006

Epitaxial 성장에서 screening 및 steering 효과 등과 같은 증착과정 중 나타나는 dynamic effects를 kinetic Monte Carlo 시뮬레이션으로 고찰하였다. 증착원자와 토대 원자와의 상호 작용을 엄밀하게 고려하기 위해 이 시뮬레이션 프로그램에 molecular dynamics 시뮬레이션을 결합시켰다. 기울어진 각도로 증착 시킬 경우 표면의 형상은 1) 증착 각도가 기울어짐에 따라 거칠기가 증가한다는 것, 2) 비대칭적인 언덕의 형성된다는 것, 그리고 3) 언덕의 면방향에 따라 비대칭적인 기울기를 갖는다는 세가지 특징을 보았다. 증착 각도나 온도 의존성에 대한 시뮬레이션 결과는 기존의 실험 결과와 잘 일치하는 것을 확인하였다. 기울어진 각도로 증착했을 때 나타나는 이러한 결과는 steering과 screening 효과에 따른 초기 증착 밀도의 불균일에 기인함을 알 수 있었고, 여기서 steering 효과가 screening 효과 보다 주요한 역할을 하는 것을 보았다. 시뮬레이션 계산에서 확인된 새로운 결과는 기울기 선택 (slope selection)이 이루어졌어도 언덕의 각 면이 단일한 기울기로 형성되어 있지 않고 여러 종류의 facet가 섞인 형태이며, 따라서 기울기 선택이 바로 facet 선택을 의미하지는 않는다는 것이다.

• 비파괴검사학회지
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• 제36권4호
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• pp.259-265
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• 2016

This paper presents a study on the use of pulsed phase thermography in the measurement of thermal barrier coating thickness with a numerical simulation. A multilayer heat transfer model was ussed to analyze the surface temperature response acquired from one-sided pulsed thermal imaging. The test sample comprised four layers: the metal substrate, bond coat, thermally grown oxide and the top coat. The finite element software, ANSYS, was used to model and predict the temperature distribution in the test sample under an imposed heat flux on the exterior of the TBC. The phase image was computed with the use of the software MATLAB and Thermofit Pro using a Fourier transform. The relationship between the coating thickness and the corresponding phase angle was then established with the coating thickness being expressed as a function of the phase angle. The method is successfully applied to measure the coating thickness that varied from 0.25 mm to 1.5 mm.

• 반도체디스플레이기술학회지
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• 제9권4호
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• pp.13-18
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• 2010

Extreme ultraviolet (EUV) lithography using 13.5 nm wavelengths is expected to be adopted as a mass production technology for 32 nm half pitch and below. One of the new issues introduced by EUV lithography is the shadowing effect. Mask shadowing is a unique phenomenon caused by using mirror-based mask with an oblique incident angle of light. This results in a horizontal-vertical (H-V) biasing effect and ellipticity in the contact hole pattern. To minimize the shadowing effect, a refilled mask is an available option. The concept of refilled mask structure can be implemented by partial etching into the multilayer and then refilling the trench with an absorber material. The simulations were carried out to confirm the possibility of application of refilled mask in 32 nm line-and-space pattern under the condition of preproduction tool. The effect of sidewall angle in refilled mask is evaluated on image contrast and critical dimension (CD) on the wafer. We also simulated the effect of refilled absorber thickness on aerial image, H-V CD bias, and overlapping process window. Finally, we concluded that the refilled absorber thickness for minimizing shadowing effect should be thinner than etched depth.

• 한국광학회지
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• 제4권2호
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• pp.162-167
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• 1993

유전체 다층박막에 빛이 사각으로 입사할 결우 편광에 의존하는 현상이 나타나므로 사용하기에 바람직하지 못하다. 본 연구에서는 이러한 편광효과를 줄이기 위하여 기존의 몇가지 설계법을 이용하여 비편광 광분리기를 설계해 보고 이 방법들을 응용하여 박막의 광학적두께가 ${\lambda}$/4로 일정할 때 최외각등가층의 반사율을 조절하는 방법을 사용하여 비편광 광분리기를 설계하였다.

• Applied Microscopy
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• 제42권4호
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• pp.218-222
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• 2012

Modern aberration-corrected transmission electron microscope (TEM) with appropriate electron beam energy is able to achieve atomic resolution imaging of single and bilayer graphene sheets. Especially, atomic configuration of bilayer graphene with a rotation angle can be identified from the direct imaging and phase reconstructed imaging since atomic resolution Moir$\acute{e}$ pattern can be obtained successfully at atomic scale using an aberration-corrected TEM. This study boosts a reliable stacking order analysis, which is required for synthesized or artificially prepared multilayer graphene, and lets graphene researchers utilize the information of atomic configuration of stacked graphene layers readily.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1772-1775
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• 2002

In this paper, we propose a Hangul character recognition method in which new letter components as recognition units are introduced and the MLP (multilayer perceptrons) neural networks are employed for two-step recognition of Hangul. To recognize Hangul character, we divide it into two or three recognition units and extract the direction angle features of them to be fed to the corresponding neural network recognizers. The recognition results of neural network recognizers are combined by another neural network. The experiments were conducted on the Hangul characters from real letter envelopes which are collected in the mail centers in Korea and the results showed that our method performs better than the conventional one.

• Journal of Magnetics
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• 제3권3호
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• pp.92-95
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• 1998

In this paper we report the low and high angle diffraction results, and the magnetic and magnetroesistive characteristics of the spin valve multilayer structure prepared by the sputter machine Emerald II in the Balzers Laboratory. The investigated system consists of a ferromagnetic free layer (7 nm NiFe) and a ferromagnetic pinned layer (7 nm NiFe), separated from each other by a nonmagnetic (2.1 nm Cu) spacer. The NiFe pinned layer is fixed by the exchange coupling with an antiferromagnetic layer (10 nm FeMn). For such system the magnetoresistance ratio ΔR/R=3.58%, the interlayer exchange coupling $H_c=6.4$ Oe and the field sensitivity 1.15%/Oe were otained.

• Bulletin of the Korean Chemical Society
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• 제19권5호
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• pp.544-548
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• 1998

A Monte Carlo simulation incorporated with the genetic algorithm is presented to describe the defect known as "transition from Y-to X-type deposition" of the cadmium arachidate Langmuir-Blodgett multilayer film. Simulation is performed based on the detachment models of XY-type deposition. The transition is simulated by introducing a probability of surface molecule detachment considering interaction between neighboring molecules. The genetic algorithm is incorporated into Monte Carlo simulation to get the optimum value of the probability factors. The distribution of layers having different thickness predicted by the simulation correlates well with the measured distribution of thickness using the small-angle X-ray reflectivity. The effect of chain length and subphase temperature on the detachment probability are investigated using the simulation. Simulation results show that an increase (or a decrease) of two hydrocarbon chain is roughly equivalent to the detachment probability to a temperature decrease (or increase) of 15 K.

• Current Applied Physics
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• 제18권11호
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• pp.1196-1200
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• 2018

We have experimentally demonstrated circular polarization generation from linear polarized soft X-ray at synchrotron by adopting a thin magnetic film polarizer. Polarizer is composed of Co/Pt multilayer with a perpendicular magnetic anisotropy, which allows us to easily accommodate without needing any tilting angle into the measurement setup since the circular polarization is generated for the X-ray with normal incidence and transmission. Generated circular polarization is examined by observing magnetic domain features based on the X-ray magnetic circular dichroism, where~11% of circular component is estimated compared to the case of full circular polarization.

• 한국자기학회지
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• 제5권5호
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• pp.461-464
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• 1995

We have investigated the effects of sputtering Ar gas pressure on magnetic anisotropy of Co/Pt multilayers, where sputtering Ar gas pressure was varied from 2 to 20 mTorr. The surface and volume anisotropies were found to be strongly dependent on sputtering Ar gas pressure. In particular, the surface anisotropy exhibited more than fourfold enhancement as Ar pressure was decreased from 20 to 5 mTorr. We have found that the surface anisotropy was closely correlated with the low-angle x-ray diffraction intensity. We believe that these results are mainly ascribed to the variation of microstructure in the Co/Pt multilayer thin films with sputtering Ar gas pressure.