• 한국산학기술학회논문지
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• 제3권2호
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• pp.74-79
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• 2002

80년대 반도체 산업의 급격한 성장으로 오늘날 반도체 산업은 반도체소자의 초고집접화, 웨이퍼의 대구경화로 발전이 거듭났으며, 소자의 성능과 생산 수율의 향상을 위하여 실리콘 웨이퍼의 세정하는 기술 및 연구를 계속 진행하고 있다. 기존의 반도체 세정은 과다한 화학약품의 사용으로 비 환경친화적이며, 이에 본 연구에서는 기존의 세정방법을 대체하기 위한 방법으로 환경친화적인 전리수를 이용한 반도체 세정법을 하였다. 이때 실리콘 웨이퍼 표면의 원자적 상태의 변화가 발생하여 다양한 방법으로 확인할 수 있다. 본 연구에 서는 이러한 분석을 하기 위하여 기존세정의 화학약품과 전리수로 세정한 웨이퍼의 표면을 비교하였으며, 또한 온도 및 시간별 표면상태변화를 분석하였다. 특히 접촉각 변하에 중점을 두어 변화를 관찰하였으며, 음극수의 경우 17.28°, 양극수의 경우 34.1°의 낮은 접촉각을 얻을 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.86-86
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• 2010

Micro- and nanoscale texturing and control of surface energy have been considered for superhydrophobicity on polymer and silicon. However these surfaces have been reported to be difficult to meet the robustness and transparency requirements for further applications, from self cleaning windows to biochip technology. Here we provided a novel method to fabricate a nearly superhydrophobic soda-lime glass using two-step method. The first step involved wet etching process to fabricate micro-sale patterns on soda-lime glass. The second step involved application of $SiO_x$-incorporated DLC to generate high intrinsic contact angle on the surface using chemical vapor deposition (CVD) process. To investigate the effect of surface roughness, we used both positive and negative micro-scale patterns on soda-limeglass, which is relatively hard for surface texturing in comparison to quartz or Pyrex glasses due to the presence of impurities, but cheaper. For all samples we tested the static wetting angle and transparency before and after 100 cycles of wear test using woolen steel. The surface morphology is observed using optical and scanning electron microscope (SEM). The results shows that negative patterns had a greater wear resistance while the hydrophobicity was best achieved using positive patterns having static contact angle up to 140 deg. with about 80% transparency. The overall experiment shows that positive patterns at etching time of 1 min shows the optimum transparency and hydrophobicity. The optimization of micro-scale pattern to achieve a robust, transparent, superhydrophobic soda-lime glass will be further investigated in the future works.

• 대한기계학회논문집B
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• 제20권3호
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• pp.988-1004
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• 1996

The characteristics of flow and oxygen concentration are numerically studied in Czochralski 8" silicon crystal growing process considering radiative heat transfer. The analysis of net radiative heat flux on all relevant surfaces shows growing crystal affects the heater power. Furthermore, the variation of the radiative heat flux along the crystal surface in the growing direction is confirmed and should be a cause of thermal stress and defect of the crystal. The calculated distributions of temperature and, heat flux along the wall boundaries including melt/crystal interface, free surface and crucible wall indicate that the frequently used assumption of the thermal boundary conditions of insulated crucible bottom and constant temperature at crucible side wall is not suitable to meet the real physical boundary conditions. It is necessary, therefore, to calculate radiative heat transfer simultaneously with the melt flow in order to simulate the real CZ crystal growth. If only natural convection is considered, the oxygen concentration on the melt/crystal interface decreases and becomes uniform by the application of a cusp magnetic filed. The heater power needed also increases with increasing the magnetic field. For the case of counter rotation of the crystal and crucible, the magnetic field suppresses azimutal flow produced by the crucible rotation, which results in the higher oxygen concentration near the interface.

• 대한치위생과학회지
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• 제5권1호
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• pp.13-19
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• 2022

Background: In this study, zirconia copings were fabricated by setting clinically acceptable inner values for prostheses using computer-aided design/computer-aided manufacturing (CAD/CAM). The processed copings were evaluated for the marginal and internal fit of each abutment shape with a CAD program using the silicone replica technique. Methods A total of 20 copings was produced by selecting models commonly used in clinical practice. After injecting the sample, the minimum thickness, internal adhesion interval, and distance to the margin line were set to 0.5, 0.05, and 1.00 mm using a dental CAD program, respectively. It was measured using a 2D section function in a three-way program of the silicon replication technology. Although the positions and number of measurements of the anterior and posterior regions differed, nine parts of each pre-tube were designated and measured by referring to a previous study to compare the two samples. Results As a result, the average margin of the mesial, distal, and buccal (labial) surfaces was 59.90 ㎛ in the anterior region and 60.40 ㎛ in the posterior region. The mean axial wall margin was 67.25 ㎛ in the anterior region and 69.25 ㎛ in the posterior region. In occlusion, the anterior teeth (77.70 ㎛), posterior teeth (77.60 ㎛), and both anterior and posterior regions were within the clinically acceptable range. Conclusion The edge and inner fit of zirconia coping manufactured using the CAD/CAM system showed clinically applicable results. To reduce errors and increase accuracy, materials and machine errors that affect the manufacture of prosthetics should be investigated. Based on our results, the completeness of prosthetics could increase if the inner value and characteristics of the material are adjusted when applied in clinical practice.

• Steel and Composite Structures
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• 제49권3호
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• pp.307-323
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• 2023

In this research, the study of the thermoelastic flexural analysis of silicon carbide/Aluminum graded (FG) sandwich 2D uniform structure (plate) under harmonic sinusoidal temperature load over time is presented. The plate is modeled using a simple two dimensional integral shear deformation plate theory. The current formulation contains an integral terms whose aim is to reduce a number of variables compared to others similar solutions and therefore minimize the computation time. The transverse shear stresses vary according to parabolic distribution and vanish at the free surfaces of the structure without any use of correction factors. The external load is applied on the upper face and varying in the thickness of the plates. The structure is supposed to be composed of "three layers" and resting on nonlinear visco-Pasternak's-foundations. The governing equations of the system are deduced and solved via Hamilton's principle and general solution. The computed results are compared with those existing in the literature to validate the current formulation. The impacts of the parameters (material index, temperature exponent, geometry ratio, time, top/bottom temperature ratio, elastic foundation type, and damping coefficient) on the dynamic flexural response are studied.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.115-116
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• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.

• 한국진공학회지
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• 제14권2호
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• pp.91-96
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• 2005

양성자 주입과 웨이퍼접합기술을 접목한 ion-cut기술로서 SOI 웨이퍼를 제조하는 기술을 개발하였다. SRIM 전산모사에 의하면 일반 SOI 웨이퍼 (200nm SOI, 400nm BOX) 제조에는 65keV의 양성자주입이 요구된다. 웨이퍼분리를 위한 최적 공정조건을 얻기 위해 조사선량과 열처리조건(온도 및 시간)에 따른 blistering 및 flaking 등의 표면변화를 조사하였다. 실험결과 유효선량범위는 $6\~9times10^{16}H^+/cm^2$이며, 최적 아닐링조건은 $550^{\circ}C$에서 30분 정도로 나타났다. RCA 세정법으로서 친수성표면을 형성하여 웨이퍼 직접접합을 수행하였으며, IR 조사에 의해 무결함접합을 확인하였다 웨이퍼 분리는 예비실험에서 정해진 최적조건에서 이루어졌으며, SOI층의 안정화를 위해 고온열처리($1,100^{\circ}C,\;60$분)를 시행하였다. TEM 측정상 SOI 구조결함은 발견되지 않았으며, BOX(buried oxide)층 상부계면상의 포획전하밀도는 열산화막 계면의 낮은 밀도를 유지함을 확인하였다.

• 원예과학기술지
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• 제31권2호
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• pp.159-164
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• 2013

오이는 품종에 따라 과실표면에 과분(果紛) 소위 'bloom'이 발생하는데 이는 외관상 과실의 품질을 저하시키는 요인이 된다. 본 시험은 주관 종자회사에서 수집하여 육성하여 오던 bloomless 대목용 호박재료를 이용하여 'bloomless 대목'을 개발하고 앞으로 새로운 대목육성에 필요한 기초자료를 얻고자 하였다. Bloomless 오이의 표면은 분비모(glandular trichome, 分泌毛)의 낭상세포(bladder cell)가 형성되어 존재하고 있음을 관찰할 수 있었으며, 낭상세포 외의 과실표면은 상각피[epicuticular waxes(EW)] 층이 형성되어 있는 것을 관찰할 수 있었다. 또한 오이의 EW 형태는 둥근 모양의 결정체가 겹쳐진 형태이었으며, 그물 모양의 능선과 능선 안쪽에 고르게 분포하는 것으로 관찰되었다. 이와 다르게 bloom 현상이 나타나는 오이의 과실표면은 낭상세포의 형태가 크게 부풀어 있거나 터져 있었으며, 또한 손상된 낭상세포 주변으로 bloomless 오이에서 관찰되지 않았던 많은 입자들을 볼 수 있었다. Bloom과 bloomless 과실표면의 색도를 조사한 결과 bloom이 발생한 과실과 발생하지 않은 과실의 색도 'a'와 'b' 값의 유의성은 없었고, 'L' 값은 bloom이 발생한 과실에서 높았다. 오이 과실의 규소 함량은 bloomless 대목에 접목한 오이 과실이 일반대목에 접목한 것에 비하여 현저히 낮았다.

• Restorative Dentistry and Endodontics
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• 제22권2호
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• pp.609-621
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• 1997

The purpose of this study was to evaluate the shear bond strength of three light-cured glass ionomer cements to blood contaminated bovine dentin. The materials used in this study were Fuji II LC, Dyract and Variglass VLC. The dentin conditioners were 10% polyacrylic acid, 10% maleic acid and 10% phosphoric acid. 180 lower anterior bovine teeth were selected in this study. The teeth were embedded in acrylic resin and were grounded with 320 to 600 grit silicon carbide paper to create a flat dentin surface. The teeth were divided into SIX groups. The experimental procedures in six groups were as follows; Group l(GF) : Samples bonded to dentin surface with Fuji II LC after 10% polyacrylic acid treatment. Group 2(BGF) : Samples bonded to dentin surface with Fuji II LC after 10% polyacrylic acid treatment and blood contamination. Group 3(MD) : Samples bonded to dentin surface with Dyract after 10% maleic acid treatment. Group 4(BMD) : Samples bonded to dentin surface with Dyract after 10% maleic acid treatment and blood contamination. Group 5(PV) : Samples bonded to dentin surface with Variglass VLC after 10% phosphoric acid treatment. Group 6(BPV) : Samples bonded-to dentin surface with Variglass VLC after 10% phosphoric acid treatment and blood contamination. Group 1,3 and 5 were classified into the control groups, while group 2,4 and 6 were classified into the experimental groups. Each group contained 30 samples. After 24 hours water storage at $37^{\circ}C$, all smples were subjected to a shear load to fracture at a cross head speed of 1.0 mm/min with Instron universal testing machine(No. 4467). Debonded surfaces were observed under Scanning Electron Microscope(Hitachi S-2300) at 20kvp. The data were evaluated statistically at the 95% confidence level with Student's t-test. The following results obtained; 1. Shear bond strengths were higher in the control groups(1,3,5 group) than in the experimental groups(2,4,6 group). 2. The shear bond strength of group 5(PV) was the highest in the control groups, and the group 5 was significantly higher than the group l(GF) on the shear bond strength. 3. The group 4(BMD) was the highest on the shear bond strength, and the group 2(BGF) was the lowest in the experimental groups. The group 4(BMD) and 6(BPV) showed a significant difference with the group 2 on the shear bond strength. 4. All the groups showed an adhesive-cohesive failure. except the group 2(BGF) showing adhesive failure.

• 마이크로전자및패키징학회지
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• 제19권1호
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• pp.39-45
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• 2012

Cu-Cu 패턴의 직접접합 공정을 위하여 Buffered Oxide Etch(BOE) 및 Hydrofluoric acid(HF)의 습식 조건에 따른 Cu와 $SiO_2$의 식각 특성에 대한 평가를 수행하였다. 접촉식 3차원측정기(3D-Profiler)를 이용하여 Cu와 $SiO_2$의 단차 및 Chemical Mechanical Polishing(CMP)에 의한 Cu의 dishing된 정도를 분석 하였다. 실험 결과 BOE 및 HF 습식 식각 시간이 증가함에 따라 단차가 증가 하였고, BOE가 HF보다 더 식각 속도가 빠른 것을 확인하였다. BOE 및 HF 습식 식각 후 Cu의 dishing도 식각시간 증가에 따라 감소하였다. 식각 후 산화막 유무를 알아보기 위해 Cu표면을 X-선 광전자 분광법(X-ray Photoelectron Spectroscopy, XPS)를 이용하여 분석 한 결과 HF습식 식각 후 BOE습식 식각보다 Cu표면산화막이 상대적으로 더 얇아 진 것을 확인하였다.