• Biotechnology and Bioprocess Engineering:BBE
• /
• 제9권4호
• /
• pp.241-244
• /
• 2004

Protein A molecular thin film was fabricated as a platform of antibody-based biosensor. For the immobilization of the protein A thin film, a viologen multilayer was built up using the Langmuir-Blodgett (LB) technique, and then, protein A was adsorbed on the viologen LB film by an electrostatic interaction force, which was formed as a hetero-film structure. For the deposition of viologen, surface pressure area ($\pi$-A) isotherm was investigated. The fabricated protein A-viologen hetero LB film was investigated using atomic force microscopy (AFM). Using the developed molecular film, antibody immobilization and fluorescence measurement was carried out.

• 한국기계가공학회지
• /
• 제2권1호
• /
• pp.75-84
• /
• 2003

In this paper, a new nano/micro-mechanical processing test machine was developed. This new test machine, which is based on the principle of the scanning force controlled probe microscope, can realize nano/micro-mechanical machining and in-process profile measurement. Experimental results of nano/micro indentation and scratching show that the controllable cutting depth of the test machine can be controlled by PZT actuator. Profile measurement of the machined surface has also been performed by using the test machine and a conventional AFM(Atomic Force Microscopy). A good agreement of the two measurement results have been achieved.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 C
• /
• pp.1887-1889
• /
• 2001

금속 재질의 MEMS 구조물의 모양을 폴리머에 전사하는 micromolding 과정에서 금속 구조물과 폴리머 사이를 분리 (demolding)시킬 때 금속 구조물과 폴리머 기판 사이에 분리를 방해하는 응착 (Adhesion) 문제가 발생한다. 이러한 응착 문제를 줄이고자 표면 에너지가 낮은 Self-Assembled Monolayer(SAM) coating을 금속(Ni) 표면에 시도하였다. SAM coating 막의 형성 여부와 응착력 (Adhesion force) 값을 구하기 위해 각각 XPS(X-ray photoelectron spectroscopy)와 AFM(Atomic force microscopy)을 이용하여 측정하였고 측정 결과 Ni 표면에 SAM이 형성되었음을 XPS로부터 알 수 있었고 SAM coating된 Ni 시편에서 더 낮은 응착력값을 보여 주었다.

• Journal of the Optical Society of Korea
• /
• 제20권1호
• /
• pp.125-129
• /
• 2016

In this study, we have investigated a high-temperature AlN nucleation layer and AlGaN epilayers on c-plane sapphire substrate by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). High resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), scanning electron microscope (SEM) and Raman scattering measurements have been exploited to study the crystal quality, surface morphology, and residual strain of the HT-AlN nucleation layer. These analyses reveal that the insertion of an LT-AlN nucleation layer can improve the crystal quality, smooth the surface morphology of the HT-AlN nucleation layer and further reduce the threading dislocation density of AlGaN epifilms. The mechanism of inserting an LT-AlN nucleation layer to enhance the optical properties of HT-AlN nucleation layer and AlGaN epifilm are discussed from the viewpoint of driving force of reaction in this paper.

• 한국수소및신에너지학회논문집
• /
• 제18권2호
• /
• pp.182-188
• /
• 2007

[ $Zr_{50}-Ni_{27}-Nb_{18}-Co_5$ ] amorphous alloys ribbon was prepared by a single-roller melt-spinning technique. In order to improve the hydrogen kinetics Pd-coating were carried out on each side of the amorphous ribbon. Pd prevents oxidation of Zr and catalyses the dissociation of molecular hydrogen to atomic hydrogen. In this work, the hydrogen embrittlement and surface properties on Zr-based amorphous alloys were investigated. The Zr-based amorphous alloys were characterized by X-ray diffractometry(XRD) and differential scanning calorimetry(DSC). The morphology of surface and roughness was observed by using scanning electron microscopy(SEM) and atomic force microscopy (AFM). A lattice parameter of both Pd and Zr-based amorphous alloy was increased after hydrogen permeation at 473 K. After hydrogen permeation at 473 K, some cracks were observed on the surface of Pd, which was the cause for the hydrogen embrittlement. The crystallization temperature of Zr-based amorphous alloy was decreased due to the permeated hydrogen.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
• /
• pp.6-11
• /
• 2001

More than ten kinds of oxide thin films and their heterostructure have been successfully fabricated on SrTiO$_3$(001) substrates by laser molecular beam epitaxy (laser MBE). Measurements of atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM) and X-ray small-angle reflectivity reveal that the surfaces and interfaces are atom-level-smooth. The unit cell layers and the lattice structure are perfect. The electrical and optical properties of BaTiO$_3$-x thin films and BaTiO$_3$/SrTiO$_3$ (BTO/STO) superlattices were examined. The all-perovskite oxide P-N junctions have been successfully fabricated and the better I-V curves were observed.

• Journal of Microbiology and Biotechnology
• /
• 제22권12호
• /
• pp.1681-1691
• /
• 2012

This work was conducted to evaluate the effect of dilute sodium hydroxide (NaOH) on barley straw at boiling temperature and fractionation of its biomass components into lignin, hemicellulose, and reducing sugars. To this end, various concentrations of NaOH (0.5% to 2%) were applied for pretreatment of barley straw at $105^{\circ}C$ for 10 min. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy studies revealed that 2% NaOH-pretreated barley straw exposed cellulose fibers on which surface granules were abolished due to comprehensive removal of lignin and hemicellulose. The X-ray diffractometer (XRD) result showed that the crystalline index was increased with increased concentration of NaOH and found a maximum 71.5% for 2% NaOH-pretreated sample. The maximum removal of lignin and hemicellulose was 84.8% and 79.5% from 2% NaOH-pretreated liquor, respectively. Reducing sugar yield was 86.5% from 2% NaOH-pretreated sample using an enzyme dose containing 20 FPU of cellulase, 40 IU of ${\beta}$-glucosidase, and 4 FXU of xylanase/g substrate. The results of this study suggest that it is possible to produce the bioethanol precursor from barley straw using 2% NaOH at boiling temperature.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.63-64
• /
• 2002

In a micro-scale contact, surface forces such as capillary force and van der Waals Interaction significantly Influence the contact between asperities of rough surfaces. Little is, however, known about the variation of these surface forces as a function of chemical property of the surface (hydrophilicity), relative humidity and deformation of asperities In the real area of contact. A better understanding of these surface forces is of great necessity in order to find an optimal solution for reducing friction and adhesion of micro surfaces. We proposed an effective method to analyze capillary and van der Waals forces In nano-scale contact. In this method, Winklerian foundation model was employed to analyze the contact of rough surfaces that were obtained from atomic force microscopy (AFM) height Images. Self-mated contact of diamond-like-carbon (DLC) coatings was analyzed, as an example, by the proposed model. It was shown that the capillary force was significantly influenced by relative humidify and wet angle of the DLC surface. The deformation of asperities to a critical magnitude by external loading led to a considerable increase of both capillary and van der Waals forces.

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
• /
• pp.193-197
• /
• 2002

The tribological properties and van der Waals attractive forces and the thermal stability of films are very important characteristics of highly hydrophobic fluorocarbon (FC) films for the long-term reliability of nano system. The effect of thermal annealing on films and van der Waals attractive forces and friction coefficient of films have been investigate d in this study. It was coated Al wafer which was treated O2 and Ar that ocatfluorocyclobutane ($C_4_{8}$) and Ar were supplied to the CVD chamber in the ratio of 2:3 for deposition of FC Films. Static contact angle and dynamic contact angle were used to characterize FC films. Thickness of films was measured by variable angle spectroscopy ellipsometer (VASE). Nanotribological data was got by atomic force microscopy (AFM) to measure roughness, lateral force microscopy (LFM) to measure friction force, and force vs. distance (FD) curve to evaluate adhesion force. FC films were cured in N2 and vacuum. The film showed the slight changes in its properties after 3 hr annealing. FTIR ATR studies showed the decrease of C-F peak intensity in the spectra as the annealing time increased. A significant decrease of film thickness has been observed. The friction force of Al surface was at least thirty times higher than ones with FC films. The adhesive force of bare Al was greater than 100 nN. After deposit FC films adhesive force was decreased to 40 nN. The adhesive force of films was decreased down to 10 nN after 24 hr annealing. During 24 hr annealing in $N_2$and vacuum at $100^{\circ}C$ film properties were not changed so much.

• 한국진공학회지
• /
• 제17권3호
• /
• pp.226-233
• /
• 2008

본 연구는 화학기상증착(Chemical Vapor Deposition)법을 이용하여 Si(100) 표면위에 Ge 나노점을 성장하여 나노점의 형성과 성장과정을 원자간력현미경(AFM)으로 조사하였다. 성장온도, Ge 증착량, 열처리시간의 변화에 따른 형성된 나노점의 모양, 크기, 표면 밀도의 변화를 분석하였다. $600^{\circ}C$의 성장온도에서 ${\sim}0.1ML/sec$의 증착율로 Ge을 증착한 결과, ${\sim}4ML$까지는 pseudomorphic한 Ge wetting 층이 형성되었으며, 증착시간을 증가하여 5ML 이상에서 Ge 나노점이 형성되기 시작하였다. Ge 증착량을 증가시킴에 따라 초기 나노점은 긴 지붕모양(elongated hut)구조로 형성되었고, 점차 크기가 증가함에 따라, 피라미드(pyramid), 돔(dome), 더 큰 Superdome 구조로 변형되었다. 초기 피라미드 형태의 나노점 평균크기는 ${\sim}20nm$이였으며, 가장 큰 superdome의 평균크기는 ${\sim}310nm$ 이상이었으며, 크기가 증가함에 따라 표면 밀도는 $4{\times}10^{10}cm^{-2}$에서 $5{\times}10^8cm^{-2}$로 감소하였다. 상대적으로 고온인 $650^{\circ}C$에서 Ge을 증착했을 경우, 피라미드 구조는 발견되지 않았으며, 대부분의 나노점은 돔 형태로 형성되었으며, 점차 superdome 형태로 변형되었다. 또한, 고온 성장된 시료의 열처리 시간을 증가함에 따라, 나노점의 크기는 점차 성장하였으나, 밀도는 거의 변화가 없었다. 이와 같은 나노점의 형태, 크기, 밀도의 변화는 나노점이 갖는 에너지의 최소화와 표면에서 원자들의 이동(diffusion)으로 설명할 수 있었다. 특히, AFM 이미지의 표면에 분포한 나노점들의 상대적인 위치를 분석한 결과, 유사한 크기의 근접한 나노점들은 점차 크기가 증가함에 따라 합쳐지는 Coalescence과정에 의해 성장하고, 크기가 다른 근접한 나노점들 사이에는 화학적 포텐셜에너지 차에 의한 ripening 과정의 성장을 관찰하였다. 즉, 형성된 나노점들은 국부적인 표면분포에 따라 나노점들은 두 성장과정이 동시 작용하여 성장함을 확인하였다.