• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.191.1-191.1
• /
• 2013

현재 산업계 전반적으로 사용되고 있는 박막형 태양전지 투명 전도막의 재료로는 ITO 와 Al, In, Ga, B, Si, F 등으로 도핑된 ZnO 박막이 사용되고 있으며, 그 중에서도 Al 이 도핑된 ZnO 박막은 넓은 밴드갭을 가진 n-type 반도체로서, 적외선 및 가시광 영역에서의 높은 투과성과 우수한 전도성을 가지며, 고온에서 안정된 전기적 특성, 낮은 원가 등의 장점을 지녀 그 응용 연구가 활발히 이루어지고 있다 [1]. 본 연구에서는 RF magnetron Sputter 법을 이용하여 Flexible 기판 위에 AZO 박막을 증착하였다. 실험변수로는 RF power, Pressure등을 이용하였고, 최적조건에서의 박막의 투과도는 90%이상, 면저항은 30 ${\Omega}/{\square}$ 이하를 나타내었다. 그리고 (주)인포비온에서 원천기술을 갖고있는 EBA technology를 이용하여 후처리 하여 전기적, 광학적, 구조적인 특성의 변화를 관찰하였다. AZO 박막의 두께를 측정하기 위해 ${\alpha}-step$과 SEM을 이용하였고, 투과도는 UV-Vis spectrometer를 사용하여 박막의 투과도 변화를 관찰 하였다. 전기적인 특성은 4-Point probe를 이용하여 측정하였다. 또한, 박막의 결정성과 거칠기의 변화는 XRD(X-ray Diffraction)와 원자간력현미경(Atomic Force Microscope; AFM) 을 이용하여 측정하였으며, 전기 광학적 특성 변화는 Figure Of Merit(FOM) 수치로 분석하였다. 본 연구에서 AZO 박막의 특성은 EBA 조사 후 특성의 향상이 이루어지는 것을 관찰할 수 있었다.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.8 s.185
• /
• pp.39-46
• /
• 2006

Nano-scale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) was demonstrated. A specially designed cantilever with diamond tip, allowing the formation of damaged layer on silicon substrate by a simple scratching process, has been applied instead of conventional silicon cantilever for scanning. A thin mask layer forms in the substrate at the diamond tip-sample junction along scanning path of the tip. The mask layer withstands against wet chemical etching in aqueous KOH solution. Diamond tip acts as a patterning tool like mask film for lithography process. Hence these sequential processes, called tribo-nanolithography, TNL, can fabricate 2D or 3D micro structures in nanometer range. This study demonstrates the novel fabrication processes of the micro cantilever and diamond tip as a tool for TNL using micro-patterning, wet chemical etching and CVD. The developed TNL tools show outstanding machinability against single crystal silicon wafer. Hence, they are expected to have a possibility for industrial applications as a micro-to-nano machining tool.

• Tribology and Lubricants
• /
• v.23 no.6
• /
• pp.288-297
• /
• 2007

Adhesion and friction tests were carried out in order to investigate the effect of temperature on the tribological characteristics of poly (methylmethacrylate) (PMMA) film using AFM. The pull-off and friction forces on the PMMA film were measured under a high vacuum condition (below $1{\times}10^{-4}$ Pa) as the temperature of the PMMA film was increased from 300 K to 420 K (heating) and decreased to 300K (cooling). Friction tests were also conducted in both high vacuum and air conditions at room temperature. When the temperature was 420 K, which is 25 K higher than the glass transition temperature $(T_g)$ of PMMA, the PMMA film surface became deformable. Subsequently, the pull-off force was proportional to the maximum applied load during the pull-off force measurement. In contrast, when the temperature was under 395 K, the pull-off force showed no correlation to the maximum applied load. The friction force began to increase when the temperature rose above 370 K, which is 25 K lower than the $T_g$ of PMMA, and rapidly increased at 420 K. Decrease of the PMMA film stiffness and plastic deformation of the PMMA film were observed at 420 K in force-displacement curves. After the heating to 420 K, the fiction coefficient was measured under the air condition at room temperature and was found to be lower than that measured before the heating. Additionally, the RMS roughness increased as a result of the heating.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.375.2-375.2
• /
• 2016

그래핀(Graphene)은 원자 한 층 두께의 얇은 특성에 기인하여 우수한 투과도(~97.3%)를 나타내며, 높은 전자 이동도($200,000cm^2V^{-1}s^{-1}$)로 인하여 전기 전도도가 우수한 2차원 전자소재이다. 또한 유연하고 우수한 기계적 물성을 가지고 있어 실제로 다양한 소자에서 활용되고 있다. 그래핀을 이용하여 다양한 소자로 응용하기 위한 과정 중 하나인 포토리소그래피 공정(Photolithography process)은 원하는 패턴을 만들기 위해 제작하고자 하는 기판 위에 포토레지스트(Photoresist)를 코팅하는 과정을 거치게 된다. 하지만 이러한 과정은 소자 제작에 있어서 포토레지스트 잔여물을 남기게 된다. 그래핀 위에 남은 포토레지스트 잔여물은 그래핀의 우수한 전기적 특성을 저하시켜 소자특성에 불이익을 주게 된다. 본 연구에서는 수소 플라즈마를 이용하여 그래핀 위에 남은 중합체(Polymer) 잔여물을 제거한다. 사용한 그래핀은 화학 기상 증착법(Chemical vapor deposition)을 이용하여 성장시켰으며, PMMA(Poly(methyl methacrylate))를 이용하여 이산화규소(silicon dioxide) 기판에 전사하였다. 그래핀의 손상 없이 중합체 잔여물을 제거하기 위해 플라즈마 처리시간을 15초부터 1분까지 늘려가며 연구를 진행하였으며, 플라즈마 처리 시간에 따른 중합체 잔여물의 제거 정도와 그래핀의 보존 여부를 확인하기 위해 라만 분광법(Raman spectroscopy)과 원자간력현미경(Atomic force microscopy)을 사용하였다. 본 연구 결과를 통해 간단한 플라즈마 처리로 보다 나은 특성의 그래핀 소자를 얻게 됨으로써, 향상된 특성을 가진 그래핀 소자로 산업적 응용 가능성을 높일 수 있을 것이라 생각된다.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.1
• /
• pp.19-33
• /
• 2010

The surface film, which is formed on graphite negative electrodes during the initial charging, is a key component in lithium secondary batteries. The battery reactions are strongly affected by the nature of the surface film. It is thus very important to understand the physicochemical properties of the surface film. On the other hand, the surface film formation is a very complicated interfacial phenomenon occurring at the graphite/electrolyte interface. In studies on electrode surfaces in lithium secondary batteries, in-situ experimental techniques are very important because the surface film is highly reactive and unstable in the air. In this respect electrochemical atomic force microscopy (ECAFM) is a useful tool for direct visualizing electrode/solution interfaces at which various electrochemical reactions occur under potential control. In the present review, mechanism of surface film formation and its correlation with electrolyte are summarized on the basis of in-situ ECAFM studies for understanding of the nature of the surface film on graphite negative electrodes.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.13 no.5
• /
• pp.217-221
• /
• 2003

In this work, chemical-solution derived silicate fibers were prepared by mixing tetraethyl orthosilicate, ethanol, distilled water, and hydrochloric acid in order to investigate surface roughness of fiber. Silicate fibers were drawn by using a viscous solution after evaporation at $80^{\circ}C$. The dried gel fibers were finally annealed at $1000^{\circ}C$, $1100^{\circ}C$, $1200^{\circ}C$ and $^1300{\circ}C$ for 60 min in dried air (flow rate = ∼200 ml/min). The crystallinity of the heat-treated silica fiber was analyzed by the X-ray diffraction $\theta$-2$\theta$ scan. A field emission-scanning electron microscope and an atomic force microscope were used to evaluate surface properties. The silicate fiber annealed at $1300^{\circ}C$ showed high value of root mean square roughness and had a relatively inhomogeneous surface structure.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.4
• /
• pp.9-16
• /
• 2014

A proton exchange membrane is a core component in the proton exchange membrane fuel cell because the role of proton exchange membrane(PEM)is supplying proton conductivity to fuel cell, a gas separator, and insulating between an anode and cathode. Among various role of PEM, supplying proton conductivity is the most important and the proton conductivity is strongly related the structural evolution of PEM by hydration. Thus a lot of studies have done by past few decade based on small angle X-ray scattering and wide angle X-ray scattering for understanding morphological structure of the PEM. Resulting from these studies, several morphological models of hydrated PEM are proposed. Current sensing atomic force microscopy (CSAFM) can map morphology and conductance on the membrane simultaneously. It can be the best tool for studying heterogenous structured materials such as PEM. In this study, the hydration of the membrane is examined by using CSAFM. Conductance and morphological images are simultaneously mapped under different relative humidity. The conductance images, which are mapped from different relative humidity, are analyzed by statistical methode for understanding ionic channel variation in PEM.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.289-290
• /
• 2006

In general, atomic force microscope (AFM) used for metrological purpose has measuring range less than a few hundred micrometers. We design and fabricate an AFM with long measuring range of $200mm{\times}200mm$ in X and Y axes. The whole stage system is composed of surface plate, global stage, microstage. By combining global stage and microstage, the fine and long movement can be provided. We measure the position of the stage and angular motions of the stage by laser interferometer. A piezoresistive type cantilever is used for compact and long term stability and a flexure structure with PZT and capacitive sensor is used for Z axis feedback control. Since the system is composed of various actuators and sensors, a real time control program is required for the implementation of AFM. Therefore, in this work, we designed a multi-axis control program using a FPGA module, which has various functions such as interferometer signal converting, PID control and data acquisition with triggering. The control program achieves a loop rate more than 500 kHz and will be applied for the measurement of grating pitch and step height.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.3
• /
• pp.186-192
• /
• 2010

In situ electrochemical atomic force microscopy (ECAFM) observations of the surface of highly oriented pyrolytic graphite (HOPG) was performed before and after cyclic voltammetry in lithium bis(fluorosulfonyl)imide (LiTFSI) dissolved in 1-buthyl-2,3-dimethylimidazolium (BDMI)-TFSI to understand the interfacial reactions between graphite and BDMI-based ionic liquids. The formation of blisters and the exfoliation of graphene layers by the intercalation of $BDMI^+$ cations within HOPG were observed instead of reversible lithium intercalation and de-intercalation. On the other hand, lithium ions are reversibly intercalated into the HOPG and de-intercalatied from the HOPG without intercalation of the $BDMI^+$ cations in the presence of 15 wt% of 4.90 mol/$kg^{-1}$ LiTFSI dissolved in propylene carbonate (PC). ECAFM results revealed that the concentrated PC-based solution is a very effective additive for preventing $BDMI^+$ intercalation through the formation of solid electrolyte interface (SEI).

• Polymer(Korea)
• /
• v.37 no.2
• /
• pp.218-224
• /
• 2013

Graphene oxide (GO) was prepared by the Hummers and Offeman method from graphite. Two different types of functionalized graphene sheets (FGSs) were synthesized by using GO. Hexamethylamine (HDA) substituted vertically to the graphene sheet (Ver-HDA-GS) was synthesized from HDA and epoxy group in GSs. Whereas, horizontally substituted hexadecanol (HDO) to the GS(Hor-HDO-GS) was synthesized from HDO and alcohol groups via reduced GO (RGO), respectively. The structures of the GO, RGO, Ver-HDA-GS, and Hor-HDO-GS were identified by Fourier transform infrared (FTIR). In addition, we examined the thermal stability and morphology. Atomic force microscope (AFM) disclosed that Ver-HDA-GS consisted of one- or two-layer graphene regions. However, the Ver-HDA-GS layers showed average thickness of 1.76 nm. The thermal stabilities of the FGSs were better than those of the GO and RGO. The Ver- HDA-GS was well dispersed in common solvents such as dimethyl sulfoxide (DMSO), toluene, chloroform, and decalin.