• 한국정밀공학회지
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• 제23권2호
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• pp.43-50
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• 2006

Recently, with rapid development of semiconductor and flat panel display, the manufacturing equipments are required to have large travel range, high productivity, and high accuracy. In this paper, an ultra precision decoupled dual servo (DDS) system is proposed to meet these requirements. And a control scheme for the DDS is studied. The proposed DDS consists of a $XY{\Theta}$ fine stage for handling work-pieces precisely and a XY coarse stage for large travel range. The fine stage consists of four voice coil motors (VCM) and air bearing guides. The coarse stage consists of linear motors and air bearing guides. The DDS is mechanically decoupled between coarse stage and fine stage. Therefore, both stages must be controlled independently and the performance of the DDS is mainly determined by the fine stage. For high performance tracking, the controller of fine stage consists of time delay control (TDC) and perturbation observer while the controller of coarse stage is TDC alone. With these individual controllers, two kinds of dual-servo control strategies are suggested: master-slave type and parallel type. By simulations and experiments, the performances of two dual-servo control strategies are compared.

• 한국정밀공학회지
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• 제24권5호
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• pp.97-103
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• 2007

A novel selective metallization process to fabricate the fine conductive line based on inkjet printing has been investigated. Recently, Inkjet printing has been widely used in flat panel display, electronic circuits, biochips and bioMEMS because direct inkjet printing is an alternative and cost-effective technology for patterning and fabricating objects directly from design without masks. The photosensitive etching resist used in this process is an organic polymer which becomes solidified when exposed to ultraviolet lights and has high viscosity at ambient temperature. A piezoelectric-driven inkjet printhead is used to dispense 20-30 ${\mu}m$ diameter droplets onto the copper substrate to prevent subsequent etching. Repeatability of circuitry fabrication is closely related to the formation of steady droplets, adhesion between etching resist and copper substrate. Therefore, the ability to form small and stable droplets and surface topography of the copper surface and chemical attack must be taken into consideration for fine and precise patterns. In this study, factors affecting the pattern formation such as adhesion strength, etching mechanism, UV curing have been investigated. As a result, microscale copper patterns with tens of urn high have been fabricated.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권8호
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• pp.451-454
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• 2000

We have grown vertically aligned carbon nanotubes in a large area of Co-Ni codeposited Si substrates by the thermal CVD usign $C_2H_2$ gas. Since the discovery of carbon nanotubes, growth of carbon nanotubes has been achieved by several methods such as laser vaporization, arc discharge, and pyrolysis. In particular, growth of vertically aligned nanotubes is important to flat panel display applications. Recently, vertically aligned carbon nanotubes have been grown on glass by PECVD. Aligned carbon nanotubes can be also grown on mesoporous silica and Fe patterned porous silicon using CVD. In this paper, we demonstrate that carbon nanotubes can be vertically aligned on catalyzed Si substrate when the domain density of catalytic particles reaches a certain value. We suggest that steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically and each nonotubes are grown in bundle.

• 한국전기전자재료학회논문지
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• 제15권2호
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• pp.110-118
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• 2002

Organic thin film transitors(OTFT) are of interest for use in broad area electronic applications. And recently organic electroluminescent devices(OELD) have been intensively investigated for using in full-color flat-panel display. We have fabricated inverted-staggered structure OTFTs at lower temperature using the fused-ring polycyclic aromatic hydrocarbon pentacene as the active eletronic material and photoacryl as the organic gate insulator. The field effect mobility is 0.039∼0.17 ㎠/Vs, on-off current ratio is 10$\^$6/, and threshold voltage is -7V. And here we report the study of driving emitting, Ir(ppy)$_3$, phosphorescent OELD with all organic thin film transistor and investigated its electrical characteristics. The OELD with a structure of ITO/TPD/8% Ir(ooy)$_3$ doped in BCP/BCP/Alq$_3$/Li:Al/Al and OTFT with a structure of inverted-stagged Al(gate electrode)/photoacry(gate insulator)/pentacene(p-type organic semiconductor)/ Au(source-drain electrode) were fabricated on the ITP patterned glass substrate. The electrical characteristics are turn-on voltage of -10V, and maximum luminance of about 90 cd/㎡. Device characteristics were quite different with that of only OELD.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2233-2235
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• 1999

The ac plasma display panel(PDP) is a flat light-emitting gas discharge device. Discharge gases directly take effects to the discharge phenomena of ac PDP. Therefore it is necessary to understand the characteristics of the discharge gases. In this paper, we have studied the effects of discharge gases by voltage transfer curves which show the discharge characteristics of ac PDP and the change of the effective wall capacitance during a discharge which depends on lateral spreading of charge distribution and the strength of discharge. As gas pressure increases, memory margins increases. and the firing voltage of a mixed gas is lower than that of a single gas such as He gas. The minimum sustain voltage and the maximum sustain voltage or firing voltage increases with decrease in the frequency. The effective wall capacitance increases as the discharge strength that is, the gap voltage between discharge electrodes increases.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1352-1354
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• 1997

Transparent conductive thin films have found many application in many active and passive electronic and opto-electronic devices as like flat Panel display electrode and window heat mirror, etc. Low resistivity and high transmittance of this films can be obtained by controlling deposition parameters, which are oxygen partial Pressure, substrate temperature and dopant concentration. In this study, We prepared non-stoichiometric and Sb-doped thin films of tin dioxide by reactive DC magnetron sputtering technology. The lowest resistivity of about $3.0{\times}10^{-3}\;{\Omega}cm$ and 80% transmittance in the visible light region have heed obtained at optimal deposition condition.

• 폴리머
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• 제36권5호
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• pp.662-667
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• 2012

평판 디스플레이에 사용되는 PET 필름의 광학적 특성을 알아보기 위하여 필름 표면 굴절률, 필름 표면조도 및 필름 내부입자가 광투과율에 미치는 영향을 알아 보았다. 필름표면에 굴절률이 낮은 코팅층을 형성함에 따라 필름의 광투과율이 향상되었고, 최대의 광투과율을 가지는 코팅두께가 있음을 확인하였다. 표면 거칠기의 영향에 대해서는 표면조도를 나타내는 Ra를 입사 파장의 1/4 이하로 조절한 경우 광손실이 발생되지 않았다. 필름 내 무기입자는 입사된 광의 흡수 및 산란을 발생시켜 광손실을 증가시켰다.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1209-1218
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• 2006

Precision servomechanisms are widely used in machine tool, semiconductor and flat panel display industries. It is important to improve contouring accuracy in high-precision servomechanisms. In order to improve the contouring accuracy, cross-coupled control systems have been proposed. However, it is very difficult to select the controller parameters because cross-coupled control systems are multivariable, nonlinear and time-varying systems. In this paper, in order to improve contouring accuracy of a biaxial servomechanism, a cross-coupled controller is adopted and an optimal tuning procedure based on an integrated design concept is proposed. Strict mathematical modeling and identification process of a servomechanism are performed. An optimal tuning problem is formulated as a nonlinear constrained optimization problem including the relevant controller parameters of the servomechanism. The objective of the optimal tuning procedure is to minimize both the contour error and the settling time while satisfying constraints such as the relative stability and maximum overshoot conditions, etc. The effectiveness of the proposed optimal tuning procedure is verified through experiments.

• 한국표면공학회지
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• 제30권6호
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• pp.406-411
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• 1997

Transparent conductive thin films have found many applications in active and passive electronic and opto-electronic devices such as flat panel display electrode, solar cell electrode and window heat mirror, etc. Low resistivity and high transmittance of these films can beotained by controlling deposition parameters which are oxygen partial pressure, substrate temperature and dopant concentration. In this study, non-stoichiometric and Sb-doped thin electrical properties of undoped films have been degraded with increase of substrate temperature and optical properties have been improved in Sb-doped films. The resistivity of $2.5\times10^{-3}\Omega\textrm{cm}$,/TEX>, average transmittance of 80% and sheet resistance of 130$\Omega$/$\square$ at thickess of 2000 $\AA$ could be obrained at optmal condimal conditions which were at $400^{\circ}C$ of substrate temperature, 58% of oxygen partial pressure and 5% of Sb doping concentration.

• 한국표면공학회지
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• 제37권3호
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• pp.146-151
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• 2004

Indium tin oxide (ITO) is widely used to make a transparent conducting film for various display devices and opto-electric devices. In this study, ITO films on glass substrate were fabricated by inductively coupled plasma (ICP) assisted dc magnetron sputtering. A two-turn rf coil was inserted in the process chamber between the substrate and magnetron for the generation of ICP. The substrates were not heated intentionally. Subsequent post-annealing treatment for as-deposited ITO films was not performed. Low-temperature deposition technique is required for ITO films to be used with heat sensitive plastic substrates, such as the polycarbonate and acrylic substrates used in LCD devices. The surface roughness of the ITO films is also an important feature in the application of OLEDs along with the use of a low temperature deposition technique. In order to obtain optimum ITO thin film properties at low temperature, the depositions were carried out at different condition in changing of Ar and $O_2$ gas mixtures, ICP power. The electrical, optical and structural properties of the deposited films were characterized by four-point probe, UV/VIS spectrophotometer, atomic force microscopy(AFM) and x-ray diffraction (XRD). The electrical resistivity of the films was -l0$^{-4}$ $\Omega$cm and the optical transmittance in the visible range was ＞85%. The surface roughness ( $R_{rms}$) was -20$\AA$.>.