• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.388-388
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• 2011

Graphene, with its unique physical and structural properties, has recently become a proving ground for various physical phenomena, and is a promising candidate for a variety of electronic device and flexible display applications. The physical properties of graphene depend directly on the thickness. These properties lead to the possibility of its application in high-performance transparent conducting films (TCFs). Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ~60 ${\Omega}/sq$ and ~85% transmittance in the visible range, the chemical vapor deposition (CVD) synthesized graphene electrodes have a higher transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. Here, we report an ingenious strategy, irradiation of MeV electron beam (e-beam) at room temperature under ambient condition,for obtaining size-homogeneous gold nanoparticle decorated on graphene. The nano-particlization promoted by MeV e-beam irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping, and energy dispersive X-ray spectroscopy. These results clearly revealed that gold nanoparticle with 10~15 nm in mean size were decorated along the surface of the graphene after 1.0 MeV-e-beam irradiation. The fabrication high-performance TCF with optimized doping condition showed a sheet resistance of ~150 ${\Omega}/sq$ at 94% transmittance. A chemical transformation and charge transfer for the metal gold nanoparticle were systematically explored by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.88-88
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• 2018

DLC(Diamond Like Carbon) 박막은 높은 열전도도, 큰 전기저항, 높은 강도 등의 다이아몬드와 유사한 특성을 가지고 있으면서 저온 저압에서도 합성이 가능하고, 합성 조건에 따라 물리 화학적 특성도 넓게 조절 할 수 있으며 상대적으로 넓은 면적에서 균일하고 평활한 박막의 합성이 가능하여 산업적 응용 면에서도 경쟁력을 갖추고 있다[1]. 이러한 DLC 박막을 합성함에 있어서 RF-PECVD(Radio Frequency Plasma Enhanced Chemical Vapor Deposition) 방법은 PECVD 방법 중 가장 보편적으로 사용되고 또 캐패시터 타입의 RF-PECVD 방법은 균일한 대면적 증착과 대량생산이 가능하다[1,2]. 본 연구에서는 우수한 특성을 갖는 DLC 박막의 증착 조건을 찾기 위해 캐패시터 타입의 RF-PECVD를 사용하여 공정 가스의 유량과 RF Power를 변화하여 박막을 증착하고, 증착된 박막의 특성을 연구하였다. DLC 박막은 ITO(Indium Tin Oxide) 유리 기판 위에 $100^{\circ}C$에서 5 min 동안 아세틸렌($C_2H_2$) 가스를 사용하여 가스 유량과 RF Power를 변화하여 증착하였다. 증착된 DLC 박막의 특성은 투과도, 평탄도, 두께를 측정하여 비교하였다. 가시광선 영역(380-780 nm)에서 투과도를 측정한 결과 ITO 유리 기판을 기준으로 한 DLC 박막의 투과도는 가시광선 영역 평균 94.8~98.8% 사이의 값으로 매우 높은 투과율을 나타내었다. 투과도는 가스 유량이 증가함에 따라 증가하는 경향을 나타내었고, RF Power의 변화에는 특정한 변화를 나타내지 않았다. 박막의 평탄도($R_a$, $R_{rms}$)와 두께는 AFM(Atomic Force Microscope)을 사용하여 측정하였다. 평탄도 $R_{rms}$는 0.8~3.3 nm, $R_a$는 0.6~2.5 nm 사이를 나타내었고 RF Power와 가스 유량의 변화에 따른 경향성을 나타내지는 않았다. 두께는 RF Power 25 W에서 55 W로 증가함에 따라 증가하는 경향을 나타내었으나 70W에서는 가스의 유량에 따라 상이한 결과를 나타내었다.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.636-641
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• 2012

In this study, we have investigated highly efficient nanoscale surface corrugated light emitting diodes (LEDs) for the enhancement of light extraction efficiency (LEE) of nitride semiconductor LEDs. Nanoscale indium tin oxide (ITO) surface corrugations are fabricated by using the conformal nanoimprint technique; it was possible to observe an enhancement of LEE for the ITO surface corrugated LEDs. By incorporating this novel method, we determined that the total output power of the surface corrugated LEDs were enhanced by 45.6% for patterned sapphire substrate LEDs and by 41.9% for flat c-plane substrate LEDs. The enhancement of LEE through nanoscale surface corrugations was studied using 3-dimensional Finite Different Time Domain (FDTD) calculation. From the FDTD calculations, we were able to separate the light extraction from the top and bottom sides of device. This process revealed that light extraction from the top and bottom sides of a device strongly depends on the substrate and the surface corrugation. We found that enhanced LEE could be understood through the mechanism of enhanced light transmission due to refractive index matching and the increase of light scattering from the corrugated surface. LEE calculations for the encapsulated LEDs devices also revealed that low LEE enhancement is expected after encapsulation due to the reduction of the refractive index contrast.

• Journal of the Semiconductor & Display Technology
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• v.6 no.2 s.19
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• pp.19-23
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• 2007

The blue emitting OLEDs using TMP-BiP[(4'-Benzoylferphenyl-4-yl)phenyl-methanone-Diethyl(biphenyl-4-ymethyl) phosphonate] host and DJNBD-1 dopant have been fabricated and characterized. In the device fabrication, 2-TNATA [4,4',4"-tris(2-naphthylphenyl-phenylamino)-triphenylamine] as a hole injection material and NPB [N,N'-bis(1-naphthyl)N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] as a hole transport material were deposited on the ITO(indium tin oxide)/glass substrate by vacuum thermal evaporation method. Followed by the deposition, blue color emission layer was deposited using TMP-BiP as a host material and DJNBD-1 as a dopant. Finally, small molecule OLEDs with structure of $ITO/2-TNATA/NPB/TMP-BiP:DJNBD-l/Alq_3/LiF/Al$ were obtained by in-situ deposition of $Alq_3$, LiF and Al as the electron transport material, electron injection material and cathode, respectively. The effect of dopant into host material of the blue OLEDs was studied. The blue OLEDs with DJNBD-1 dopant showed that the maximum current and luminance were found to be about 34 mA and $8110\;cd/m^2$ at 11 V, respectively. In addition, the color coordinate was x=0.17, y=0.17 in CIE color chart, and the peak emission wavelength was 440 nm. The maximum current efficiency of 2.15 cd/A at 7 V was obtained in this experiment.

• Journal of Biomedical Engineering Research
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• v.36 no.6
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• pp.283-290
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• 2015

We proposed blink based online speller for the locked-in syndrome (LIS) patients, paralyzed in nearly all voluntary muscles expect for the eyes, with a simple and easy-to-use eye blink detection glasses. Electrooculogram (EOG) is the golden standard method of eye movement or blink measurement with Ag/AgCl electrodes. However, this method has several drawbacks such as skin irritation and dehydration of conductive gel. To resolve the shortcomings, we used a blink detection system based on a transparent capacitively coupled electrode, which is conductive indium tin oxide (ITO) films. The films make it possible to measure eye blink without direct skin contact and obstruction of field of view. We finally developed user-friendly blink based online speller with the blink detection system. To classify voluntary and non-voluntary blink, we used the double blink for command of the speller. The online speller experiment result with six healthy subjects shows that mean accuracy is 98.96% and letter per minute (LPM) is 4.73, which are better result by comparison with conventional P300 or auditory brain-computer interface (BCI) paradigm. The result of the experiment demonstrates the possibility of applying the proposed system as a communication method for the LIS patients.

• Journal of the Korean Applied Science and Technology
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• v.20 no.2
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• pp.94-100
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• 2003

We studied electrochemical characteristics of Langmuir-Blodgett(LB) films by using cyclic voltammetry with a three-electrode system. An Ag/AgCl as a reference electrode, a platinum wire as a counter electrode and LB film-coated indium tin oxide(ITO) as a working electrode were used to study electrochemical characteristics at a various concentration of $NaClO_4$ solution. LB films were reduced from initial potential to -1350 mV, continuously oxidized to l650mV and returned to the initial point. The scan rate was l00mV/s. The monolayer surface morphology of the LB film have been measured by Atomic Force Microscope(AFM). As a result, We comfirmed that the microscopic properties of LB film by AFM showed the good orientation of momolayer molecules and the thickness of monolayer was 3.5-4.lnm. The cyclic voltammograms(CV) of the ITO-coated glass showed the peak potentials for the reduction-oxidation reation. LB films of 4-octyl-4'-(5-carboxypentamethyleneoxy) azobenzene(8A5H) / L-${\alpha}$-phosphayidyl choline, dilauroyl(DLPC) seemed to be irreversible process caused by only the oxidation current from the cyclic voltammogram. The current of oxidatation increased at cyclic voltammogram by increasing 8A5H density in LB films. The diffusivity(D) of LB films increased with increasing of a 8A5H amount and was inversely proportional to the concentration of $NaClO_4$ solution.

• Journal of Environmental Science International
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• v.14 no.8
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• pp.801-810
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• 2005

The phosphor and ITO(Indium Tin Oxide) films for video phone tube (VPT) were simply prepared by the screen printing and thermal transfer methods. The increasing order of thermal firing of acrylic binder for phosphor and ITO was M6003 < M6664 < A/A 1919 < M500l < M670 1 and all mass of binders were perfectly decomposed at lower temperature than $400^{\circ}C.$ After thermal firing of phosphor paste, the residual of binder on the surface of phosphor could not be found by SEM. Aerosil as thickner provides the thixotropy property for phosphor paste but decrease the brightness of phosphor screen as residual after thermal firing. Since the thixotropy of M5001 binder without aerosil was shown and the storage modulus of phosphor paste by increasing the angular frequency was not nearly changed and the decrease of the storage modulus of phosphor paste by increasing the strain was remarkably shown. It was possible to prepare the phosphor paste which was predominant in the plate separation and the reproduction of pattern after the screen printing. Since the addition of dispersing agent to improve the printing process decreases the electrical conductivity and light transmission of ITa film, it could be found to be necessary the development of binder for phosphor paste that decreases the amount of dispersing agent possibly and does not use the aerosil as additive.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.49-53
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• 2008

The yellow base polymer light emitting diodes(PLEDs) with double emission and hole blocking layers were prepared to improve the light efficiency. ITO(indium tin oxide) and PEDOT : PSS[poly(3,4-ethylenedioxythiophene) : poly(styrene sulfolnate)] were used as cathode and hole transport materials. The PFO[poly(9,9-dioctylfluorene)] and MEH-PPV[poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and guest materials, respectively. TPBI[Tpbi1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene] was used as hole blocking layer. To investigate the optimization of device structure, we prepared four kinds of PLED devices with different structures such as single emission layer(PFO : MEH-PPV), two double emission layer(PFO/PFO : MEH-PPV, PFO : MEH-PPV/PFO) and double emission layer with hole blocking layer(PFO/PFO : MEH-PPV/TPBI). The electrical and optical properties of prepared devices were compared. The prepared PLED showed yellow emission color with CIE color coordinates of x = 0.48, y = 0.48 at the applied voltage of 14V. The maximum luminance and current density were found to be about 3920 cd/$m^2$ and 130 mA/$cm^2$ at 14V, respectively for the PLED device with the structure of ITO/PEDOT : PSS/PFO/PFO : MEH-PPV/TPBI/LiF/Al.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1645-1646
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• 2006

Micro ElectroMechanical Systems (MEMS) 기술을 이용한 초미세 유체 제어 시스템 (마이크로 펌프, 마이크로 밸브, 마이크로 채널, 마이크로 믹서 등)은 화학, 생명분야의 DNA 분석, 항원-항체 분석, 질병의 진단 등에 사용되는 lab-on-a-chip, micro total analysis system ($\mu$-TAS) 등에서 화학 및 바이오 유체를 제어하는 분석 시스템의 일부분으로서 사용되며 필수적으로 요구된다. 본 논문에서는 이러한 microchip을 구현하기 위해 초미세 유체 제어 소자인 마이크로 펌프와 밸브를 같은 기관 위에 polydimethylsiloxane (PDMS)와 indium tin oxide (ITO)-Glass를 사용하여 동일한 구조로 집적 하였다. 마이크로 펌프의 pumping rate은 인가 직류 펄스 전력의 주파수와 duty 비를 변화시켜 최적화하였다. 직류 펄스 전력 500 mW를 인가하였을 때 주파수 2 Hz, duty 비 7 %에서 약 $1.05{\mu}l/min$의 최대 유량이 측정되었다. 마이크로 밸브는 ITO 히터에 전력을 인가함으로서 유량의 on/off 제어가 잘 됨을 확인할 수 있었고 유체를 closing하기 위해 필요한 전력은 약 300 mW이다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.817-821
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• 2011

We have proposed an optical thin film and micro lens to improve the luminance of organic light emitting device. The first method, optical thin film was calculated refractive index of dielectric layer material that was modulated refractive index of organic material, ITO (indium tin oxide)and glass. The second method, microlens was applied with lenses on the organic device. Optical thin films were designed with Macleod Simulator and Micro Lenses were calculated by FDTD (finite-difference time-domain) solution. The structure of thin film was designed in organic material/ITO/dielectric layer/glass. The lenses size, height and distance were 5 ${\mu}m$, 1 ${\mu}m$, 1 ${\mu}m$, respectively. The material of micro lenses used silicon dioxide. Result, The highest luminance of OLED which applied with microlens was 11,185 $cd/m^2$, when approval voltage was 14.5 V, applied thin film was 5,857 $cd/m^2$. The device efficiency applying microlens increased 3 times than the device which does not apply microlens.