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PVDF 필름 위에 제작된 고전도도 Ag 나노와이어 투명전극 특성 연구
라용호,이영진,박혜림,Soyeon An,김진호,Dae-Woo Jeon,김선욱,Mi Jai Lee,황종희,임태영 한국센서학회 2019 센서학회지 Vol.28 No.6
In this study, we have successfully fabricated a highly conductive transparent electrode using Ag nanowires, based on piezoelectric polyvinylidene difluoride (PVDF) film, that can be applied as transparent and flexible speakers. The structural morphology of the Ag nanowires was confirmed by a detailed scanning electron microscopy. Ultraviolet-visible spectroscopy demonstrated that the transparent electrode fabricated by the Ag nanowires exhibited a transmittance of above 70%. The transparent electrode also showed very low sheet resistance with high flexibility. We have further developed an anti-oxidation coating layer by using a tetraethyl orthosilicate-poly trimethyloxyphenylsilane (TEOS-PTMS) slurry technique. It was confirmed that the transmittance and sheet resistance of the antioxidant film depends critically on the humidity of the film surface. We believe such Ag nanowire electrodes are a very promising next-generation transparent electrode technology that can be used in future flexible and transparent devices.
HVPE 방법으로 성장한 Alpha-Ga<sub>2</sub>O<sub>3</sub>의 특성 분석
손호기,라용호,이영진,이미재,김진호,황종희,김선욱,임태영,전대우,Son, Hoki,Ra, Yong-Ho,Lee, Young-Jin,Lee, Mi-Jai,Kim, Jin-Ho,Hwang, Jonghee,Kim, Sun Woog,Lim, Tae-Young,Jeon, Dae-Woo 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.6
We demonstrated a crack-free ${\alpha}-Ga_2O_3$ on sapphire substrate by horizontal halide vapor phase epitaxy (HVPE). Oxygen-and gallium chloride-synthesized Ga metal and HCl were used as the precursors, and $N_2$ was used as the carrier gas. The HCl flow and growth temperature were controlled in the ranges of 10~30 sccm and $450{\sim}490^{\circ}C$, respectively. The surface of ${\alpha}-Ga_2O_3$ template grown at $470^{\circ}C$ was flat and the root-mean-square (RMS) roughness was ~2 nm. The full width at half maximum (FWHM) values for the symmetric-plane diffractions, were as small as 50 arcsec and those for the asymmetric-plane diffractions were as high as 1,800 arcsec. The crystal quality of ${\alpha}-Ga_2O_3$ on sapphire can be controlled by varying the HCl flow rate and growth temperature.
HVPE 방법으로 성장된 알파-갈륨 옥사이드의 전처리 공정에 따른 특성 변화
최예지,손호기,라용호,이영진,김진호,황종희,김선욱,임태영,전대우,Choi, Ye-ji,Son, Hoki,Ra, Yong-Ho,Lee, Young-Jin,Kim, Jin-Ho,Hwang, Jonghee,Kim, Sun Woog,Lim, Tae-Young,Jeon, Dae-Woo 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.5
In this study, we report the effect of pre-treatment of alpha-$Ga_2O_3$ grown on a sapphire substrate by halide vapor phase epitaxy (HVPE). During the pre-treatment process, 10 sccm of GaCl gas was injected to the sapphire substrate at $470^{\circ}C$. The surface morphologies of the alpha-$Ga_2O_3$ layers grown with various pre-treatment time (3, 5, and 10 min) were flat and crack-free. The transmittance of the alpha-$Ga_2O_3$ epi-layers was measured to analyze their optical properties. The transmittance was over 80% within the range of visible light. The strain in the alpha-$Ga_2O_3$ grown with a pre-treat 5 min was measured, and was found to be close to the theoretical XRD peak position. This can be explained by the reduction of strain having caused a lattice mismatch between the alpha-$Ga_2O_3$ layer and sapphire substrate. The calculated dislocation density of the screw and edge were $2.5{\times}10^5cm^{-2}$ and $8.8{\times}10^9cm^{-2}$, respectively.
이지선,김선욱,라용호,이영진,임태영,황종희,전대우,김진호 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.6
This study investigated the influence of the viscoelastic property of slag when producing glass fiber, MFS631 with 60% of manganese slag, 30% of steel slag, and 10% of silica stone. To fabricate the MFS631 glass bulk, slag materials were placed in an alumina crucible, melted at 1,550℃ for 2 h, and then annealed at 600℃ for 2 h. It was found that glass is non-crystalline through X-ray diffraction analysis. MFS631 fiber was produced at speed in the range of 100~300 rpm at 1,150℃. The loss modulus (G″) and storage modulus (G′) of the produced glass fiber were evaluated at high temperatures. G′ and G″ of MFS631 were greater than 893℃, and the modulus value was 136,860 pa. This is similar to the results of a general E-glass fiber graph. Therefore, it was concluded that its spinnability is similar to that of E-glass fiber; therefore, it can be commercialized. 본 연구에서는 망간슬래그 60%, 제강슬래그 30%, 규사 10% 를 이용해서 MFS631 부르는 유리 섬유를 제조하였고, 점탄성 특성(Visco-elastic)이 섬유 제조할 때에 미치는 영향에 관해 확인하였다. MFS631 모유리를 제조하기 위해서, 슬래그 원료를 알루미나 도가니에 넣고 1550℃에서 2시간 용융한 후 600℃에서 2시간 서냉하였다. 제조된 유리는 XRD 분석을 통해 비정질을 확인하였다. MFS631 섬유는 1150℃에서 100~300rpm으로 와인딩 속도를 변화시켜 제조하였다. 제조된 섬유의 Loss modulus (G``)과 Storage Modulus( G`) 값을 고온 온도 영역대에서 평가하였다. MFS631 섬유의 G`,G``값은 893℃에서 교차하며 그때 Modulus 값은 136,860pa이다. 일반적인 E-galss 섬유의 그래프와 유사한 경향성을 확인하였다. 따라서, E-glass fiber 수준의 방사 능력을 가질 것으로 확인하였고, 충분히 실용화가 가능할 수 있을 것으로 판단되었다.
이지선,김선욱,라용호,이영진,임태영,황종희,전대우,김진호,Lee, Ji-Sun,Kim, Sun-Woog,Ra, Yong-Ho,Lee, Youngjin,Lim, Tae-Young,Hwang, Jonghee,Jeon, Dae-Woo,Kim, Jin-Ho 한국재료학회 2019 한국재료학회지 Vol.29 No.11
In this study, the glass melting properties are evaluated to examine the possibility of using refused coal ore as replacement for ceramic materials. To fabricate the glass, refused coal ore with calcium carbonate and sodium carbonate in it (which are added as supplementary materials) is put into an alumina crucible, melted at $1,200{\sim}1,500^{\circ}C$ for 1 hr, and then annealed at $600^{\circ}C$ for 2 hrs. We fabricate a black colored glass. The properties of the glass are measured by XRD (X-ray diffractometry) and TG-DTA (thermogravimetry-differential thermal analysis). Glass samples manufactured at more than $1,300^{\circ}C$ with more than 60 % of refused coal ore are found by XRD to be non-crystalline in nature. In the case of the glass sample with 40 % of refused coal ore, from the sample melted at $1,200^{\circ}C$, a sodium aluminum phosphate peak, a disodium calcium silicate peak, and an unknown peak are observed. On the other hand, in the sample melted at $1,300^{\circ}C$, only the sodium aluminum phosphate peak and unknown peak are observed. And, peak changes that affect crystallization of the glass according to melting temperature are found. Therefore, it is concluded that glass with refused coal ore has good melting conditions at more than $1,200^{\circ}C$ and so can be applied to the construction field for materials such as glass tile, foamed glass panels, etc.
이지선,김선욱,라용호,임태영,이영진,전대우,김진호,Lee, Ji-Sun,Kim, Sun-Woog,Ra, Yong-Ho,Lim, Tae-Young,Lee, Youngjin,Jeon, Dae-Woo,Kim, Jin-Ho 한국재료학회 2018 한국재료학회지 Vol.28 No.12
In this study, glass fibers are fabricated via a continuous spinning process using manganese slag, steel slag, and silica stone. To fabricate the glass fibers, raw materials are put into an alumina crucible, melted at $1550^{\circ}C$ for 2 hrs, and then annealed at $600^{\circ}C$ for 2 hrs. We obtain a black colored glass. We identify the non-crystalline nature of the glass using an XRD(x-ray diffractometer) graph. An adaptable temperature for spinning of the bulk marble glass is characterized using a high temperature viscometer. Spinning is carried out using direct melting spinning equipment as a function of the fiberizing temperature in the range of $1109^{\circ}C$ to $1166^{\circ}C$, while the winder speed is in the range of 100rpm to 250rpm. We investigate the various properties of glass fibers. The average diameters of the glass fibers are measured by optical microscope and FE-SEM. The average diameter of the glass fibers is $73{\mu}m$ at 100rpm, $65{\mu}m$ at 150rpm, $55{\mu}m$ at 200rpm, and $45{\mu}m$ at 250rpm. The mechanical properties of the fibers are confirmed using a UTM(Universal materials testing machine). The average tensile strength of the glass fibers is 21MPa at 100rpm, 31MPa at 150rpm, 34MPa at 200rpm, and 45MPa at 250rpm.
권민형 ( Min-hyeong Kwon ),라용호 ( Yong-ho Ra ),전대우 ( Dae-woo Jeon ),이영진 ( Young-jin Lee ) 한국센서학회 2018 센서학회지 Vol.27 No.4
High-sensitivity signal-to-noise ratio (SNR) microphones are essentially required for a broad range of automatic speech recognition applications. Piezoelectric microphones have several advantages compared to conventional capacitor microphones including high stiffness and high SNR. In this study, we designed a new piezoelectric membrane structure by using the finite elements method (FEM) and an optimization technique to improve the sensitivity of the transducer, which has a high-quality AlN piezoelectric thin film. The simulation demonstrated that the sensitivity critically depends on the inner radius of the top electrode, the outer radius of the membrane, and the thickness of the piezoelectric film in the microphone. The optimized piezoelectric transducer structure showed a much higher sensitivity than that of the conventional piezoelectric transducer structure. This study provides a visible path to realize micro-scale high-sensitivity piezoelectric microphones that have a simple manufacturing process, wide range of frequency and low DC bias voltage.
MBE 법에 의해 성장된 고종횡비 InGaN 나노와이어 광촉매
안소연,전대우,황종희,라용호,An, Soyeon,Jeon, Dae-Woo,Hwang, Jonghee,Ra, Yong-Ho 한국결정성장학회 2019 한국결정성장학회지 Vol.29 No.4
우리는 분자선 에피택시(Molecular Beam Epitaxy) 법을 사용하여 광전기화학적 물분해 수소생산용 고종횡비 GaN 기반 나노와이어를 Si 기판 위에 성공적으로 제작하였다. 주사전자현미경(SEM)과 에너지분산형 분광법(EDX)은 p-GaN:Mg 및 p-InGaN 나노와이어가 고밀도와 함께 수직으로 성장 되었음을 증명하였다. 또한, p-InGaN 나노와이어의 발광 파장을 552 nm에서 590 nm까지의 조절이 가능하다는 것을 확인하였다. 이렇게 제작된 p-InGaN 나노와이어는 태양광을 통해 외부 전위 없이 물분해가 가능한 수소생산용 광촉매로써 매우 유용하게 사용될 수 있다. We have successfully fabricated high aspect-ratio GaN-based nanowires on Si substrates using molecular beam epitaxy (MBE) system for high-efficiency hydrogen generation of photoelectrochemical water splitting. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) demonstrated that p-GaN:Mg and p-InGaN nanowires were grown vertically on the substrate with high density. Furthermore, it was also confirmed that the emission wavelength of p-InGaN nanowire can be adjusted from 552 nm to 590 nm. Such high-aspect ratio p-InGaN nanowire structure will be a solid foundation for the realization of ultrahigh-efficiency photoelectrochemical water splitting through sunlight.