• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.427-427
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• 2012

Ferroelectric-gate field effect transistor based memory using a nanowire as a conducting channel offers exceptional advantages over conventional memory devices, like small cell size, low-voltage operation, low power consumption, fast programming/erase speed and non-volatility. We successfully fabricated ferroelectric nonvolatile memory devices using both n-type and p-type Si nanowires coated with organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] via a low temperature fabrication process. The devices performance was carefully characterized in terms of their electrical transport, retention time and endurance test. Our p-type Si NW ferroelectric memory devices exhibit excellent memory characteristics with a large modulation in channel conductance between ON and OFF states exceeding $10^5$; long retention time of over $5{\times}10^4$ sec and high endurance of over 105 programming cycles while maintaining ON/OFF ratio higher $10^3$. This result offers a viable way to fabricate a high performance high-density nonvolatile memory device using a low temperature fabrication processing technique, which makes it suitable for flexible electronics.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.973-974
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• 2008

Optically transparent and flexible electronic circuits and displays are attractive for next-generation visual technologies, including windshield displays, head-mounted displays, and transparent screen monitors. Here we report on the fabrication of transparent transistors and circuits based on the combination of nanoscopic dielectrics and organic, inorganic, or hybrid semiconductors. Furthermore, the first demonstration of a transparent and flexible AMOLED display driven solely by $In_2O_3$ nanowire transistors (NWTs) is reported. The display region exhibits an optical transmittance of ~35% and a green peak luminance of ${\sim}300\;cd/m^2$. These results indicate that NWT-based drive circuits are attractive for fully transparent display technologies.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.488.2-488.2
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• 2014

Carbon-based materials such as carbon nanotubes and graphene have emerged as promising building blocks in applications for nanoelectronics and energy devices due to electrical property, ease of processability, and relatively inert electrochemistry. In recent years, there has been considerable interest in core-shell nanomaterials, in which inorganic nanowires are surrounded by inorganic or organic layers. Especially, carbon encapsulated semiconductor nanowires have been actively investigated by researchers in lithium ion batteries. We report a method to synthesize silicon nanowire (SiNW) core/carbon shell structures by chemical vapor deposition (CVD), using methane (CH4) as a precursor at growth temperature of $1000{\sim}1100^{\circ}C$. Unlike carbon-based materials synthesized via conventional routes, this method is of advantage of metal-catalyst free growth. We characterized these materials with FE-SEM, FE-TEM, and Raman spectroscopy. This would allow us to use these materials for applications ranging from optoelectronics to energy devices such as solar cells and lithium ion batteries.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.317-317
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• 2010

ZnO나노와이어는 높은 투과도, 화학 및 열적 안정성을 가지며, 유기태양전지에 적용하였을 때 Active Layer의 표면적 증가, 전자의 수집 및 전달에 용이한 장점가지고 있어 하이브리드 유기 태양전지에 적용되고 있다. ZnO나노와이어와 P3HT/PCBM을 사용한 하이브리드 유기태양전지는 Active Layer의 열처리 온도를 변화시켜 ITO/AZO/ZnO wire/PCBM:P3HT/PEDOT:PSS/Ag구조로 제작되었다. ZnO나노와이어는 AZO를 Seed로 사용하고 Znc nitrate hydrate와 hexamethylenetetramine을 혼합하여 수열합성법으로 성장 후, P3HT:PCBM, PEDOT:PSS을 Spin Coating법으로 형성하였다. UV-vis와 Solar simulator를 통하여 Active Layer의 열처리 온도에 따른 태양전지의 특성을 분석하였다.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.360-364
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• 2018

A facile method to fabricate freestanding CuO nanoleaves and CuO nanowires-based films was demonstrated. $Cu(OH)_2$ nanoleaves and nanowires were prepared by a hydrolysis reaction in aqueous solution including pyridine and NaOH with the tailored concentrations at room temperature. The films of freestanding CuO nanoleaves and CuO nanowires can be successfully obtained via the simple vacuum infiltration following a thermal dehydration reaction. The morphologies and crystallinity of the $Cu(OH)_2$ nanoleaves/nanowires and CuO nanoleaves/nanowires were characterized by XRD, SEM, TEM and FT-IR. The films fabricated with freestanding CuO nanoleaves and nanowires in this study may be applicable for building high-efficiency organic binder-free devices, such as gas sensors, batteries, photoelectrodes for water splitting and so on.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.299-299
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• 2013

Indium Tin Oxide (ITO) has widely been used as a transparent conductive oxide (TCE) for photovoltaic devices. Lately, flexibility of ITO becomes an issue as demand of flexible device increases. Several scientists have tried to substitute ITO to different materials such as conductive polymer, graphene, CNT, and metal nanowire because of ITO brittleness. Among the substitute materials, PEDOT:PSS has mostly paid attention because PEDOT:PSS has excellent flexibility and good conductivity. The conductivity of PEDOT:PSS increases up to 1000 S/cm with additives such as DMSO, EG, sorbitol, and so on. In our research group, we introduce a conductive polymer PEDOT:PSS as a buffer layer to improve not only flexibility but also conductivity. As PEDOT:PSS layer forms beneath ITO thin film (20 nm), sheet resistance decreases from $230{\Omega}$/${\Box}$ to $85{\Omega}$/${\Box}$ and crack initiation decreases from 4.5 mm to 3.5 mm as well. We have fabricated organic photovoltaic device and power conversion efficiencies using conventional ITO electrode and ITO/PEDOT:PSS hybrid electrode. The photovoltaic property such as power conversion efficiency for ITO/PEDOT:PSS hybrid electrode is comparable to the value obtained using conventional ITO electrode on glass substrate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.23-23
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• 2009

Recently, the nanowire configuration of GST showed nanosecond-level phase switch at very low power dissipation, suggesting that the nanowires could be ideal for data storage devices. In spite of many advantages of IST materials, their feasibility in both thin films and nanowires for electronic memories has not been extensively investigated. The synthesis of the chalcogenide nanowires was mainly preformed via a vapor transport process such as vapor-liquid-solid (VLS) growth at a high temperature. However, in this study, IST nanowires as well as thin films were prepared at a low temperature (${\sim}250^{\circ}C$) by metal organic chemical vapor deposition(MOCVD) method, which is possible for large area deposition. The IST films and/or nanowires were selectively grown by a control of working pressure at a constant growth temperature by MOCVD. In-Sb-Te NWs will be good candidate materials for high density PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.328.2-328.2
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• 2014

Semiconductor nanowires (NWs) have attracted research interests due to the distinct physical properties that can lead to variousoptical and electrical applications. In this paper, we have grown InAs NWs viagold (Au)-assisted vapor-liquid-solid (VLS) and catalyst-free vapor-solid (VS) mechanisms and investigated on the p-type doping profile of the NWs. Metal-organic chemical vapor deposition (MOCVD) is used for the growth of the NWs. Trimethylindium (TMIn) and arsine (AsH3) were used for the precursor and diethyl zinc (DEZn) was used for the p-type doping source of the NWs. The effectiveness of p-type doping was confirmed by electrical measurement, showing an increase of the electron density with the DEZn flow. The structural properties of the InAs NWs were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, we characterize atomic distribution of InAs NWs using energy-dispersive X-ray spectroscopy (EDX) analysis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.1-8
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• 2017

Catalytic synthesis and properties of ${\beta}-Ga_2O_3$ nanowires grown by metal organic chemical vapor deposition are reported. Au, Ni and Cu catalysts were suitable for the growth of $Ga_2O_3$ nanowires under our experimental conditions. The $Ga_2O_3$ nanowires grown by using Au, Ni and Cu catalysts showed different growth rates and morphologies in each case. We found the $Ga_2O_3$ nanowires were grown by the Vapor-Solid (VS) process when Ni was used as a catalyst while the Vapor-Liquid-Solid (VLS) was a dominant process in case of Au and Cu catalysts. Also, we found nanowires showed different optical properties depend on catalytic metals. On the other hand, for the cases of Ti, Sn and Ag catalysts, nanowires could not be obtained under the same condition of Au, Cu and Ni catalytic synthesis. We found that these results are related to the different characteristics of each catalyst, such as, melting points and phase diagrams with gallium metal.

• Journal of IKEEE
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• v.13 no.2
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• pp.126-131
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• 2009

To overcome short channel effects, wrap-around field effect transistors have drawn a great deal of attention for their superior electrostatic coupling between the channel and the surrounding gate electrode. In this paper, we introduce a bottom-up technique to fabricate a wrap-around field effect transistor using silicon nanowires as the conduction channel. Device fabrication was consisted mainly of electron-beam lithography, dielectrophoresis to accurately align the nanowires, and the formation of gate electrode using electrochemical deposition. The electrolyte for electrochemical deposition was made up of non-toxic organic-based solution and liquid nitrogen was used as a method of maintaining the shape of polymethyl methacrylate(PMMA) during the process of electrochemical deposition. Patterned PMMA can be used as a nano-template to produce wrap-around gate nano-structures.