• 한국생산제조학회지
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• 제25권1호
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• pp.62-67
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• 2016

This paper presents a silicon nanostructure array embedded in a polymer film. The silicon nanostructure array was fabricated by using basic microelectromechanical systems (MEMS) processes such as photolithography, reactive ion etching, and anisotropic KOH wet etching. The fabricated silicon nanostructure array was transferred into polymer substrates such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polycarbonate (PC) through the hot-embossing process. In order to determine the transfer conditions under which the silicon nanostructures do not fracture, hot-embossing experiments were performed at various temperatures, pressures, and pressing times. Transfer was successfully achieved with a pressure of 1 MPa and a temperature higher than the transition temperature for the three types of polymer substrates. The transferred silicon nanostructure array was electrically evaluated through measurements with a semiconductor parameter analyzer (SPA).

• KEPCO Journal on Electric Power and Energy
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• 제2권1호
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• pp.97-101
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• 2016

산화아연은 다양한 나노 구조와 특유의 특성으로 인하여 여러 분야에서 많은 관심을 받고있는 물질이다. 산화아연을 합성하는 다양한 방법 중에서, 수열합성법은 간단하고 친환경적인 장점을 가지고 있다. 나노 구조를 가지는 산화아연 박막은 수열합성법을 통하여 FTO 전극 위에 제작되었다. 성장된 산화아연은 X-ray diffraction (XRD)와 Field-emission scanning electron microscopy (FESEM)을 통하여 분석되었다. XRD 분석에서 산화아연 박막이 자연상태의 hexagonal wurtzite 상으로 구성되어 있음을 확인하였으며 SEM 사진에서는 나노 로드 형태를 구성하고 있는 것을 확인할 수 있었다. 본 연구에서는 UV 영역의 흡수 스펙트럼을 분석하여 산화아연이 보이는 365 nm 파장에서의 흡수를 확인하였다. 또한 photoluminescence 방출을 분석한 결과, 424 nm의 band edge emission과 500 nm에서 산화아연의 oxygen vacancies에 의한 방출을 확인하였다. 또한 라만 스펙트럼 분석을 통하여 본 연구진이 제작한 산화아연이 높은 결정성을 가지고 있는 것을 확인할 수 있었다. 이러한 연구를 통하여 다양한 특성을 가진 산화아연의 광촉매적 적용을 기대할 수 있다.

• ETRI Journal
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• 제38권3호
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• pp.469-478
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• 2016

In this paper, we investigate the effects of pre-reducing Sb-doped $SnO_2$ (ATO) electrodes in viologen-anchored $TiO_2$ (VTO) nanostructure-based electrochromic devices. We find that by pre-reducing an ATO electrode, the operating voltage of a VTO nanostructure-based electrochromic device can be lowered; consequently, such a device can be operated more stably with less hysteresis. Further, we find that a pre-reduction of the ATO electrode does not affect the coloration efficiency of such a device. The aforementioned effects of a pre-reduction are attributed to the fact that a pre-reduced ATO electrode is more compatible with a VTO nanostructure-based electrochromic device than a non-pre-reduced ATO electrode, because of the initial oxidized state of the other electrode of the device, that is, a VTO nanostructure-based electrode. The oxidation state of a pre-reduced ATO electrode plays a very important role in the operation of a VTO nanostructure-based electrochromic device because it strongly influences charge movement during electrochromic switching.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.48-48
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• 2011

We have developed a chemically-driven top-down approach using vapor phase HCl to form various GaN nanostructures and successfully demonstrated dislocation-free and strain-relaxed GaN nanostructures without etching damage formed by a selective dissociation method. Our approach overcomes many limitations encountered in previous approaches. There is no need to make a pattern, complicated process, and expensive equipment, but it produces a high-quality nanostructure over a large area at low cost. As far as we know, this is the first time that various types of high-quality GaN nanostructures, such as dot, cone, and rod, could be formed by a chemical method without the use of a mask or pattern, especially on the Ga-polar GaN. It is well known that the Ga-polar GaN is difficult to etch by the common chemical wet etching method because of the chemical stability of GaN. Our chemically driven GaN nanostructures show excellent structure and optical properties. The formed nanostructure had various facets depending on the etching conditions and showed a high crystal quality due to the removal of defects, such as dislocations. These structure properties derived excellent optical performance of the GaN nanostructure. The GaN nanostructure had increased internal and external quantum efficiency due to increased light extraction, reduced strain, and improved crystal quality. The chemically driven GaN nanostructure shows promise in applications such as efficient light-emitting diodes, field emitters, and sensors.

• 센서학회지
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• 제27권5호
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• pp.306-310
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• 2018

In order to develop a highly sensitive infrared sensor, it is necessary to develop techniques for decreasing the rate of heat absorption and the transition of the absorption wavelength to a longer wavelength, both of which can be induced by decreasing the pixel size of the bolometer. Therefore, in this study, $1{\mu}m$ hole-arrays with a subwavelength smaller than the incident infrared wavelength were formed on the amorphous silicon-based microbolometer pixels in the absorber, which consisted of a TiN absorption layer, an a-Si resistance layer and a SiNx membrane support layer. We demonstrated that it is possible to reduce the thermal time constant by 16% relative to the hole-patternless bolometer, and that it is possible to shift the absorption peak to a shorter wavelength as well as increase absorption in the $4-8{\mu}m$ band to compensate for the infrared long-wavelength transition. These results demonstrate the potential for a new approach to improve the performance of high-resolution microbolometers.

• 대한화장품학회지
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• 제33권4호
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• pp.239-243
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• 2007

PFCs는 독특한 사용감과 특성으로 인하여 화장품에 응용되어질 때 많은 특장점을 가지고 있다. 그러나 이러한 장점에도 불구하고 화장품 제형에 적용하기에 많은 어려움을 가지고 있다. 즉, 물과 오일에 불용성, 높은 비중, 높은 증기압 등과 같은 원료의 특징으로 인하여 PFCs는 화장품에 적용하기 위하여 특별한 안정화 시스템을 필요로 한다. 본 연구에서 PFCs를 안정화하기 위하여 gel network, spherulite lamellar, nanostructure 이상의 세 가지 시스템을 이용하였으며 사용된 세 가지 시스템 중 nanostructure system이 가장 안정함을 알 수 있었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.31.1-31.1
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• 2010

Various ZnO nanostructures were synthesized and ZnO nanostructure-based self-assembled transistors were fabricated. Compared to spindle and flower like nanostructure, the ZnO nanorod (NR) structure showed much stronger gate controllability, and greatly enhanced device performance, demonstrating that this structural variation leads to significant differences of the nanostructure network-based device performance. Also, patterned dry transfer-printing technique that can generate monolayer-like percolating networks of ZnO NRs has been developed. The method exploits the contact area difference between NR-NR and NR-substrate, rather than elaborate tailoring of surface chemistry or energetic. The devices prepared by the transferring method exhibited on/off current ratio, and mobility of ${\sim}2.7{\times}10^4$ and ${\sim}1.03\;cm^2/V{\cdot}s$, respectively. Also, they exhibited showing lower off-current and stronger gate controllability due to defined-channel between electrodes and monolayer-like network channel configuration. With multilayer stacks of nanostructures on stamp, the monolayer-like printing can be repeated many times, possibly on large area substrate, due to self-regulating printing characteristics. The method may enable high-performance macroelectronics with materials that have high aspect ratio.

• 전기화학회지
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• 제16권2호
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• pp.81-84
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• 2013

We demonstrate rutile $TiO_2$ branched nanostructure ($TiO_2$-BN) electrodes synthesized by seeding method for enhanced lithium intercalation properties. The morphology and crystalline nature of the $TiO_2$-BN were clearly observed by field-emission transmission electron microscopy and fast Fourier transform pattern. The $TiO_2$-BN electrodes showed excellent capacity and high rate performance. The improved lithium-ion intercalation properties of the $TiO_2$- BN may be attributed to relatively large specific surface area and short transport distance of the branched nanostructure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1493-1494
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• 2011

CdS nanostructure materials have been fabricated in porous anodic aluminum oxide (AAO) template by using chemical bath deposition (CBD). These nanostructure materials had uniform diameters of about 15e200 nm, which correspond to the pore sizes of the templates used, and the length was up to 40 mm. X-ray diffraction (XRD) investigation demonstrates that CdS nanostructure materials were hexagonal polycrystalline in nature. As the pore diameter of AAO templates was enlarged, the preferential orientation of c-axis was improved. From PL analysis, the sulfur-deficient defects at the surfaces of CdS nanostructure materials were increasedwhen the samplewas synthesized in the template with larger pore diameter.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.459.1-459.1
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• 2014

Because both $TiO_2$ and ZnO has superior characteristic optically and electrically, there are various of research for these materials. However, they have large band gap energy which correspond with not visible light, but UV light. To make up for this disadvantage, Quantum dots (CdS, CdSe) which can absorb the visible light could be deposited on $ZnO/TiO_2$ nanostructure so that the the photoelectrochecmical cell can absorb the light that has larger region of wavelength. Both $TiO_2$ and ZnO can be grown to one-dimensional nanowire structure at low temperature through solutional method. Three-dimensional hierarcical $ZnO/TiO_2$ nanostructure is fabricated by applying these process. Large surface area of this structure make the light absorbed more efficiently. Through type 2 like-cascade energy band structure of nanostructure, the efficient separation of electron-hole pairs is expected. Photoelectrochemical charateristics are found by using these nanostructure to photoelectrode.