• 한국전기전자재료학회논문지
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• 제23권3호
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• pp.222-227
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• 2010

ZnO nanorods array have been grown on the seed crystal coated Si(100) substrate by hydrothermal method. The growth, structural and optical properties of ZnO nanorods array were investigated with a variation of precursor concentration from 0.01 M to 0.04 M. The array density of grown ZnO nanorods per same area was increased with increasing the concentration of precursor solution. Vertically aligned ZnO nanorods with hexagonal wurtzite structure have highly preferred c-axis orientation along (002) lattice plane. Especially, ZnO nanorods array developed from 0.04 M precursor solution showed a diameter of about 85 nm and length of 1.2 {\mu}m$ without any crystallographic defects. The photoluminescence spectra of ZnO nanorods from heavier precursor concentration exhibited stronger UV emission around 380 nm corresponding with near-band-edge emission.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.355-356
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• 2013

• 한국표면공학회지
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• 제52권5호
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• pp.258-264
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• 2019

Assembling heterostructures by combining dissimilar oxide semiconductors is a promising approach to enhance charge separation and transfer in photoelectrochemical (PEC) water splitting. In this work, the CuO nanorods array/$Cu_2O$ thin film bilayered heterostructure was successfully fabricated by a facile method that involved a direct electrodeposition of the $Cu_2O$ thin film onto the vertically oriented CuO nanorods array to serve as the photoelectrode for the PEC water oxidation. The resulting copper-oxide-based heterostructure photoelectrode exhibited an enhanced PEC performance compared to common copper-oxide-based photoelectrodes, indicating good charge separation and transfer efficiency due to the band structure realignment at the interface. The photocurrent density and the optimal photocurrent conversion efficiency obtained on the CuO nanorods/$Cu_2O$ thin film heterostructure were $0.59mA/cm^2$ and 1.10% at 1.06 V vs. RHE, respectively. These results provide a promising route to fabricating earth-abundant copper-oxide-based photoelectrode for visible-light-driven hydrogen generation using a facile, low-cost, and scalable approach of combining electrodeposition and hydrothermal synthesis.

• 한국표면공학회지
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• 제54권5호
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• pp.260-266
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• 2021

Synthesizing low-dimensional structures of oxide semiconductors is a promising approach to fabricate highly efficient gas sensors by means of possible enhancement in surface-to-volume ratios of their sensing materials. In this work, vertically aligned zinc oxide (ZnO) nanorods are successfully synthesized on a transparent glass substrate via seed-mediated hydrothermal synthesis method with the use of a ZnO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Zn metal film. Structural and optical characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy reveals the successful preparation of the ZnO nanorods array of the single hexagonal wurtzite crystalline phase. From gas sensing measurements for the nitrogen dioxide (NO₂) gas, the vertically aligned ZnO nanorod array is observed to have a highly responsive sensitivity to NO₂ gas at relatively low concentrations and operating temperatures, especially showing a high maximum sensitivity to NO₂ at 250 ℃ and a low NO₂ detection limit of 5 ppm in dry air. These results along with a facile fabrication process demonstrate that the ZnO nanorods synthesized on a transparent glass substrate are very promising for low-cost and high-performance NO₂ gas sensors.

• 한국표면공학회지
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• 제56권4호
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• pp.219-226
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• 2023

Utilizing low-dimensional structures of oxide semiconductors is a promising approach to fabricate relevant gas sensors by means of potential enhancement in surface-to-volume ratios of their sensing materials. In this work, vertically aligned cupric oxide (CuO) nanorods are successfully synthesized on a transparent glass substrate via seed-mediated hydrothermal synthesis method with the use of a CuO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Cu metal film. Structural and optical characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy reveals the successful preparation of the CuO nanorods array of the single monoclinic tenorite crystalline phase. From gas sensing measurements for the nitrogen monoxide (NO) gas, the vertically aligned CuO nanorod array is observed to have a highly responsive sensitivity to NO gas at relatively low concentrations and operating temperatures, especially showing a high maximum sensitivity to NO at 200 ℃ and a low NO detection limit of 2 ppm in dry air. These results along with a facile fabrication process demonstrate that the CuO nanorods synthesized on a transparent glass substrate are very promising for low-cost and high-performance NO gas sensors.

• 한국재료학회지
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• 제28권4호
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• pp.214-220
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• 2018

We report on the fabrication and photoelectrochemical(PEC) properties of a $Cu_2O$ thin film/ZnO nanorod array oxide p-n heterojunction structure with ZnO nanorods embedded in $Cu_2O$ thin film as an efficient photoelectrode for solar-driven water splitting. A vertically oriented n-type ZnO nanorod array was first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method and then a p-type $Cu_2O$ thin film was directly electrodeposited onto the vertically oriented ZnO nanorods array to form an oxide semiconductor heterostructure. The crystalline phases and morphologies of the heterojunction materials were characterized using X-ray diffraction and scanning electron microscopy as well as Raman scattering. The PEC properties of the fabricated $Cu_2O/ZnO$ p-n heterojunction photoelectrode were evaluated by photocurrent conversion efficiency measurements under white light illumination. From the observed PEC current density versus voltage (J-V) behavior, the $Cu_2O/ZnO$ photoelectrode was found to exhibit a negligible dark current and high photocurrent density, e.g., $0.77mA/cm^2$ at 0.5 V vs $Hg/HgCl_2$ in a $1mM\;Na_2SO_4$ electrolyte, revealing an effective operation of the oxide heterostructure. In particular, a significant PEC performance was observed even at an applied bias of 0 V vs $Hg/HgCl_2$, which made the device self-powered. The observed PEC performance was attributed to some synergistic effect of the p-n bilayer heterostructure on the formation of a built-in potential, including the light absorption and separation processes of photoinduced charge carriers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.61.2-61.2
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• 2015

In the past decades, green energy, such as solar energy, wind power, hydropower, biomass energy, geothermal energy, and so on, has been widely investigated and developed to solve energy shortage. Recently, organic solar cells have attracted much attention, because they have many advantages, including low-cost, flexibility, light weight, and easy fabrication [1-3]. Organic solar cells are as a potential candidate of the next generation solar cells. In this abstract, to improve the power conversion efficiency and the stability, the inverted polymer solar cells with various structures were developed [4-6]. The novel cell structures included the P3HT:PCBM inverted polymer solar cells with AZO nanorods array, with pentacene-doped active layer, and with extra P3HT interfacial layer and PCBM interfacial layer. These three difference structures could respectively improve the performance of the P3HT:PCBM inverted polymer solar cells. For the inverted polymer solar cells with AZO nanorods array as the electronic transportation layer, by using the nanorod structure, the improvement of carrier collection and carrier extraction capabilities could be expected due to an increase in contact area between the nanorod array and the active layer. For the inverted polymer solar cells with pentacene-doped active layer, the hole-electron mobility in the active layer could be balanced by doping pentacene contents. The active layer with the balanced hole-electron mobility could reduce the carrier recombination in the active layers to enhance the photocurrent of the resulting inverted polymer solar cells. For the inverted polymer solar cells with extra P3HT and PCBM interfacial layers, the extra PCBM and P3HT interfacial layers could respectively improve the electron transport and hole transport. The extra PCBM interfacial layer served another function was that led more P3HT moving to the top side of the absorption layer, which reduced the non-continuous pathways of P3HT. It indicated that the recombination centers could be further reduced in the absorption layer. The extra P3HT interfacial layer could let the hole be more easily transported to the MoO3 hole transport layer. The high performance of the novel P3HT:PCBM inverted polymer solar cells with various structures were obtained.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.23.1-23.1
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• 2009

ZnO is of great interest for various technological applications ranging from optoelectronics to chemical sensors because of its superior emission, electronic, and chemical properties. In addition, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. To date, several approaches have been proposed for the growth of one-dimensional (1D) ZnO nanostructunres. Several groups have been reported the MOCVD growth of ZnO nanorods with no metal catalysts at $400^{\circ}C$, and fabricated a well-aligned ZnO nanorod array on a PLD prepared ZnO film by using a catalyst-free method. It has been suggested that the synthesis of ZnO nanowires using a template-less/surfactant-free aqueous method. However, despite being a well-established and cost-effective method of thin film deposition, the use of magnetrons puttering to grow ZnO nanorods has not been reported yet. Additionally,magnetron sputtering has the dvantage of producing highly oriented ZnO film sat a relatively low process temperature. Currently, more effort has been concentrated on the synthesis of 1D ZnO nanostructures doped with various metal elements (Al, In, Ga, etc.) to obtain nanostructures with high quality,improved emission properties, and high conductance in functional oxide semiconductors. Among these dopants, Ga-doped ZnO has demonstrated substantial advantages over Al-doped ZnO, including greater resistant to oxidation. Since the covalent bond length of Ga-O ($1.92\;{\AA}$) is nearly equal to that of Zn-O ($1.97\;{\AA}$), high electron mobility and low electrical resistivity are also expected in the Ga-doped ZnO. In this article, we report the successful growth of Ga-doped ZnO nanorods on c-Sapphire substrate without metal catalysts by magnetrons puttering and our investigations of their structural, optical, and field emission properties.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.377-377
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• 2012

반도체 물질로서 Zinc oxide (ZnO) nanorod (NR)는 Hydrothermal growth method로 제작 시 고가의 장비가 필요치 않기에 저비용 대면적 박막을 제작하는데 적합하지만 NR들의 array 조절과 각각의 rod와 전극 간의 연결에서 어려움을 가지고 있다. 최근 연구에서는 이러한 NR array 형상 조절과 소자의 성능 향상을 위하여 tilted sputtering method를 이용해 seed layer를 lateral 하게 형성하여 성장시켜 표면적을 극대화함으로서 응용되는 센서의 성능을 향상시키는 연구가 진행되고 있다. 본 연구에서는 이렇게 향상된 수평구조의 ZnO NR과 다양한 전극 금속 간의 schottky barrier의 높이 차이에 따라 sensitivity와 response time의 차이를 측정하였다. NR들을 전계방출형 전자현미경과 XRD로 분석 NR의 lateral structure 및 결정성을 확인하였다. 그리고 이렇게 형성한 NR을 소자화하여 Au, Ag, Al을 전극 금속물질로 사용한 경우에 대하여 sensing performance와 전극 금속의 schottky barrier의 상관관계를 확인하였다.

• Korean Chemical Engineering Research
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• 제46권3호
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• pp.465-472
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• 2008

나노재료의 합성이나 나노구조물질의 제작은 나노기술을 기반으로 하는 전자소자를 구현하기 위해서 많은 연구가 진행되고 있다. 나노다공성 알루미나 마스크(nanoporous alumina mask) 를 이용하여 균일도와 정렬도가 우수한 나노구조물들을 제조할 수 있고 이들의 크기와 밀도는 알루미나 마스크의 동공의 직경과 동공밀도를 조절하여 제어할 수 있다. 이러한 방법은 낮은 비용으로 나노구조물의 대면적 제조 공정 개발이 가능하고, 정보통신기술와 바이오기술-나노기술을 융합하는 새로운 물질의 제조에 응용할 수 있을 것이다. 그러므로, 알루미나 마스크를 사용하여 다양한 크기와 밀도를 갖는 나노물질을 제조하는 기술은 새로운 형태의 다양한 전자소자의 구현을 위해 가능성이 큰 기술이라 할 것이다. 본 논문에서는 나노다공성 알루미나 마스크를 제조하는 기술과 이를 이용한 양자점(quantum dots), 나노홀(nanoholes), 나노막대(nanorods) 등의 나노구조물 제조와 그 구조물의 응용성에 대해 알아보고자 한다.