• Journal of the Korean Vacuum Society
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• v.21 no.4
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• pp.205-211
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• 2012

We investigated the optical and hydrophobic properties of the deposited silver (Ag) zinc oxide (ZnO) nanorods (NRs) on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates (i.e., ITO/PET). The ZnO NRs were grown by an electrochemical deposition using a sputtered ZnO seed layer and the Ag was deposited by using a thermal evaporator. For comparison, the same fabrication process was carried out on the bare ITO/PET without ZnO NRAs. Due to the discrete surface of ZnO NRs, the deposited Ag was formed as nano-scale particles, while the Ag became film-like for bare ITO/PET. In order to control the size and amount of Ag particles, the Ag deposition time was changed from 100 to 600 s. When the deposition time was increased, the Ag particles became larger and denser, and the absorptance was increased. This enhanced absorptance may be due to the localized surface plasmon resonance of Ag particles. Furthermore, the relatively high hydrophobicity was observed for the deposited Ag on the ZnO NRs/ITO/PET. These improved optical and surface properties are expected to be useful for flexible photovoltaic and optoelectronic devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.145-150
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• 2014

GaN nanorods were grown on the apex of GaN stripes by three dimensional selective growth method. $SiO_2$ mask was partially removed only on the apex area of the GaN stripes by an optimized photolithography for the selective growth. Metallic Au was deposited only on the apex of the GaN stripes and a selective growth of GaN nanorods was followed by a metal organic vapor phase epitaxy (MOVPE). We confirmed that the shape and size of the GaN nanorods depend on growth temperature and flow rates of group III precursor. GaN nanorods were grown having a taper shape which have sharp tip and triangle-shaped cross section. From the TEM result, we confirmed that threading dislocations were rarely observed in GaN nanorods because of the very small contact area for the selective growth. Stacking faults which might be originated from a difference of the crystal facet directions between the GaN stripe and the GaN nanorods were observed in the center area of the GaN nanorods.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.189.2-189.2
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• 2013

1차원 산화아연 나노구조물은 광대역 에너지 밴드갭(~3.3 eV)과 독특한 물리적 특성을 갖고 있어, 전계효과 트랜지스터(field effect transistor), 발광다이오드(light emitting diode), 자외선 광검출기 (ultraviolet photodetector) 및 태양전지(photovoltaic cell)에 널리 이용되고 있다. 특히, 1차원 산화아연 나노구조물은 직접천이형 에너지 밴드갭(direct bandgap)을 갖고 있으며, 빛으로부터 여기된 전자가 1차원 나노구조물을 통해 향상된 이동경로를 제공할 수 있어서 차세대 자외선 광검출기 응용에 대한 연구가 활발히 진행되고 있다. 한편, 수열합성법(hydrothermal method)을 통해서 1차원 산화아연 나노구조물을 비교적 간단하고 저온공정을 통해서 합성할 수 있는데, 이를 광검출기 소자구조에 응용에서 양전극에 연결하기 위해서는 복잡하고 정교한 공정이 필요하다. 이에 본 연구에서는 수열합성법을 통해 합성된 산화아연 나노로드가 포함된 에탄올 용액을 금(Au) 패턴에 drop-casting을 통해서 간단한 방법으로 metal-semiconductor-metal (MSM) 광검출기를 제작하여 광반응 특성을 분석하였다. 또한 염료를 통해 가시광을 흡수하여 광전류(photocurrent)를 발생시킬 수 있도록 염료를 흡착한 산화아연 나노로드를 이용하여 같은 구조의 MSM 광검출기를 제작하여 가시광에 대한 광반응 특성을 관찰하였다.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.211-216
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• 2011

In this study, the effects of growth temperature on structural and optical properties of hydrothermally grown ZnO nanorod arrays have been investigated. Zinc nitrate ($Zn(NO_3)_2$) and hexamethylenetetramine were used as precursors. The ZnO buffered Si(100) with a thickness of 40 nm was used as the substrates. The ZnO nanorods were grown on these substrates with the temperature ranging from 55 to $115^{\circ}C$. The results were characterized by scanning electron microscope, X-ray diffraction and room temperature photoluminescence measurements. Well-aligned ZnO nanorods arrays were obtained from all samples. The tips of nanorods were flat when the temperature was less than $95^{\circ}C$, and the sharp-tip nanoneedle-like morphologies were obtained with the temperature of $115^{\circ}C$. In addition, some bundles were on the nanorods arrays with $115^{\circ}C$ due to the non-equilibrium growth. The growth temperature could affect the crystal and optical properties of ZnO. For the effects on crystal properties, the intensity of (002) peak was increased as the temperature was increased to $75^{\circ}C$, then decreased as the temperature was further increased to $115^{\circ}C$. As for the effects on optical properties, the intensity ratio of UV peak to visible peak is increased with the temperature increasing and the strongest UV peak intensity was obtained with the growth temperature of $95^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.2
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• pp.74-79
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• 2016

The lanthanum oxide nano-rods were grown on the surface of 3 mol% Yttria Partially Stabilized Zirconia ceramic composite which containing Lanthanum-Strontium Manganate, $La_xSr_yMn_zO_3$ for the purpose of endorsing the antistatic property. The diameter and the aspect ratio of the nano-rods were greatly changed according to the growing condition. With the optical microscope observation, the nano-rods shining brightly. It was confirmed that the major components of nano-rods is La, and Sr, Mn, Si are minor components by SEM and TEM analyses.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.1
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• pp.33-37
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• 2013

In this research, we investigated the effect of mole concentration of precursor on morphological, structural and optical properties of ZnO nanorods. ZnO nanorods were hydrothermally grown on c-plane sapphire substrates in aqueous solution which contains zinc nitrate hexahydrate and hexamethylenetetramine at 90oC in the precursor range of 0.01 M to 0.025 M. With the increase of mole concentration, length and diameter of ZnO nanorods increased. In all the conditions, the growth direction of rods was longitudinally c-axis direction. From the strong emission peak at 380 nm of PL spectra at room temperature, we could confirm that the crystal quality of ZnO nanorods is good to emit radiative recombination spectra.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.406-406
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• 2012

ZnO는 큰 여기자 결합 에너지, 낮은 유전 상수, 높은 화학적 안정도를 가지고 있기 때문에 전자소자 및 광소자로 많이 응용되고 있다. 여러 가지 불순물을 주입하여 ZnO의 전기적 및 광학적 성질을 향상시키기 위한 연구가 진행되고 있다. 여러 가지 불순물 중에 Zn와 물리적 및 화학적 성질이 유사한 Cu를 도핑하여 전기화학적성장(electrochemical deposition) 방법으로 ITO가 코팅된 유리 기판 위에 ZnO 박막을 성장하였다. Cu를 도핑하여 ZnO박막을 성장한 결과 구조적으로 ZnO 박막이 나노로드 형태에서 부분적으로 나노세선 또는 나노로드 형태로 변화함을 확인하였다. 광류미네센스 측정 결과는 벌크 ZnO 박막과 비교하여 Cu를 도핑함으로써 ZnO 나노세선이 3.37 eV의 에너지를 가지는 파장의 크기가 줄어들었고 여러 방향으로 ZnO 나노세선이 형성됨을 알 수 있었다. Cu를 도핑함으로써 ZnO 나노세선의 구조적 변화는 크기 않으나 에너지 밴드갭을 변화할 수 있음을 알 수 있었다. ZnO 나노세선의 광학적 성질을 Cu를 도핑하여 변화할 수 있음을 관측하였으며 불순물을 도핑하여 밴드갭을 변화하여 전자소자 및 광소자를 제작하는 기초지식으로 사용할 수 있다.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.189-195
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• 2009

$\beta-Ga_{2}O_{3}$ nanorods were synthesized by chemical vapor deposition method using nickel-oxide nanoparticle as a catalyst and gallium metal powder as a source material. The average diameter of nanorods was around 160 nm and the average length was $4{\mu}m$. Also, we confirmed that the synthesis of nanorods follows the vapor-solid growth mechanism. From the results of X-ray diffraction and HR-TEM observation, it can be found that the synthesized nanorods consisted of a typical core-shell structure with single-crystalline $\beta-Ga_{2}O_{3}$ core with a monoclinic crystal structure and an outer amorphous gallium oxide layer. Li/$\beta-Ga_{2}O_{3}$ nanorods cell delivered capacity of 867 mAh/g-$\beta-Ga_{2}O_{3}$ at first discharge. Although the Li/$\beta-Ga_{2}O_{3}$ nanorods cell showed low coulombic efficiency at first cycle, the cell exhibited stable cycle life property after fifth cycle.

• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.599-605
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• 2016

Recently, photodynamic and photothermal therapies have received increasing attention as an effective cancer treatment. In this study, a gold nanorod (AuNR) colloidal solution was synthesized as a hyperthermia agent for photothermal therapy and also modified with photosensitizer (PS) for photodynamic therapy. PEG (polyethylene glycol) and FA (folic acid) ligand were also introduced into AuNR for the long circulation in human body and efficient targeting of cancer cells, respectively and AuNRs were modified with FA-PEG and poly-${\beta}$-benzyl-L-aspartate (PBLA) block copolymers through a 3,4-dihydroxy hydrocinnamic acid (HCA) linker. A series of AuNRs with various aspect ratios were synthesized by controlling the feeding ratio of $AgNO_3$. The physicochemical property and morphology of synthesized AuNR100 and FA-PEG-$P(Asp)_{50}$-HCA-AuNR100 were analyzed by UV-visible spectrophotometer, $^1H$ NMR, XPS measurements, TEM. The surface modified AuNR carrier with biocompatibility could be applied for the effective diagnosis as well tumor phototherapy.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.101-101
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• 2011

투명전도성산화물(transparent conducting oxides, TCOs) 박막으로써 널리 쓰이는 산화인듐주석(indium tin oxide, ITO)은 전기 전도성과 광 투과성이 우수하여 주로 유기발광다이오드(organic light-emitting diode, OLED)의 전극, 발광다이오드(light-emitting diode, LED)의 current spreading 층 및 태양전지(solar cell)의 윈도우층(window layer) 등의 광전자 소자로 응용되고 있으나, 고가의 indium 가격과 인체에 유해한 독성 등이 문제점으로 지적되고 있다. 따라서 indium의 함량을 저감한 새로운 조성의 TCO 또는 indium을 함유하지 않은 친환경적인 TCO 대체 재료 개발의 필요성이 증대되고 있다. 이러한 재료 중 하나인 AZO (Al-doped zinc oxide, $Al_2O_3$: 2 wt.%)는 3.82eV의 넓은 에너지 밴드갭을 가지며, 가시광선 및 근 적외선 파장 영역에 대하여 90% 이상의 높은 투과율을 나타낸다. 또한, 습식식각이 가능하며, 매우 풍부하여 원가가 매우 저렴하고, 독성이 없다. 본 연구에서는 박막 증착율이 높고, 제작과정의 조정이 용이한 RF magnetron 스퍼터를 이용하여 glass 기판 위에 AZO 박막을 성장하고, $N_2$ 분위기에서 다양한 온도 조건에서 열처리(rapid thermal annealing, RTA)하여 전기 및 광학적 특성에 대하여 비교 분석하였다. 또한, 이후에 기존의 성장방법과 달리 고가의 진공 장비를 사용하지 않고, 저온에서도 간단한 구조의 장비를 이용하여 균일한 나노구조를 성장시킬 수 있는 전기화학증착법(electrochemical deposition)으로 AZO 박막위에 ZnO 나노로드를 다양한 성장조건에 따라 성장시켜 광학적 특성을 비교 분석하였다.