Structural Analysis of ZnO Nanorods Grown on a ZnO Homo-Buer Layer by Using MOCVD

S.-W. Han 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1

Vertically well-aligned ZnO nanorods were fabricated on Al2O3 with ZnO homo-buer layers or GaN interlayers by using a catalyst-free metal-organic chemical vapor deposition (MOCVD). X-ray diraction (XRD) measurements demonstrated that, compared with the nanorods grown on the GaN interlayer, a substantial amount of structural disorders existed in the ZnO nanorods grown on the ZnO homo-buer layer. Field-emission transmission electron microscope (FE-TEM) measurements from the interfaces of the nanorods and the substrates also exhibited structural disorders existing in the bottom part of the ZnO nanorods grown on the sapphire and on the ZnO homo-buer layer while no distinguishable disorder was observed at the ZnO/GaN interface. However, extended X-ray absorption ne structure measurements at the Zn K edge revealed that a small, but distinguishable, amount of structural disorder existed in the Zn-O pairs in the beginning of the nanorod growth. Our observation strongly suggests that structural strain due to the surface roughness of the ZnO homo-buer layer and to the lattice mismatch between the ZnO and the GaN mainly contributed to island growth in the beginning of the ZnO nanorod growth. Vertically well-aligned ZnO nanorods were fabricated on Al2O3 with ZnO homo-buer layers or GaN interlayers by using a catalyst-free metal-organic chemical vapor deposition (MOCVD). X-ray diraction (XRD) measurements demonstrated that, compared with the nanorods grown on the GaN interlayer, a substantial amount of structural disorders existed in the ZnO nanorods grown on the ZnO homo-buer layer. Field-emission transmission electron microscope (FE-TEM) measurements from the interfaces of the nanorods and the substrates also exhibited structural disorders existing in the bottom part of the ZnO nanorods grown on the sapphire and on the ZnO homo-buer layer while no distinguishable disorder was observed at the ZnO/GaN interface. However, extended X-ray absorption ne structure measurements at the Zn K edge revealed that a small, but distinguishable, amount of structural disorder existed in the Zn-O pairs in the beginning of the nanorod growth. Our observation strongly suggests that structural strain due to the surface roughness of the ZnO homo-buer layer and to the lattice mismatch between the ZnO and the GaN mainly contributed to island growth in the beginning of the ZnO nanorod growth.

Nonlinear Optical Properties of ZnO Nanorods Prepared by Using the Electro-deposition Method

Soon-Ki Min,오차환,Geon Joon Lee,이영백,민선기,한성환 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3

We studied the nonlinear optical properties of ZnO nanorods. ZnO nanorods were deposited by using the electro-deposition method, and these samples were annealed at a temperature of 400 ˚C for 5 hours. The nonlinear absorption properties of ZnO nanorods with two different rod diameters of 500 nm and 100 nm were measured by using the femtosecond nonlinear transmission method at an incident wavelength of 800 nm. The nonlinear absorption coefficients of ZnO nanorods were 5.9 × 10−7 cm/W and 2.3 × 10−7 cm/W for rod diameters of 500 nm and 100 nm, respectively, and these nonlinear absorption coefficients were about 100 times larger than those already reported for ZnO thin films. The enhanced nonlinear absorption in ZnO nanorods was due to the combination of the two-photon absorption and optical confinement. We studied the nonlinear optical properties of ZnO nanorods. ZnO nanorods were deposited by using the electro-deposition method, and these samples were annealed at a temperature of 400 ˚C for 5 hours. The nonlinear absorption properties of ZnO nanorods with two different rod diameters of 500 nm and 100 nm were measured by using the femtosecond nonlinear transmission method at an incident wavelength of 800 nm. The nonlinear absorption coefficients of ZnO nanorods were 5.9 × 10−7 cm/W and 2.3 × 10−7 cm/W for rod diameters of 500 nm and 100 nm, respectively, and these nonlinear absorption coefficients were about 100 times larger than those already reported for ZnO thin films. The enhanced nonlinear absorption in ZnO nanorods was due to the combination of the two-photon absorption and optical confinement.

CBD 방법에 의해 제조된 ZnO 나노로드의 전기적 특성

김진호,이미재,황종희,임태영,Kim, Jin-Ho,Lee, Mi-Jai,Hwang, Jonghee,Lim, Tae-Young 한국재료학회 2012 한국재료학회지 Vol.22 No.12

ZnO nanorods were successfully fabricated on Zn foil by chemical bath deposition (CBD) method. The ZnO precursor concentration and immersion time affected the surface morphologies, structure, and electrical properties of the ZnO nanorods. As the precursor concentration increased, the diameter of the ZnO nanorods increased from ca. 50 nm to ca. 150 nm. The thicknesses of the ZnO nanorods were from ca. $1.98{\mu}m$ to ca. $2.08{\mu}m$. ZnO crystalline phases of (100), (002), and (101) planes of hexagonal wurtzite structure were confirmed by XRD measurement. The fabricated ZnO nanorods showed a photoluminescene property at 380 nm. Especially, the ZnO nanorods deposited for 6 h in solution with a concentration of 0.005M showed a stronger (101) peak than they did (100) or (002) peaks. In addition, these ZnO nanorods showed a good electrical property, with the lowest resistance among the four samples, because the nanorods were densely in contact and relatively without pores. Therefore, a ZnO nanorod substrate is useful as a highly sensitive biochip substrate to detect biomolecules using an electrochemical method.

수열법으로 성장한 ZnO Nanorod/ZnO/Si(100)의 특성

정민호,진용식,최성민,한덕동,최대규,Jeong, Min-Ho,Jin, Yong-Sik,Choi, Sung-Min,Han, Duk-Dong,Choi, Dae-Kue 한국재료학회 2012 한국재료학회지 Vol.22 No.4

Nanostructures of ZnO, such as nanowires, nanorods, nanorings, and nanobelts have been actively studied and applied in electronic or optical devices owing to the increased surface to volume ratio and quantum confinement that they provide. ZnO seed layer (about 40 nm thick) was deposited on Si(100) substrate by RF magnetron sputtering with power of 60 W for 5 min. ZnO nanorods were grown on ZnO seed layer/Si(100) substrate at $95^{\circ}C$ for 5 hr by hydrothermal method with concentrations of $Zn(NO_3)_2{\cdot}6H_2O$ [ZNH] and $(CH_2)_6N_4$ [HMT] precursors ranging from 0.02M to 0.1M. We observed the microstructure, crystal structure, and photoluminescence of the nanorods. The ZnO nanorods grew with hexahedron shape to the c-axis at (002), and increased their diameter and length with the increase of precursor concentration. In 0.06 M and 0.08 M precursors, the mean aspect ratio values of ZnO nanorods were 6.8 and 6.5; also, ZnO nanorods had good crystal quality. Near band edge emission (NBE) and a deep level emission (DLE) were observed in all ZnO nanorod samples. The highest peak of NBE and the lower DLE appeared in 0.06 M precursor; however, the highest peak of DLE and the lower peak of NBE appeared in the 0.02 M precursor. It is possible to explain these phenomena as results of the better crystal quality and homogeneous shape of the nanorods in the precursor solution of 0.06 M, and as resulting from the bed crystal quality and the formation of Zn vacancies in the nanorods due to the lack of $Zn^{++}$ in the 0.02 M precursor.

Amorphous Pd-assisted H₂ detection of ZnO nanorod gas sensor with enhanced sensitivity and stability

Kim, Hyeonghun,Pak, Yusin,Jeong, Yeonggyo,Kim, Woochul,Kim, Jeongnam,Jung, Gun Young Elsevier 2018 Sensors and actuators. B Chemical Vol.262 No.-

<P><B>Abstract</B></P> <P>For monitoring H<SUB>2</SUB> concentrations in air, diverse resistive gas sensors have been demonstrated. In particular, Pd-decorated metal oxides have shown remarkable selectivity and sensing response for H<SUB>2</SUB> detection. In this work, H<SUB>2</SUB> sensing behavior of amorphous Pd layer covering ZnO nanorods (am-Pd/ZnO NRs) is investigated. This is the first report on the enhanced gas sensing performance attained by using an amorphous metal layer. The amorphous Pd layer is generated by reduction reaction with a strong reducing agent (NaBH<SUB>4</SUB>), and it covers the ZnO nanorods completely with a thickness of 2–5 nm. For comparison, crystalline Pd nanoparticles-decorated ZnO nanorods (c-Pd/ZnO NRs) are produced using a milder reducing agent like hydrazine. Comparing the c-Pd/ZnO NRs sensor and other previously reported hydrogen sensors based on the crystalline Pd and metal oxides, the am-Pd/ZnO NRs sensor exhibits a remarkable sensing response (12,400% at 2% H<SUB>2</SUB>). The enhancement is attributed to complete cover of the amorphous Pd layer on the ZnO NRs, inducing larger interfaces between the Pd and ZnO. In addition, the amorphous Pd layer prevents surface contamination of the ZnO NRs. Therefore, the am-Pd/ZnO NRs sensor maintains initial sensing performance even after 5 months.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Facile synthesis of ultrathin amorphous Pd layer (2–5 nm) on ZnO nanorods. </LI> <LI> Comparison of sensing behavior between amorphous and crystalline Pd-coated ZnO nanorods sensors. </LI> <LI> Demonstration of superior sensing response (12,400%) of amorphous Pd-coated ZnO nanorods sensors. </LI> <LI> High stability of amorphous Pd-coated ZnO nanorods sensors. </LI> </UL> </P>

A facile route to ionic liquids-functionalized ZnO nanorods for the fluorometric sensing of thiabendazole drug

Kaur, Narinder,Raj, Pushap,Singh, Amanpreet,Singh, Narinder,Kim, Deuk Young Elsevier 2018 Journal of molecular liquids Vol.261 No.-

<P>In this report, we introduce a simple and cost-effective hydrothermal method for the functionalization of ZnO nanorods with three different ionic liquids (ILs (1-3)) to check their sensing response with various drugs including thiabendazole, phenylbutazone, chloramphenicol, neomycin, and theophylline through fluorescence spectroscopy. The rod like-microstructure and hexagonal wurtzite structure of synthesized ZnO nanorods were examined with SEM-EDS and XRD techniques. On the other hand, ionic liquids-functionalized ZnO nanorods (ILs (1-3)/ZnO) exhibited various self-organized (layered-sheet similar to IL1, distorted nanorods similar to IL2, peanut beaded surface similar to IL3/ZnO) structures due to the intercalation of ILs on the surface of ZnO nanorods. Compared to ZnO nanorods, similar to ILs (1-3)/ZnO nanorods showed a blue shift in UV-absorption band which resulted to the variation in optical bandgap values. Ionic liquids-functionalized nanorods samples (ILs (1-3)/ZnO) have been selected for their recognition behaviour with available drug molecules using fluorescence spectroscopic technique. Interestingly, with the addition of thiabendazole drug molecules to two samples (ILs (1,3)/ZnO), a significant response corresponding to the peaks at similar to 350 nm and similar to 357 nm was observed, which led to the development of fluorescent sensors with a detection limit of 12 and 304 nM, respectively. (C) 2018 Elsevier B.V. All rights reserved.</P>

수열합성법을 이용한 ZnO 나노 막대의 선택 성장 연구

김아라,장판,김창회,김홍승 한국물리학회 2012 새물리 Vol.62 No.8

We have investigated the effects of surface pattern size on the characteristics of hydrothermally grown ZnO nanorods. The sputtered ZnO seed layer on a Si substrate was patterned with features of various sizes by using nano-imprint technology for the selective growth of ZnO nanorods. The diameters and the lengths of the ZnO nanorods depended on the pattern feature size within several micrometers. The ZnO nanorods grown on small-pattern regions had large diameters and small lengths relative to those grown on large-pattern regions. The observation in this study suggests that controlling the pattern size of the ZnO seed layer on a substrate can control the morphology of the ZnO nanorod array. 본 연구에서는 수열합성법을 이용하여 패턴 영역의 크기에 대한 산화아연(ZnO, zinc oxide) 나노 막대 성장을 살펴보았다. ZnO와 Si기판의 격자상수 차이를 이용하여 ZnO 나노 막대를 선택적 영역에 성장시키고자스퍼터링 시스템으로 증착된 ZnO 씨앗층을 원하는 크기와 모양으로패턴화 하고자 하였으며 사용된 노광 기법은 광원의 파장에 제약을 받지않고 비교적 나노 스케일의 패턴을 재현성 있게 제작 가능한나노임프린트 공정을 이용하였다. ZnO 나노 막대는 패턴된 ZnO 씨앗층영역에 선택적으로 성장하였으며, ZnO 나노 막대의 직경과 길이의 크기는패턴된 ZnO 씨앗층의 수 μm크기의 변화에 따라 큰 영향을 받아 패턴크기가 작아질수록 큰 직경과 짧은 길이를 가지는 ZnO 나노 막대가 성장되었다.

Enhancement of local surface plasmon resonance (LSPR) effect by biocompatible metal clustering based on ZnO nanorods in Raman measurements

Lee, Sanghwa,Lee, Seung Ho,Paulson, Bjorn,Lee, Jae-Chul,Kim, Jun Ki Elsevier 2018 Spectrochimica acta. Part A, Molecular and biomole Vol.204 No.-

<P><B>Abstract</B></P> <P>The development of size-selective and non-destructive detection techniques for nanosized biomarkers has many reasons, including the study of living cells and diagnostic applications. We present an approach for Raman signal enhancement on biocompatible sensing chips based on surface enhancement Raman spectroscopy (SERS). A sensing chip was fabricated by forming a ZnO-based nanorod structure so that the Raman enhancement occurred at a gap of several tens to several hundred nanometers. The effect of coffee-ring formation was eliminated by introducing the porous ZnO nanorods for the bio-liquid sample. A peculiarity of this approach is that the gold sputtered on the ZnO nanorods initially grows at their heads forming clusters, as confirmed by secondary electron microscopy. This clustering was verified by finite element analysis to be the main factor for enhancement of local surface plasmon resonance (LSPR). This clustering property and the ability to adjust the size of the nanorods enabled the signal acquisition points to be refined using confocal based Raman spectroscopy, which could be applied directly to the sensor chip based on the optimization process in this experiment. It was demonstrated by using common cancer cell lines that cell growth was high on these gold-clad ZnO nanorod-based surface-enhanced Raman substrates. The porosity of the sensing chip, the improved structure for signal enhancement, and the cell assay make these gold-coated ZnO nanorods substrates promising biosensing chips with excellent potential for detecting nanometric biomarkers secreted by cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A surface enhanced Raman spectroscopy (SERS) chip was fabricated by depositing gold on a ZnO - based nanorod structure. </LI> <LI> The nanorod heads grow first to form clusters as gold is sputtered on the ZnO nanorods. </LI> <LI> The process was optimized by adjusting the ZnO nanorod size and Au clusters, and verified by finite element analysis (FEM). </LI> <LI> Biocompatibility testing confirmed that the Raman-based sensing chip was suitable for monitoring of living cells. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

산화아연 나노로드 전극을 이용한 전기화학발광 셀의 제작 및 발광특성 고찰

오형석(Hyung-Suk Oh),성열문(Youl-Moon Sung) 대한전기학회 2014 전기학회논문지 Vol.63 No.1

We report Zinc oxide (ZnO) nanorods synthesis and electrochemical luminescence (ECL) cell fabrication. The ECL cell was fabricated using the electrode of ZnO nanorods and Ru(II) complex (Ru(bpy)3 <SUP>2+</SUP>) as a luminescence materials. The fabricated ECL cell is composed of F-doped SnO₂ (FTO) glass/ Ru(II)/ZnO nanorods/FTO glass. The highest intensity of the emitting light was obtained at the wavelength of ∼620 nm which corresponds to dark-orange color. At a bias voltage of 3V, the measured ECL efficiencies were 5 cd/m2 for cell without ZnO nanorod, 145 cd/㎡ for ZnO nanorods-5μm, 208 cd/㎡ for ZnO nanorods-8μm and 275 cd/㎡ for ZnO nanorods-10μm, respectively. At a bias voltage of 3.5V, the use of ZnO nanorods increases ECL intensities by about 3 times compared to the typical ECL cell without the use of ZnO nanorods.

Mn-doped ZnO nanorod gas sensor for oxygen detection

Ahmed, F.,Arshi, N.,Anwar, M.S.,Danish, R.,Koo, B.H. Elsevier 2013 Current Applied Physics Vol.13 No.suppl2

In this work, we have used resistive sensor measurements regarding the oxygen gas sensitivity of un-doped and Mn-doped ZnO nanorods prepared by microwave-hydrothermal method. X-ray diffraction (XRD) results indicated that the Mn-doped ZnO nanorods have single phase nature with the wurtzite structure. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) results suggested that Mn-doped ZnO nanorods possessed higher aspect ratio (27) than un-doped ZnO (24). The selected area electron diffraction (SAED) pattern inferred that the ZnO nanorods have single crystalline nature with preferentially growth along [001] direction. Raman scattering spectra of Mn-doped ZnO nanorods revealed the modification in E<SUB>2</SUB> (high) mode that is related to the vibration of oxygen atoms in wurtzite ZnO, suggested the successful doping of Mn into Zn site in ZnO. The gas sensing properties measured at room temperature revealed that the Mn-doped ZnO nanorods exhibited high sensitivity as compared to un-doped ZnO.