Quasi-Symmetric Wheatstone Bridge Zinc Oxide Nanorod UV Detectors

Vasudevan, Arun,Soyoun Jung,Taeksoo Ji,Ang, Simon S. IEEE 2014 IEEE SENSORS JOURNAL Vol.14 No.9

<P>Zinc oxide (ZnO) nanorod-based ultraviolet (UV) detectors have high responsivity at room temperature due to carrier generation assisted by the depletion region formed by oxygen adsorbed on the surface of nanorods. As such, the amount of oxygen adsorbed on the ZnO nanorod surface and the number of electron-hole pairs that reaches the depletion region on the surface can change the response of the detector. In this paper, the transient responses of metal-semiconductor-metal ZnO nanorod-based UV detectors based on a quasi-symmetric Wheatstone bridge configuration were investigated. Responsivity, defined as the ratio of the Wheatstone bridge detector output current to the total power of the UV light incident on the active area of the detector, as high as 54 A/W was obtained in some of these UV detectors at 30 °C. It was found that the responsivity and the temperature effects on the UV response of the Wheatstone bridge ZnO nanorod UV detectors can be tailored by the difference in the diameters and lengths of the rods grown in the two quadrants.</P>

Effect of the pH of an Aqueous Solution on the Structural, Optical, and Photoresponse Properties of Hydrothermally Grown ZnO Nanorods and the Fabrication of a High Performance Ultraviolet Sensor

김동완,임재영 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.3

Of the various parameters related to the hydrothermal method for growing ZnO nanorods, the pHof the aqueous solution has a pronounced effect on the growth rate, morphology, and photoresponseof the fabricated ZnO nanorods. Here, we investigated the effects of the pH of the aqueous solutionon the structural, optical, and photoresponse properties of hydrothermally grown ZnO nanorods. When the pH of the solution was kept at 8, the ZnO nanorods exhibited improved vertical orientation,a higher growth rate, and directional growth along the (002) plane confirmed by scanningelectron microscopy. In contrast, the growth rate of the ZnO nanorods grown at a pH of 10 waslower, as the ZnO nanorods were dissolved because of the presence of excessive OH− ions in thesolution. The ultraviolet (UV) sensor based on the ZnO nanorods grown at a pH of 8 showed higherphotoresponsivity as compared to those of the sensors based on the ZnO nanorods grown at pHvalues of 7, 9, and 10. Thus, the use of an aqueous solution with the optimal pH values (8 in thiscase) resulted in uniform ZnO nanorods, which could be employed to fabricate a high-performanceUV sensor suitable for use in practical applications.

Post-Annealing Effects on Properties of ZnO Nanorods Grown on Au Seed Layers

Cho, Min-Young,Kim, Min-Su,Choi, Hyun-Young,Yim, Kwang-Gug,Leem, Jae-Young Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.3

ZnO nanorods were grown by hydrothermal method. Two kinds of seed layers, Au film and island seed layers were prepared to investigate the effect of seed layer on ZnO nanorods. The ZnO nanorod on Au island seed layer has more unifom diameter and higher density compared to that of ZnO nanorod on Au film seed layer. The ZnO nanorods on Au island seed layer were annealed at various temperatures ranging from 300 to $850^{\circ}C$. The pinholes at the surface of the ZnO nanorods is formed as the annealing temperature is increased. It is noted that the pyramid structure on the surface of ZnO nanorod is observed at $850^{\circ}C$. The intensity of ZnO (002) diffraction peak in X-ray diffraction pattern and intensity of near band edge emission (NBE) peak in photoluminescence (PL) are increased as the ZnO nanorods were annealed at the temperature of $300^{\circ}C$.

Effect of Zinc Oxide Morphology on the Antimicrobial Activity and UV Absorbance of Nylon 6/Zinc Oxide Composite Filaments

정민기,임영민,손태원,오태환 한국섬유공학회 2019 Fibers and polymers Vol.20 No.8

Two zinc oxide (ZnO) morphologies, nanorods and nanoplates, were synthesized using solvothermal synthesis,and the effect of the ZnO morphologies on the UV absorbance and anitmicrobial activity of nylon 6/ZnO composite filamentswas investigated. The ZnO nanorods and nanoplates exhibited a hexagonal wurtzite crystal structure. The ZnO nanorodswere 50 nm in diameter and 300 nm in length, and the ZnO nanoplates were 150 nm in width and 25 nm in thickness. Photoluminescence (PL) measurements showed that the intensity of the deep level emission of the ZnO plates in the visiblelight range was lower than that of the ZnO nanorods, indicating that amount of surface defects on the ZnO nanoplates wasrelatively small compared that of the ZnO nanorods. The strong crystal diffraction peaks of the ZnO nanorods confirmed thatthey exhibited higher crystallinity than the ZnO nanoplates. Both the nylon 6/ZnO nanorod and nylon 6/ZnO nanoplatecomposite filaments showed very good antimicrobial activity even when only 0.5 wt% of ZnO particles was added. Thespecific surface area of the ZnO nanorods and nanoplates were 10.353 and 11.249 m2/g, respectively. UV protection of thenanoplates was higher than that of the nanorods. The larger specific surface area of the ZnO nanoplates led to higher UVabsorbance of the nylon 6/ZnO nanoplate composite filaments.

Fabrication of Porous ZnO Nanorods with Nano-sized Pores and Their Properties

전수민,이동율,김진수,김종수,이주인,김민수,조민영,최현영,임광국,김건식,김형근,임재영 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.6

Porous ZnO nanorods were fabricated by using an annealing process at 300, 500, and 700 ℃ for 20 min in an argon atmosphere. The structural and the optical properties of the porous ZnO nanorods were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The pore density of the porous ZnO nanorods decreased and the average diameter of the pores increased with increasing annealing temperature. The intensity of the ZnO (002) diffraction peak for the porous ZnO nanorods was stronger than that of the as-grown ZnO nanorod. The PL intensity ratio of the near-band-edge emission (NBE) to the deep-level emission (DLE) of the porous ZnO nanorods was larger than that of the as-grown ZnO nanorods. In addition, as the average diameter of the pores increased, the PL intensity ratio of the porous ZnO nanorods gradually increased.

Post-Annealing Effects on Properties of ZnO Nanorods Grown on Au Seed Layers

Min Young Cho,김민수,Hyun Young Choi,Kwang Gug Yim,임재영 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.3

ZnO nanorods were grown by hydrothermal method. Two kinds of seed layers, Au film and island seed layers were prepared to investigate the effect of seed layer on ZnO nanorods. The ZnO nanorod on Au island seed layer has more unifom diameter and higher density compared to that of ZnO nanorod on Au film seed layer. The ZnO nanorods on Au island seed layer were annealed at various temperatures ranging from 300 to 850 ^oC. The pinholes at the surface of the ZnO nanorods is formed as the annealing temperature is increased. It is noted that the pyramid structure on the surface of ZnO nanorod is observed at 850 ^oC. The intensity of ZnO (002)diffraction peak in X-ray diffraction pattern and intensity of near band edge emission (NBE) peak in photoluminescence (PL) are increased as the ZnO nanorods were annealed at the temperature of 300 ^oC.

Hydrothermally Grown Boron-Doped ZnO Nanorods for Various Applications: Structural, Optical, and Electrical Properties

김소아람,박형길,남기웅,윤현식,김병규,지익수,김영규,김익현,박영빈,Daeho Kang,임재영 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1

The structural, optical, and electrical properties of ZnO and BZO nanorods were investigated using fieldemission scanning electron microscopy, x-ray diffraction (XRD), photoluminescence (PL), and van der Pauw Hall-effect measurements. All the nanorods had grown well on the ZnO seed layers and were hexagonal. The BZO nanorods were shorter than the undoped ZnO nanorods, and the BZO nanorods grew shorter with increasing concentration of B to 2.0 at. % while the average length of the nanorods doped with 2.5 at. % B increased from 1620 to 1830 nm. The XRD patterns suggest that the amount of residual stress in the nanorods decreased with increasing concentration of B in the nanorods. The PL spectra showed near-bandedge and deep-level emissions, and B doping also varied the PL properties of the ZnO nanorods. The Halleffect data suggest that B doping also varied the electrical properties such as the carrier concentration, mobility, and resistivity of the ZnO nanorods.

Evaluation of the Mechanical Properties of ZnO Nanorods Treated with Oxygen Plasma using Atomic Force Microscopy

박동혁,양이준,김관래 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.3

Zinc oxide (ZnO) simultaneously exhibits semiconducting and piezoelectric properties. ZnO in the form of nanorods has been studied intensively for application in self-powering devices. The power generation in piezoelectric nanogenerators based on ZnO nanorods can be improved via several approaches, including an oxygen plasma treatment. When ZnO nanorods are exposed to oxygen plasma, the charge carrier concentration decreases and the piezoelectric output voltage consequently increases. However, the effects of oxygen plasma on the mechanical properties of ZnO nanorods has not been systematically studied using a precise measurement technique. Given the size of ZnO nanorods, atomic force microscopy (AFM) is a suitable method for manipulating individual ZnO nanorods and measuring their elastic properties. In the present work, we observed the effects of oxygen plasma on the elemental composition and microstructure of ZnO nanorods. First of all, the surface roughness of the ZnO nanorods was analyzed using AFM, revealing that it increased due to the etching effect of the oxygen plasma. From X-ray photoelectron spectroscopy (XPS) measurements, three distinct peaks corresponding to lattice oxygen, oxygen vacancies, and absorbed oxygen on the surface were identified. The XPS analysis results showed that oxygen vacancy defects on the ZnO nanorods were decreased by oxygen plasma treatment. Next, the effects of oxygen plasma on the elastic properties of ZnO nanorods were studied using lateral force microscopy. It was confirmed that the elastic modulus of ZnO nanorods increased due to the reduced number of defects originating from oxygen vacancies.

원자적층법을 이용한 공정 온도에 따른 Zinc Oxide Nanorod의 배열에 대한 연구

김경민(K. Kim),홍민표(M. P. Hong),송용남(Y. Song) Korean Society for Precision Engineering 2022 한국정밀공학회 학술발표대회 논문집 Vol.2022 No.5

저온수열합성방법에 의해 성장한 ZnO 나노로드의 전구체 몰농도 변화에 따른 특성 연구

문대화,하준석,Mun, D.H.,Ha, J.S. 한국마이크로전자및패키징학회 2013 마이크로전자 및 패키징학회지 Vol.20 No.1

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. 전구체의 농도가 ZnO 나노로드의 성장에 미치는 영향에 대하여 알아보았다. ZnO 나노로드는 수열합성법에 의하여 c-plane 사파이어 상에서 성장되었으며, 전구체 농도가 0.01M에서 0.025M로 증가할 때의 형태적, 구조적, 광학적 성질의 변화에 대하여 주사전자현미경, X-선 회절분석기, 그리고 Photoluminescence(PL) 분석을 통하여 알아보았다. 전구체의 몰 분율이 증가함에 따라서 나노로드의 두께와 길이가 모두 증가하는 경향을 보였으며, 성장 방향은 모두 c-axis 방향임을 알 수 있었다. PL 측정에서의 380 nm파장의 강한 emission으로부터, 수열합성법에 의하여 성장된 ZnO 나노로드는 결함의 영향이 적고 양호하게 성장되어 있음을 확인할 수 있었다.