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Growth of vertically aligned ZnO nanorods using textured ZnO films  [cached]
Solís-Pomar Francisco,Martínez Eduardo,Meléndrez Manuel,Pérez-Tijerina Eduardo
Nanoscale Research Letters , 2011,
Abstract: A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells. PACS 61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
Growth of Zinc Oxide (ZnO) Nanorods and Their Optical Properties  [cached]
L.M. AL-Harbi,E. H. El-Mossalamy,H.M. Arafa,A. Al-Owais
Modern Applied Science , 2011, DOI: 10.5539/mas.v5n2p87
Abstract: We herein, report growth of zinc oxide nanorods by a simple reaction of zinc powder and de-ionized water at very low temperature of ~ 110oC without using any organics. The formation of nanorods by the reaction of metals with water is suggested to occur due to the decomposition of water. The decomposed water produces controlled supply of OH- which further reacts with metal to form ZnO and releases hydrogen. The synthesized ZnO products were characterized in terms of their structural and optical properties. It was observed that the grown nanorods possess good optical property. Compared with other methods, the present method is simple, soft, inexpensive and environmentally benign which will make it suitable for large-scale production for devices and other applications.
Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles  [PDF]
Zafar Hussain Ibupoto,Kimleang Khun,Martin Eriksson,Mohammad AlSalhi,Muhammad Atif,Anees Ansari,Magnus Willander
Materials , 2013, DOI: 10.3390/ma6083584
Abstract: Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.
Structural and Morphology of ZnO Nanorods Synthesized Using ZnO Seeded Growth Hydrothermal Method and Its Properties as UV Sensing  [PDF]
Nur Syafinaz Ridhuan, Khairunisak Abdul Razak, Zainovia Lockman, Azlan Abdul Aziz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050405
Abstract: In this study, zinc oxide (ZnO) nanorod arrays were synthesized using a simple hydrothermal reaction on ZnO seeds/n-silicon substrate. Several parameters were studied, including the heat-treatment temperature to produce ZnO seeds, zinc nitrate concentration, pH of hydrothermal reaction solution, and hydrothermal reaction time. The optimum heat-treatment temperature to produce uniform nanosized ZnO seeds was 400°C. The nanorod dimensions depended on the hydrothermal reaction parameters. The optimum hydrothermal reaction parameters to produce blunt tip-like nanorods (770 nm long and 80 nm in top diameter) were 0.1 M zinc nitrate, pH 7, and 4 h of growth duration. Phase analysis studies showed that all ZnO nanorods exhibited a strong (002) peak. Thus, the ZnO nanorods grew in a c-axis preferred orientation. A strong ultraviolet (UV) emission peak was observed for ZnO nanorods grown under optimized parameters with a low, deep-level emission peak, which indicated high optical property and crystallinity of the nanorods. The produced ZnO nanorods were also tested for their UV-sensing properties. All samples responded to UV light but with different sensing characteristics. Such different responses could be attributed to the high surface-to-volume ratio of the nanorods that correlated with the final ZnO nanorods morphology formed at different synthesis parameters. The sample grown using optimum synthesis parameters showed the highest responsivity of 0.024 A/W for UV light at 375 nm under a 3 V bias.
Effects of Oxygen Source Ionization on the Growth and Properties of MOCVD ZnO Material
氧源的射频离化对ZnO MOCVD材料生长与性质的影响

Li Feng,Gu Shulin,Ye Jiandong,Zhu Shunming,Zhang Rong,Zheng Youdou,
李峰
,顾书林,叶建东,朱顺明,张荣,郑有炓

半导体学报 , 2007,
Abstract: ZnO thin films were deposited with low-pressure MOCVD at different substrate temperatures.The effects of oxygen source ionization on the growth and properties of MOCVD ZnO material were investigated.The crystal structure and surface morphology of ZnO films were characterized by X-ray diffraction and atomic force microscopy,respectively.Room temperature and low temperature photoluminescence were used to investigate the optical properties of ZnO.It was found that the ionization of the oxygen source has a marked influence on the growth rate,crystal orientation,surface morphology,and other properties
Growth of ZnO Nanorod Arrays on Flexible Substrates: Effect of Precursor Solution Concentration  [PDF]
Fei Tong,Kyusang Kim,Yaqi Wang,Resham Thapa,Yogesh Sharma,Aaron Modic,Ayayi Claude Ahyi,Tamara Issacs-Smith,John Williams,Hosang Ahn,Hyejin Park,Dong-Joo Kim,Sungkoo Lee,Eunhee Lim,Kyeong K. Lee,Minseo Park
ISRN Nanomaterials , 2012, DOI: 10.5402/2012/651468
Abstract: We report a low-temperature aqueous solution growth of uniformly aligned ZnO nanorod arrays on flexible substrates. The substrate is Indium Tin Oxide (ITO) film coated on polyethylene terephthalate (PET). Solutions with five different concentrations of the precursors with equimolar Zinc Nitrate and Hexamethylenetetramine (HMT) in distilled water were prepared to systematically study the effect of precursor solution concentration on the structural and optical properties of ZnO nanorods. It was concluded that the precursor concentration have great influence on the morphology, crystal quality, and optical property of ZnO nanorods. The diameter, density, and orientation of the nanorods are dependent on the precursor solution concentration. X-ray diffraction and micro-Raman spectroscopy showed that the ZnO nanorods with the highest concentration of 50?mM were highly aligned and have the highest level of surface coverage. It was also found that the diameter and length of the nanorods increases upon increasing precursor solution concentration. This is the first systematic investigation of studying the effect of precursor solution concentration on the quality of ZnO nanorods grown on ITO/PET substrates by low-temperature solution method. We believe that our work will contribute to the realization of flexible organic-inorganic hybrid solar cell based on ZnO nanorods and conjugated polymer. 1. Introduction Zinc oxide (ZnO) is a semiconductor with a wide direct band gap of 3.37?eV and a large exciton binding energy of 60?meV, which makes the material useful for optoelectronic application [1, 2]. Nanostructures of ZnO such as ZnO nanorods and nanowires have received increased attention due to their excellent electrical and optical properties [3]. Due to the high surface-to-volume ratio provided by the one-dimensional (1D) nanostructure, ZnO nanorod arrays are considered suitable to the application for hybrid photovoltaic devices [4–7]. In the past few years, ZnO nanorods have been synthesized via various physical and chemical methods including vapor phase synthesis [8–10], metalorganic chemical vapor deposition (MOCVD) [11–13], and solution-based synthesis [14–17]. Among these routes, solution-based method has the advantages of simplicity, low costs, low growth temperature, and easy coating of large surfaces Intensive research has been focused on the solution growth process of ZnO nanorods on ITO-coated glass substrates. Guo et al. [18] have systematically studied the effect of processing conditions such as pretreatment of the substrates, growth temperature,
Growth and Structure of ZnO Nanorods on a Sub-Micrometer Glass Pipette and Their Application as Intracellular Potentiometric Selective Ion Sensors  [PDF]
Muhammad H. Asif,Omer Nur,Magnus Willander,Peter Str?lfors,Cecilia Br?nnmark,Fredrik Elinder,Ulrika H. Englund,Jun Lu,Lars Hultman
Materials , 2010, DOI: 10.3390/ma3094657
Abstract: This paper presents the growth and structure of ZnO nanorods on a sub-micrometer glass pipette and their application as an intracellular selective ion sensor. Highly oriented, vertical and aligned ZnO nanorods were grown on the tip of a borosilicate glass capillary (0.7 μm in diameter) by the low temperature aqueous chemical growth (ACG) technique. The relatively large surface-to-volume ratio of ZnO nanorods makes them attractive for electrochemical sensing. Transmission electron microscopy studies show that ZnO nanorods are single crystals and grow along the crystal’s c-axis. The ZnO nanorods were functionalized with a polymeric membrane for selective intracellular measurements of Na +. The membrane-coated ZnO nanorods exhibited a Na +-dependent electrochemical potential difference versus an Ag/AgCl reference micro-electrode within a wide concentration range from 0.5 mM to 100 mM. The fabrication of functionalized ZnO nanorods paves the way to sense a wide range of biochemical species at the intracellular level.
Effect of Different Seed Solutions on the Morphology and Electrooptical Properties of ZnO Nanorods  [PDF]
M. Kashif,U. Hashim,M. E. Ali,Syed M. Usman Ali,M. Rusop,Z. H. Ibupoto,Magnus Willander
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/452407
Abstract: The morphology and electrooptical properties of ZnO nanorods synthesized on monoethanolamine-based seed layer and KOH-based seed layer were compared. The seed solutions were prepared in monoethanolamine in 2-methoxyethanol and potassium hydroxide in methanol, respectively. Zinc acetate dihydrate was as a common precursor in both solutions. The nanorod-ZnOs were synthesized via the spin coating of two different seed solutions on silicon substrates followed by their hydrothermal growth. The scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Raman studies revealed that the ZnO nanorods obtained from monoethanolamine-based seed layer had fewer defects, better crystals, and better alignment than those realized via KOH-based seed layer. However, the current-voltage (I-V) characteristics demonstrated better conductivity of the ZnO nanorods obtained via KOH-based seed layer. The current measured in forward bias was 4?mA and 40?μA for ZnO-nanorods grown on KOH-based seed layer and monoethanolamine-based with the turn on voltage of approximately 1.5?V and 2.5?V, respectively, showing the feasibility of using both structures in optoelectric devices. 1. Introduction Zinc oxide (ZnO) which belongs to II–IV group of semiconducting materials is increasingly getting more and more research interests because of its attractive and fascinating properties such as approximately 3.37?eV of direct wide bandgap and about 60?meV of exciton binding energy. In fact, these properties are suitable for numerous applications in optoelectronic and biomedical devices. For examples micro- and nanostructures ZnO were successfully used in various sensing appliances such as UV sensors, biosensors (protein, DNA, and cancer cell detection) as well as gas sensors [1–5]. In the last few decades, ZnO-nanostructures with many fascinating forms such as nanorods, nano-flakes, nanorings, and nanoribbons, were synthesized [6–9]. To obtain these structures, various methods such as MOCVD, sol-gel, molecular beam epitaxy, thermal evaporation, and site-selective deposition techniques were documented [10–16]. Among these techniques, sol-gel methods have got huge interests because of their reduced growth temperature, reduced cost, and superior simplicity. However, a comparative study of ZnO nanorods synthesized on monoethanolamine-based seed layer and KOH-based seed layer using sol-gel method to realize nanorod-ZnOs has yet to be systematically reported. In this study, nanorod-ZnOs were synthesized on two different seeded substrates and their morphological,
Synthesis and Luminescent Properties of Planar-tip and Tapered-tip ZnO Nanorod Arrays

Chun-wen WANG,Jr-hau HE,Lih-juann CHEN,

材料科学技术学报 , 2008,
Abstract: Vertically aligned ZnO nanorods were synthesized on a-plane sapphire via a metal catalyzed vapor phase transport and condensation process in a two-zone vacuum furnace. Planar-tip and tapered-tip ZnO nanorods were successfully synthesized by utilizing different source materials under the same growth conditions. The growth mechanisms were proposed to be vapor-liquid-solid (VLS) process for planar-tip ZnO nanorods and a combination of VLS and self-catalyzed processes for tapered-tip ZnO nanorods. From cathodoluminescence (CL) measurements, tapered-tip ZnO nanorods have more intense green emission than planar-tip ZnO nanorods, and therefore possess higher oxygen vacancy concentration than planar-tip ZnO nanorods. From CL characteristics, well-aligned planar-tip ZnO nanorods shall serve effectively as laser source, while well-aligned tapered-tip ZnO nanorods are suitable for direction-related optical applications.
Growth and Photoluminescence of ZnO and Zn1-xMgxO Nanorods by High-pressure Pusled Laser Deposition  [PDF]
ZHANG Peng, WANG Pei-Ji, CAO Bing-Qiang
无机材料学报 , 2012, DOI: 10.3724/sp.j.1077.2012.12015
Abstract: The influence of the experimental parameters such as temperature, target, and thickness of catalyst layer on the growth of nanorods were systemically studied by a newly designed and home-built high-pressure pulsed laser deposition Zn1-xMgxO (PLD). The growth mechanism and photoluminescence properties of ZnO and Zn1-xMgxO nanorods were also investigated. It was found that c-orientated ZnO nanorod arrays grown on silicon substrate were obtained when the growth temperature was 925 nd the thickness of gold catalyst layer was 2 nm. It was also proved that growth temperature and catalyst layer thickness were both crucial for the diameter and growth density of ZnO nanorods. A combination of vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism was proposed to describe the growth of ZnO nanorods by high-pressure PLD. Zn1-xMgxO nanorods and nanobelts with random orientation were grown by doping the ZnO target with MgO. The bandgap of ZnO was effectively expanded together with defect-related levels formation in the forbidden gap, which also induced enhancement of visible peak emission.
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