Fabrication and Characterization of ZnO Nanorods Based Intrinsic White Light Emitting Diodes (LEDs) PDF Download
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Author: Nargis Bano
Publisher:
ISBN: 9789173930543
Category :
Languages : en
Pages : 68
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Author: Nargis Bano
Publisher:
ISBN: 9789173930543
Category :
Languages : en
Pages : 68
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Author: Chi-man Luk
Publisher:
ISBN:
Category : Semiconductors
Languages : en
Pages : 190
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With the optimized growth parameters, n-ZnO:Al/i-ZnO/p-GaN:Mg heterojunction LEDs were fabricated. The electrical characteristics of the diodes were investigated. The ultraviolet (UV) electroluminescence (EL) from the device was detected at room temperature. The emission is attributed to the electron-hole radiative recombination in the ZnO region and is explained in detail by an energy band diagram. ZnO nanostructures are expected to have improved optical and electronic properties because of the quantum confinement effect. Using low-temperature aqueous chemical method, the ZnO nanorods arrays were grown on the buffer layers prepared at various temperatures. The nanorods were grown along [0001] direction. The PL measurement indicated that the emission spectrum covered a UV peak at ~ 380 nm and a broad visible band at ~ 560 nm. The PL spectra of the ZnO nanorods are independent on the growth temperature of the buffer layer. Moreover, the buffer-layer-thickness-dependent structural and optical properties were studied. The as-grown ZnO nanorods were utilized to fabricate hybrid LED with an organic semiconductor, N, N'-diphenyl-N, N'-bis(1-naphthyl)-1, 1'-biphenyl-4, 4'-diamine (?NPD), which is one of the most widely used hole transport and blue-emitting organic semiconductors. Current-voltage characteristics of the devices exhibited nonlinear rectifying behaviour. The EL spectra of the hybrid LEDs reveal a blue and broad yellowish green emission originated from the?NPD layer and the defect levels of the ZnO respectively. The origin of the emission bands from the hybrid structures will be examined.
Author: Leelaprasanna Mandalapu Jayaramulu
Publisher:
ISBN:
Category : Optoelectronic devices
Languages : en
Pages : 314
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Author: Abdul Samad Syed
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659189814
Category :
Languages : en
Pages : 84
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Book Description
Fabrication of efficient Ultraviolet Light Emitting Diodes (UV LEDs) is a challenging task for the semiconductor industry of the modern times. Finding the suitable semiconducting material is the key in order to make efficient LEDs. This book aims at understanding the use of ZnO in UV LEDs that demands the understanding of its optical properties first. Structural and optical properties of any semiconducting material are strongly correlated. An adequate knowledge and understanding of this relationship is necessary for fabrication of devices with desired optical properties. The aim of this work was to investigate the change in optical properties caused by growth techniques and substrate modification. To study the influence of growth technique on optical properties, ZnO nanostructures were grown using atmospheric pressure metal organic chemical vapor deposition (APMOCVD) and chemical bath deposition (CBD) techniques. Off-cut angle of SiC substrates were modified to observe the change on the optical properties. The results that are obtained demonstrate a significant contribution in the fields of ZnO based nano-optoelectronics and nano-electronics.
Author: Hatim Alnoor
Publisher: Linköping University Electronic Press
ISBN: 9176854817
Category :
Languages : en
Pages : 96
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One-dimensional (1D) nanostructures (NSs) of Zinc Oxide (ZnO) such as nanorods (NRs) have recently attracted considerable research attention due to their potential for the development of optoelectronic devices such as ultraviolet (UV) photodetectors and light-emitting diodes (LEDs). The potential of ZnO NRs in all these applications, however, would require synthesis of high crystal quality ZnO NRs with precise control over the optical and electronic properties. It is known that the optical and electronic properties of ZnO NRs are mostly influenced by the presence of native (intrinsic) and impurities (extrinsic) defects. Therefore, understanding the nature of these intrinsic and extrinsic defects and their spatial distribution is critical for optimizing the optical and electronic properties of ZnO NRs. However, identifying the origin of such defects is a complicated matter, especially for NSs, where the information on anisotropy is usually lost due to the lack of coherent orientation. Thus, the aim of this thesis is towards the optimization of the lowtemperature solution-based synthesis of ZnO NRs for device applications. In this connection, we first started with investigating the effect of the precursor solution stirring durations on the deep level defects concentration and their spatial distribution along the ZnO NRs. Then, by choosing the optimal stirring time, we studied the influence of ZnO seeding layer precursor’s types, and its molar ratios on the density of interface defects. The findings of these investigations were used to demonstrate ZnO NRs-based heterojunction LEDs. The ability to tune the point defects along the NRs enabled us further to incorporate cobalt (Co) ions into the ZnO NRs crystal lattice, where these ions could occupy the vacancies or interstitial defects through substitutional or interstitial doping. Following this, high crystal quality vertically welloriented ZnO NRs have been demonstrated by incorporating a small amount of Co into the ZnO crystal lattice. Finally, the influence of Co ions incorporation on the reduction of core-defects (CDs) in ZnO NRs was systematically examined using electron paramagnetic resonance (EPR).
Author: Yu Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 139
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Author: Saima Zaman
Publisher:
ISBN: 9789175198187
Category :
Languages : en
Pages : 59
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Research on nanomaterials has become increasingly popular because of their unique physical, chemical, optical and catalytic properties compared to their bulk counterparts. Therefore, many efforts have been made to synthesize multidimensional nanostructures for new and efficient nanodevices. Among those materials, zinc oxide (ZnO), has gained substantial attention owing to many outstanding properties. ZnO besides its wide bandgap of 3.34 eV exhibits a relatively large exciton binding energy (60 meV) at room temperature which is attractive for optoelectronic applications. Likewise, cupric oxide (CuO), having a narrow band gap of 1.2 eV and a variety of chemo-physical properties that are attractive in many fields. Moreover, composite nanostructures of these two oxides (CuO/ZnO) may pave the way for various new applications.??This thesis can be divided into three parts concerning the synthesis, characterization and applications of ZnO, CuO and their composite nanostructures.??In the first part the synthesis, characterization and the fabrication of ZnO nanorods based hybrid light emitting diodes (LEDs) are discussed. The low temperature chemical growth method was used to synthesize ZnO nanorods on different substrates, specifically on flexible non-crystalline substrates. Hybrid LEDs based on ZnO nanorods combined with p-type polymers were fabricated at low temperature to examine the advantage of both materials. A single and blended light emissive polymers layer was studied for controlling the quality of the emitted white light.??The second part deals with the synthesis of CuO nanostructures (NSs) which were then used to fabricate pH sensors and exploit these NSs as a catalyst for degradation of organic dyes. The fabricated pH sensor exhibited a linear response and good potential stability. Furthermore, the catalytic properties of petals and flowers like CuO NSs in the degradation of organic dyes were studied. The results showed that the catalytic reactivity of the CuO is strongly depending on its shape.??In the third part, an attempt to combine the advantages of both ZnO and CuO NSs was performed by developing a two-step chemical growth method to synthesize the composite NSs. The synthesized CuO/ZnO composite NSs revealed an extended light absorption and enhanced defect related visible emission.
Author: Augustine Che Mofor
Publisher: Cuvillier Verlag
ISBN: 3736922868
Category : Technology & Engineering
Languages : en
Pages : 138
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Book Description
Since ZnO resurfaced as a very promising semiconductor material for applications in microelectronics, optoelectronics, sensor technology, biomedicine and spin electronics, producing high purity ZnO nanostructures for such applications has rather proven to be challenging. This book first revises the main properties of ZnO as a semiconductor and nanomaterial and also some fabrication techniques for nanostructures. It later concentrates on the development of a vapour transport system for the growth of high quality ZnO nanostructures (mainly nanorods). The book attempts to explain the influence of reactor pressure, growth temperature and growth time on the morphology and quality of ZnO nanorods. While intrinsic (undoped) ZnO nanorods were grown for extensive analysis, transition metal-doped ZnO nanorods were also fabricated and investigated for possible applications in magnetoelectronics/spintronics. Conventional material characterisation methods are also revisited and employed to analyse the crystalline quality, optical, electrical and magnetic properties of ZnO nanorods. Since the book is writtenin an application-oriented fashion, it extends to the fabrication of ZnO nanrorod-based device structures. Here, nano p-n junctions and nano ZnO/ZnMgO quantum well structures are also presented. At the end, the reader clearly sees how ZnO nanorods of extremely high crystalline quality can be grown using an unconventional technique.
Author: Yu-Hang Leung
Publisher: Open Dissertation Press
ISBN: 9781361417188
Category :
Languages : en
Pages :
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This dissertation, "Fabrication and Characterization of Zinc Oxide (ZnO) Nanostructures" by Yu-hang, Leung, 梁宇恆, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled FABRICATION AND CHARACTERIZATION OF ZINC OXIDE (ZnO) NANOSTRUCTURES Submitted by Leung Yu Hang For the degree of Master of Philosophy at The University of Hong Kong in January 2006 Since the discovery of carbon nanotubes by Iijima in 1991, increasing research effort has been devoted to the synthesis and characterization of nanostructured materials. Materials at this scale exhibit novel properties which cannot be found in their bulk form. In silicon nanowires, for example, the bandgap of Si nanowires increases from 1.1 eV to 3.7 eV when the nanowire diameter decreases from 7 nm to 1.3 nm. In recent years, nanostructures of various semiconductors like Si, gallium arsenide, gallium nitride, and zinc oxide have been demonstrated. Among them, ZnO has been recognized as a promising material for a variety of applications in the field of photonics, optoelectronics, gas sensing, field emission, and piezoelectrics. To realize the incorporation of ZnO nanostructures into real life applications, lots of work need to be done, including synthesis of the nanostructures, and understanding of their properties. In this study, a number of ZnO nanostructures (tetrapods, nanorods, nanoribbons/combs, multipods) were fabricated by thermal evaporation and hydrothermal synthesis methods. The morphologies and, structural and optical properties of the resultant nanostructures were then characterized by various techniques, such as scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy, X-ray diffractometry, photoluminescence and electron paramagnetic resonance. It was observed that fabrication conditions could significantly affect the properties of the nanostructures. All nanostructures exhibited one UV peak and one broad peak in the visible spectrum. The major difference is that the nanostructures fabricated by thermal evaporation exhibited green PL emission while the nanorods synthesized by hydrothermal method gave yellow emission. Green emission was observed even without the presence of the EPR signal at g 1.96 in some samples. This result contradicts the commonly cited oxygen vacancy hypothesis of green emission of ZnO. Obviously, that hypothesis does not apply to all ZnO samples. The nanorod sample with yellow emission also exhibited strong EPR signal similar to the green emitting sample. A possible explanation for the obtained results is that there are two different deep levels responsible for the green and yellow emission respectively. Stimulated UV emission of three different nanostructures (tetrapods, nanoribbons/combs, and nanorods) was studied by time-resolved photoluminescence (TRPL). It was observed that different nanostructures exhibited different lasing thresholds, emission delay times and decay times. The difference in the lasing behaviors of the nanostructures is likely due to the difference in morphology, mode of cavity, or even native defects present in the material. DOI: 10.5353/th_b3617532 Subjects: Nanostructures Zinc oxide
Author: Marco Mazzeo (t.d.-)
Publisher:
ISBN:
Category :
Languages : en
Pages :
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