Fabrication, Structural and Spectroscopic Studies of Wide Bandgap Semiconducting Nanoparticles of ZnO for Application as White Light Emitting Diodes PDF Download
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Author: Yu Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 139
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Book Description
Author: Yu Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 139
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Book Description
Author: Kai-Hang Tam
Publisher:
ISBN: 9781374667136
Category :
Languages : en
Pages :
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Book Description
This dissertation, "Zinc Oxide Nanorods: Hydrothermal Growth, Properties and Applications" by Kai-hang, Tam, 譚啟鏗, 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 ZINC OXIDE NANORODS: HYDROTHERMAL GROWTH, PROPERTIES AND APPLICATIONS Submitted by Tam Kai Hang for the degree of Master of Philosophy at The University of Hong Kong in December 2007 One-dimensional wide band-gap semiconductor nanostructures, such as nanorods, nanowires and nanobelts, have recently attracted much attention for their potential use as fundamental building blocks for new generation of electronic and photonic devices. Various semiconducting 1-D nanostructures have been synthesized, such as TiO, SnO, 2 2 GaN, GaAs, Si and ZnO. Among these nanostructures, zinc oxide (ZnO) has became particularly intersting in optoelectronic, field emission, gas sensing and biomedicine applications. ZnO is a wide band-gap (3.37 eV) semiconductor with high excitonic binding energy ( 60 meV), and it is non-toxic and environmentally friendly. Hydrothermal growth of ZnO provides an inexpensive method to fabricate large amounts of ZnO nanorods or nanowires on various substrates. However, the controversies still remain about the native defects in ZnO. In this work, ZnO nanorod arrays were fabricated by a hydrothermal method. The structural properties were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). Well-oriented nanorods, which exhibited strong defect-related photoluminescence (PL) were obtained. Stimulated UV emission was achieved in forming gas or oxygen annealed nanorods. Change in lasing threshold and defect emission, as well as spontaneous decay time, indicated that yellow defect emission was not caused by interstitial oxygen, which was commonly assumed to be dominant in the yellow emitted ZnO. The origins of defects emissions were investigated by x-ray photoelectron spectroscopy (XPS) and positron annihilation spectroscopy (PAS). The results showed that yellow emission of the as-grown nanorods originated from the presence of Zn(OH) on surface, while the green emission which appeared after annealing was due to the defect complex related to zinc vacancy. On the other hand, it was also observed that green emission originated from grain boundary in other ZnO nanostructures, such as nanoshells. The origin of the green emission has not yet been determined, but there was evidence that the emission was surface-related. Heterojunction of n-ZnO nanorod arrays / p-GaN film light-emitting-diodes (LEDs) were fabricated. Influence of annealing conditions on the performance of devices was examined. It was found that the position of recombination zone was shifted after annealing in some cases. Emission wavelength could be controlled through annealing processes. This study could help improve the performance of these heterojunction devices. In order to have more comprehensive studies on applications of these versatile ZnO nanorods, antibacterial properties of the nanorods were investigated. ZnO nanorods coating have exhibited great antibacterial activity. Other ZnO morphologies (nanoparticles and powder) were also studies for comparison. Mechanisms of ZnO against different bacteria were investigated. It was found that damaging of E. coli cell was partly due to the relaxation of hydrogen peroxide (H O ) from the structures. 2 2 DOI: 10.5353/th_b3955734 Subjects: Zinc oxide Nanostructures Nanotechnology
Author: Won Kook Choi
Publisher: Springer
ISBN: 9811009805
Category : Technology & Engineering
Languages : en
Pages : 84
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Book Description
This book offers a comprehensive overview of ZnO-nano carbon core shell hybrid issues. There is significant interest in metal oxide/nanocarbon hybrid functional materials in the field of energy conversion and storage as electrode materials for supercapacitors, Li ion secondary battery, electrocatalysts for water splitting, and optoelectronic devices such as light emitting diodes and solar photovoltaic cells. Despite efforts to manipulate more uniform metal oxide-nanocarbon nanocomposite structures, they have shown poor performance because they are randomly scattered and non-uniformly attached to the nanocarbon surface. For higher and more effective performance of the hybrid structure, 3D conformal coating on metal oxides are highly desirable. In the first part of the book, the physical and chemical properties of ZnO and nanocarbons and the state-of-the-art in related research are briefly summarized. In the next part, the 3D conformal coating synthetic processes of ZnO templated nanocarbon hybrid materials such as ZnO-graphene,-C60, single-walled (SWCNT) are introduced with the aid of schematic illustrations. Analysis of their chemical bonding and structure are also presented. In the final section, several applications are presented: UV photovoltaic cells and photoelectrochemical anodes for water splitting using ZnO-C60 and ZnO-graphene, white-light-emitting diodes based on ZnO-graphene quantum dots(GQDs), inverted solar cells using ligand-modified ZnO-graphene QDs, and P(VDF-TrFE) copolymer with mixed with nano-ring SWCNT. The book describes how strong anchoring bonds between a ZnO core and carbon nanomaterial shell will ultimately prevail over the main drawbacks of ZnO with high charge recombination and poor electrochemical stability in liquid solutions. Due to the moderate energy states and excellent electric properties of the nanocarbons, ultrafast charge carrier transport from the ZnO core to the nanocarbon shell is guaranteed with the use of the photoluminescence (PL) lifetime measurement. Given the growing interest and significance of future research in optoelectronic and electrochemical devices applications, the contents are very timely. This book is targeted towards researchers looking for highly efficient metal oxide-nanocarbon hybrid functional materials in the fields of nano-optoelectronics, photoelectrochemistry, energy storage and conversion.
Author: Yue Zhang (Materials scientist)
Publisher: Royal Society of Chemistry
ISBN: 1782627413
Category : Science
Languages : en
Pages : 307
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Book Description
As wide band semiconductors with rich morphologies and interesting electric, optical, mechanical and piezoelectric properties, ZnO nanostructures have great potential in applications, such as strain sensors, UV detectors, blue LED, nano generators, and biosensors. ZnO Nanostructures: Fabrication and Applications covers the controllable synthesis and property optimization of ZnO nanostructures through to the preparation and performance of nanodevices for various applications. The book also includes recent progress in property modulation of ZnO nanomaterials and new types of devices as well as the latest research on self-powered devices and performance modulation of ZnO nanodevices by multi-field coupled effects. Authored by a leading researcher working within the field, this volume is applicable for those working in nanostructure fabrication and device application in industry and academia and is appropriate from advanced undergraduate level upwards.
Author: Chi-man Luk
Publisher:
ISBN:
Category : Semiconductors
Languages : en
Pages : 190
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Book Description
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: , Prof. Dr. Ahmed Nahhas
Publisher: BoD – Books on Demand
ISBN: 1789239575
Category : Technology & Engineering
Languages : en
Pages : 148
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Book Description
This book presents a review of recent advances in ZnO-based nanomaterials and devices. ZnO as a nanomaterial has gained substantial interest in the research area of wide bandgap semiconductors and is considered to be one of the major candidates for electronic and photonic applications. ZnO has distinguished and interesting electrical and optical properties and is considered to be a potential material in optoelectronic applications such as solar cells, surface acoustic wave devices, and UV emitters. ZnO's unique properties have attracted several researchers to study its electrical and optical properties. As a nanostructured material, ZnO exhibits many advantages for nanodevices. Moreover, it has the ability to absorb the UV radiation.
Author: Gaurav Sharma
Publisher: Materials Research Forum LLC
ISBN: 1644902389
Category : Technology & Engineering
Languages : en
Pages : 333
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Book Description
ZnO and its hybrid nanostructures have unique optical, physical and chemical properties. The book covers recent trends in processing techniques and applications. Topics include solar cells, photo-voltaic devices, fuel cells, uv filters, lasers, light-emitting diodes, photo-detectors, spin-tronic devices, magnetic semiconductors, nano-generators, piezotronics, photo-catalytic applications against harmful organic pollutants like dyes, heavy metals, antibiotics, and sensors such as bio sensors, chemical sensors, gas sensors. Keywords: ZnO, Nano ZnO, Point Defects, Magnetic Semiconductors, Hybrid Nanostructures, Cell Applications, Nanoadsorbant for Heavy Metal Removals, Diagnostics, ZnO Nano-Carriers, ZnO Thin Films Fabrication.
Author: Hatim Alnoor
Publisher: Linköping University Electronic Press
ISBN: 9176854817
Category :
Languages : en
Pages : 96
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Book Description
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: Joseph Lionel Waters
Publisher:
ISBN:
Category :
Languages : en
Pages : 268
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Book Description
One of the main complications in the synthesis of Zinc oxide (ZnO) nanowires (NWs), is the ability to reproduce well aligned wires. ZnO was studied due to its optoelectronic applications. Its simple crystal growth abilities, lead to potentially lower cost for ZnO based devices. Other semiconductors such as MoS2 in bulk form contain an indirect bandgap of 1.2 eV. As layers are removed, the materials band gap undergoes a shift and switches from indirect to direct bandgap for a single monolayer. This monolayer of MoS2 contains a bandgap of 1.8 eV, therefore the goal was to synthesis single layer MoS2 on various substrates. In this doctoral research wide bandgap ZnO and emerging MoS2 were studied individually. These novel semiconductors were then fabricated together to form heterostructures to enhance the functionality of ZnO and MoS2 by covering the UV (380 nm) to the visible region (650 nm). ZnO powders were reduced by carbo-thermal reduction and grown onto sapphire substrates to act as a ZnO NW scaffold. The material properties such as the crystalline phase of the hexagonal wurtzite ZnO were examined by SEM, TEM and complemented by optical characterizations. X-ray photoelectron spectroscopy determined the chemical species and lack of impurities present in the NW. Local electrode atom probe analysis of the crystal stoichiometry and concentration gradient of oxygen content from the center of the NW to the edge wall. A single ZnO NW was removed from the surface and a Schottky diode device was fabricated to determine the effects of UV illumination. Defects at the edge of the wire can lead to external growth of MoS2 and good bonding at the interface of the heterostructure. The triangular formation, thickness and edge effects at the grain boundaries were studied by SEM and AFM. The two main phonon modes in MoS2 are used to determine the number of layers present by Raman spectroscopy. TEM led to determination of the 2H phase of MoS2. When the 1D-2D hybrid structure is fabricated regions of molybdenum and sulfur on the ZnO NW were mapped by EDS on a SEM and TEM.
Author: Zhe Chuan Feng
Publisher: CRC Press
ISBN: 1439855749
Category : Technology & Engineering
Languages : en
Pages : 565
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Book Description
Through their application in energy-efficient and environmentally friendly devices, zinc oxide (ZnO) and related classes of wide gap semiconductors, including GaN and SiC, are revolutionizing numerous areas, from lighting, energy conversion, photovoltaics, and communications to biotechnology, imaging, and medicine. With an emphasis on engineering and materials science, Handbook of Zinc Oxide and Related Materials provides a comprehensive, up-to-date review of various technological aspects of ZnO. Volume Two focuses on devices and nanostructures created from ZnO and similar materials. The book covers various nanostructures, synthesis/creation strategies, device behavior, and state-of-the-art applications in electronics and optoelectronics. It also provides useful information on the device and nanoscale process and examines the fabrication of LEDs, LDs, photodetectors, and nanodevices. Covering key properties and important technologies of ZnO-based devices and nanoengineering, the handbook highlights the potential of this wide gap semiconductor. It also illustrates the remaining challenging issues in nanomaterial preparation and device fabrication for R&D in the twenty-first century.
