Download or read book Fundamental Understanding of the Growth Doping and Characterization of Aligned ZNO Nanowires written by Gang Shen and published by . This book was released on 2014 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc oxide (ZnO) is a II-VI semiconductor whose wide direct bandgap (3.37 eV) and large exciton binding energy (60 meV) make it compelling for optoelectronic devices such as light emitting diodes, lasers, photodetectors, solar cells, and mechanical energy harvesting devices. One dimensional structures of ZnO (nanowires) have become significant due to their unique physical properties arising from quantum confinement, and they are ideal for studying transport mechanisms in one-dimensional systems. In this doctoral research work, ZnO nanowire (NW) arrays were synthesized on sapphire substrates through carbo-thermal reduction of ZnO powders, and the effects of growth parameters on the properties of ZnO NW arrays were studied by scanning and transmission electron microscopy, X-ray diffraction, photoluminescence and Raman spectroscopy. Based on the phonon mode selection rules in wurtzite ZnO, confocal Raman spectroscopy was used to assess the alignment of ZnO NWs in an array, thereby complementing X-ray diffraction. Al doped ZnO NW arrays were achieved by mixing Al powder into the ZnO and graphite source mixture, and the presence of Al was confirmed by Energy-dispersive X-ray spectroscopy. The incorporation of Al had the effects of lowering the electrical resistivity, slightly deteriorating crystal quality and suppressing defect related green emission. Two models of ZnO NW growth were developed by establishing the relationship between NW length and diameter for undoped and Al doped ZnO NWs separately. The growth of undoped ZnO NWs followed the diffusion-induced model which was characterized by thin wires being longer than thick wires, while the growth of Al doped ZnO was controlled by Gibbs-Thomson effect which was characterized by thin wires being shorter than thin wires. Local electrode atom probe analysis of ZnO NWs was carried out to study the crystal stoichiometry and Al incorporation. Undoped ZnO NWs were found to be high purity with no detectable impurities. Possible Al incorporation related peaks were observed in the mass spectrum of Al doped ZnO NWs. Further work on Al doped ZnO LEAP analysis is needed to better understand the Al dopant.

Download or read book Growth and Characterization of ZnO Nanowires written by Dong Sik Kim and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fundamental aspects of growth and physical characteristic of the ZnO in the form of one-dimensional nanostructures are studied. In Au-assisted ZnO nanowire growth, Au nanoparticles are sometimes observed at the root of wires after growth and in other cases at the tip of the wires. A selection mechanism is proposed defining whether the Au particle remains on the substrate at the root of the nanowire serving as an initial template for wire nucleation or is lifted up from the substrate, catalyzing wire growth at the tip. In addition, it is demonstrated that the surface migration of Au atoms on a lattice matched substrate limits the position-controlled growth of ZnO nanowires. Based on the understanding of such nanowire growth behavior epitaxial grown ZnO nanowire arrays on GaN substrates are demonstrated which is important for device applications. By the use of laser interference lithography for patterning of Au nanodots, well arranged ZnO nanowires over larger area are fabricated. Since device applications based on ZnO nanowires require reliable p-type ZnO materials attempts to grow phosphorus-doped nanowires are made based on a single source precursor, Zn2P3. Single-crystalline phosphorus-doped ZnO nanowires are produced in a reproducible way. Low temperature PL spectra show that the presence of phosphorus strongly enhances a peak at 3.316 eV. However, the amphoteric nature of compensating native defects makes it difficult to realize stable and reliable p-type doping in ZnO nanowires. ZnO shows n-type conductivity without any intentional doping due to intrinsic native point defects. The influence of the relative content of residual oxygen during wire growth on the physical properties of the nanowire is studied by means of electrical transport as well as by photoluminescence. It is disclosed that the relatively high density of n-type defect density is observed in the ZnO nanowires grown under comparably oxygen poor conditions, which is attributed to the low formation energy of oxygen vacancies. Furthermore the relative free carrier densities are roughly estimated based on the intensity ratio between the surface exciton (SX) emission and the bound exciton emission.

Download or read book Growth Doping and Characterization of ZnO Nanowires written by Svetlana Spitsina and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Nanoelectrochemistry written by Mahmood Aliofkhazraei and published by Springer. This book was released on 2015-11-03 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This edited book is devoted to different electrochemical aspects of nano materials. This comprehensive reference text is basically divided in 3 parts: electrochemical synthesis routes for nanosized materials, electrochemical properties of nano materials and electrochemical characterization methods for nanostructures. The Handbook is a reference work to chemists and materials scientists interested in the nano aspects of electrochemistry. The chapters are written by a number of international experts in the field and the content will assist members of both electrochemical and materials communities to keep abreast of developments in the field.

Download or read book Hydrothermal Synthesis of Al doped ZnO Nanowires and Their Application for Photovoltaic Devices written by Hyoungwon Park and published by . This book was released on 2014 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor nanostructures exhibit distinct properties by virtue of nano-scale dimensionality, resulting in recent interest in semiconducting nanowires for electronic, photonic, and energy applications. Along with nanowires, quantum dots are solution-processable nanocrystals with tunable band gap energies as a function of their size. Based on all of these promising properties that nanostructures exhibit, nanowires and quantum dots are excellent candidates for next-generation optoelectronic devices, including solar cells and light-emitting diodes. However, the realization of nanostructured materials for solar cell device applications is limited by the fundamental trade-off between light absorption and photocarrier collection. Vertically aligned ZnO nanowire arrays can decouple absorption and collection by acting as highly-conductive channels for extracting photogenerated electrons from deep within the film. This thesis illustrates a scheme for the development of ordered bulk heterojunction photovoltaic devices incorporating solution-based n-type doped ZnO nanowires and PbS quantum dots. In order to improve the electrical properties of ZnO nanowires, Al doping of hydrothermally synthesized ZnO nanowires is studied along with the optimization of doping concentration. The morphology of ZnO nanowire arrays is also studied as a function of the doping concentration in the growth solution. Finally, photovoltaic devices are fabricated and the effect of Al-doping of ZnO nanowires is investigated by device characterization techniques.

Download or read book Electrochemical Growth and Characterization of ZnO Nanowires written by Lilei Hu and published by . This book was released on 2014 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO semiconductor materials, especially nanostructured materials, have potential applications in large-area electronics, photonics and optoelectronics due to their unique electrical and optical properties. ZnO nanowires have advantages of high surface area to volume ratio, with the prospective for nanoscale control of doping the electrical properties for 1-D nanoelectronic devices. Many techniques have been tried to achieve high quality ZnO nanowires in large scale with low cost and simple fabrication. However, most of these techniques require high temperatures that exclude applications in flexible electronics. P-type conductivity is another impediment for fully realizing ZnO materials for electronic device application; and this limitation has prevented advances in optoelectronic and integrated circuit applications for ZnO. To overcome the problems, this study investigated the synthesis and doping of ZnO nanowires at low temperature through a rapid electrochemical deposition growth technique. Material properties were studied using scanning electron microscopy (SEM), photoluminescence spectroscopy (PL), Raman spectroscopy, X-ray diffraction (XRD), ultraviolet to visible (UV-Vis) transmission spectroscopy, and electrical current-voltage measurements. ZnO nanowire doping was investigated using Al for n-type doping and for p-type doping, Ag/Al (co-doping) and Li. Al and Ag have significant influences on ZnO nanowire structures, while Li was found to improve the nanowire structure quality. The mechanisms for electrochemical deposition were studied through characterization of the chemical reactions, interface science and semiconductor/solution interface. It was found that the low temperature grown nanowires had high oxygen vacancy condition induced donor defect states, while, incorporation of Li dopants contributed to trap states (deep acceptor states), rather than shallow acceptor states in the band gap. Shown by XRD and PL, oxygen assisted post-growth annealing was found to promote recrystallization of ZnO and elimination of oxygen vacancies for better crystal quality and photoluminescence emission. Cr, Al or Au metals were used as contacts to Li-doped ZnO nanowires to examine electrical properties of the doped nanowires, turning out high ideal factor were obtained because of the poor contact quality due to significant surface and interface states in ZnO nanowires. At last, mechanisms of surface states related tunneling current at the metal-semiconductor interface were discussed.

Download or read book Zinc Oxide Nanowire Array based Optoelectronic Devices written by Guoping Wang and published by . This book was released on 2011 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO nanowire array-based optoelectronic devices are discussed in this dissertation. ZnO has a wide band gap of 3.37 eV and a large exciton binding energy of 60 meV at room temperature, which make it a promising candidate for optoelectronic devices such as blue-light emitting diodes, ultraviolet laser diodes and photodiodes. Recently, there have been tremendous interests in ZnO nanowire arrays. It is well known that one of the biggest challenges toward good ZnO-based optoelectronic devices is the difficulty of reliably fabricating p-type ZnO due to the self-compensating effect from native defects (for example, oxygen vacancy V o and zinc interstitial Zni) and/or H incorporation. There has already been a great deal of efforts on the fabrication of p-type ZnO films by doping group I (Na, Ag) and group V elements (N, P, As, Sb) as p-type dopants. In contrast, there have been only a few reports on p-type ZnO nanowires (doped with N, P and Na). Recently, researchers are interested in developing optoelectronic devices based on ZnO nanowires such as biosensors, ultraviolet detectors, ultraviolet light emitting diodes and electrically driven nanowire lasers. The growth of p-type ZnO nanowires with good stability will be an essential step for the applications of nanowires in nanoelectronics and optoelectronics. In this dissertation, first, n-type ZnO nanowire array and its application have been discussed. ZnO has very high electronic carrier mobility and electron affinity, making it a very possible candidate as an effective dye-sensitized solar cell (DSSC) semiconductor. The great properties of vertically aligned ZnO-nanowire array, such as large surface area and fast electron-transport rate, make it a very promising option for the photoanode of DSSCs. Nanowires provide electrons injected from optically excited dye a direct effective path to collecting electrode via the semiconductor conduction band, offering the potential for much faster charge transport than nanoparticle cells. In order to make homojunctional devices based on ZnO nanowire, a great deal of efforts has been made on the growth of p-type ZnO nanowire. Ag, a group Ib element, was predicted to be an acceptor in ZnO when incorporated into substitutional Zn sites and researchers experimentally demonstrated reliable fabrication of p-type ZnO thin films doped with Ag on sapphire substrate and also demonstrated the possibility of achieving Ag-doped p-type ZnO nanowires. Also Sb as an effective dopant for reproducible p-type ZnO thin films has been shown in our group. In chapter 3 of this dissertation, the synthesis and characterization of single-crystalline Ag-doped p-type ZnO nanowires and also Sb-doped p-type ZnO nanowire arrays have been discussed. In chapter 4 of this dissertation, ZnO homojunction photodiodes based on Sb-doped p-type nanowire array have been discussed. In chapter 5 of this dissertation, LED devices based on Sb-doped p-type nanowire array have been discussed. In chapter 6 of this dissertation, electrically pumped ZnO nanowirewaveguided lasing based on Sb-doped p-type nanowire array has been discussed. In chapter 7, the gain calculation for ZnO has been made and a brief discussion about the comparison between the calculation results and the experimental results has also been made. In chapter 8, Lists of conclusions are made for this dissertation.

Download or read book Growth and Characterization of ZnO Nanowires and Thin Films written by Young-Woo Heo and published by . This book was released on 2003 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanoscopic ZnO Growth Doping and Characterization written by and published by . This book was released on 2007 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors have demonstrated the aqueous growth of ZnO nanorods on a wide variety of substrates, including Au, Al, Si, Pt, Ag, ITO, and silica. The rate of nucleation and the form of the crystals depends slightly upon the substrate. Additives can dramatically change growth behavior. The nanorods grow in the (1000) direction and are 0.1-10?m long. Short, squat rods are appropriate as MEMS actuators, and the authors are acquiring a nanoindenter to characterize their piezo-electric properties. Long, thin rods may be used as photovoltaic antennae, sensors, or field-effect transistors. They are in the process of testing the conductivity of these crystals by placing the crystal across a metallization pattern and contacting it. The metallization pattern provides the capability of making four-point contact. Integrity is ensured by the deposition of Pt using a focused ion beam. The surface of the ZnO will be passivated with Si3N4 and SiO2.

Download or read book Optical Characterization of Doped Zinc Oxide Nanowires written by Faezeh Mohammadbeigi and published by . This book was released on 2017 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO is a promising semiconductor material with a direct band gap energy of 3.3 eV which makes it a good candidate for UV and visible range light emitting devices. Metalorganic chemical vapour epitaxy (MOVPE) provides the possibility of industrial scale growth of ZnO, with very fine control of impurity dopants. Despite the vast recent literature on ZnO, there are very few studies of systematic intentional doping. ZnO nanowires (NWs) can be grown easily on various substrates with high crystalline quality and low defect densities and tend to exhibit reduced substrate induced strain. This enables us to perform careful spectroscopic analysis of impurity related optical transitions and identify the physical nature of various dopant species. A detailed study of low temperature photoluminescence (PL) transitions in doped ZnO NWs, thin films, and bulk crystals grown by MOVPE and chemical vapour transport (CVT) methods is presented. The standard group III donors were first investigated. Donor bound exciton (D0X) transitions previously assigned to Ga, Al, and In were confirmed in intentionally doped samples. Group IV dopants such as carbon, and tin are interesting since they can act in principle as double donors or double acceptors. We report four new shallow D0X transitions (Z-lines), at 3360.8 (Z1), 3361.2 (Z2), 3361.7 (Z3) and 3361.9 (Z4) meV, which can be greatly enhanced by co-doping with carbon tetrachloride and hydrogen. These shallow donors appear to be due to carbon impurities complexed with other unknown defects in four distinct configurations. Carbon-doped samples also exhibit two distinct acceptors with binding energies of 133 ± 5 and 181 ± 5 meV. Doping concentration and temperature dependent PL studies of unintentionally doped and Sn-doped ZnO single crystals confirmed emission from the I10 D0X transition which was recently proven to contain Sn on a Zn site. Sb-doped ZnO NWs were grown in an attempt to produce p-type material as reported by some groups. Our PL studies including Magneto PL, have shown that rather than p-doped material, the addition of small amounts of Sb-dopant resulted in a new PL transition at 3364.3 meV, which turns out to be the shallowest D0X transition so far observed in ZnO.

Download or read book Zinc Oxide written by Hadis Morkoç and published by Wiley-VCH. This book was released on 2009-02-17 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first systematic, authoritative and thorough treatment in one comprehensive volume presents the fundamentals and technologies of the topic, elucidating all aspects of ZnO materials and devices. Following an introduction, the authors look at the general properties of ZnO, as well as its growth, optical processes, doping and ZnO-based dilute magnetic semiconductors. Concluding sections treat bandgap engineering, processing and ZnO nanostructures and nanodevices. Of interest to device engineers, physicists, and semiconductor and solid state scientists in general.

Download or read book Nanowires written by Simas Rackauskas and published by BoD – Books on Demand. This book was released on 2019-04-10 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanowires are attracting wide scientific interest due to the unique properties associated with their one-dimensional geometry. Developments in the understanding of the fundamental principles of the nanowire growth mechanisms and mastering functionalization provide tools to control crystal structure, morphology, and the interactions at the material interface, and create characteristics that are superior to those of planar geometries. This book provides a comprehensive overview of the most important developments in the field of nanowires, starting from their synthesis, discussing properties, and finalizing with nanowire applications. The book consists of two parts: the first is devoted to the synthesis of nanowires and characterization, and the second investigates the properties of nanowires and their applications in future devices.

Download or read book Synthesis and Characterization of Zinc Oxide Nanowires and Their Use in Spintronic and Photovoltaic Applications written by Benjamin Daniel Yuhas and published by . This book was released on 2009 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optical Characterization of ZnO Nanowires as a Function of the Growth Conditions written by Sergio Roso Casares and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: [ANGLÈS] In the present work we have grown ZnO nanowires over different substrates by the vapour-liquid-solid growth method, changing several growth parameters, such as the Au sputtered thin layer, temperature, pressure and gas flow. We have characterized their optical properties measuring the optical absorption and photoluminescence spectra at room temperature. The near-band edge and defect-related emission bands have been discussed as a function of the growth conditions.

Download or read book Zinc Oxide Bulk Thin Films and Nanostructures Processing Properties and Applications written by Chennupati Jagadish and published by Elsevier Science. This book was released on 2006-09 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an in-depth exploration of the following topics, this book covers the broad uses of zinc oxide within the fields of materials science and engineering: - Recent advances in bulk, thin film and nanowire growth of ZnO (including MBE, MOCVD and PLD), - The characterization of the resulting material (including the related ternary systems ZgMgO and ZnCdO), - Improvements in device processing modules (including ion implantation for doping and isolation, Ohmic and Schottky contacts, wet and dry etching), - The role of impurities and defects on materials properties - Applications of ZnO in UV light emitters/detectors, gas, biological and chemical-sensing, transparent electronics, spintronics and thin film

Download or read book Doping and Characterisation of ZnO Nanowires and Crystals written by Liangchen Zhu and published by . This book was released on 2015 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Piezoelectric Nanostructures of Zinc Oxide Synthesis Characterization and Devices written by Puxian Gao and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, a systematic study has been carried out on the synthesis, characterization and device fabrication of piezoelectric ZnO nanstructures. The achieved results are composed of the following four parts. Firstly, through a systematic investigation on the Sn-catalyzed ZnO nanostructure, an improved understanding of the chemical and physical process occurring during the growth of hierarchical nanostructures has been achieved. Decomposed Sn from SnO2 has been successfully demonstrated and proved to be an effective catalyst guiding the growth of not only aligned ZnO nanowires, but also the hierarchical nanowire-nanoribbon junction arrays and nanopropeller arrays. During the vapor-liquid-solid (VLS) catalyzing growth process at high temperature, Sn in the liquid state has been proved to be able to guide the growth of nanowires and nanoribbons in terms of growth directions, side facets, and crystallographic interfaces between Sn and ZnO nanostructures. Secondly, using pure ZnO as the only source material, by precisely tuning and controlling the growth kinetics, a variety of hierarchical polar surface dominated nanostructures have been achieved, such as single crystal nanorings, nanobows, nanosprings and superlattice nanohelices. High yield synthesis of ZnO nanosprings over 50% has been successfully obtained by mainly controlling the pre-pumping level associated with the partial pressure of residual oxygen during the vapor-solid growth process. The rigid superlattice nanohelices of ZnO have been discovered, which is a result of minimization of the electrostatic energy induced by polar surfaces. The formation process of the nanohelix has been systematically characterized. Thirdly, two new strategies have been successfully developed for fabricating ZnO quantum dots and synthesis of ZnO nanodiskettes and nanotubes. The formation process is based on a common concept of self-assembly. Finally, a series of devices and applications studies based on several piezoelectric ZnO nanostructures, such as nanobelts, nanopropellers and nanohelices, have been carried out utilizing the electro-mechanical resonance, bio-surface functionalization, devices fabrication and electrical characterization. Individual nanobelt and nanohelix based nanodevices have been successfully fabricated for applications in chemical and biological sensing. The study opens a few new areas in oxide nanostructures and applications.