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Development Of Resist Free Fabrication Protocols And Performance Characterization Of Micro Devices Based On Metal Oxide Nanowires
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Book Synopsis Development of Resist Free Fabrication Protocols and Performance Characterization of Micro Devices Based on Metal Oxide Nanowires by : Bradly K. Button
Download or read book Development of Resist Free Fabrication Protocols and Performance Characterization of Micro Devices Based on Metal Oxide Nanowires written by Bradly K. Button and published by . This book was released on 2006 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Certain current methods of nanostructure device fabrication such as wet or in solution nanostructure synthesis and photo-resist electrode patterning, expose the surface of the micro and nanostructure to contaminants.
Book Synopsis Fabrication and Characterization of Metal Oxide Nanowires by : Yao Cheng
Download or read book Fabrication and Characterization of Metal Oxide Nanowires written by Yao Cheng and published by . This book was released on 2009 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Chemically Modified Metal Oxide Nanostructures Electrodes for Sensing and Energy Conversion by : Sami Elhag
Download or read book Chemically Modified Metal Oxide Nanostructures Electrodes for Sensing and Energy Conversion written by Sami Elhag and published by Linköping University Electronic Press. This book was released on 2017-02-02 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this thesis is the development of scalable, low cost synthesis of metal oxide nanostructures based electrodes and to correlate the chemical modifications with their energy conversion performance. Methods in energy conversion in this thesis have focused on two aspects; a potentiometric chemical sensor was used to determine the analytical concentration of some components of the analyte solution such as dopamine, glucose and glutamate molecules. The second aspect is to fabricate a photo-electrochemical (PEC) cell. The biocompatibility, excellent electro-catalytic activities and fast electron transfer kinetics accompanied with a high surface area to volume ratio; are properties of some metal oxide nanostructures that of a potential for their use in energy conversion. Furthermore, metal oxide nanostructures based electrode can effectively be improved by the physical or a chemical modification of electrode surface. Among these metal oxide nanostructures are cobalt oxide (Co3O4), zinc oxide (ZnO), and bismuth-zincvanadate (BiZn2VO6) have all been studied in this thesis. Metal oxide nanostructures based electrodes are fabricated on gold-coated glass substrate by low temperature (< 100 0C) wet chemicalapproach. X-ray diffraction, x-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the electrodes while ultraviolet-visible absorption and photoluminescence were used to investigate the optical properties of the nanostructures. The resultant modified electrodes were tested for their performance as chemical sensors and for their efficiency in PEC activities. Efficient chemically modified electrodes were demonstrated through doping with organic additives like anionic, nonionic or cationic surfactants. The organic additives are showing a crucial role in the growth process of metal oxide nanocrystals and hence can beused to control the morphology. These organic additives act also as impurities that would significantly change the conductivity of the electrodes. However, no organic compounds dependence was observed to modify the crystallographic structure. The findings in this thesis indicate the importance of the use of controlled nanostructures morphology for developing efficient functional materials.
Book Synopsis Development of Zinc Oxide Nanowire Arrays on Flexible Conductive Substrates for Energy Applications by : Santhosh Sankaranarayanan Nair
Download or read book Development of Zinc Oxide Nanowire Arrays on Flexible Conductive Substrates for Energy Applications written by Santhosh Sankaranarayanan Nair and published by . This book was released on 2013 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: AbstractNano/micro scale devices have attracted a lot of interest due to the emergence of wearable/portable devices. One of the challenging tasks in the miniaturization is to reduce the size and weight of the powering unit. Harvesting mechanical energy and making the device a self-powered one, not only helps in reducing the size/weight ratio but also in designing a maintenance free and sustainable device. Piezoelectric energy harvesting research has gained new momentum with the discovery of piezoelectric charges in semiconducting zinc oxide nanowires (ZnO NWs). Semiconducting ZnO NWs provide an opportunity to integrate with electronic devices and circuits directly unlike non-conducting traditional piezoelectric materials. The coupling of piezoelectric and semiconducting properties was used to design energy generating devices called nanogenerators (NGs). The basic working principle involves application of a mechanical force to create a piezopotential across the wurtzite structured NWs and this piezopotential is channelled employing metal-semiconducting pathways such as p-n junctions. These junctions also play a key role in various other devices such as solar cells, capacitors, fuel cells and water splitting devices. This thesis concentrates mainly on the fabrication of semiconducting piezoelectric nanowires on functionalised flexible substrates and the junctions thereby obtained. It is based on the idea that ZnO NWs can be grown directly on poly(3,4-ethylendioxydithiophene) (PEDOT) or graphene-functionalised substrates using low temperature aqueous synthesis. ZnO NWs can be fabricated using a low temperature aqueous processing route on flexible substrates and fibres. ZnO creates a wide variety of nanostructures due to the polar terminating layers and the surface chemistry of the substrate. The position of the substrate in the growth solution was therefore investigated and found to dictate the morphology and aspect ratio of the nanostructure in seed mediated low temperature aqueous synthesis on polyethersulfone (PES)-based flexible substrates. Vapour phase polymerisation was used to fabricate PEDOT coated 2-D and 3-D PES. To produce graphene-coated flexible substrates, colloidal graphene was synthesized and functionalised onto 2-D and 3-D PES using layer by layer technique (LbL) with polyelectrolytes such as polyallylamine hydrochloride (PAH) and polystyrenesulfonate (PSS). The LbL modification was achieved by exploiting the surface functional groups in the colloidal graphene. Various surface treatments and heat treatments were carried out to tune the system to obtain higher conductivity. ZnO seed solution was coated and NWs were grown on the functionalized substrates. The newly formed junctions were characterised for their I-V characteristics to determine if they have similar function to junctions formed with ZnO on ITO or metals. ZnO NWs grown on PEDOT shows an ohmic contact and gives linear I-V characteristics. On the other hand when a PEDOT coated substrate was made to form a junction at the top of the ZnO NWs, it forms a Schottky contact and gives rectification. However the ZnO-graphene interface shows a Schottky contact. When a top graphene electrode was made to form a junction with ZnO NWs grown on graphene, the I-V characteristics shows a symmetrical and rectifying junction on both sides. Nanogenerators were designed and tested using ZnO NWs grown on PEDOT coated 2-D and 3-D PES. Thus, the fabricated PEDOT-NGs produced a higher current by a factor of 106 and a 102 times increase in the voltage compared to the traditional ITO grown NG design. Vapour phase polymerised PEDOT on flexible substrates eliminated the use of expensive and less efficient electrodes such as ITO and Au. It has also been shown that this approach can be extended to fibre substrates by sandwiching them between PEDOT sheets which make them more suitable for wearable energy harvesting with 102 times improved efficiency compared to ITO sandwiched fibre NG. The higher performance of PEDOT NGs was accounted by the new junctions formed at the interfaces which reduce the screening of free charge carriers in the system. Graphene NGs were fabricated using gold top electrodes. The NG fabricated on surface treated PES was found to outperform the NG fabricated without surface treatment due to the higher conductivity of the surface treated electrode. The output of the surface treated NG was found to be much less than the ITO based or PEDOT based NGs.
Book Synopsis Fabrication and Characterization of Semiconductor Nanowires by : Colm O'Regan
Download or read book Fabrication and Characterization of Semiconductor Nanowires written by Colm O'Regan and published by LAP Lambert Academic Publishing. This book was released on 2016-01-15 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: One-dimensional semiconductor nanowires are considered to be promising materials for future nanoelectronic applications. However, before these nanowires can be integrated into such devices, a thorough understanding of their growth behaviour is necessary. In particular, methods that allow the control over nanowire growth are deemed especially important, as it is these methods that will enable the control of nanowire dimensions such as length and diameter. The production of nanowires with high-aspect ratios is vital in order to take advantage of the unique properties experienced at the nanoscale, thus allowing us to maximise their use in next-generation electronics. Additionally, the development of low-resistivity interconnects is desirable in order to connect such nanowires in multi-nanowire components. Consequently, this book aims to discuss the synthesis and characterisation of semiconductor nanowires and metal interconnects, as they apply to future electronics applications.
Book Synopsis Fabrication and Characterization of Nanowires by : Francis R. Phillips
Download or read book Fabrication and Characterization of Nanowires written by Francis R. Phillips and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of nanostructures has become very common throughout high-tech industries. In order to enhance the applicability of Shape Memory Alloys (SMAs) in systems such as Nano-Electromechanical Systems, the phase transformation behavior of SMA nanostructures should be explored. The primary focus of this work is on the fabrication of metallic nanowires and the characterization of the phase transformation of SMA nanowires. Various metallic nanowires are fabricated through the use of the mechanical pressure injection method. The mechanical pressure injection method is a template assisted nanowire fabrication method in which an anodized aluminum oxide (AAO) template is impregnated with liquid metal. The fabrication procedure of the AAO templates is analyzed in order to determine the effect of the various fabrication steps. Furthermore, metallic nanowires are embedded into polymeric nano bers as a means to incorporate nanowires within other nanostructures. The knowledge obtained through the analysis of the AAO template fabrication guides the fabrication of SMA nanowires of various diameters. The fabrication of SMA nanowires with di fferent diameters is accomplished through the fabrication of AAO templates of varying diameters. The phase transformation behavior of the fabricated SMA nanowires is characterized through transmission electron microscopy. By analyzing the fabricated SMA nanowires, it is found that none of the fabricated SMA nanowires exhibit a size eff ect on the phase transformation. The lack of a size e ffect on the phase transition of SMA nanowires is contrary to the results for SMA nanograins, nanocrystals, and thin films, which all exhibit a size eff ect on the phase transformation. The lack of a size eff ect is further studied through molecular dynamic simulations. These simulations show that free-standing metallic nanowires will exhibit a phase transformation when their diameters are sufficiently small. Furthermore, the application of a constraint on metallic nanowires will inhibit the phase transformation shown for unconstrained metallic nanowires. Therefore, it is concluded that free-standing SMA nanowires will exhibit a phase transformation throughout the nanoscale, but constrained SMA nanowires will reach a critical size below which the phase transformation is inhibited.
Book Synopsis Fabrication and Characterization of Nanodevices Based on III-V Nanowires by : Andrès de Luna bugallo
Download or read book Fabrication and Characterization of Nanodevices Based on III-V Nanowires written by Andrès de Luna bugallo and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor nanowires are nanostructures with lengths up to few microns and small cross sections (10ths of nanometers). In the recent years the development in the field of III-N nanowire technology has been spectacular. In particular they are consider as promising building in nanoscale electronics and optoelectronics devices; such as photodetectors, transistors, biosensors, light source, solar cells, etc. In this work, we present fabrication and the characterization of photodetector and light emitter based devices on III-N nanowires. First we present a study of a visible blind photodetector based on p-i-n GaN nanowires ensembles grown on Si (111). We show that these devices exhibit a high responsivity exceeding that of thin film counterparts. We also demonstrate UV photodetectors based on single nanowires containing GaN/AlN multi-axial quantum discs in the intrinsic region of the nanowires. Photoluminescence and cathodoluminescence spectroscopy show spectral contributions above and below the GaN bandgap according to the variation of the discs thickness. The photocurrent spectra show a sub-band-gap peak related to the interband absorption between the confined states in the large Qdiscs. Finally we present a study of photodetectors and light emitters based on radial InGaN/GaN MQW embedded in GaN wires. The wires used as photodetectors showed a contribution below the GaN bandgap. OBIC measurements demonstrate that, this signal is exclusively generated in the InGaN MQW region. We showed that LEDs based on this structure show a electroluminescence emission and a red shift when the In content present in the QWs increases which is in good agreement with photoluminescence and cathodoluminescence results.
Book Synopsis Semiconductor Nanowires for Future Electronics by : Shadi A. Dayeh
Download or read book Semiconductor Nanowires for Future Electronics written by Shadi A. Dayeh and published by . This book was released on 2008 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation concerns with fundamental aspects of organo-metallic vapor phase epitaxy (OMVPE) of III-V semiconductor nanowires (NWs), and their structural and electrical properties inferred from a variety of device schemes. An historical perspective on the NW growth techniques and mechanisms, and an overview of demonstrated NW devices and their performance is summarized in chapter 1. In part I of the dissertation, OMVPE synthesis of InAs NWs on SiO2/Si and InAs (111)B surfaces is discussed and their growth mechanism is resolved. Nucleation, evolution, and the role of Au nanoparticles in the growth of InAs NWs on SiO2/Si surfaces are presented in chapter 2. Our results indicate that In droplets can lead to InAs NW growth and that Au nanoparticles are necessary for efficient AsH3 pyrolysis. Chapter 3 discusses the key thermodynamic and kinetic processes that contribute to the InAs NW growth on InAs (111)B surfaces. Controversy in the interpretation of III-V NW growth is overviewed. Experimental evidence on the nucleation of InAs NWs from In droplets as well as the catalytic effect of Au nanoparticles on the InAs (111)B surfaces are described. NW cessation at high growth temperatures or at increased input molar V/III ratios is explained via a switch-over from vapor-liquid-solid (VLS) NW growth to vapor-solid thin film growth, in contrast to previous interpretation of vapor-solid-solid growth of III-V NWs. The substrate-NW adatom exchange is also treated, and experimental distinction of two NW growth regimes depending on this exchange is demonstrated for the first time. Our results indicate that when growing extremely uniform InAs NWs, solid-phase diffusion of In adatoms on the NW sidewalls is the dominant material incorporation process with surface diffusion lengths of ̃1 [mu]m. This understanding was further utilized for the growth of axial and radial InAs-InP heterostructure NWs. Polymorphism in III-V NW crystal structure is also discussed and growth conditions that lead to its observation are summarized. In part II of the dissertation, transport coefficient extraction, field-, diameter-, and surface state-dependent transport properties, and their correlation with crystal structure in InAs NWs is presented. Chapter 4 overviews the fabrication of top-gate InAs NW field-effect transistors (NWFETs), presents a model for accurate extraction of carrier mobility and carrier concentration from NWFETs, and demonstration of high electron mobility values in InAs NWs is illustrated. Chapter 5 describes the effects of surface states on transport properties and parameter extraction from InAs NWFETs. Mobility values in excess of 10000 cm2/V·s are obtained from measurements at slow gate voltage sweep rates at which charge balance in carrier capture and emission from interface states is achieved. Chapter 6 discusses scaling effects on the NW transport properties and provides experimental evidence of ballistic electron transport over length scales of ̃200 nm in InAs NWs at room temperature. Diameter-dependent mobility and free carrier concentration is observed and is attributed to Fermi energy pinning in the conduction band that leads to surface electron accumulation and enhanced surface scattering. Chapter 7 discusses direct correlation of InAs NW microstructures with their transport properties. Our results show that the distinct difference observed in the subthreshold characteristics between wurtzite and zinc blende InAs NWFETs is due to the presence of spontaneous polarization charges at the WZ {0001} plane interfaces with ZB segments. Numerical simulations point out that a polarization charge density of ̃1013 cm−2 is required to surpass surface state induced electron accumulation and result in high Ion/Ioff ratios for the WZ NWFETs. Chapter 8 presents detailed experimental studies on the gate and source-drain field-dependent transport properties in InAs NWFETs. Mobility degradation at high injection fields is observed and is attributed to enhanced phonon scattering, which was verified through electro-thermal simulations and ex-situ transmission electron microscopy (TEM) and scanning TEM compositional studies on NWs exposed to high injection fields. Chapter 9 presents a novel scheme for III-V NW integration to the standard Si mainstream utilizing ion-cut induced transferred III-V layers to SiO2/Si. Vertically integrated and electrically isolated III-V NWs on Si are achieved for the first time. Key challenges related to growth and implementation of vertical devices in future technology nodes are also summarized.
Book Synopsis Synthesis, Characterization, and Dielectrophoretic Assembly of Metal-oxide Nanowires by : Michael Lau
Download or read book Synthesis, Characterization, and Dielectrophoretic Assembly of Metal-oxide Nanowires written by Michael Lau and published by . This book was released on 2008 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fabrication of Poly-SiNW Devices for TE Characterization by : Nahida Akhter
Download or read book Fabrication of Poly-SiNW Devices for TE Characterization written by Nahida Akhter and published by LAP Lambert Academic Publishing. This book was released on 2014-08-05 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal conductivity measurement has always been a challenging and difficult task for thermoelectric characterization of semiconductor nanowire. A process flow for poly-Si nanowire device fabrication has been reported in this thesis. The device includes the nanowires as a part of its fabrication which avoids complicated placement of nanowire on the device for experiment and also avoids the contact resistance on the both sides of nanowire. The process flow is repeatable, reliable, and able to produce functional devices. Specifically, processes were found in this research to optimize the stress of Si nitride thin films and isotropic etching of Si substrate by using particular gas mixtures. By this device, thermal conductivity of nanowires of any materials compatible to micro/nano- fabrication, can be measured rather than poly-Si nanowires only.
Book Synopsis Probing Local Vacancy-driven Resistive Switching in Metal Oxide Nanostructures by : Jiaying Wang
Download or read book Probing Local Vacancy-driven Resistive Switching in Metal Oxide Nanostructures written by Jiaying Wang and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Novel nonvolatile memory technologies garner intense research interest as conventional ash devices approach their physical limit. Memristors, often comprising an insulating thin film between two metal electrodes to constitute a class of two-terminal devices, enable a variety of important large data storage and data-driven computing applications. In addition to nonvolatile behavior, other features such as high scalability, low power consumption, and sub-nanosecond response times make memristors among the most attractive candidate systems. Their strength in electronic storage relies on the unique properties of the tunable variations in resistance induced from the accumulation of charged defects based on the applied bias history. Metal oxides serve as the most common "storage" materials, demonstrating advantages including simple fabrication, high reliability, and fast operation speeds. While the basic working concepts and the underlying conduction mechanisms have been established through combined experimental and simulation studies, the role of metal insulator interface, which acts as the crux of coupled electronic-ionic interactions, has not been fully understood. Continuous scaling, for the purpose of high density memories, also requires a detailed understanding of the switching behavior and transport mechanism. Other technical challenges include the development of innovative, low-cost fabrication methods that effectively enable high-performance structures as an alternative to complicated process modules. Stable retention and endurance of the switching characteristics, as well as uniformity of the switching parameters to ensure a valid program/read operation also represent significant challenges. Studies in device and materials optimization remain in the formative stages, and thus motivate this work to drive progress in the most attractive areas, including size dependent behavior and switching performance of memristors. This collection of work aims to correlate resistive switching within metal oxide based memristors with the fundamental physical mechanisms and material properties on a highly localized scale. Chapter 3 relates the device size and the resulting performance matrix of memory cells in the first step towards fully understanding the scaling projection and reliability issues that affect nanoscale architectures. Chapter 4 demonstrates a convective self-assembly, transferable approach that enables the fabrication of highly-controlled nanoribbon comprising solution-processed nanocrystals, providing multiple degrees of freedom for understanding the interfacial memristive behavior of functional oxide nanostructures. As a powerful tool in the study of resistive switching, conductive AFM probes the homogeneity of the charge transport properties, thus offering electrical information by locally applied bias when it is placed in direct contact with desired regime. Finally we also focus on the improving the cycle-to-cycle uniformity by embedding nanostructure into conventional metal-insulator-metal (MIM) geometry in Chapter 5. This improvement is attributed to the concentration of electric field when metal nanoislands are inserted into the oxide film matrix. The details of this work will highlight the tunable and optimizable template-driven method that can be applied on any memristive systems, yielding a superior uniformity of operating voltage and resistance states. In summary, this thesis promotes the development of novel, high-performance metal oxide based memristors enabled by the availability of new, nanostructured materials and innovations in device structure engineering. The switching performance, underlying mechanisms, area/defect concentration effects, development of solution-processed nanocrystals assemblies and chemistries, and highly enhanced uniformity in memristors are addressed by combining systematic deposition approaches with the advanced nanoscopic observation of the conducting filament, leading to the strongest competitor among future nonvolatile memory solution.
Book Synopsis Fabrication and Characterization of Silicon Nanowires and Metal Nanostructures [microform] by : Lui, Vicki Wai-Shum
Download or read book Fabrication and Characterization of Silicon Nanowires and Metal Nanostructures [microform] written by Lui, Vicki Wai-Shum and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2005 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Metal Oxide-based Hybrid Semiconductor Nanowires by : Wenjie (Andy). Cai
Download or read book Metal Oxide-based Hybrid Semiconductor Nanowires written by Wenjie (Andy). Cai and published by . This book was released on 2012 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis High Throughput Manufacturing of Silicon Nanobridges for the Fabrication of 3D Gate-all-around Field Effect Transistors by : Jin Yong Oh
Download or read book High Throughput Manufacturing of Silicon Nanobridges for the Fabrication of 3D Gate-all-around Field Effect Transistors written by Jin Yong Oh and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Self-assembled nanowires chemically synthesized by bottom-up approaches have attracted considerable attention due to their properties that are not common in their bulk or thin film counterparts. Their potential to offer novel functionality opens up opportunities for innovative genres of devices. Indeed, a number of innovative devices, such as transistors, diodes, bio/chemical sensors, photovoltaic devices, and even embryonic low-density integrated circuits, have been demonstrated by using various kinds of nanowires. In contrast to nanostructured materials created by the microfabrication technology pursued by the microelectronics industry, self-assembled nanowires inheritedly exhibit a high degree of variability in their dimensions, densities, locations, and alignment, etc. Despite the promise of nanowires, such uncertainty prevents them from utilization in mass-manufacturing processes and large-scale device integration. This dissertation aimed to devise a viable and high-throughput growth-in-place technique for creating well-ordered nanowire arrays without costly and tedious post-growth processing. This dissertation also intended to demonstrate novel devices using the nanobridges created by the growth-in-place technique and nanowire ensembles. In the first section of the dissertation, a couple of popular modalities for creating nanowire devices, including growth-in-place techniques, were briefly reviewed to improve our understanding of their various aspects. Among multiple bottom-up growth techniques, a revised nanobridging technique with new process recipes for depositing catalytic gold nanoparticles was explored to enhance its repeatability and throughput. Yields of the nanobridges were improved with the new schemes such as adding HF acid to nanoparticle colloid and employing a surface linker treatment on the substrate for catalyst deposition while maintaining deposition selectivity. This dissertation demonstrated that Si nanobridges could become building blocks of 3D gate-all-around FETs, charge-trap nonvolatile memory devices, and photosensitive transistors. Here, high yields of the nanobridges with improved arrangement allowed integration of multiple devices per batch. The nanobridge FETs showed successful switching characteristics, and the nanobridge memory devices showed low voltage programming/erasing operations due to the enhanced electric fields exerted by the surround gate. High photosensitivity of the off currents of the nanobridge MOSFET offered an opportunity to create novel electro-optical switching devices. Although these bridge devices exhibited proof-of-concept level performance and needed far more optimization for attaining competitive performance, they showed the feasibility of expanding the realm of nanobridge applications. Other than exploring the bottom-up approach of synthesizing nanowires right onto the electrodes in a well-organized fashion, the dissertation looked into protocols for maneuvering 1D nanostructure ensembles and manufacturing devices thereof. Exploiting nanowire ensemble en masse is attractive because this approach allows substrate recycling and simple device fabrication. One example of nanowire ensemble devices was capacitive chemical sensors, which had nanowire ensembles in the active sensing regions. These sensors showed pH sensitivities as high as the theoretical limit owing to their surface areas and high-density surface sites. Another example was flexible 2D devices created by transferring and then interfacing 1D structures with elastomer (polyurethane) films. Here, the mechanism of harvesting 1D structures was discussed with the help of simulation-based analysis, and electrical interfacing of the transferred structures was presented for creating flexible devices. In the last part of this dissertation, the nanobridging technique was evaluated from the practical point of view, and its perspectives were discussed thoroughly. The presented nanobridging technique seems to be uncompetitive compared to the matured and state-of-the-art modern microfabrication technology. However, the work carried out in this dissertation indicates that the bridging technique can help integrating heteroepitaxial nanowires on the Si platform. In particular, catalyst-free heteroepitaxial growth of nanowires on Si substrates can help the continuation of the microelectronics paradigm, 'Saller and Faster,' typically represented by 'Moore's Law.'
Book Synopsis Flame Synthesis and Doping of Metal Oxide Nanowires and Their Application in Solar Water Splitting by : Lili Cai
Download or read book Flame Synthesis and Doping of Metal Oxide Nanowires and Their Application in Solar Water Splitting written by Lili Cai and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Considering the increasing energy and environmental problems associated with the exhaustible fossil fuels, renewable energy conversion devices have attracted tremendous attention, which hold the promise to supply the fuel and electricity in a sustainable way. For many of these devices, such as batteries, fuel cells, solar cells and solar water splitting cells, metal oxides are very important functional materials due to their earth abundance, good stability and diverse properties. Recently nanowire-based metal oxides have enabled revolutionary advances in various energy conversion devices, because of their unique physical and chemical properties resulting from the high aspect ratio and large surface area. Despite their advantages, practical applications of metal oxide nanowires are hindered, as conventional synthesis methods have limitations for large scale production. Flame synthesis can potentially solve this large-scale production issue for metal oxide nanowires, given its demonstrated scalability in the industrial production of nanoparticles. However, only until very recently has flame synthesis been applied to metal oxide nanowires. More research is needed to develop advanced flame synthesis method for metal oxide nanowires, to understand the mechanism to well control the size, shape and compositions for reliable manufacture, and to evaluate their quality and functionalities in real devices. This thesis presents a novel flame vapor deposition method for the synthesis of metal oxide nanowires with the capabilities of rapid rate, good uniformity over large area and broad substrate choice. Through the investigation of growth mechanism, good control over the morphology and composition was achieved by tuning the process parameters such as fuel/air ratio, source temperature, substrate material and temperature. In addition to synthesis, flame-based doping method (sol-flame doping) was innovated for controllable doping of metal oxide NWs to modify the properties of host materials at the nanometer scale. This sol-flame doping method not only preserves the morphology and crystallinity of the host NWs, but also allows fine control over the dopant concentration by simply varying the concentration of dopant precursor solution. With this method, significant enhancement of the electrocatalytic activity towards oxygen evolution reaction was achieved for TiO2 NWs (up to 760 mV reduction of the overpotential), attributing to simultaneously improved surface charge transfer kinetics and increased bulk conductivity by doping. Finally, the flame-synthesized metal oxide nanowires were implemented as a photoanode in photoelectrochemical water splitting. By rational design and scalable fabrication, the WO3/BiVO4/Ni:FeOOH composite nanowire photoanode generated a high photocurrent of 4.5 mA/cm2 at a potential of 1.23 VRHE under simulated sunlight, which is among the highest produced by any WO3/BiVO4 based photoanodes. With the demonstrated rapid rate, good controllability and superior performance of the flame-produced metal oxide nanowires, these flame synthesis and doping methods can potentially enable future generation of energy devices by removing the barrier for large-scale production of tailored metal oxide nanowires.
Book Synopsis Large-scale Patterned Oxide Nanostructures by : Xudong Wang
Download or read book Large-scale Patterned Oxide Nanostructures written by Xudong Wang and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology is experiencing a flourishing development in a variety of fields covering all of the areas from science to engineering and to biology. As an active field in nanotechnology, the work presented in this dissertation is mostly focused on the fundamental study about the fabrication and assembly of functional oxide nanostructures. In particular, Zinc Oxide, one of the most important functional semiconducting materials, is the core objective of this research, from the controlled growth of nanoscale building blocks to understanding their properties and to how to organize these building blocks. Thermal evaporation process based on a single-zone tube furnace has been employed for synthesizing a range of 1D nanostructures. By controlling the experimental conditions, different morphologies, such as ultra-small ZnO nanobelts, mesoporous ZnO nanowires and core-shell nanowire were achieved. In order to pattern the nanostructures, a large-scale highly-ordered nanobowl structure based on the self-assembly of submicron spheres was created and utilized as patterning template. The growth and patterning techniques were thereafter integrated for aligning and patterning of ZnO nanowires. The aligning mechanisms and growth conditions were thoroughly studied so as to achieve a systematic control over the morphology, distribution and density. The related electronic and electromechanical properties of the aligned ZnO nanowires were investigated. The feasibility of some potential applications, such as photonic crystals, solar cells and sensor arrays, has also been studied. This research may set a foundation for many industrial applications from controlled synthesis to nanomanufacturing.
Book Synopsis Fabrication and Characterization of Silicon Nanowires and Metal Nanostructures by : Vicki Wai-Shum Lui
Download or read book Fabrication and Characterization of Silicon Nanowires and Metal Nanostructures written by Vicki Wai-Shum Lui and published by . This book was released on 2005 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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