Dissertations / Theses on the topic 'Piezoelectric nanogenerators'

Energy harvesting using piezoelectric nanomaterials provides an opportunity for advancement towards self-powered systems. Self-powered systems are a new emerging technology, which allows the use of a system or a device that perform a function without the need for external power source like for example, a battery or any other type of source. This technology can for example use harvested energy from sources around us such as ambient mechanical vibrations, noise, and human movement, etc. and convert it to electric energy using the piezoelectric effect. For nanoscale devices, the size of traditional batteries is not suitable and will lead to loss of the concept of “nano”. This is due to the large size and the relatively large magnitude of the delivered power from traditional sources. The development of a nanogenerator (NG) to convert energy from the environment into electric energy would facilitate the development of some self-powered systems relying on nano- devices. The main objective of this thesis is to fabricate a piezoelectric Zinc Oxide (ZnO) NGs for low frequency (˂ 100 Hz) energy harvesting applications. For that, different types of NGs based on ZnO nanostructures have been carefully developed, and studied for testing under different kinds of low frequency mechanical deformations. Well aligned ZnO nanowires (NWs) possessing high piezoelectric coefficient were synthesized on flexible substrates using the low temperature hydrothermal route. These ZnO NWs were then used in different configurations to demonstrate different low frequency energy harvesting devices. Using piezoelectric ZnO NWs, we started with the fabrication of sandwiched NG for hand writing enabled energy harvesting device based on a thin silver layer coated paper substrate. Such device configurations can be used for the development of electronic programmable smart paper. Further, we developed this NG to work as a triggered sensor for wireless system using foot-step pressure. These studies demonstrate the feasibility of using ZnO NWs piezoelectric NG as a low-frequency self-powered sensor, with potential applications in wireless sensor networks. After that, we investigated and fabricated a sensor on PEDOT: PSS plastic substrate either by one side growth technique or by using double sided growth. For the first growth technique, the fabricated NG has been used as a sensor for acceleration system; while the fabricated NG by the second technique has worked as anisotropic directional sensor. This fabricated configurations showed stability for sensing and can be used in surveillance, security, and auto-mobil applications. In addition to that, we investigated the fabrication of a sandwiched NG on plastic substrates. Finally, we demonstrated that doping ZnO NWs with extrinsic element (such as Ag) will lead to the reduction of the piezoelectric effect due to the loss of crystal symmetry. A brief summary into future opportunities and challenges are also presented in the last chapter of this thesis.

We are surrounded by enormous amounts of ambient mechanical energy that goes to waste such as rain drops, human footfalls, air flow, ocean waves, just to name a few. If such otherwise wasted mechanical energy can be effective converted into electricity, self-powered electronics are very likely to be realized, which can address the limitations of traditional power supplies in many cases, such as wireless sensor networks. Here in this work, two types of energy-harvesting nanogenerators (NGs) based were studied. For piezoelectric nanogenerators, zinc oxide (ZnO) nanowires (NWs) were used as building blocks to develop integrated NGs based on a number of ZnO NWs instead of a single NW. Two types of integrated NGs were developed, which consist of lateral NW arrays and vertical NW arrays. The electric output power was substantially enhanced compared to the design with a single NW. For triboelectric nanogenerators, triboelectric effect was innovatively used as an effective means of harvesting mechanical energy. The operating principle can be explained by the coupling between triboelectric and electrostatic effect. Two types of operating modes were invented, i.e. contact mode and sliding mode. Triggered by commonly available ambient mechanical energy such as footfalls, the maximum output power reached up to 1.2 W. More importantly, self-powered systems were built by using the NG as a power source. It can provide real time power for up to 600 commercial LED bulbs. This research not only provides the fundamentals for NGs but also demonstrates the practicability of using the self-powered technology in our daily life.

Les nanomatériaux et nanotechnologies sont devenus un élément incontournable dans l'électronique de faible puissance, la production énergétique / gestion et les réseaux sans fil, offrant la possibilité de construire une vision pour les capteurs autonomes. Cette thèse s’intéresse au concept de systèmes basse température utilisant des structures de matériaux hybrides organique/inorganique pour la réalisation de dispositifs électroniques faible coût, dont les transistors à effet de champ (FET) et les nanogénérateurs piézoélectriques (nommés PENGs) et ce, sur divers substrats en particulier plastiques. Pour atteindre ces objectifs, ce travail décrit d'abord la croissance contrôlée de nanostructures monocristallines de ZnO en utilisant des approches vapeur-liquide-solide (VLS) et hydrothermales à haute et basse température respectivement. Pour les dispositifs FET, les nanostructures ZnO obtenues par VLS sont utilisées en raison de leur haute qualité structurale et optique. Les sections suivantes présentent des différentes études menées pour optimiser les prototypes FET, comprenant (i) les contacts métal-semiconducteur, (ii) la qualité de l'interface semi-conducteur/isolant et (iii) l'épaisseur de diélectrique organique. La dernière section examine la possibilité de fabriquer des systèmes hybrides organiques/inorganiques pour PENGs utilisant l'approche hydrothermale. Certaines des questions clés, ce qui limitent les performances PENG sont abordés : (i) l'effet de porteurs libres et (ii) l'encapsulation polymère. Ce travail démontre le fort potentiel des ZnO nanostructures pour l'avenir de l'électronique
Nanomaterials and nanotechnology has become a crucial feature in low-power electronics, energy generation/management and wireless networks, providing the opportunity to build a vision for autonomous sensors. The present thesis delivers the concept of low-temperature processable organic / inorganic hybrid systems for the realization of inexpensive electronic devices including field-effect transistors (FETs) and piezoelectric nanogenerators (PENGs) on various substrates including plastics. To achieve these objectives, this work first describes the controlled growth of single-crystalline ZnO nanostructures using high-temperature vapor-liquid-solid (VLS) and low-temperature hydrothermal approaches. For the FET devices, VLS grown ZnO nanostructures are used, owing to their high structural and optical quality. Later sections present different studies conducted to optimize the FET prototypes, includes: (i) metal-semiconductor contacts, (ii) semiconductor/insulator interface quality and (iii) organic dielectric thickness. The last section investigates the possibility to fabricate organic / inorganic hybrid systems for PENGs using hydrothermal approach. Some of the key issues, restricting the PENG performances are addressed: (i) screening effect from free charge carriers and (ii) polymer encapsulation. This work demonstrates the high potential of ZnO nanostructure for the future of electronics

L’alimentation en énergie des réseaux de capteurs miniaturisés pose une question fondamentale, dans la mesure où leur autonomie est un critère de qualité de plus en plus important pour l’utilisateur. C’est même une question cruciale lorsque ces réseaux visent à assurer une surveillance d’infrastructure (avionique, machines, bâtiments…) ou une surveillance médicale ou environnementale. Les matériaux piézoélectriques permettent d’exploiter l’énergie mécanique inutilisée présente en abondance dans l’environnement (vibrations, déformations liées à des mouvements ou à des flux d’air…). Ils peuvent ainsi contribuer à rendre ces capteurs autonomes en énergie. Sous la forme de nanofils (NF), les matériaux piézoélectriques offrent une sensibilité qui permet d’exploiter des sollicitations mécaniques très faibles. Ils sont également intégrables, éventuellement sur substrat souple.Dans cette thèse nous nous intéressons au potentiel des nanofils de matériaux semi-conducteurs piézoélectriques, tels que ZnO ou les composés III-V, pour la conversion d’énergie mécanique en énergie électrique. Depuis peu, ceux-ci ont fait l’objet d’études relativement nombreuses, avec la réalisation de nanogénérateurs (NG) prometteurs. De nombreuses questions subsistent toutefois avec, par exemple, des contradictions notables entre prédictions théoriques et observations expérimentales.Notre objectif est d’approfondir la compréhension des mécanismes physiques qui définissent la réponse piézoélectrique des NF semi-conducteurs et des NG associés. Le travail expérimental s’appuie sur la fabrication de générateurs de type VING (Vertical Integrated Nano Generators) et sur leur caractérisation. Pour cela, un système de caractérisation électromécanique a été construit pour évaluer les performances des NG réalisés et les effets thermiques sous une force compressive contrôlée. Le module d’Young et les coefficients piézoélectriques effectifs de NF de GaN; GaAs et ZnO et de NF à structure cœur/coquille à base de ZnO ont été évalués également dans un microscope à force atomique (AFM). Les nanofils de ZnO sont obtenus par croissance chimique en milieu liquide sur des substrats rigides (Si) ou flexibles (inox) puis sont intégrés pour former un générateur. La conception du dispositif VING s’est appuyée sur des simulations négligeant l’influence des porteurs libres, comme dans la plupart des études publiées. Nous avons ensuite approfondi le travail théorique en simulant le couplage complet entre les effets mécaniques, piézoélectriques et semi-conducteurs, et en tenant compte cette fois des porteurs libres. La prise en compte du piégeage du niveau de Fermi en surface nous permet de réconcilier observations théoriques et expérimentales. Nous proposons notamment une explication au fait que des effets de taille apparaissent expérimentalement pour des diamètres au moins 10 fois plus grands que les valeurs prévues par simulation ab-initio ou au fait que la réponse du VING est dissymétrique selon que le substrat sur lequel il est intégré est en flexion convexe ou concave
Energy autonomy in small sensors networks is one of the key quality parameter for end-users. It’s even critical when addressing applications in structures health monitoring (avionics, machines, building…), or in medical or environmental monitoring applications. Piezoelectric materials make it possible to exploit the otherwise wasted mechanical energy which is abundant in our environment (e. g. from vibrations, deformations related to movements or air fluxes). Thus, they can contribute to the energy autonomy of those small sensors. In the form of nanowires (NWs), piezoelectric materials offer a high sensibility allowing very small mechanical deformations to be exploited. They are also easy to integrate, even on flexible substrates.In this PhD thesis, we studied the potential of semiconducting piezoelectric NWs, of ZnO or III-V compounds, for the conversion from mechanical to electrical energy. An increasing number of publications have recently bloomed about these nanostructures and promising nanogenerators (NGs) have been reported. However, many questions are still open with, for instance, contradictions that remain between theoretical predictions and experimental observations.Our objective is to better understand the physical mechanisms which rule the piezoelectric response of semiconducting NWs and of the associated NGs. The experimental work was based on the fabrication of VING (Vertical Integrated Nano Generators) devices and their characterization. An electromechanical characterization set-up was built to evaluate the performance and thermal effects of the fabricated NGs under controlled compressive forces. Atomic Force Microscopy (AFM) was also used to evaluate the Young modulus and the effective piezoelectric coefficients of GaN, GaAs and ZnO NWs, as well as of ZnO-based core/shell NWs. Among them, ZnO NWs were grown using chemical bath deposition over rigid (Si) or flexible (stainless steel) substrates and further integrated to build VING piezoelectric generators. The VING design was based on simulations which neglected the effect of free carriers, as done in most publications to date. This theoretical work was further improved by considering the complete coupling between mechanical, piezoelectric and semiconducting effects, including free carriers. By taking into account the surface Fermi level pinning, we were able to reconcile theoretical and experimental observations. In particular, we propose an explanation to the fact that size effects are experimentally observed for NWs with diameters 10 times higher than expected from ab-initio simulations, or the fact that VING response is non-symmetrical according to whether the substrate on which it is integrated is actuated with a convex or concave bending

La demande de nouvelles technologies de conversion d'énergie augmente considérablement. Elle a pour but d’offrir une durée de vie augmentée aux microsystèmes et garantir ainsi leur autonomie sans aucune intervention humaine. Dans cette thèse, nous exploitons les nanotechnologies pour le développement d’une nouvelle génération de récupérateurs d’énergie mécanique flexibles et robustes, à partir des matériaux piézoélectriques. Des études expérimentales et des simulations numériques ont été effectuées afin d’améliorer les performances des NanoGénérateurs PiézoElectriques (PENG). Le dispositif piézoélectrique actif choisi est à base de nanofils de ZnO, synthétisé via une voie de synthèse hydrothermale à faible coût et basse température, compatible avec l’utilisation de substrats souples. Des études ont été effectuées dans le but d’optimiser les propriétés des nanostructures piézoélectriques, tels que la densité de charge libre dans le semi-conducteur, mais aussi la densité surfacique et la morphologie des nanofils. Des PENGs flexibles sur substrat de polydiméthylsiloxane, ont également été fabriqués et soumis à une force de compression à basse fréquence, montrant une bonne reproductibilité des performances, avec une puissance moyenne de 0,25 µW sur une charge de 56 MΩ, pour une force de 6 N appliquée à la fréquence de 5 Hz. Cette thèse ouvre d’intéressantes perspectives de développement des systèmes de récupération d'énergie mécanique totalement flexibles pour un développement de microsystèmes autonomes
The demand for new technologies of energy conversion is dramatically increasing that can offer increased life to the micro-systems and also ensures their energy autonomy without any human intervention. By exploiting nanotechnologies, the present thesis focuses on the development of new generation of flexible and robust piezoelectric mechanical energy harvesters, from piezoelectric materials. Both experiment and theoretical simulation studies are performed to improve the performance of PiezoElectric NanoGenerators (PENGs). The active piezoelectric material, ZnO nanowires, are synthesized via cost-effective and low-temperature hydrothermal synthesis route, compatible with different types of flexible substrates. Studies have been carried out in order to optimize the properties of piezoelectric material properties such as effect of free charge density in semiconductor, density and morphology of nanowires. Flexible PENGs on a polydimethylsiloxane substrate are also manufactured and subjected to a low frequency compression force, showing good performance reproducibility, with an average power of 0,25 µW on a load of 56 MΩ, for an applied force of 6 N at the frequency of 5 Hz. This thesis can open up interesting opportunities to develop fully flexible mechanical energy recovery systems for the development of autonomous micro systems

Piezoelectric nanogenerators (PNGs) are a new class of energy harvesting materials that show potential as a direct energy source for low powered electronics. Recently, piezoelectric polymers have been utilized for PNG technology due to low toxicity, high flexibility, and facile solution processing which provide manufacturing opportunities such as screen printing. Throughout the last decade, countless projects have focused on how to enhance the energy harvesting capabilities of these PNGs through the incorporation of nanoparticle fillers, which have been reported to enhance the piezoelectric properties of the film either directly through their intrinsic piezoelectric properties or through acting as surfaces for the interfacial nucleation of piezoelectric polymer crystals. Herein, two systems of PNGs formed from piezoelectric copolymers poly(vinylidene fluoride-co-hexafluropropylene) or poly(vinylidene fluoride-co-trifluoroethylene) mixed with high aspect ratio zinc oxide nanowires, hydroxyl functionalized multi-walled carbon nanotubes, or carboxylic acid functionalized single walled carbon nanotubes were investigated. Variations of filler type and loading are tested to determine influences on film morphology and piezoelectric properties. Power harvesting tests are conducted to directly determine the effect of nanoparticle addition on the output power of the non-poled devices. Both copolymer systems are found to exhibit a non-linear increase in output power with the increase of nanoparticle filler loading. The crystal polymorph properties of both systems are investigated by Fourier transform infrared spectroscopy. The microstructure of the poly(vinylidene fluoride-co-trifluoroethylene) films are further examined using X-ray diffraction, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy to determine the mechanism behind the increased power harvesting capabilities. As well, explanations for perceived output power from “self-poled” films are briefly explored.

碩士
國立虎尾科技大學
光電與材料科技研究所
100
Zinc oxide is a II-VI semiconductor material with direct band-gap of 3.37eV corresponding to the wavelength in the ultraviolet region. ZnO also has large exction binding energy (~60 meV). In addition, ZnO has low resistivity and high transparency in the visible region. As a result, ZnO is considered as a promising material for the application of the optoelectronics. In this study, ZnO film is deposited by sputter on ITO glass substrate,one dimensional type of ZnO nanorods nanostructure are grown by Hydrothermal. One dimensional type of nanostructure is analyed physical properties of ZnO nanorods and ZnO nanorods doped Ni and optical properties by XRD、FE-SEM、UV-VIS、photoluminescence.First, ZnO nanorods are grown respectively on ITO glass and PET substrate, then fabricate naogeneratator by making top electrode. Nanogenerator are driven by ultrasonic waves. ZnO nanorods are grown 9 hours and measured its voltage and current. The average current and average voltage are respectively 2.11×10-6 A and 0.08V. It can obtained well after deflecting by fabricating piezoelectric nanogenerator used ZnO films. Second, ZnO nanorods are grown on ITO glass, then fabricat top electode. We use ultrasonic waves to drive nanogenerator. The average current and average voltage of 0.007 moles are 9.6×10-6A and 0.96V at 3 hours, 6.02×10-5A and 0.06V at 6 hours, 1.05×10-5 A and 0.07V at 9 hours. ZnO nanorods with more Ni doped can obtained better characteristic of voltage – current then undoped.

碩士
國立虎尾科技大學
光電與材料科技研究所
97
Using low temperature wet chemical growth of one-dimensional aluminum-doped zinc oxide nanostructure on indium-tin oxide (ITO) substrates and flexible plastic substrates. Discuss effects of growth temperatures, concentrations, and reaction time on the morphology and characteristics of the ZnO nanorods. Photoluminescence (PL) and UV/Vis spectrometer were also employed to understand the luminescent and transmittance characteristics of the nanorods. This was due to the combination of Zn+ ions and OH- ions which affected by doping concentration. The results showed that when the temperatures and reaction time increased, the diameters of the nanorods increased. The photoluminescence measurements showed that the ZnO nanorods had good ultraviolet emission and blue emission. Furthermore, we assembled the ZnO nanorods arrays with zigzag electrodes for nanogenerators which driver by ultrasonic vibration. The current performance and Schottky barrier of the nanogenerators were also discussed.

碩士
國立成功大學
材料科學及工程學系
107
Wurtzite structure materials such as ZnO are considered to be the promising candidate for nanogenerators because of its unique properties. In this paper, we investigate the effect of yttrium(Y) doping on the piezoelectric coefficient of ZnO thin films synthesized on p-type Si (111) substrates via RF magnetron sputtering. XRD diffraction patterns show that all films presented ZnO wurtzite structure with c-axis preferential orientation and high crystallinity under small amount of yttrium doping. The chemical binding energy and composition of the thin films are measured by XPS, and the results confirm the substitution of zinc by yttrium. The electric hysteresis loop exhibits the ferroelectric property of Y doped ZnO thin films, which is the key to the enhancement of piezoelectric properties. The measurement of piezoelectric coefficient (d33) by PFM showing that Y doped ZnO thin films reach 49.6 pm/V at yttrium concentration is 1.6 a.t.%, which is higher than d33 of pure ZnO thin films. The Y doped ZnO based-nanogenetors present better output performance than that of ZnO based-nanogenerators, so it is considered that Y doped ZnO thin films have more potential to be developed on the field of nanogenerators.

碩士
國立虎尾科技大學
光電工程系光電與材料科技碩士班
106
Zinc oxide is II-VI compound semiconductor with a direct bandgap energy band structure (energy gap of 3.37 eV) and it also has large exction binding energy 60 meV. In addition, ZnO has the characteristic of low resistivity and high transparency, therefore, it is considered as a promising material for the application of the optoelectronics. In this study, ZnO film is deposited by sputter on ITO glass substrate, and Sulfur-doped ZnO nanorod Arrays structure are grown by hydrothermal method. Then, the shape of Sulfur-doped ZnO nanorod Arrays was analyzed by field Emission Scanning Electron Microscope (FE-SEM) and Transmission Electron Microscope (TEM). Analysis of Sulfur-doping into ZnO nanorod Arrays by Energy-Dispersive Spectroscopy (EDS) and Secondary Ion Mass Spectrometry (SIMS). Analysis of Sulfur-doping ZnO nanorod Arrays was crystallization and optical properties by Spectrum Analysis (XRD) and Fluorescence Spectroscopy (PL). In this study, the ITO etching paste was used to define the pattern. An electrode of Aluminum film was deposited on the ITO substrate by sputtering, then assembled with a sulfur-doped ZnO nanorod Arrays to form a nanogenerators, Using ultrasonic was driven nanogenerators. In this study, Sulfur-doping concentration of 0.005 mol is the best parameter, and the nanogenerator are measured with an average voltage of 150 mV, an average current of 0.16 μA, and an average power of 24 nW, respectively.

碩士
國立成功大學
材料科學及工程學系
107
This study investigates the piezopotential of porous ＆ non-porous ZnO nanowire arrays, and the porous one shows the ultra-high enhancement from COMSOL simulations and experimental results. First, we growth ZnO seed layer on silicon substrate by sputter in room temperature, then growth ZnO NWs by chemical bath deposition method, followed by hydrogen annealing to create surface pores and inner pores. We use SEM(HITACHI SU8000) to see the morphology, including diameter, length, and porosity, then use TEM(JEOL JEM-2100F-CS) to see inner pores and surface roughness. From the COMSOL result, piezopotential is proportional to porosity both in normal and lateral force, which is consistence with AFM measurements.

碩士
國立臺南大學
電機工程學系碩博士班
102
In this study, the S doped ZnO nanowires were successfully synthesized on flexible PET substrate by hydrothermal. The crystalline structure of these S doped samples were measured with SEM, EDS, XRD, PL and TEM. The doping concentration of sulfur into ZnO nanowires was 2.03 atm % in EDS. All XRD peaks of S doped ZnO shift to smaller angle. Photoluminescence spectra of S-doped ZnO nanowires show blue shift phenomenon of the green emissions compared with that of pure ZnO nanowires. By TEM EDS-Mapping analysis, we also can see that the S atomic were uniform distributed over the ZnO nanowires. In the S doped ZnO nanowires on flexible PET substrate, we combined it with device for measured the piezoelectric properties with different relative humidity (RH) and different temperature conditions. We also measured the piezoelectric properties with different relative humidity and used the 365nm UV lamp to discuss its resistance variation. In the last section, we used environmental vibration for driving our device to measure with different strain and 365nm UV lamp conditions to investigate the piezoelectric properties of it.

碩士
國立虎尾科技大學
光電與材料科技研究所
96
ZnO has some of the greatest potential among semiconductor materials for application in ultraviolet regions and nanotechnology. It has large exciton binding energy of about 60 meV, which is much greater than the thermal energy at room temperature, makes it a promising candidate for applications in blue-UV light emission and room-temperature UV lasing. ZnO is known to have wurtzite strucuture with lattice constant a = 3.249 Å, c = 5.207 Å. Furthermore, its highly piezoelectric constant makes it a highly valuable material for fabricating mechanical devices. For instance, ZnO thin film structures can be utilized as piezoelectrical device and ultraviolet light emitting diode. Several physical or chemical methods have been developed in succession for the preparation of ZnO nanorod/nanowire array, including vapor-liquid-solid process untilizing gold or tin as catalyst, metalorganic vapor-phase epitaxial growth, seed-layer assisted solution route, electrochemical deposition based on anodic alumina membranes, and so on. Compared with physical vapor methods, the solution based approaches exhibited obvious advantages in cost, facilities, complexity, energy consumption, and large scale up production. Self-powered nanosystems are of great importance for real-time and implantable biosensing, environmental monitoring, and electromechanical systems. We have developed a direct-current nanogenerator that is driven by ultrasonic wave. The basic principle is to use piezoelectric and semiconducting coupled nanorods(NRs), such as ZnO, to convert mechanical energy into electricity. The ZnO nanostructures were symthesized on different substrates using chemical depostion methods. In this experiment, ZnO nanostructrues grown included vapor and liquid solution epitaxial methods. In vapor epitaxial, effect of growth temperatures, Zn/C powder ratios, of gas ratios on the morphology and characteristics of ZnO naonowires were carried out. In liquid epitaxial, effect of growth temperatures, growth times, and of solutions of pH on the morphology and characteristics of ZnO naonorods were discused. The photoluminescence(PL) and transmittance of the ZnO nanostructures were measured by UV-VIS spectrophotometer and fluorescence spectrophotometer. The sanning electron microscope(SEM) results showed when the temperatures increased, the diameters of the ZnO grains increased. The ZnO nanowires and nanorods had a mean diameter of ~80 nm. The XRD results found that the ZnO nanorods had monocrystalline(002) structure by low temperature that the highest intensity at 90℃ and concentration ratio 2：4, and the ZnO nanowires exhibited polycrystalline structure by high -temperature method that the highest intensity at 800℃ and oxygen ratio 12：1. ZnO is a II-VI semiconductor with a band gap of 3.2 eV at room temperature. The photoluminescence measurements showed that the high-temperature epitaxial ZnO nanostructures had good ultraviolet emission at 382 nm and blue emission at 500 nm. The high-temperature epitaxial method PL characteristic quality more than low-temperature epitaxial method. Raman scattering spectrum was used to measure substance structure of the ZnO nanostructure. The raman scattering spectrum appeared two peaks at 438 cm-1 and 582 cm-1. The transmittance and absorption spectrums measurements showed that the ZnO nanorods had high transmittance 90% at 900 nm and good ultraviolet absorption at 350 nm. Transmission electron microscope(TEM) was used to measure crystal image and inner structure. Finally, making on top of electrode to fabricate nanogenerator(NG) with ZnO nanorods and measured micro-current driven by ultrasonic waves with a frequency of 43 kHz. When the ultrasonic wave was on for an extended period of time, the generated current was ~25 nA for a NG with 25 mm2 in size, corresponding to an output current density of 0.1μA/cm2 .

碩士
國立虎尾科技大學
光電與材料科技研究所
97
The ZnO nanostructures were synthesized on flexible soft substrate using chemical deposition methods. We applied the epitaxial growth to produce ZnO nanorods and assembled the nanogenerator with the nanorods. ZnO nanostructures were grown using liquid solution epitaxial method. In liquid epitaxial, effects of growth temperatures, growth times, and growth concentrations on the morphology and characteristics of ZnO nanorods were discussed. The results showed when the temperatures increased, the diameters of the nanowires increased. The XRD results found that the ZnO nanowires had monocrystalline (0002) structure. The ZnO nanostructures had good peak values in ultraviolet emission and blue emission. Finally, making on top of electrode to fabricate nanogenerator with ZnO nanorods and measured micro-current driven by ultrasonic waves, and measuring its voltage and current characteristics. To explore how different deflections of the electromechanical characteristics change with the state of bending in the substrate.

碩士
國立中央大學
能源工程研究所
101
This thesis mainly research fabrication of nanogenerator, piezoelectric technology and application in electrospinning. The focus of the study is (1) Massively parallel aligned nanofibers-based nanogenerator deposited via near-field electrospinning, (2) Superposition of nanogenerator and measurement, (3) A flexible, self-powered deformation sensor based on nanogenerator. we demonstrate a direct-write, in-situ poled polyvinylidene fluoride (PVDF) nanofiber arrays that could functions as a self-powered active deformation sensor. The fabricated hybrid structure of sensor/nanogenerator (NG) is realized via direct deposition of near-field electrospun nanofibers on Cu-foil electrode of thickness ~200 μm and fully encapsulated on a flexible substrate. Capable of integrating into fabric such as a waving flag due to high flexibility and excellent conformability, the nanofiber-based device can serve as an active deformation sensor under ambient wind-speed and the feasibility of efficiently convert the flutter motion into electricity are also demonstrated. This low-cost, simple structure, high sensitivity and good environment-friendly nanofibers is a very promising material/technology as practical energy harvesting devices and self-powered sensors and capable of scavenging very small wind power or mechanical induced vibration.

碩士
國立成功大學
材料科學及工程學系
106
The piezoelectric nanogenerators based on MgZnO can convert the mechanical energy into electrical energy via piezoelectric effect and are considered to be the promising environmentally friendly devices. We investigate the effect of Ga doping over the piezoelectric property of MgZnO thin films deposited on p-type Si (111) substrates through RF magnetron sputtering. The deposition is carried out at a fixed temperature (250℃ ) under argon (10 sccm)/oxygen (20 sccm) atmosphere and the thickness is maintained at around 500 nm. All of the films exhibit wurtzite structure with strong [0002] preferential orientation. In addition, gallium doping influences the magnesium concentration in Ga doped MgZnO films which balances the lattice deformation formed by the larger gallium and smaller magnesium at zinc site. The piezoelectric coefficient (d33) is improved to 40.32 pm/V at a gallium concentration (XGa) of 0.041 as that with pure ZnO (d33 ~ 12.4 pm/V). Ga doped MgZnO thin films have great potential to be fabricated as piezoelectric nanogenerators.

碩士
國立成功大學
物理學系
103
Piezoelectric Nanogenerator is a new frontier of harvesting ambient mechanical energy. Currently, the most common structure of piezoelectric nanogenerators is vertical integrated nanowire nanogenerator (VING). However, the VING was hardly utilized the piezoelectric advantage of blending nanowires. Here, using molecular beam epitaxy system (MBE), we have built a GaN nanowires nanogenerator based on silicon pyramid substrate to harvesting more mechanical energy and compare with traditional VING structure. The experimental results show that nanowire nanogenerator based on silicon pyramid substrate is substantially superior than the VING nanogenerator in terms of output piezoelectric voltage.

碩士
國立虎尾科技大學
電子工程系碩士班
107
Piezoelectric nanogenerator (PENG) is an emerging green energy alternative. ZnO has the characteristic of low resistivity and high transparency, therefore, it is considered as a promising material for the application of the optoelectronics. By changing the doping of the semiconductor surface chemistry is an effective method, the study proved that zinc oxide nanorods array chlorine doping can significantly improve the output performance of PENG. Hydrothermal growth of low density chlorine-doped zinc oxide nano-pillar structure on ITO glass without seed layer and preparation of nanogenerator. Then investigate the effect of the presence or absence nanorods seed layer and the difference in chemical doping of the nanorods grown on the substrate. After sputtering Pt film on ZnO nanorod arrays, the ZnO nanorod arrays with Pt film was assembled with the unsputtered nanostructure, which was driven by ultrasonic waves. The optimal I-V characteristics of ZnO nanogenerator were 5.62⨯10-6 A and 4.17⨯10-2 V.

In this work, SnS2 is used as a nanofiller material to improve the response of the polymer-based piezoelectric nanogenerator because of its better inherent piezoelectric properties in comparison to other 2D materials. For this, first, nanoflakes of tin sulfide (SnS2) were synthesized via the hydrothermal method, where the high purity of SnS2 powder is confirmed by Raman spectroscopy and X-ray diffraction studies. The obtained powder of SnS2 was then mixed with PVDF-TrFE in different weight percentages (0%, 1%, 3%, 5%, and 7%) of SnS2 to synthesize polymer composite film via the drop-casting method. These films are then characterized with XRD and FTIR spectrometers, which show enhancement in the electroactive beta phase of the nanocomposite films after doping with SnS2 powder, from 58.30% to 93.07%, which is in agreement with the polarization versus electric field (P-E) measurements that show increased remnant polarization after doping. These films are then used to fabricate a piezoelectric nanogenerator by adhering aluminum tape to both sides of the films. The piezoelectric nanogenerator's (PENG) output performance is analyzed by measuring the open-circuit voltage (Voc) and short-circuits (Isc) by tapping the nanogenerator with the help of a dynamic shaker, which shows that the output performance of Trifluoroethylene (PVDF-TrFE) based PENGs gets enhanced after the introduction of SnS2 powder. The maximum piezoelectric voltage corresponding to the PENG made with 5% SnS2 was 14.4 V, which was almost 1.5 times that of the PENG made with bare PVDF-TrFE. The output piezoelectric current followed a similar trend, with the 5% SnS2 PENG producing 3.9�A of current, which was roughly 1.62 times more than the output of the bare PVDF TrFE thin film. As a result, the present study demonstrates that adding SnS2 to the PVDF matrix can significantly improve energy harvesting technologies based on PVDF's piezoelectric properties.

This thesis present the fabrication of 2 types of soft wearable electrical devices, utilizing the 3D printing technique. The devices are capable to detect human heart pulse waves and sound waves for health evaluation and speech recognition.