Organizational Unit:
School of Materials Science and Engineering
School of Materials Science and Engineering
Permanent Link
Research Organization Registry ID
Description
Previous Names
Parent Organization
Parent Organization
Organizational Unit
Includes Organization(s)
ArchiveSpace Name Record
Publication Search Results
Now showing
1 - 8 of 8
-
ItemAcoustics in nanotechnology: manipulation, device application and modeling(Georgia Institute of Technology, 2007-12-19) Buchine, Brent AlanAdvancing the field of nanotechnology to incorporate the unique properties observed at the nanoscale into functional devices has become a major scientific thrust of the 21st century. New fabrication tools and assembly techniques are required to design and manufacture devices based on one-dimensional nanostructures. Three techniques for manipulating nanomaterials post-synthesis have been developed. Two of them involve direct contact manipulation through the utilization of a physical probe. The third uses optically generated surface acoustic waves to reproducibly control and assemble one-dimensional nanostructures into desired locations. The nature of the third technique is non-contact and limits contamination and defects from being introduced into a device by manipulation. While the effective manipulation of individual nanostructures into device components is important for building functional nanosystems, commercialization is limited by this one-device-at-a-time process. A new approach to nanostructure synthesis was also developed to site-specifically nucleate and grow nanowires between two electrodes. Integrating synthesis directly with prefabricated device architectures leads to the possible mass production of NEMS, MEMS and CMOS systems based upon one-dimensional nanomaterials. The above processes have been pursued to utilize piezoelectric ZnO nanobelts for applications in high frequency electronic filtering as well as biological and chemical sensing. The high quality, single crystal, faceted nature of these materials make them ideal candidates for studying their properties through the designs of a bulk acoustic resonator. The first ever piezoelectric bulk acoustic resonator based on bottom-up synthesized belts will be demonstrated. Initial results are promising and new designs are implemented to scale the device to sub-micron dimensions. Multiple models will be developed to assist with design and testing. Some of models presented will help verify experimental results while others will demonstrate some of the problems plaguing further investigations.
-
ItemTransport Properties and Nanosensors of Oxide Nanowires and Nanobelts(Georgia Institute of Technology, 2007-10-29) Lao, ChangshiZnO is one of the most important materials for electronics, optoelectronics, piezoelectricity and optics. With a wide band gap of 3.37eV and an exiton binding energy of 60meV, ZnO 1D nanostructures exhibit promising properties in a lot of optical device applications. It is also an important piezoelectric material and has applications in a new category of nanodevices, nano-piezotronics. Demonstrated prototype of devices includes nanogenerators, piezoelectric-FET, and a series of evolutive devices based on the concept of nanogenerator. This is based on working principle of a semiconductor and piezoelectric coupled property. This thesis is about the growth, characterization and device fabrication of ZnO nanowires and nanobelts for sensors and UV detectors. First, the fundamental synthesis of ZnO nanostructurs is investigated, particularly polar surface dominated nanostructues, to illustrate the unique growth configurations of ZnO. Detail study in this part includes nanobelts, nanorings, nanocombs, nanonetworks, and nanodiskettes synthesis. Important factors in driving the nanostructure synthesis mechanism are analyzed, such as the chemical activities of different surface of ZnO and the polar surface dominated effects. Then, the devices fabricated methods using individual nanowires/nanobelts and their electrical transport properties were carefully characterized. In this part, dominant factors which are critical for nanobelt device performance are investigated, such as the contact properties, interface effects, and durability testing. Also, a metal doping method is studied to explore the controlling and modification of nanowire electric and optical properties. Further more, I will present the surface functionalization of nanobelt for largely improving its electrical, optoelectronic and chemical performance. Surface functionalization of nanobelts is proven to be an effective method in enhancing the semiconductor and metal contact. Piezoelectric field-effect transistors will be demonstrated as a powerful approach as chemical sensors. Finally, a technique is illustrated for functionalizing the surfaces of ZnO nanobelts for enhancing its UV sensitivity by over five orders of magnitude. This demonstrates an effective approach for fabricatiing ultrasensitive UV detectors. The research results presented in this thesis have made great contribution to the growth, device fabrication and novel applications of ZnO nanostructures for photonics, optoelectronics and sensors.
-
ItemOxide nanomaterials: synthesis, structure, properties and novel devices(Georgia Institute of Technology, 2007-06-22) Yang, RusenOne-dimensional and hierarchical nanostructures have acquired tremendous attention in the past decades due to their possible application. In spite of the rapid emergence of new morphologies, the underlying growth mechanism is still not well understood. The lack of effective p-type or n-type doping is another obstacle for many semiconducting nanomaterials. A deeper investigation into these structures and new methods to fabricate devices are of significant impact for nanoscience and nanotechnology. Motivated by a desire to understand the growth mechanism of nanostructures and investigate novel device fabrication method, the research described in this thesis carried out on the synthesis, characterization, and device fabrication of semiconducting nanostructures. The main focus of the research was on ZnO, SnO2, and Zn3P2 for their great capability for fundamental phenomena studying, promising applications in sensors and optoelectronics, and the potential generalization of results to other materials. Within this study the following goals have been achieved: 1) Improved understanding of polar-surface-induced growth mechanism in wurtzite-structured ZnO and generalization of this growth mechanism with the discovery and analysis of rutile ¨Cstructured SnO2, 2) observation of the significance of the transversal growth, which is usually ignored, in interpenetrative ZnO nanowires, 3) rational design and growth control over versatile nanostructures of ZnO and Zn3P2, and 4) conjunction of p-type Zn3P2 and n-type ZnO semiconducting nanostructures for device fabrications. The framework for the research is reviewed first in chapter 1. Chapter 2 gives the detailed experimental setup, synthesis procedure, and common growth mechanism for nanostructure growth. A detailed discussion on the growth of ZnO nanostructures in chapter 3 provides more insight into the polar-surface-induced growth, transversal growth, vapor-solid growth, and vapor-liquid-solid growth during the formation of nanostructures. Polar-surface-induced growth is also confirmed in the growth of SnO2 nanostructures, which is also included in chapter 2. Chapter 3 presents Zn3P2 nanostructures from the newly designed experiment setup and the device fabrication from ZnO and Zn3P2 crossed nanowires.
-
ItemNovel ZnS Nanostructures: Synthesis, Growth Mechanism, and Applications(Georgia Institute of Technology, 2006-10-27) Moore, Daniel FrankelMotivated by a desire to understand the basic concepts of one-dimensional nanostructure growth, the research described in this thesis aims at understanding the basic mechanisms controlling the synthesis and formation of a specific group of II-VI semiconducting nanostructures. In particular, this thesis examines one-dimensional nanostructures (such as nanobelts and nanowires) and different morphologies of ZnS that result from the interesting properties that the materials have at the nanoscale. In order to understand how to tune these properties in the nanostructure, it is necessary to have an understanding of the growth mechanism that dictates the morphology, structure, and rate of growth of the nanomaterial. It is necessary to understand what impact changes to the macroscopic setup in the experiment have on the nanoscopic scale of the nanomaterials. Having a larger understanding and exerting more precise control over the growth of nanomaterials will allow a higher level of selectivity, more control over dimensionality and the type of morphology, easier manipulation, and the simpler incorporation of these structures into a nanotechnological device. The main focus of the research was on CdSe and ZnS, with the bulk of the research being conducted on ZnS nanostructures. These materials were chosen for their potential for extensive research, their possible applications in optoelectronics, their potential to form the wurtzite crystal structure, and the potential generalization of results to other nanomaterials. The framework for the research is given first. Then a description of the experimental setup and a model for the growth of nanostructures is discussed. A brief overview of the synthesis of CdSe nanostructures is given and then a detailed analysis of the synthesis of specific ZnS one-dimensional morphologies is presented.
-
ItemSynthesis and characterization of zinc oxide nanostructures for piezoelectric applications(Georgia Institute of Technology, 2006-08-24) Hughes, William L.Union between top-down and bottom-up assembly is inevitable when scaling down physical, chemical, and biological sensors and probes. Current sensor/probe-based technologies are firmly founded on top-down manufacturing, with limitations in cost of production, manufacturing methods, and material constraints. As an alternative to such limitations, contemporary synthesis techniques for one-dimensional nanostructures have been combined with established methods of micro-fabrication for the development of novel tools and techniques for nanotechnology. More specifically, this dissertation is a systematic study of the synthesis and characterization of ZnO nanostructures for piezoelectric applications. Within this study the following goals have been achieved: 1) rational design and control of a diversity of novel ZnO nanostructures, 2) improved understanding of polar-surface-dominated (PSD) phenomena among Wurtzite crystal structures, 3) confirmation of Taskers Rule via the synthesis, characterization, and modeling of polar-surface-dominated nanostructures, 4) measurement of the surface-charge density for real polar surfaces of ZnO, 5) confirmation of the electrostatic polar-charge model used to describe polar-surface-dominated phenomena, 6) dispersion of ZnO nanobelts onto the selective layers of surface acoustic wave (SAW) devices for gas sensing applications, 7) manipulation of ZnO nanostructures using an atomic force microscope (AFM) for the development of piezoelectric devices, 8) fabrication of bulk acoustic resonator (BAR) and film bulk acoustic resonator (FBAR) devices based on the integrity of individual ZnO belts, 9) electrical characterization of a ZnO belt BAR device, 10) prediction and confirmation of the electrical response from a BAR device using a one-dimensional Krimholt-Leedom-Matthaei (KLM) model, and 11) development of a finite element model (FEM) to accurately predict the electrical response from ZnO belt BAR and FBAR devices in 3D.
-
ItemPiezoelectric Nanostructures of Zinc Oxide: Synthesis, Characterization and Devices(Georgia Institute of Technology, 2005-11-28) Gao, PuxianIn 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.
-
ItemLarge-Scale Patterned Oxide Nanostructures: Fabrication, Characterization and Applications(Georgia Institute of Technology, 2005-11-28) Wang, XudongNanotechnology 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.
-
ItemSystematic Investigation On The Growth Of One-Dimensional Wurtzite Nanostructures(Georgia Institute of Technology, 2005-07-20) Ma, ChristopherA systematic investigation into the growth of one-dimensional nanostructures of select II-VI compounds with the wurtzite crystal structure. Two process parameters are systematically altered to observe how each affects deposition. The results of which give a further understanding into the formation of one nanostructure over another, as well as experimental parameters for optimizing the growth of particular CdSe nanomaterials. A statistical analysis is conducted on the experimental data to quantitatively determine the variability and robustness of the experimental setup and process. The information complied from this extensive study will yield a more complete understanding of the experimental setup and how improvements can be made to reduce variability, increase yield, and gain insight into the mechanisms controlling this class of materials.