Nanoscience and Nanotechnology Commons^™

Synthesis Of Metal Oxide Surface And Interface Arrays By A Combined Solid-Liquid- Vapor/Vapor-Liquid-Solid Approach, Alexandra J. Riddle

Theses and Dissertations--Chemistry

This project was motivated by an in situ heating experiment in the transmission electron microscope (TEM) in which gold (Au) nanoparticles were observed to dissolve tin dioxide (SnO2) nanowires (NWs) under vacuum. The explanation for this observation was that the high-temperature and low-pressure environment of the TEM caused the reverse reaction of the well-known vapor-liquid-solid (VLS) method commonly used to grow NWs. In the VLS process, a metal catalyst absorbs reactant vapor until it becomes supersaturated. The precipitation of the NW occurs at the liquid-solid interface, which ceases when there is no longer reactant vapor, and the diameter of the …

Zno Nanowires For Advanced X-Ray Source Applications, Vance Scott Robinson

Legacy Theses & Dissertations (2009 - 2024)

X-ray system technology trends tend towards simpler, smaller and more efficient devices. A broad range of applications are driving contemporary efforts in X-ray source miniaturization: Portable and/or remote nondestructive evaluation; High throughput protein crystallography, invasive radiotherapy; monitoring fluid flow and particulate generation in situ; and portable radiography devices for battle-front or large scale disaster triage scenarios. Most of the x-ray sources for these applications follow a top-down approach focused on improving portability, and reducing mass and/or size.

Deconvolving The Steps To Control Morphology, Composition, And Structure, In The Synthesis Of High-Aspect-Ratio Metal Oxide Nanomaterials, Lei Yu

Theses and Dissertations--Chemistry

Metal oxides are of interest not only because of their huge abundance but also for their many applications such as for electrocatalysts, gas sensors, diodes, solar cells and lithium ion batteries (LIBs). Nano-sized metal oxides are especially desirable since they have larger surface-to-volume ratios advantageous for catalytic properties, and can display size and shape confinement properties such as magnetism. Thus, it is very important to explore the synthetic methods for these materials. It is essential, therefore, to understand the reaction mechanisms to create these materials, both on the nanoscale, and in real-time, to have design control of materials with desired …

Laser Direct Written Silicon Nanowires For Electronic And Sensing Applications, Woongsik Nam

Open Access Dissertations

Silicon nanowires are promising building blocks for high-performance electronics and chemical/biological sensing devices due to their ultra-small body and high surface-to-volume ratios. However, the lack of the ability to assemble and position nanowires in a highly controlled manner still remains an obstacle to fully exploiting the substantial potential of nanowires. Here we demonstrate a one-step method to synthesize intrinsic and doped silicon nanowires for device applications. Sub-diffraction limited nanowires as thin as 60 nm are synthesized using laser direct writing in combination with chemical vapor deposition, which has the advantages of in-situ doping, catalyst-free growth, and precise control of position, …

Frequency Multiplication In Silicon Nanowires, Marius Mugurel Ghita

Dissertations and Theses

Frequency multiplication is an effect that arises in electronic components that exhibit a non-linear response to electromagnetic stimuli. Barriers to achieving very high frequency response from electronic devices are the device capacitance and other parasitic effects such as resistances that arise from the device geometry and are in general a function of the size of the device. In general, smaller device geometries and features lead to a faster response to electromagnetic stimuli. It was posited that the small size of the silicon nanowires (SiNWs) would lead to small device capacitance and spreading resistance, thus making the silicon nanowires useful in …

Doped Tio2 Nanowires For Applications In Dye Sensitized Solar Cells And Sacrifical Hydrogen Production, Qasem Alsharari

Electronic Thesis and Dissertation Repository

This thesis explores the synthesis of metal oxide 1-D nanowires using a sol-gel method in supercritical carbon dioxide (sc-CO₂), as an environmental friendly enabling solvent. Porous nanowires were synthesized and their performance was tested in dye sensitized solar cell and sacrifical hydrogen production. Titanium isopropoxide (TIP) was used as a precursor for titania synthesis while copper, bismuth and indium were examined as dopants, respectively. The sol-gel reactions were catalyzed by acetic acid in CO₂ at a temperature of 60 °C and pressure of 5000 psi. It was observed that acetic acid/monomer ratio > 4 produced nanowires while a …

Tailoring Optical And Plasmon Resonances In Core-Shell And Core-Multishell Nanowires, Sarath Ramadurgam

Open Access Dissertations

Semiconductor nanowires (NWs) are sub-wavelength structures which exhibit strong optical (Mie) resonances in the visible range. In addition to such optical resonances, the localized surface plasmon resonances (LSPR) in metal and semiconductor (or dielectric) based core-shell (CS) and core-multishell (CMS) NWs can be tailored to achieve novel negative-index metamaterials (NIM), extreme absorbers, invisibility cloaks and sensors. Particularly, in this dissertation, the versatility of CS and CMS NWs for the design of negative-index metamaterials in the visible range and, plasmonic light harvesting in ultrathin photocatalyst layers for water splitting are studied.

Utilizing the LSPR in the metal layer and the magnetic …

Development Of Integrated Tio₂ On Carburized Si Nanowires As A Catalyst/Support Structure For Alkaline Fuel Cells, Adam Lemke

Legacy Theses & Dissertations (2009 - 2024)

Due to a combination of environmental and economic motivations, there is a strong impetus to transition away from fossil fuels towards renewable sources of energy. Critical to achieving this goal will be technologies that allow for the storage and transmission of energy derived from renewable sources. Hydrogen fuel cells may play a significant role in making this a reality, allowing for the use of hydrogen as a non-carbon based fuel, in particular for vehicle applications. Hydrogen fuel cells directly convert chemical energy into electrical energy, with only water vapor and heat as waste products.

Radiation Effects In Gate-All-Around Silicon Nanowire Mosfets And Carbon Nanotube P-N Diodes, Everett Steven Comfort

Legacy Theses & Dissertations (2009 - 2024)

The scaling of MOSFETs has resulted in short channel effects that increase their power consumption above acceptable levels. In order to lower the power dissipation, new device designs and materials are being considered. For example, multiple-gate MOSFETs, including the gate-all-around silicon nanowire (GAA SiNW) MOSFET, are known to reduce short channel effects. Furthermore, new high-mobility channel materials such as single-walled carbon nanotubes (SWNTs) can be integrated to allow for further scaling of the supply voltage, again aiding in lowering power dissipation.

Development Of Nanostructured Limpo4 (M=Fe, Mn) As Cathodes For High Performance Lithium-Ion Batteries, Jinli Yang

Electronic Thesis and Dissertation Repository

Olivine LiFePO₄ has garnered the most interest because of its environmental benignity, high safety and theoretical capacity. However, the major limitation for LiFePO₄ is the intrinsically poor electronic conductivity and ionic conductivity. The sluggish kinetics for LiFePO₄ could be overcome by reducing the size, coating with conductive carbon, or doping with isovalent ions. The decrease of the size to nanoscale could shorten the diffusion time of Li ions in LiFePO₄ during intercalation/deintercalation process, but the nano-size active material usually accompanies with low tap density. Carbon coating and carbon addition could alleviate the poor electronic conductivity. However, …

Nanowire Giant Magnetoresistance Thin Films For Magnetic Sensors, Bryan Cox

Doctoral Dissertations

This dissertation details a novel method to fabricate magnetic sensors using nanowire giant magnetoresistance (GMR) thin films. In 1988, Albert Fert and Peter Grünberg both independently discovered a new physical phenomenon called GMR. GMR is a quantum mechanical effect found in thin film materials that are composed of alternating nanoscale ferromagnetic and non-magnetic conductive layers. When a GMR material is in the presence of a magnetic field, a change in electrical resistance is observed. The GMR effect has been utilized to produce magnetic sensors that have been used in a variety of applications, such as computer hard drive read heads, …

Exploring Bacterial Nanowires: From Properties To Functions And Implications, Kar Man Leung

Electronic Thesis and Dissertation Repository

The discovery of electrically conductive bacterial nanowires from a broad range of microbes provides completely new insights into microbial physiology. Shewanella oneidensis strain MR-1, a dissimilatory metal-reducing bacterium, produces extracellular bacterial nanowires up to tens of micrometers long, with a lateral dimension of ~10 nm. The Shewanella bacterial nanowires are efficient electrical conductors as revealed by scanning probe techniques such as CP-AFM and STM.

Direct electrical transport measurements along Shewanella nanowires reveal a measured nanowire resistivity on the order of 1 Ω∙cm. With electron transport rates up to 10⁹/s at 100 mV, bacterial nanowires can serve as a …

Synthesis, Processing And Characterization Of Silicon-Based Templated Nanowires, Jae Ho Lee

Legacy Theses & Dissertations (2009 - 2024)

Semiconductor and metallic nanowires have attracted substantial attention due to their wide variety of applications, ranging from nanoelectronics to energy storage devices. In particular, self-assembled silicon nanowires (SiNWs) may be an attractive alternative to conventionally processed planar silicon since SiNWs can potentially function as both the switch (i.e. transistor) and local interconnect (e.g. metal silicide nanowire) to form an inherently integrated nanoelectronic system. Also, hierarchical (branched) nanowire systems hold potential for catalysts or porous electrode applications for energy applications