Nanoscience and Nanotechnology Commons^™

Nanomechanics Modeling Of Carbon Nanotubes Interacting With Surfaces In Various Configurations, Yu-Chiao Wu

Mechanical Engineering Dissertations

Carbon nanotubes (CNTs) have been widely used as potential components in reported nanoelectromechanical (NEM) devices due to their excellent mechanical and electrical properties. This thesis models the experiments by the continuum mechanics in two distinct scenarios.

In the first situation, measurements are made of CNT configurations after manipulations. Modeling is then used to determine the interfacial properties during the manipulation which led to the observed configuration. This technique is used to determine the shear stress between a SWNT bundle and other materials. During manipulation, a SWNT bundle slipped on two micro-cantilevers. According to the slack due to the slippage after ...

Study Of Ultrashort Laser-Pulse Induced Ripples Formed At The Interface Of Silicon-Dioxide On Silicon, Bing Liu

Open Access Dissertations and Theses

In this thesis, the ripple formation at the interface of SiO2 and Si were studied in a systematic fashion by irradiating the SiO2-Si samples with ultrashort laser pulses under a broad variety of experimental conditions. They consist of di↵erent irradiating laser wavelengths, incident laser energies, translation speeds, translation directions, spot sizes of the laser beam, as well as oxide thicknesses. The ripples produced by laser irradiation are examined using various microscopy techniques in order to characterize their surface morphology, detailed structures, crystalline properties, and so on. For the experiments carried out at ! = 800 nm, the ripples formed on the ...

Development Of Nano-Zro2 Reinforced Self-Flowing Low And Ultra Low Cement Refractory Castables, Cem Gogtas

Theses and Dissertations

The main goal of this research is to develop high strength high toughness nano-ZrO2 reinforced self flow low cement (5%) and ultra low cement (3 and 1%) castables based on tabular alumina. In processing these castables, the Andreassen model was used to obtain optimum self flow properties in both, low and ultra low castables. The castables thus produced were fired at 110 and 1000, 1300 and 1500oC and the phases obtained were investigated by X-ray diffraction (XRD) including energy dispersive X-ray (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In addition, the other castable properties ...

Colloidal Nano-Apatite Particles With Active Luminescent And Magentic Properties For Biotechnology Applications, Rajendra Kasinath, Kumar Ganesan

Environmental Engineering

Colloidal Nano-apatite Particles with Active Luminescent and Magentic Properties for Biotechnology Applications. The synthesis of functional nano-materials is a burgeoning field that has produced remarkable and consistent breakthroughs over the last two decades. Individual particles have become smaller and shown potential for well defined functionality. However, there are still unresolved problems, a primary one being the loss of functionality and novelty due to uncontrolled aggregation driven by surface energy considerations. As such the first design criteria to harness the true potential of nanoparticles is to prevent unwanted agglomeration by: (1) improving, and, if possible, (2) controlling aggregation behavior. This requires ...

Ph Responsive Hydrogen Bonding Motif To Improve The Sensitivity Of Tumor Imaging, Fatimah Mohammed Algarni

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) is a powerful non-invasive medical diagnostic technique. Superparamagnetic iron oxide nanoparticles (SPIO) are effective contrast agents and provide high sensitivity contrast in MRI. Recent research has demonstrated that nanoparticle clusters exhibit significantly higher relaxivity than individual nanoparticles.

In order to increase the sensitivity of tumor imaging, supramolecular chemistry was introduced to this field and a novel conjugation method was developed using click chemistry between azide functionalized nanoparticles and pH-sensitive hydrogen bonding building blocks. This pH-sensitive hydrogen bonded complex was synthesized to cluster nanoparticles under mildly acidic biological conditions.

Due to the unexpected X-ray crystal structure of ...

On The Scaling Behavior Of Organic Ferroelectric Copolymer Pvdf-Trfe For Memory Application, Saptarshi Das, Joerg Appenzeller

Birck and NCN Publications

We report an interesting scaling trend in the switching time and the switching voltage of the organic ferroelectric copolymer PVDF-TrFE as a function of the device area. We have found that shrinking the lateral dimensions of the ferroelectric film results in a dramatic decrease in the switching time and the switching voltage. The phenomenological theory, that explains this abnormal scaling trend, involves in-plane interaction of the polymeric chains of the two-dimensional Langmuir-Blodgett (LB) films of the copolymer PVDF-TrFE interchain and intrachain coupling results in a weak power-law dependence of the switching field on the device area (E-SW alpha A(CH ...

Increased Normal Incidence Photocurrent In Quantum Dot Infrared Photodetectors, Jiayi Shao, Thomas E. Vandervelde, Ajit Barve, Andreas Stintz, Sanjay Krishna

Birck and NCN Publications

We have increased the ratio of s-polarization (normal incidence) to p-polarization photocurrent to 50% in a quantum dot-in-a-well based infrared photodetector form the typical s-p polarization ratio about 20%. This improvement was achieved by engineering the dot geometry and the quantum confinement via post growth capping materials of the Stranski Krastanov growth mode quantum dots (QDs). The TEM images show that the height to base ratio of shape engineered QDs was increased to 8 nm/12 nm from the control sample's ratio 4 nm/17 nm. The dot geometry correlates with the polarized photocurrent measurements of the detector. (C ...

Contrasting Energy Scales Of Reentrant Integer Quantum Hall States, Nianpei Deng, J. D. Watson, L. P. Rokhinson, M. J. Manfra, G. A. Csathy

Birck and NCN Publications

We report drastically different onset temperatures of the reentrant integer quantum Hall states in the second and third Landau level. This finding is in quantitative disagreement with the Hartree-Fock theory of the bubble phases which is thought to describe these reentrant states. Our results indicate that the number of electrons per bubble in either the second or the third Landau level is likely different than predicted.

Wavelength-Dependent Absorption In Structurally Tailored Randomly Branched Vertical Arrays Of Insb Nanowires, Asaduzzaman Mohammad, Suprem R. Das, Mohammad R. Khan, Muhammad A. Alam, David B. Janes

Birck and NCN Publications

Arrays of semiconductor nanowires are of potential interest for applications including photovoltaic devices and IR detectors/imagers. While nominally uniform arrays have typically been studied, arrays containing nanowires with multiple diameters and/or random distributions of diameters could allow tailoring of the photonic properties of the arrays. In this Letter, we demonstrate the growth and optical properties of randomly branched InSb nanowire arrays. The structure mentioned can be approximated as three vertically stacked regions, with average diameters of 20, 100, and 150 nm within the respective layers. Reflectance and transmittance measurements on structures with different average nanowire lengths have been ...

Dc-Dynamic Biasing For > 50x Switching Time Improvement In Severely Underdamped Fringing-Field Electrostatic Mems Actuators, J. Small, A. Fruehling, A. Garg, X. Liu, D. Peroulis

Birck and NCN Publications

This paper presents the design and experimental validation of dc-dynamic biasing for >50x switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators. The electrostatic fringing-field actuator is used to demonstrate the concept due to its robust device design and inherently low damping conditions. In order to accurately quantify the gap height versus voltage characteristics, a heuristic model is developed. The difference between the heuristic model and numerical simulation is less than 5.6% for typical MEMS geometries. MEMS fixed-fixed beams are fabricated and measured for experimental validation. Good agreement is observed between the calculated and measured results. For a ...

Indirectly Pumped 3.7 Thz Ingaas/Inalas Quantum-Cascade Lasers Grown By Metal-Organic Vapor-Phase Epitaxy, Kazuue Fujita, Masamichi Yamanishi, Shinichi Furuta, Kazunori Tanaka, Tadataka Edamura, Tillmann Kubis, Gerhard Klimeck

Birck and NCN Publications

Device-performances of 3.7 THz indirect-pumping quantum- cascade lasers are demonstrated in an InGaAs/InAlAs material system grown by metal-organic vapor-phase epitaxy. The lasers show a low threshold-current-density of ~420 A/cm² and a peak output power of ~8 mW at 7 K, no sign of parasitic currents with recourse to well-designed coupled-well injectors in the indirect pump scheme, and a maximum operating temperature of T_max~100 K. The observed roll-over of output intensities in current ranges below maximum currents and limitation of T_max are discussed with a model for electron-gas heating in injectors. Possible ways toward ...

Observation Of 1d Behavior In Si Nanowires: Toward High-Performance Tfets, Ramon B. Salazar, Saumitra R. Mehrotra, Gerhard Klimeck, Navab Singh, Joerg Appenzeller

Birck and NCN Publications

This article provides experimental evidence of one-dimensional behavior of silicon (Si) nanowires (NWs) at low-temperature through both transfer (Id−VG) and capaci- tance−voltage characteristics. For the first time, operation of Si NWs in the quantum capacitance limit (QCL) is experimentally demonstrated and quantitatively analyzed. This is of relevance since working in the QCL may allow, e.g., tunneling field-effect transistors (TFETs) to achieve higher on-state currents (Ion) and larger on-/off-state current ratios (Ion/Ioff), thus addressing one of the most severe limitations of TFETs. Comparison of the experimental data with simulations finds excellent agreement using a simple capacitor ...

Growth Of Inas/Inp Nanowires By Molecular Beam Epitaxy, Christopher M. Haapamaki

Open Access Dissertations and Theses

InP nanowires with short InAs segments were grown on InP (111)B substrates by Au assisted vapour-liquid-solid growth in a gas source molecular beam epitaxy system. Nanowire crystal structure and morphology were investigated by transmission electron microscopy as a function of temperature, growth rate, and V/III flux ratio. At 370C predominantly kinked nanowires with random morphology and low areal density were observed with a rough parasitic 2D film. At 440C, nanowire density was also reduced but the 2D film growth was smoother and nanowires grew straight without kinking. An optimum temperature of 400C maximized areal density with uniform nanowire ...

Quantum Dot Deposition Into Pdms And Application Onto A Solar Cell, Christopher Marcus Botros, Richard N. Savage

Master's Theses and Project Reports

Research to increase the efficiency of conventional solar cells is constantly underway. The goal of this work is to increase the efficiency of conventional solar cells by incorporating quantum dot (QD) nanoparticles in the absorption mechanism. The strategy is to have the QDs absorb UV and fluoresce photons in the visible region that are more readily absorbed by the cells. The outcome is that the cells have more visible photons to absorb and have increased power output. The QDs, having a CdSe core and a ZnS shell, were applied to the solar cells as follows. First, the QDs were synthesized ...

Ecotoxicological Assessment Of Silica And Polystyrene Nanoparticles Assessed By A Multitrophic Test Battery, Maria Casado, Ailbhe Macken, Hugh J. Byrne

Articles

The acute ecotoxicity of different diameters of silica and polyethyleneimine polystyrene (PS-PEI)nanoparticles (NPs)was assessed on a test battery of aquatic organisms representing different trophic levels. Daphnia magna, Thamnocephalus platyurus, Pseudokirchneriella subcapitata and Vibrio fischeri, were employed in a series of standard acute ecotoxicity tests and work was complemented with two cytotoxicological end points on a rainbow trout gonadal cell line (RTG-2). Physico-chemical characterization of the NPs was performed in the different test media employed, using dynamic light scattering (DLS) and zeta potentiometry. In contrast to silica NPs exposure, for which no effect was observed for concentrations up to ...

Anti-Bacterial Activity Of Indoor Light Activated Photocatalysts, Suresh Pillai, Michael Seery, Damian W. Synnott, Stephen Hinder, Georg Michlits

Articles

Nanocrystalline photocatalysts, prepared under ambient conditions using a microwave assisted syn-thesis, show indoor light photocatalytic activity for the degradation of Staphylococcus aureus and Escherichia coli. The zinc sulphide (ZnS) nanomaterials, prepared by a microwave assisted synthesis, are shown to be cubic blende structure with an average crystallite size of 4–6 nm. The anti-bacterial activ-ity of these nanomaterials is investigated under irradiation from a 60 W light bulb and photocatalytic activity is revealed to be due to the defects present in the crystal structure. The ZnS shows anti-bacterial action as both a bacteriostatic and bacteriocidal (88% reduction in the amount ...

Microwave-Assisted Surface Synthesis Of A Boron-Carbon-Nitrogen Foam And Its Desorption Enthalpy, Rajib Paul, Andrey A. Voevodin, Dimitry Zemlyanov, Ajit K. Roy, Timothy S. Fisher

Birck and NCN Publications

The modification of microporous carbon foam with boron and nitrogen through a facile microwave chemical treatment are reported. The resulting surfaces of the foam exhibit distinct BN and carbon domains based on chemical and microscopic analysis, in keeping with theoretical predictions. The resultant materials are shown to exhibit exceptionally high methanol desorption enthalpy and thermal stability in comparison to untreated carbon foam and consequently are suggested as candidate materials for sorption cooling and thermal storage applications using methanol as the adsorbate.

Frequency Response Of Laalo3/Srtio3 All-Oxide Field-Effect Transistors, Qingmin Liu, Lin Dong, Yiqun Liu, Roy Gordon, Peide D. Ye, Patrick Fay, Alan Seabaugh

Birck and NCN Publications

The frequency response of all oxide field-effect transistors with amorphous LaAlO3 on a crystalline SrTiO3 substrate is reported. The intrinsic cut-off frequencies of 4 mu m gate-length devices are found to be approximately 17 MHz indicating that with gate length scaling gigahertz cut-off frequency is possible. The low cut-off frequency is primarily limited by the low effective mobility. The estimated effective mobility value determined from the S-parameter measurement is 3.8 cm(2)/Vs, which is consistent with previous reports. Small-signal equivalent circuit model parameters are extracted by fitting to on-wafer measured S-parameters. Good agreement is obtained between measured and ...

Spectral Engineering Via Silicon Nanocrystals Grown By Ecr-Pecvd For Photovoltaic Applications, Justin Sacks

Open Access Dissertations and Theses

The aim of third-generation photovoltaics (PV) is ultimately to achieve low-cost, high-efficiency devices. This work focused on a third-generation PV concept known as down-shifting, which is the conversion of high-energy photons into low-energy photons which are more useful for a typical solar cell. Silicon nanocrystals (Si-NCs) fabricated using electron-cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD) were studied as a down-shifting material for single-junction silicon cells. A calibration was done to determine optimal deposition parameters for Si-NC formation. An experiment was then done to determine the effect of film thickness on emission, optical properties, and photoluminescence quantum efficiencies.

Photoluminescence (PL) peaks ...

Molecular Dynamics Studies Of Ultrafast Laser-Induced Phase And Structural Change In Crystalline Silicon, Chengjuan Yang, Yaguo Wang, Xianfan Xu

Birck and NCN Publications

In this work, thermodynamic phenomena in crystalline silicon irradiated by an ultrafast laser pulse were studied using the method of molecular dynamics simulations. The Stillinger-Weber potential was used to model the crystalline silicon. The temperature development in silicon when heated by an ultrafast laser pulse was tracked. Melting and resolidification processes and the resulting structural change were investigated. Radial Distribution Functions were used to track the liquid-amorphous interface during resolidification. It was found that the temperature at the solid-liquid interface could deviate from the equilibrium melting temperature by several hundred degrees. After the melted layer was solidified, some melted material ...