Nanoscience and Nanotechnology Commons^™

Encapsulated 2d Materials And The Potential For 1d Electrical Contacts, Sarah Wittenburg

Physics Undergraduate Honors Theses

The utilization of two-dimensional materials and heterostructures, particularly graphene and hexagonal boron nitride, have garnered significant attention in the realm of nanoelectronics due to their unique properties and versatile functionalities. This study focuses on the synthesis and fabrication processes of monolayer graphene encapsulated between layers of hBN, aiming to explore the potential of these heterostructures for various electronic applications. The encapsulation of graphene within hBN layers not only enhances device performance but also shields graphene from environmental contaminants, ensuring long-term stability. Experimental techniques, including mechanical exfoliation and stamp-assisted transfer, are employed to construct three-layer stacks comprising hBN-graphene-hBN. The fabrication process …

Gate-Controlled Supercurrent Effect In Dry-Etched Dayem Bridges Of Non-Centrosymmetric Niobium Rhenium, Jennifer Koch, Carla Cirillo, Sebastiano Battisti, Leon Ruf, Zahra Makhdoumi Kakhaki, Alessandro Paghi, Armen Gulian, Serafim Teknowijoyo, Giorgio De Simoni, Francesco Giazotto, Carmine Attanasio, Elke Scheer, Angelo Di Bernardo

Mathematics, Physics, and Computer Science Faculty Articles and Research

The application of a gate voltage to control the superconducting current flowing through a nanoscale superconducting constriction, named as gate-controlled supercurrent (GCS), has raised great interest for fundamental and technological reasons. To gain a deeper understanding of this effect and develop superconducting technologies based on it, the material and physical parameters crucial for the GCS effect must be identified. Top-down fabrication protocols should also be optimized to increase device scalability, although studies suggest that top-down fabricated devices are more resilient to show a GCS. Here, we investigate gated superconducting nanobridges made with a top-down fabrication process from thin films of …

Impact Of Silicon Ion Irradiation On Aluminum Nitride-Transduced Microelectromechanical Resonators, David D. Lynes, Joshua Young, Eric Lang, Hengky Chandrahalim

Faculty Publications

Microelectromechanical systems (MEMS) resonators use is widespread, from electronic filters and oscillators to physical sensors such as accelerometers and gyroscopes. These devices' ubiquity, small size, and low power consumption make them ideal for use in systems such as CubeSats, micro aerial vehicles, autonomous underwater vehicles, and micro-robots operating in radiation environments. Radiation's interaction with materials manifests as atomic displacement and ionization, resulting in mechanical and electronic property changes, photocurrents, and charge buildup. This study examines silicon (Si) ion irradiation's interaction with piezoelectrically transduced MEMS resonators. Furthermore, the effect of adding a dielectric silicon oxide (SiO₂) thin film is …

Superheating Field In Superconductors With Nanostructured Surfaces, W. P. M. R. Pathirana, A. Gurevich

Physics Faculty Publications

We report calculations of a dc superheating field H_sh in superconductors with nanostructured surfaces. Numerical simulations of the Ginzburg-Landau (GL) equations were performed for a superconductor with an inhomogeneous impurity concentration, a thin superconducting layer on top of another superconductor, and superconductor-insulator-superconductor (S-I-S) multilayers.The superheating field was calculated taking into account the instability of the Meissner state with a nonzero wavelength along the surface, which is essential for realistic values of the GL parameter κ. Simulations were done for the materials parameters of Nb and Nb₃Sn at different values of κ and the mean free paths. We …

Carrier Transport Engineering In Wide Bandgap Semiconductors For Photonic And Memory Device Applications, Ravi Teja Velpula

Dissertations

Wide bandgap (WBG) semiconductors play a crucial role in the current solid-state lighting technology. The AlGaN compound semiconductor is widely used for ultraviolet (UV) light-emitting diodes (LEDs), however, the efficiency of these LEDs is largely in a single-digit percentage range due to several factors. Until recently, AlInN alloy has been relatively unexplored, though it holds potential for light-emitters operating in the visible and UV regions. In this dissertation, the first axial AlInN core-shell nanowire UV LEDs operating in the UV-A and UV-B regions with an internal quantum efficiency (IQE) of 52% are demonstrated. Moreover, the light extraction efficiency of this …

Characterization Of Electrophoretic Deposited Zinc Oxide Nanopartices For The Fabrication Of Next-Generation Nanoscale Electronic Applications, Fawwaz Abduh A. Hazzazi

LSU Doctoral Dissertations

Several reports state that it is crucial to analyze nanoscale semiconductor materials and devices with potential benefits to meet the need for next-generation nanoelectronics, bio, and nanosensors. The progress in the electronics field is as significant now, with modern technology constantly evolving and a greater focus on more efficient robust optoelectronic applications. This dissertation focuses on the study and examination of the practicality of Electrophoretic Deposition (EPD) of zinc oxide (ZnO) nanoparticles (NPs) for use in semiconductor applications.

The feasibility of several synthesized electrolytes, with and without surfactants and APTES surface functionalization, is discussed. The primary objective of this study …

Designing Cryogenic Strain Device For 2d Materials, Jake Carter

Mechanical Engineering Undergraduate Honors Theses

The Churchill lab working within the Physics Department at the University of Arkansas is working to create important quantum states including weak topological insulators (TIs) through the use of symmetry engineering and topological electronic states in two-dimensional (2D) crystals of WHM materials. Experimental results of these topological states have been obstructed due to the difficulty to perform controlled in situ strain. This project strives to create a mount to utilize a piezoelectric nanopositioner within cryostats achieving an in situ strain that creates the quantum states the lab is looking to observe. This report also examines the necessary equations to determine …

Surface Acoustic Waves Increase Magnetic Domain Wall Velocity, Anil Adhikari, Shireen Adenwalla

Shireen Adenwalla Papers

Domain walls in magnetic thin films are being explored for memory applications and the speed at which they move has acquired increasing importance. Magnetic fields and currents have been shown to drive domain walls with speeds exceeding 500 m/s. We investigate another approach to increase domain wall velocities, using high frequency surface acoustic waves to create standing strain waves in a 3 micron wide strip of magnetic film with perpendicular anisotropy. Our measurements, at a resonant frequency of 248.8 MHz, indicate that domain wall velocities increase substantially, even at relatively low applied voltages. Our findings suggest that the strain wave …

Treated Hfo2 Based Rram Devices With Ru, Tan, Tin As Top Electrode For In-Memory Computing Hardware, Yuvraj Dineshkumar Patel

Theses

The scalability and power efficiency of the conventional CMOS technology is steadily coming to a halt due to increasing problems and challenges in fabrication technology. Many non-volatile memory devices have emerged recently to meet the scaling challenges. Memory devices such as RRAMs or ReRAM (Resistive Random-Access Memory) have proved to be a promising candidate for analog in memory computing applications related to inference and learning in artificial intelligence. A RRAM cell has a MIM (Metal insulator metal) structure that exhibits reversible resistive switching on application of positive or negative voltage. But detailed studies on the power consumption, repeatability and retention …

3-D Fabry–Pérot Cavities Sculpted On Fiber Tips Using A Multiphoton Polymerization Process, Jonathan W. Smith, Jeremiah C. Williams, Joseph S. Suelzer, Nicholas G. Usechak, Hengky Chandrahalim

Faculty Publications

This paper presents 3-D Fabry–Pérot (FP) cavities fabricated directly onto cleaved ends of low-loss optical fibers by a two-photon polymerization (2PP) process. This fabrication technique is quick, simple, and inexpensive compared to planar microfabrication processes, which enables rapid prototyping and the ability to adapt to new requirements. These devices also utilize true 3-D design freedom, facilitating the realization of microscale optical elements with challenging geometries. Three different device types were fabricated and evaluated: an unreleased single-cavity device, a released dual-cavity device, and a released hemispherical mirror dual-cavity device. Each iteration improved the quality of the FP cavity's reflection spectrum. The …

Investigating New Methods To Develop Perovskite Solar Cells, Amani Hussain Alfaifi

Electronic Theses and Dissertations

Discovering the potential of organic-inorganic metal halide perovskites (MHP) as a harvesting material in solar cells has strongly affected the research direction in solar energy. The fascinating optical and electronic properties offered by MHP combined with tremendous effort from scientists around the world have improved the efficiency to about 25% in a decade.

In the first part of the dissertation, we studied the lamination process as a new fabrication method for producing self-encapsulated perovskite solar cells based on laminating half stacks,as opposed to the conventional layer-by-layer method. Our work focused on optimizing the lamination process of complex triple cations perovskite …

Studies Of Initial Growth Of Gan On Inn, Alaa Alnami

Graduate Theses and Dissertations

III-nitride materials have recently attracted much attention for applications in both the microelectronics and optoelectronics. For optoelectronic devices, III-nitride materials with tunable energy band gaps can be used as the active region of devices to enhance the absorption or emission. A such material is indium nitride (InN), which along with gallium nitride (GaN) and aluminum nitride (AlN) embody the very real promise of forming the basis of a broad spectrum, a high efficiency solar cell. One of the remaining complications in incorporating InN into a solar cell design is the effects of the high temperature growth of the GaN crystal …

Multifunctional Properties Of Gan Nws Applied To Nanometrology, Nanophotonics, And Scanning Probe Microscopy/Lithography, Mahmoud Behzadirad

Optical Science and Engineering ETDs

GaN nanowires are promising for optical and optoelectronic applications because of their waveguiding properties and large optical bandgap. Recent researches have shown superior mechanical properties of GaN nanowires which promises their use in new research areas e.g. nanometrology. In this work, we develop a scalable two-step top-down approach using interferometric lithography as well a bottom-up growth of NWs using MOCVD, to manufacture highly-ordered arrays of nanowires with atomic surface roughness and desired aspect-ratios to be used in nanophotonics and atomic precision metrology and lithography. Using this method, uniform nanowire arrays were achieved over large-areas (~1 mm²) with aspect-ratio …

Modeling Multiphase Flow And Substrate Deformation In Nanoimprint Manufacturing Systems, Andrew Cochrane

Nanoscience and Microsystems ETDs

Nanopatterns found in nature demonstrate that macroscopic properties of a surface are tied to its nano-scale structure. Tailoring the nanostructure allows those macroscopic surface properties to be engineered. However, a capability-gap in manufacturing technology inhibits mass-production of nanotechnologies based on simple, nanometer-scale surface patterns. This gap represents an opportunity for research and development of nanoimprint lithography (NIL) processes. NIL is a process for replicating patterns by imprinting a fluid layer with a solid, nano-patterned template, after which ultraviolet cure solidifies the fluid resulting in a nano-patterned surface. Although NIL has been demonstrated to replicate pattern features as small as 4 …

Straintronic Nanomagnetic Devices For Non-Boolean Computing, Md Ahsanul Abeed

Theses and Dissertations

Nanomagnetic devices have been projected as an alternative to transistor-based switching devices due to their non-volatility and potentially superior energy-efficiency. The energy efficiency is enhanced by the use of straintronics which involves the application of a voltage to a piezoelectric layer to generate a strain which is ultimately transferred to an elastically coupled magnetostrictive nanomaget, causing magnetization rotation. The low energy dissipation and non-volatility characteristics make straintronic nanomagnets very attractive for both Boolean and non-Boolean computing applications. There was relatively little research on straintronic switching in devices built with real nanomagnets that invariably have defects and imperfections, or their adaptation …

Quasi-Particle Band Structure And Excitonic Effects In One-Dimensional Atomic Chains, Eesha Sanjay Andharia

Graduate Theses and Dissertations

The high exciton binding energy in one dimensional (1D) nano-structures makes them prominent for optoelectronic device applications, making it relevant to theoretically investigate their electronic and optical properties. Many-body effects that are not captured by the conventional density functional theory (DFT) have a huge impact in such selenium and tellurium single helical atomic chains. This work goes one step beyond DFT to include the electron self-energy effects within the GW approximation to obtain a corrected quasi-particle electronic structure. Further, the Bethe-Salpeter equation was solved to obtain the absorption spectrum and to capture excitonic effects. Results were obtained using the Hyberstein-Louie …

Cementitious Sensors Exhibiting Stopbands In Acoustic Transmission Spectra, Shreya Vemuganti

Shared Knowledge Conference

Ultrasonic monitoring in cementitious materials is challenging due to the high degree of attenuation. In wellbore environments, monitoring becomes more challenging due to inaccessibility. Meta materials, also known as acoustic bandgap materials, exhibit an interesting feature of forbidding the propagation of elastic/sound waves and isolate vibration in a certain frequency band. Traditionally, acoustic bandgap materials are developed with inclusions such as tin, aluminum, gold, steel in a polymer matrix. In this study, we present the development of three-dimensional cementitious sensors capable of exhibiting stopbands in the acoustic transmission spectra using carbon nanotubes. Relatively wide stopbands were engineered using Floquet-Bloch periodic …

Microwave Acoustic Saw Resonators For Stable High-Temperature Harsh-Environment Static And Dynamic Strain Sensing Applications, Anin K. Maskay

Electronic Theses and Dissertations

High-temperature, harsh-environment static and dynamic strain sensors are needed for industrial process monitoring and control, fault detection, structural health monitoring in power plant environments, steel and refractory material manufacturing, aerospace, and defense applications. Sensor operation in the aforementioned extreme environments require robust devices capable of sustaining the targeted high temperatures, while maintaining a stable sensor response. Current technologies face challenges regarding device or system size, complexity, operational temperature, or stability.

Surface acoustic wave (SAW) sensor technology using high temperature capable piezoelectric substrates and thin film technology has favorable properties such as robustness; miniature size; capability of mass production; reduced installation …

Mesoscale Computational Studies Of Thin-Film Bijels, Joseph M. Carmack

Graduate Theses and Dissertations

Bijels are a relatively new class of soft materials that have many potential applications in the technology areas of energy, medicine, and environmental sustainability. They are formed by the arrest of binary liquid spinodal decomposition by a dispersion of solid colloidal nanoparticles. This dissertation presents an in-depth simulation study of Bijels constrained to thin-film geometries and in the presence of electric fields. We validate the computational model by comparing simulation results with previous computational modeling and experimental research. In the absence of suspended particles, we demonstrate that the model accurately captures the rich kinetics associated with diffusion-based surface-directed spinodal decomposition. …

Nanostructural Origin Of Semiconductivity And Large Magnetoresistance In Epitaxial Nico2O4/Al2O3 Thin Films, Congmian Zhen, Xiaozhe Zhang, Wengang Wei, Wenzhe Guo, Ankit Pant, Xiaoshan Xu, Jian Shen, Li Ma, Denglu Hou

Xiaoshan Xu Papers

Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo₂O₄, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo₂O₄ films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo₂O₄ epitaxial films grown on MgAl₂O₄ (1 1 1) and on Al₂O₃ (0 0 1) substrates. Although the optimal growth conditions are similar for the …

Saw Assisted Domain Wall Motion In Co/Pt Multilayers, Westin Edrington, Uday Singh, Maya Abo Dominguez, James Rehwaldt Alexander, Rabindra Nepal, Shireen Adenwalla

Shireen Adenwalla Papers

The motion of domain walls in thin ferromagnetic films is of both fundamental and technological interest. In particular, the ability to use drivers other than magnetic fields to control the positions of domain walls could be exciting for memory applications. Here, we show that high frequency dynamic strain produced by surface acoustic waves is an efficient driver of magnetic domain walls in ferromagnetic films with perpendicular anisotropy. A standing surface acoustic wave of resonant frequency 96.6MHz increases the domain wall velocities in thin films of [Co/Pt]n by an order of magnitude compared to magnetic fields alone. This effect is highly …

Interplay Of Quantum Size Effect, Anisotropy And Surface Stress Shapes The Instability Of Thin Metal Films, Mikhail Khenner

Mathematics Faculty Publications

Morphological instability of a planar surface ([111], [011], or [001]) of an ultra-thin metal film is studied in a parameter space formed by three major effects (the quantum size effect, the surface energy anisotropy and the surface stress) that influence a film dewetting. The analysis is based on the extended Mullins equation, where the effects are cast as functions of the film thickness. The formulation of the quantum size effect (Z. Zhang et al., PRL 80, 5381 (1998)) includes the oscillation of the surface energy with thickness caused by electrons confinement. By systematically comparing the effects, their contributions into the …

Characterization Of Nanoparticles Using Solid State Nanopores, Santoshi Nandivada

Graduate Theses and Dissertations

Solid state nanopores are widely used in detection of highly charged biomolecules like DNA and proteins. In this study, we use a solid state nanopore based device to characterize spherical nanoparticles to estimate their size and electrical charge using the principle of resistive pulse technique. The principle of resistive pulse technique is the method of counting and sizing particles suspended in a fluid medium, which are electrophoretically driven through a channel and produce current blockage signals due to giving rise to a change in its initial current. This change in current is denoted as a current blockage or as a …

Elastic Properties Of Superconductors And Materials With Weakly Correlated Spins, Christian Binek

Christian Binek Publications

It is shown that in the ergodic regime, the temperature dependence of Young’s modulus is solely determined by the magnetic properties of a material. For the large class of materials with paramagnetic or diamagnetic response, simple functional forms of the temperature derivative of Young’s modulus are derived and compared with experimental data and empirical results. Superconducting materials in the Meissner phase are ideal diamagnets. As such, they display remarkable elastic properties. Constant diamagnetic susceptibility gives rise to a temperature independent elastic modulus for ceramic and single crystalline superconductors alike. The thermodynamic approach established in this report, paves the way to …

Formation Of Mound-Like Multiscale Surface Structures On Titanium By Femtosecond Laser Processing, Edwin Peng, Alfred Tsubaki, Craig A. Zuhlke, Ryan Bell, Meiyu Wang, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Surface Functionalization Technique • Femtosecond Laser Surface Processing (FLSP) • Utilize high power, femtosecond (10-15 s) laser pulses • Produce self-organized, multiscale surface micro/nanostructures • Diverse range of applicable substrates: semiconductors, metals, polymers, & composites

Why? • What are the different types of FLSP structures on Ti? • Physical evidence needed for FLSP formation models • Optimize FLSP of Ti for biomedical & other applications

How? • Obtain evidence of mound growth processes by examining underlying microstructure • Utilize dual beam Scanning Electron Microscope-Focused Ion Beam instrument to cross section surface structures & fabricate transmission electron microscopy samples

Ferroelectricity And The Phase Transition In Large Area Evaporated Vinylidene Fluoride Oligomer Thin Films, Keith Foreman, Shashi Poddar, Stephen Ducharme, Shireen Adenwalla

Shireen Adenwalla Papers

Organic ferroelectric materials, including the well-known poly(vinylidene fluoride) and its copolymers, have been extensively studied and used for a variety of applications. In contrast, the VDF oligomer has not been thoroughly investigated and is not widely used, if used at all. One key advantage the oligomer has over the polymer is that it can be thermally evaporated in vacuum, allowing for the growth of complex heterostructures while maintaining interfacial cleanliness. Here, we report on the ferroelectric properties of high-quality VDF oligomer thin films over relatively large areas on the order of mm². The operating temperature is identified via …

Local Writing Of Exchange Biased Domains In A Heterostructure Of Co/Pd Pinned By Magnetoelectric Chromia, Uday Singh, William Echtenkamp, M. Street, Christian Binek, Shireen Adenwalla

Shireen Adenwalla Papers

The writing of micrometer-scaled exchange bias domains by local, laser heating of a thin-film heterostructure consisting of a perpendicular anisotropic ferromagnetic Co/Pd multilayer and a (0001) oriented film of the magnetoelectric antiferromagnet Cr₂O₃ (chromia) is reported. Exchange coupling between chromia’s boundary magnetization and the ferromagnet leads to perpendicular exchange bias. Focused scanning magneto-optical Kerr measurements are used to measure local hysteresis loops and create a map of the exchange bias distribution as a function of the local boundary magnetization imprinted in the antiferromagnetic pinning layer on field cooling. The robust boundary magnetization of the Cr₂O …

Photoluminescence Measurement On Low-Temperature Metal Modulation Epitaxy Grown Gan, Yang Wu

Graduate Theses and Dissertations

A low-temperature photoluminescence (PL) study was conducted on low-temperature metal modulation epitaxy (MME) grown GaN. By comparing the PL signal from high temperature grown GaN buffer layers, and MME grown cap layers on top of the buffer layers, it was found that MME grown GaN cap has a significantly greater defect-related emission. The band edge PL from MME grown GaN found to be 3.51eV at low temperature. The binding energy of the exciton in GaN is determined to be 21meV through temperature dependence analysis. A PL peak at 3.29eV was found in the luminescence of the MME grown cap layer, …

Model For Computing Kinetics Of The Graphene Edge Epitaxial Growth On Copper, Mikhail Khenner

Mathematics Faculty Publications

A basic kinetic model that incorporates a coupled dynamics of the carbon atoms and dimers ona copper surface is used to compute growth of a single-layer graphene island. The speed of theisland's edge advancement on Cu[111] and Cu[100] surfaces is computed as a function of the growthtemperature and pressure. Spatially resolved concentration pro les of the atoms and dimers aredetermined, and the contributions provided by these species to the growth speed are discussed.Island growth in the conditions of a thermal cycling is studied.

Enhanced Adhesion Of Superhydrophobic Zno Surface, Liqiu Zheng Dr., Chan Kwaichow B.

Georgia Journal of Science

The superhydrophobicity and the strong solid-liquid adhesion of the dually structured ZnO surface are attributed to the suitable size of microstructure and nanostructure. This phenomenon, so different from the Lotus effect, can be called the Petal effect— the super hydrophobicity and the enhanced solid-liquid adhesion coexist on the same surface. The Cassie impregnating model was proposed to understand the underlying reason.