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Understanding Heterostructure Chemiresistive Gas Sensing At Room Temperature, Yale Wang

Theses and Dissertations

Chemiresistive sensors are the most widely investigated gas sensors due to their ease in fabrication, cost-effectiveness, simplicity of operation, and offer advances in miniaturization. Up to date, typical and well-researched resistive-type sensing materials include semiconductor metal oxides, noble metals, carbon-based nanomaterials (e.g., graphene and carbon nanotubes), and conducting polymers. Gas sensors based on a single material were found difficult to meet the practical requirements for multi-sensing properties, including sensitivity, selectivity, speed of response/recovery, stability, limit of detection, and room temperature operation. Rational design through a combination of chemically or electronically dissimilar nanomaterials is an effective route to enhancing gas sensing …

Interface Structure And Luminescence Properties Of Epitaxial Pbse Films On Inas(111)A, Kevin D. Vallejo, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

Epitaxial heterostructures of narrow-gap IV-VI and III-V semiconductors offer a platform for new electronics and mid-infrared photonics. Stark dissimilarities in the bonding and the crystal structure between the rocksalt IV–VIs and the zincblende III–Vs, however, mandate the development of nucleation and growth protocols to reliably prepare high-quality heterostructures. In this work, we demonstrate a route to single crystal (111)-oriented PbSe epitaxial films on nearly lattice-matched InAs (111)A templates. Without this technique, the high-energy heterovalent interface readily produces two populations of PbSe grains that are rotated 180° in-plane with respect to each other, separated by rotational twin boundaries. We find that …

Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh

USF Tampa Graduate Theses and Dissertations

Atomically thin two-dimensional (2D) materials have attracted a growing interest in the lastdecade from the fundamental point of view as well as their potential applications in functional devices. Due to their high surface-to-volume ratio, the physical properties of 2D materials are very sensitive to the environmental factor such as surrounding media and illumination conditions (e.g. light-mater interaction). In the first part of this dissertation I will present recent advances in developing laser-assisted methods to tune the physical properties of 2D transition metal dichalcogenides (TMDs). We demonstrate laser-assisted chemical modification ultrathin TMDs, locally replacing selenium by sulfur atoms. The photo-conversion process …

Structure And Properties Of Zno-Zns Heterostructures, Sanchali Das

MSU Graduate Theses

Heterostructures consisting of at least two layers of dissimilar materials have always been well studied due to potential applications in nano-electronic and optoelectronic devices. In this study, I have investigated the structural and physical properties of zinc oxide -zinc sulfide (ZnO-ZnS) based heterostructures of thin films and core-shell nanoparticles. Pulsed laser deposition technique was employed to grow ZnO thin film on sapphire substrate. ZnO-ZnS heterostructures were obtained using hydrothermal synthesis where thiourea has served as a precursor solution for the source of sulfur. X-ray diffraction analysis on the parent and the sulfidized samples gives the information about the crystallinity and …

Magnetic Studies Of Multiferroic Heterostructures, Ahmed Rayhan Mahbub

MSU Graduate Theses

Multiferroic heterostructures (MHS) consisting of at least two materials with ferroic properties have been a major focus for researchers recently due to its immense potential in device applications. Almost all MHS use ferromagnetic layers making it a very important research area. In this thesis the magnetic properties of different ferromagnetic heterostructures have been investigated. Different bilayers of hard ferromagnet cobalt ferrite (CFO)-soft ferromagnet lanthanum strontium manganese oxide (LSMO) and hard ferromagnet CFO-antiferromagnet nickel oxide (NiO) were fabricated. Pulsed laser deposition technique was used to deposit the thin films on LAO and sapphire substrates. Purpose of using a hard ferromagnetic CFO …

Growth, Characterization, And Function Of Ferroelectric, Ferromagnetic Thin Films And Their Heterostructures, Mahesh Hordagoda

USF Tampa Graduate Theses and Dissertations

With recent trends in miniaturization in the electronics sector, ferroelectrics have gained popularity due to their applications in non-volatile RAM. Taking one step further researchers are now exploring multiferroic devices that overcome the drawbacks of ferroelectric (FE) and ferromagnetic (FM) RAM’s while retaining the advantages of both. The work presented in this dissertation focuses on the growth of FE and FM thin film structures. The primary goals of this work include, (1) optimization of the parameters in the pulsed laser deposition (PLD) of FE and FM films and their heterostructures, (2) development of a structure-property relation that leads to enhancements …

Single And Double Heterojunction Nanorods For Optoelectronics, Moonsub Shim

Composites at Lake Louise (CALL 2015)

Understanding charge separation and recombination processes and developing materials that can efficiently direct charge carriers with nanoscale precision are of fundamental importance in advancing next-generation electronics, optoelectronics and energy technologies. As semiconductor heterostructures have enabled today’s electronics and optoelectronics, the introduction of active heterojunctions can impart new and improved capabilities that will facilitate integration of colloidal quantum dots into high performance devices. With anisotropic shapes that can be exploited for assembly, charge carrier manipulation and optical anisotropy, incorporating heterojunctions in colloidal semiconductor nanorods presents a promising direction. Various motifs of epitaxial heterojunctions introduced in nanorods through solution chemistry will be …

Tin Dioxide–Carbon Heterostructures Applied To Gas Sensing: Structure-Dependent Properties And General Sensing Mechanism, Catherine Marichy, Patricia A. Russo, Mariangela Latino, Jean-Philippe Tessonnier, Marc-Georg Willinger, Nicola Donato, Giovanni Neri, Nicola Pinna

Jean-Philippe Tessonnier

Carbon materials such as carbon nanotubes (CNTs), graphene, and reduced graphene oxide (RGO) exhibit unique electrical properties, which are also influenced by the surrounding atmosphere. They are therefore promising sensing materials. Despite the existence of studies reporting the gas-sensing properties of metal oxide (MOx) coated nanostructured carbon, an incomplete understanding of their sensing mechanism remains. Here we report a systematic study on the preparation, characterization, and sensing properties of CNT and RGO composites with SnO2 coating. Atomic layer deposition (ALD) was applied to the conformal coating of the inner and outer walls of CNTs with thin films of SnO2 of …

Mott Transition And Electronic Structure In Complex Oxide Heterostructures, Jian Liu

Graduate Theses and Dissertations

Strongly correlated electron systems, particularly transition metal oxides, have been a focus of condensed matter physics for more than two decades since the discovery of high-temperature superconducting cuprates. Diverse competing phases emerge, spanning from exotic magnetism to unconventional superconductivity, in proximity to the localized-itinerant transition of Mott insulators. While studies were concentrated on bulk crystals, the recent rapid advance in synthesis has enabled fabrication of high-quality oxide heterostructures, offering a new route to create novel artificial quantum materials.

This dissertation details the investigation on ultrathin films and heterostructures of 3d⁷(t_2g⁶e_g¹) systems with …

Modified Statistical Dynamical Diffraction Theory : A Novel Metrological Analysis Method For Partially Relaxed And Defective C Doped Si And Sige Heterostructures, Paul Kenneth Shreeman

Legacy Theses & Dissertations (2009 - 2024)

The statistical dynamical diffraction theory, which has been initially developed by late Kato remained in obscurity for many years due to intense and difficult mathematical treatment that proved to be quite challenging to implement and apply. With assistance of many authors in past (including Bushuev, Pavlov, Pungeov, and among the others), it became possible to implement this unique x-ray diffraction theory that combines the kinematical (ideally imperfect) and dynamical (the characteristically perfect diffraction) into a single system of equations controlled by two factors determined by long range order and correlation function within the structure. The first stage is completed by …