Matching Items (7)
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Description
Integrated oxide/semiconductor heterostructures have attracted intense interest for device applications which require sharp interfaces and controlled defects. The research of this dissertation has focused on the characterization of perovskite oxide/oxide and oxide/semiconductor heterostructures, and the analysis of interfaces and defect structures, using scanning transmission electrom microscopy (STEM) and related techniques.

Integrated oxide/semiconductor heterostructures have attracted intense interest for device applications which require sharp interfaces and controlled defects. The research of this dissertation has focused on the characterization of perovskite oxide/oxide and oxide/semiconductor heterostructures, and the analysis of interfaces and defect structures, using scanning transmission electrom microscopy (STEM) and related techniques.

The SrTiO3/Si system was initially studied to develop a basic understanding of the integration of perovskite oxides with semiconductors, and successful integration with abrupt interfaces was demonstrated. Defect analysis showed no misfit dislocations but only anti-phase boundaries (APBs) in the SrTiO3 (STO) films. Similar defects were later observed in other perovskite oxide heterostructures.

Ferroelectric BaTiO3 (BTO) thin films deposited directly onto STO substrates, or STO buffer layers with Ge substrates, were grown by molecular beam epitaxy (MBE) in order to control the polarization orientation for field-effect transistors (FETs). STEM imaging and elemental mapping by electron energy-loss spectroscopy (EELS) showed structurally and chemically abrupt interfaces, and the BTO films retained the c-axis-oriented tetragonal structure for both BTO/STO and BTO/STO/Ge heterostructures. The polarization displacement in the BTO films of TiN/BTO/STO heterostructures was investigated. The Ti4+ atomic column displacements and lattice parameters were measured directly using HAADF images. A polarization gradient, which switched from upwards to downwards, was observed in the BTO thin film, and evidence was found for positively-charged oxygen vacancies.

Heterostructures grown on Ge substrates by atomic layer deposition (ALD) were characterized and compared with MBE-grown samples. A two-step process was needed to overcome interlayer reaction at the beginning of ALD growth. A-site-rich oxide films with thicknesses of at least 2-nm had to be deposited and then crystallized before initiating deposition of the following perovskite oxide layer in order to suppress the formation of amorphous oxide layers on the Ge surface. BTO/STO/Ge, BTO/Ge, SrHfTiO3/Ge and SrZrO3/Ge thin films with excellent crystallinity were grown using this process.

Metal-insulator-metal (MIM) heterostructures were fabricated as ferroelectric capacitors and then electrically stressed to the point of breakdown to correlate structural changes with electrical and physical properties. BaTiO3 on Nb:STO was patterned with different top metal electrodes by focused-ion-beam milling, Au/Ni liftoff, and an isolation-defined approach.
ContributorsWu, Hsinwei (Author) / Smith, David J. (Thesis advisor) / Mccartney, Martha R (Thesis advisor) / Alford, Terry (Committee member) / Bertoni, Mariana (Committee member) / Arizona State University (Publisher)
Created2018
Description

Sun Stop Solar, is a solar module development and manufacturing company that utilizes a unique class of materials, perovskites, as the solar cells’ absorption layer. Perovskites are a unique class of compounds with some perovskites being able to absorb photons and excite electrons to create current. Sun Stop Solar will

Sun Stop Solar, is a solar module development and manufacturing company that utilizes a unique class of materials, perovskites, as the solar cells’ absorption layer. Perovskites are a unique class of compounds with some perovskites being able to absorb photons and excite electrons to create current. Sun Stop Solar will focus on first developing the patent, licensing the technology to a manufacturer, and slowly garnering funds to launch our own manufacturing eventually. Sun Stop Solar is offering a domestic, affordable, and sustainable solution for the current solar market.

ContributorsAboudi, Joseph (Author) / Hofer, David (Co-author) / Matyushov, Ivan (Co-author) / Byrne, Jared (Thesis director) / Higashino, Katsuko (Committee member) / Barrett, The Honors College (Contributor) / Department of Finance (Contributor)
Created2023-05
Description
Sun Stop Solar, is a solar module development and manufacturing company that utilizes a unique class of materials, perovskites, as the solar cells’ absorption layer. Perovskites are a unique class of compounds with some perovskites being able to absorb photons and excite electrons to create current. Sun Stop Solar will

Sun Stop Solar, is a solar module development and manufacturing company that utilizes a unique class of materials, perovskites, as the solar cells’ absorption layer. Perovskites are a unique class of compounds with some perovskites being able to absorb photons and excite electrons to create current. Sun Stop Solar will focus on first developing the patent, licensing the technology to a manufacturer, and slowly garnering funds to launch our own manufacturing eventually. Sun Stop Solar is offering a domestic, affordable, and sustainable solution for the current solar market.
ContributorsAboudi, Joseph (Author) / Hofer, David (Co-author) / Matyushov, Ivan (Co-author) / Byrne, Jared (Thesis director) / Higashino, Katsuko (Committee member) / Barrett, The Honors College (Contributor) / Department of Finance (Contributor)
Created2023-05
Description
Sun Stop Solar, is a solar module development and manufacturing company that utilizes a unique class of materials, perovskites, as the solar cells’ absorption layer. Perovskites are a unique class of compounds with some perovskites being able to absorb photons and excite electrons to create current. Sun Stop Solar will

Sun Stop Solar, is a solar module development and manufacturing company that utilizes a unique class of materials, perovskites, as the solar cells’ absorption layer. Perovskites are a unique class of compounds with some perovskites being able to absorb photons and excite electrons to create current. Sun Stop Solar will focus on first developing the patent, licensing the technology to a manufacturer, and slowly garnering funds to launch our own manufacturing eventually. Sun Stop Solar is offering a domestic, affordable, and sustainable solution for the current solar market.
ContributorsAboudi, Joseph (Author) / Hofer, David (Co-author) / Matyushov, Ivan (Co-author) / Byrne, Jared (Thesis director) / Higashino, Katsuko (Committee member) / Barrett, The Honors College (Contributor) / Department of Finance (Contributor)
Created2023-05
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Description
The mechanism of loss in high performance microwave dielectrics with complex perovskite structure, including Ba(Zn1/3Ta2/3)O3, Ba(Cd1/3Ta2/3)O3, ZrTiO4-ZnNb2O6, Ba(Zn1/3Nb2/3)O3, and BaTi4O9-BaZn2Ti4O11, has been investigated. We studied materials synthesized in our own lab and from commercial vendors. Then the measured loss tangent was correlated to the optical, structural, and electrical properties of

The mechanism of loss in high performance microwave dielectrics with complex perovskite structure, including Ba(Zn1/3Ta2/3)O3, Ba(Cd1/3Ta2/3)O3, ZrTiO4-ZnNb2O6, Ba(Zn1/3Nb2/3)O3, and BaTi4O9-BaZn2Ti4O11, has been investigated. We studied materials synthesized in our own lab and from commercial vendors. Then the measured loss tangent was correlated to the optical, structural, and electrical properties of the material. To accurately and quantitatively determine the microwave loss and Electron Paramagnetic Resonance (EPR) spectra as a function of temperature and magnetic field, we developed parallel plate resonator (PPR) and dielectric resonator (DR) techniques. Our studies found a marked increase in the loss at low temperatures is found in materials containing transition metal with unpaired d-electrons as a result of resonant spin excitations in isolated atoms (light doping) or exchange coupled clusters (moderate to high doping) ; a mechanism that differs from the usual suspects. The loss tangent can be drastically reduced by applying static magnetic fields. Our measurements also show that this mechanism significantly contributes to room temperature loss, but does not dominate. In order to study the electronic structure of these materials, we grew single crystal thin film dielectrics for spectroscopic studies, including angular resolved photoemission spectroscopy (ARPES) experiment. We have synthesized stoichiometric Ba(Cd1/3Ta2/3)O3 [BCT] (100) dielectric thin films on MgO (100) substrates using Pulsed Laser Deposition. Over 99% of the BCT film was found to be epitaxial when grown with an elevated substrate temperature of 635 C, an enhanced oxygen pressures of 53 Pa and a Cd-enriched BCT target with a 1 mol BCT: 1.5 mol CdO composition. Analysis of ultra violet optical absorption results indicate that BCT has a bandgap of 4.9 eV.
ContributorsLiu, Lingtao (Author) / Newman, Nathan (Thesis advisor) / Marzke, Robert (Committee member) / Chamberlin, Ralph (Committee member) / Arizona State University (Publisher)
Created2013
Description
Perovskite films are the future of solar cell technology as they are not only low cost to produce and lightweight but also have a 26% conversion efficiency. This is extremely close to the standard silicon solar cell. The key challenge limiting the commercialization potential of these films is their fragility

Perovskite films are the future of solar cell technology as they are not only low cost to produce and lightweight but also have a 26% conversion efficiency. This is extremely close to the standard silicon solar cell. The key challenge limiting the commercialization potential of these films is their fragility and durability to outdoors conditions. This project investigates the mechanical and material properties of these perovskite materials in order to understand their future manufacturing capabilities. Through the use of a spin coater, blade coater, and a double cantilever beam testing set up, the fracture energy (or toughness), Gc, of Perovskite films is determined. Understanding the properties of these films can help manufacturers determine how to best make durable films that can be used in everyday energy generation. Furthermore, this study offers strategies to improve the fracture energy of these films by adding polymers and food-additive starches to the recipe. The findings collected in this project present a technique to study the mechanical properties of perovskite-based solar technology and films and further aid the technology to become commercially viable.
ContributorsBakshi, Kayshavi (Author) / Rolston, Nicholas (Thesis director) / Li, Muzhi (Committee member) / Barrett, The Honors College (Contributor) / Materials Science and Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2023-12
Description

Understanding perovskite degradation and stress responses under practical conditions is necessary to design efficient and stable photovoltaic devices. This experiment creates an in-situ stress testing system, in which the stress of a sample may be tested while it is subjected to conditions that it may experience in operation, such as

Understanding perovskite degradation and stress responses under practical conditions is necessary to design efficient and stable photovoltaic devices. This experiment creates an in-situ stress testing system, in which the stress of a sample may be tested while it is subjected to conditions that it may experience in operation, such as cycles of sunlight. This immediate stress response is valuable in understanding what factors directly contribute to the stresses that degrade perovskite solar cells. Perovskite may be 2D or 3D and are composed of many different elements and additives. Each ink responds differently to sunlight exposure due to their different structures, which is important to characterize and comprehend. Preliminary testing and characterization for 2D, 3D and MAPI with gellan gum additive perovskite inks is conducted in this experiment. It is reported that the lattice expansion causing degradation-inducing stress is due to photon dosage rather than heat, and both 3D and 2D perovskites are sensitive to minute photon dosage.

ContributorsBurgard, Erin (Author) / Rolston, Nicholas (Thesis director) / Yu, Zhengshan (Committee member) / Barrett, The Honors College (Contributor) / School of International Letters and Cultures (Contributor) / School of Sustainable Engineering & Built Envirnmt (Contributor) / Department of English (Contributor)
Created2023-05