The long-term goal of the research project initiated with this thesis is the development of lead-free, fully-transparent ferroelectric devices, such as ferroelectric capacitors or ferroelectric-gate field-effect transistors. Ferroelectric materials exhibit spontaneous polarization with the application of an external electric field, which is persistent upon removal of the applied field, and...
Ferrites have been used for various high frequency applications as bulk
materials. These applications, however, are limited to large dimension devices. In
this thesis, thin film ferrites were deposited from a low temperature solution-based
deposition process that is suitable for micro-scale high frequency applications. The
low temperature nature of this...
Solid solutions based on the perovskite ferroelectrics Bi₀.₅Na₀.₅TiO₃ (BNT) and Bi₀.₅K₀.₅TiO₃ (BKT) might someday replace current Pb-based ferroelectric and piezoelectric devices. This is one goal of the Restrictions on Hazardous Substances (RoHS) guidelines seeking to limit Pb in consumer devices. Although the Bi-based ferroelectrics are well suited to the task...
Magnetic thin films have potential to improve devices such as on-chip inductors, and enable new technologies such as magnetic random access memory (MRAM).
The use of magnetic cores in on-chip inductors is typically limited to applications well under 1 GHz. At higher frequencies, the performance of the magnetic core is...
Metal-organic frameworks (MOFs) have gained increasing attention due to their promising applications (e.g., gas storage/separations, and catalysis) as nanoporous materials stemming from generally ultrahigh porosities and surface areas. Recently, research has shifted to synthesize MOF thin films and micropatterns that enable new applications (e.g., optoelectronics, smart coatings, and sensors).
In...
Exciton polaritons are quasiparticles composed of a quantum superposition of matter and light states that arises from the coupling of a standing wave photon and an exciton. This research has two primary objectives: to design and fabricate a Fabry-Perot microcavity system in which to produce exciton polaritons; and to show...
The amorphous to crystalline phase change is of great interest for the production and operation of phase change memory and germanium electronic devices. Phase change memory relies on the ability to differentiate between differences in optical or electrical properties between the amorphous and crystalline phases of a single material. Amorphous...
In this dissertation, the structure and electronic properties of multiple metal oxide thin films are characterized and presented. Prompt inorganic condensation (PIC) of metal-oxo and –hydroxo clusters was evaluated as a technique for making metal oxide clusters in two separate studies. The first focuses on the synthesis of lithium niobate...
A series of seven magnesium-doped copper scandium oxide films were made by radio frequency sputtering, and intercalated at various oxygen pressures to create different oxygen concentrations in each film. The objectives of this study were to verify the p-type nature of these transparent conductive thin films, to determine the correlation...
We have investigated a second-order phase transition of the vortex lattice in thin-film Nd₁.₈₅Ce₀.₁₅CuO[subscript 4-y] from 1 mT to 1 T applied magnetic fields. The dc resistivity-current density data for each field exhibit critical scaling consistent with a second-order vortex-liquid to vortex-solid phase transition. The high-field data support the vortex-glass...
The growth of YMn₀.₃₅In₀.₆₅O₃ thin films and their optical and magnetic behavior are reported. The YMn₀.₃₅In₀.₆₅O₃ thin film grows along the (0001) orientation with hexagonal structure similar to YMnO₃ on c-plane sapphire. The film shows paramagnetic behavior in the temperature range measured. The film exhibits a blue color due to...
Epitaxial LaRh₁/₂Mn₁/₂O₃ thin films have been grown on (001)-oriented LaAlO₃ and SrTiO₃ substrates using pulsed laser deposition. The optimized thin film samples are semiconducting and ferromagnetic with a Curie temperature close to 100 K, a coercive field of 1200 Oe, and a saturation magnetization of 1.7μB per formula unit. The...
The use of a permeable membrane to mechanically constrain a film of water with an area of 12 cm² and a thickness of 150 μm in a gas/liquid contactor was investigated. The membrane separated the vapor and liquid phases, and a stiffener
plate made from a gas-permeable material was used...
Zinc tin oxide (ZTO) films deposited by pulsed laser deposition (PLD) are
investigated as a channel layers for transparent thin-film transistors (TTFTs).
Films are deposited on glass for characterization, and transistor channel layers are
deposited onto aluminum oxide-titanium oxide/tin doped indium oxide/glass
substrates (ATO/ITO/glass) to produce TTFTs.
UV-visible spectroscopy on...
Spectroscopic ellipsometry (SE) is used to characterize amorphous and crystalline thin films of TiO2. Amorphous precursor films of TiO2 are deposited by radio frequency magnetron sputtering on fused silica and silicon substrates. Annealing the amorphous precursor films induces them to crystallize into either pure or mixed phases of the three...
The optical transition in high-fraction polymorphs of titania (TiO2) were investigated to determine the band gap behavior of the most common polymorphs—brookite, rutile, and anatase—the values of which are varied in the literature. The direct optical band gaps of brookite, rutile, and anatase, were determined to be 3.37(7)eV, 3.41(11)eV and...
Zinc Sulfide (ZnS) thin film, with a wide band gap, has been used for many applications, such as buffer layer for CIGS solar cells, light emitting diodes and thin film electroluminescent devices.
In this work, ZnS thin films were prepared using two different deposition processes. In the first method, ZnS...
The focus of this thesis is developing materials for thin-film transistors (TFTs). Cu₃SbS₄ is explored as p-channel layer. Cu₃SbS₄ TFTs show p-type, depletion-mode behavior with a small amount of gate-controlled modulation of the channel conductance. This behavior is consistent with Hall measurements indicating a mobility of 17 cm²V⁻¹s⁻¹ and hole...
Copper sulfides (Cu[subscript x]S) are compound semiconductor materials that exhibit considerable optical and electrical properties varying significantly as a function of the composition. Copper sulfide thin films can be used in many applications, such as solar control coatings, solar cells, photothermal conversion of solar energy, electroconductive coatings, and microwave shielding...
Recent superconducting thin films studies have attempted to create pure metal layer films of Niobium and Titanium with the same properties of superconducting NbTi wire used in industry. These studies have all reported depression of the superconducting properties of the pure metal films which has been attributed to the proximity...
A low pressure halide transport chemical vapor deposition (HTCVD) system to grow ZnS:Mn electroluminescent phosphors is characterized. Reactor parameters such as gas composition, gas flow rate, and source and substrate temperature are investigated. Crystal structure is investigated using x-ray diffraction, electron spin resonance, and transmission electron microscopy. Chemical characterization includes...
β-SiC is a semiconductor for high temperature devices, which exhibits several outstanding properties such as high thermal stability, good chemical stability and wide band gap. There is a possibility of fabricating a crack-free ultrathin SiC film on silicon wafers by pyrolysis of polymethylsilane (PMS) film.
This study looks into the...
The digital revolution has brought information to every corner of our daily lives. Inexpensive and flexible integrated circuits are needed for this continuing revolution. Silicon technology, the current workhorse of microelectronic industry, is far from inexpensive and flexible. Researchers are taking several different routes to achieve this goal. Amorphous silicon...
Solid-state amorphous materials show amazing promise in thin-film electronics. The interface-to-bulk ratio of thin films makes interfacial chemistries of these systems of utmost importance. Thin films of amorphous metals, dielectrics and semiconductors have novel chemistries that are not only based upon their elemental constituent makeup, but also based upon the...
A class of high-performance thin-film transistor (TFT) channel materials has emerged
involving oxides composed of heavy-metal cations (HMCs) with (n-1)d¹⁰ns⁰ (n≥4)
electronic configurations. This thesis is devoted to the pursuit of three topics involving
the development of these materials for TFT applications: modeling TFT currentvoltage
characteristics, an exploratory method for...
Nonlinear optical processes can be described as multiphoton scattering events in terms of high order perturbation theory. The standard procedure for quantitative calculation of high order terms is to impose a steady state condition on the perturbative radiation fields. In the present work, this condition will be lifted, and explicit...
Researchers around the world use various solution-based deposition techniques to deposit thin films with multiple layers that typically require multiple rounds of deposition. Some such techniques include successive ionic layer adsorption and reaction (SILAR), and layer-by-layer (LBL) deposition.
One of the main issues with deposition of these types of films...
This thesis focuses on two aspects of oxide-based thin-film transistors (TFTs), contact resistance and instability assessment.
First, determination of the contact resistance of indium tin oxide (ITO) on two wide-band gap semiconductors, zinc oxide (ZnO) and indium gallium oxide (IGO), is attempted and the effects of contact resistance on device...
The critical contribution of this dissertation is to provide a better
understanding of the fundamental Chemical Bath Deposition (CBD) growth
kinetic and mechanism for the well known II-VI semiconductor CdS using the
newly developed continuous flow microreactor. This continuous flow microreactor
provides the temporal resolution to control the homogeneous reaction...
Pb(Zr,Ti)O₃ (PZT) is a very attractive material for use in piezoelectric-based microelectromechanical systems (MEMS) due to its high piezoelectric coefficients and ability for large displacements with relatively low applied fields (as compared to electrostatic-based MEMS). The piezoelectric effect is strongly anisotropic, thus it is very desirable to control the crystallographic...
The objective of the research presented herein is to elucidate the effect of traps in determining amorphous oxide semiconductor thin-film transistor (AOS TFT) performance using modeling and characterization. A novel method is proposed to extract the interface state distribution from a TFT transfer curve. Analysis of zinc-indium oxide (ZIO), zinc-tin...
The primary focus of this thesis is modifying the comprehensive depletion-mode model and extending its applicability to p-channel thin-film transistor (TFT) behavior and subthreshold (subpinchoff) operation. The comprehensive depletion-mode model accurately describes depletion-mode TFT behavior and establishes a set of equations, different from those obtained from square-law theory, which can...
The goal of this thesis study is to develop an activated reactive evaporation (ARE) system and to demonstrate its utility by fabricating-alternating current thin-film electroluminescent (ACTFEL) oxide phosphor devices. ARE entails evaporation in an activated gas. The main ARE system components are three thermal evaporation sources, a microwave power supply,...
The objective of the research presented in this thesis is to develop, implement, and demonstrate the utility of an n-sheet, state-space alternating-current thin-film electroluminescent (ACTFEL) device model. In this model, the phosphor layer is discretized into n + 1 layers, with band-to-band impact ionization, space charge creation/ annihilation, and luminescent...
The code is developed for the calculation of the magneto-crystalline anisotropy (MAE) in thin films using a classical Heisenberg hamiltonian with a correction developed by Van Vleck. A Metropolis style Monte Carlo algorithm was used with adequate corrections to accelerate the calculation. The MAE was calculated for the case of...
Thin films are an enabling technology for a wide range of applications, from microprocessors to diffusion barriers. Nanolaminate thin films combine two (or more) materials in a layered structure to achieve performance that neither film could provide on its own. Atomic layer deposition (ALD) is a chemical vapor deposition technique...
Crystals of an incongruent-melting compound, Ba₃MgSi₂O₈, were grown by the flux method and its structure was determined by single crystal X-ray diffraction methods. Ba₃MgSi₂O₈ crystallizes in trigonal space group P-3[bar]m1 with a = 5.6123(3) Å, c = 7.2667(9) Å and Z = 1. Eu²⁺ ions prefer one crystallographic Ba site...
The aim of this dissertation is to develop oxide semiconductors by radio-frequency
sputtering for thin-film transistor (TFT) applications. A variety of oxide semiconductors
are used as the TFT channel layer, including indium gallium oxide (IGO), zinc tin
oxide (ZTO), and indium gallium zinc oxide (IGZO). The variety of materials used...
The variegated aqueous chemistries of metal cations are applied to the design and synthesis of non-toxic solution precursors suitable for additive printing of large-area oxide electronics. Polycondensation behaviors of aqueous Al+3 and PO4 +3 are manipulated in the deposition of atomically smooth amorphous aluminum oxide phosphate (AlPO) dielectric films. AlPO...
A class of inorganic thin-film transistor (TFT) semiconductor materials has emerged involving oxides composed of post-transitional cations with (n-1)d¹⁰ns⁰ (n≥4) electronic configurations. This thesis is devoted to the pursuit of topics involving the development of these materials for TFT applications: Deposition of zinc oxide and zinc tin oxide semiconductor
layers...
Metal-Organic Frameworks (MOFs) are crystalline compounds formed from reacting a metal ion with an organic ligand. They represent a promising new avenue in materials science for gas separations and storage. Certain MOFs, in particular Mg-MOF-74, have shown a strong affinity for the capture of CO2. This project investigated a known...
Digital printing techniques offer several advantages in manufacturing electronics such as direct writing of materials, reduction of chemical waste, and scalability. In particular, printing can significantly simplify manufacturing processes by directly defining the channel area, the gate, and the source and drain contacts, allowing for lower costs and higher throughput...
The aim of the research undertaken for this thesis was to develop a new high-performance amorphous oxide semiconductor (AOS) for use as a channel layer in a thin-film transistor (TFT). AOS TFTs offer higher electron mobility than the established amorphous silicon based technology. A new channel material comprised of aluminum...
Advances in energy technologies and electronics have typically occurred through either heightened performance or cost reduction. This dissertation explores both routes through a series of fundamental material studies that may contribute to the enabling of next generation devices. Solution based syntheses and deposition of chemical products offer a low cost...
The atomic solid state energy (SSE) scale is introduced as a tool for inorganic materials design. The SSE scale is obtained by assessing an average electron affinity (EA) (for a cation) or an average ionization potential (IP) (for an anion) for each atom using data from compounds having that specific...