Physics Commons^™

Magnetic Domain Morphology In [Co(4a)/Pt(7a] Thin Film, Jeremy Metzner

Student Works

A collection of results for multi-layered thin films and their magnetic domains.

Nanostructure Evolution Of Magnetron Sputtered Hydrogenated Silicon Thin Films, Dipendra Adhikari, Maxwell M. Junda, Sylvain X. Marsillac, Robert W. Collins, Nikolas J. Podraza

Electrical & Computer Engineering Faculty Publications

Hydrogenated silicon (Si:H) thin films have been prepared by radio frequency (RF) magnetron sputtering. The effect of hydrogen gas concentration during sputtering on the resultant film structural and optical properties has been investigated by real time spectroscopic ellipsometry (RTSE) and grazing incidence x-ray diffraction (GIXRD). The analysis of in-situ RTSE data collected during sputter deposition tracks the evolution of surface roughness and film bulk layer thickness with time. Growth evolution diagrams depicting amorphous, nanocrystalline and mixed-phase regions for low and high deposition rate Si:H are constructed and the effects of process parameter (hydrogen gas concentration, total pressure and RF power) …

Optical Signatures Of Spin-Orbit Exciton In Bandwidth-Controlled Sr2Iro4 Epitaxial Films Via High-Concentration Ca And Ba Doping, Maryam Souri, B. H. Kim, John H. Gruenewald, John G. Connell, J. Thompson, J. Nichols, Jsaminka Terzic, B. I. Min, Gang Cao, Joseph W. Brill, Sung S. Ambrose Seo

Physics and Astronomy Faculty Publications

We have investigated the electronic and optical properties of (Sr_1−xCa_x)₂IrO₄ (x = 0–0.375) and (Sr_1−yBa_y)₂IrO₄ (y = 0–0.375) epitaxial thin films, in which the bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca and Ba. Transport measurements indicate that the thin-film series exhibits insulating behavior, similar to the J_eff = 1/2 spin-orbit Mott insulator Sr₂IrO₄. As the average A-site ionic radius increases from (Sr_1−xCa_x)₂IrO₄ to (Sr …

Synthesis And Characterization Of The 2-Dimensional Transition Metal Dichalcogenides, Robert Browning

Dissertations and Theses

In the last 50 years, the semiconductor industry has been scaling the silicon transistor to achieve faster devices, lower power consumption, and improve device performance. Transistor gate dimensions have become so small that short channel effects and gate leakage have become a significant problem. To address these issues, performance enhancement techniques such as strained silicon are used to improve mobility, while new high-k gate dielectric materials replace silicon oxide to reduce gate leakage. At some point the fundamental limit of silicon will be reached and the semiconductor industry will need to find an alternate solution. The advent of graphene led …

Annealing And Deposition Time Effects On The Structural, Optical, And Electrical Properties Of Indium Sulfide Thin Films Produced By Chemical Bath Deposition Method, Emi̇ne Güneri̇, Fatma Göde

Turkish Journal of Physics

Indium sulfide thin films were deposited onto indium-doped tin-oxide substrates with different deposition times (60 h, 63 h, 66 h, and 69 h) at room temperature by using a chemical bath deposition method to obtain new structures for solar cells. The film obtained at 60 h was annealed at 400 $^{\circ}$C for 1 h in nitrogen media. The crystallographic structure of the films was observed via the X-ray diffraction pattern while the size and shape of the grains were characterized by scanning electron microscopy. Moreover, the optical transmission spectra of the films were obtained at room temperature in the wavelength …

Direct Imaging Of Coexisting Ordered And Frustrated Sublattices In Artificial Ferromagnetic Quasicrystals, Barry Farmer, Vinayak Shantaram Bhat, Eric Teipel, J. Unguris, D. J. Keavney, Jeffrey Todd Hastings, Lance E. De Long

Physics and Astronomy Faculty Publications

We have used scanning electron microscopy with polarization analysis and photoemission electron microscopy to image the two-dimensional magnetization of permalloy films patterned into Penrose P2 tilings (P2T). The interplay of exchange interactions in asymmetrically coordinated vertices and short-range dipole interactions among connected film segments stabilize magnetically ordered, spatially distinct sublattices that coexist with frustrated sublattices at room temperature. Numerical simulations that include long-range dipole interactions between sublattices agree with images of as-grown P2T samples and predict a magnetically ordered ground state for a two-dimensional quasicrystal lattice of classical Ising spins.

Interface‐Coupled Bifeo3/Bimno3 Superlattices With Magnetic Transition Temperature Up To 410 K, Eun-Mi Choi, Josée E. Kliebeuker, Thomas Fix, Jie Xiong, Christy J. Kinane, Dario Arena, Sean Langridge, Aiping Chen, Zhenxing Bi, Joon Hwan Lee, Quanix Jia, Mark G. Blamire, Judith L. Macmanus-Driscoll

Physics Faculty Publications

Enhanced magnetic transition temperatures are demonstrated in 50 nm thick (001)‐oriented (BiFeO₃)_m/(BiMnO₃)_m (BFO/BMO) superlattices (SL). Highly strained ultra‐short SLs showed a magnetic transition, T_C2, up to ≈410 K as a result of ferrimagnetic interaction between BFO/BMO. All SL showed a new ferromagnetic transtion, T_C1, of ≈150 K coming from Fe⁴⁺‐Fe⁴⁺ interaction explained by electron transfer/leakage from Fe³⁺ to Mn³⁺.

Identification Of Photocurrents In Topological Insulators, Derek A. Bas, Rodrigo A. Muniz, Sercan Babakiray, David Lederman, J. E. Sipe, Alan D. Bristow

Faculty & Staff Scholarship

Optical injection and detection of charge currents is an alternative to conventional transport and photoemission measurements, avoiding the necessity of invasive contact that may disturb the system being examined. This is a particular concern for analyzing the surface states of topological insulators. In this work one- and two-color sources of photocurrents are isolated and examined in epitaxial thin films of Bi2Se3. We demonstrate that optical excitation and terahertz detection simultaneously captures one- and two-color photocurrent contributions, which has not been required for other material systems. A method is devised to extract the two components, and in doing so each can …

Crystallization Engineering As A Route To Epitaxial Strain Control, Andrew R. Akbashev, Aleksandr V. Plokhikh, Dmitri Barbash, Samuel Lofland, Jonathan E. Spanier

Faculty Scholarship for the College of Science & Mathematics

The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001)SrTiO3 and (001)LaAlO3substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001)BiFeO3 phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001)SrTiO3 results in a coherently strained film, the same films obtained on (001)LaAlO3 …

Improved Terahertz Modulation Using Germanium Telluride (Gete) Chalcogenide Thin Films, Alexander H. Gwin, Christopher H. Kodama, Tod V. Laurvick, Ronald Coutu Jr., Philip F. Taday

Faculty Publications

We demonstrate improved terahertz (THz) modulation using thermally crystallized germanium telluride (GeTe) thin films. GeTe is a chalcogenide material that exhibits a nonvolatile, amorphous to crystalline phase change at approximately 200 °C, as well as six orders of magnitude decreased electrical resistivity. In this study, amorphous GeTe thin films were sputtered on sapphire substrates and then tested using THz time-domain spectroscopy (THz-TDS). The test samples, heated in-situ while collecting THz-TDS measurements, exhibited a gradual absorbance increase, an abrupt nonvolatile reduction at the transition temperature, followed by another gradual increase in absorbance. The transition temperature was verified by conducting similar thermal …

Engineering The Ground State Of Complex Oxides, Derek Joseph Meyers

Graduate Theses and Dissertations

Transition metal oxides featuring strong electron-electron interactions have been at the forefront of condensed matter physics research in the past few decades due to the myriad of novel and exciting phases derived from their competing interactions. Beyond their numerous intriguing properties displayed in the bulk they have also shown to be quite susceptible to externally applied perturbation in various forms. The dominant theme of this work is the exploration of three emerging methods for engineering the ground states of these materials to access both their applicability and their deficiencies.

The first of the three methods involves a relatively new set …

Epitaxial Crn Thin Films With High Thermoelectric Figure Of Merit, Eric L. Thies, Daniel A. Hillsberry, Dmitri A. Tenne

Physics Faculty Publications and Presentations

A large enhancement of the thermoelectric figure of merit is reported in single crystalline films of CrN. The strong reduction of the lattice thermal conductivity in the rock-salt phase of this material is shown to be related to intrinsic lattice instabilities, which is similar to the resonant bonding effect proposed for cubic IV-VI compounds. These results demonstrate that useful ideas from classic thermoelectrics and phase change materials can be extended to transition metal nitrides and oxides.

Applications Of High Throughput (Combinatorial) Methodologies To Electronic, Magnetic, Optical, And Energy-Related Materials, Martin L. Green, Ichiro Takeuchi, Jason R. Hattrick-Simpers

Jason R. Hattrick-Simpers

High throughput (combinatorial) materials science methodology is a relatively new research paradigm that offers the promise of rapid and efficient materials screening, optimization, and discovery. The paradigm started in the pharmaceutical industry but was rapidly adopted to accelerate materials research in a wide variety of areas. High throughput experiments are characterized by synthesis of a “library” sample that contains the materials variation of interest (typically composition), and rapid and localized measurement schemes that result in massive data sets. Because the data are collected at the same time on the same “library” sample, they can be highly uniform with respect to …

Properties Of Cu(In,Ga,Al)Se² Thin Films Fabricated By Magnetron Sputtering, Talaat A. Hameed, Wei Cao, Bahiga A. Mansour, Inas K. Elzawaway, El-Metwally M. Abdelrazek, Hani E. Elsayed-Ali

Applied Research Center Publications

Cu (In,Ga,Al)Se₂ (CIGAS) thin films were studied as an alternative absorber layer material to Cu(In_xGa_1-x)Se₂. CIGAS thin films with varying Al content were prepared by magnetron sputtering on Si(100) and soda-lime glass substrates at 350 °C, followed by postdeposition annealing at 520 °C for 5 h in vacuum. The film composition was measured by an electron probe microanalyzer while the elemental depth profiles were determined by secondary ion mass spectrometry. X-ray diffraction studies indicated that CIGAS films are single phase with chalcopyrite structure and that the (112) peak clearly shifts to higher 2θ …

Maximum Screening Fields Of Superconducting Multilayer Structures, Alex Gurevich

Physics Faculty Publications

It is shown that a multilayer comprised of alternating thin superconducting and insulating layers on a thick substrate can fully screen the applied magnetic field exceeding the superheating fields H_sof both the superconducting layers and the substrate, the maximum Meissner field is achieved at an optimum multilayer thickness. For instance, a dirty layer of thickness ~0.1μm at the Nb surface could increase H_s similar or equal to 240 mT of a clean Nb up to H_s similar or equal to 290 mT. Optimized multilayers of Nb₃Sn, NbN, some of the iron pnictides, or alloyed …

Strain Relaxation In Nm-Thick Cu And Cu-Alloy Films Bonded To A Rigid Substrate, Ashley Herrmann

Legacy Theses & Dissertations (2009 - 2024)

In the wide scope of modern technology, nm-thick metallic films are increasingly used as lubrication layers, optical coatings, plating seeds, diffusion barriers, adhesion layers, metal contacts, reaction catalyzers, etc. A prominent example is the use of nm-thick Cu films as electroplating seed layers in the manufacturing of integrated circuits (ICs). These high density circuits are linked by on-chip copper interconnects, which are manufactured by filling Cu into narrow trenches by electroplating. The Cu fill by electroplating requires a thin Cu seed deposited onto high-aspect-ratio trenches. In modern ICs, these trenches are approaching 10 nm or less in width, and the …

Fabrication Of Robust Superconducting Granular Aluminium/Palladium Bilayer Microbolometers With Sub-Nanosecond Response, Thomas E. Wilson

Thomas E. Wilson

We provide a convenient recipe for fabricating reliable superconducting microbolometers as acoustic phonon detectors with sub-nanosecond response, using imagereversal optical lithography and dc-magnetron sputtering, and our recipe requires no chemical or plasma etching. Our approach solves the traditional problem for granular aluminium bolometers of unreliable (i.e., non-Ohmic) electrical contacts by sequentially sputtering the granular aluminium film and then a palladium capping layer. We use dc calibration data, the method of Danilchenko et al. [1], and direct nanosecond-pulsed photoexcitation to obtain the microbolometer’s characteristic current, thermal conductance, characteristic relaxation time, and heat capacity. We also demonstrate the use of the deconvolution …

Influence Of Composition On The Structure And Optoelectronic Properties Of Pb_Xin_{25-X}Se_{75} Thin Films, Hesham Azmi Elmeleegi, Zeinab El Sayed El Mandouh, Ahmed Abdel Moez

Turkish Journal of Physics

Pb_xIn_{25-x}Se_{75} thin films with 2 compositions were prepared by thermal evaporation. The surface topography of these films was studied by transmission electron microscope. The optical reflectance and transmittance were studied in order to determine the optical parameters such as optical energy gap, refractive index, extinction coefficient, dielectric loss, and dielectric tangent loss for these films. A single oscillator theory equation was applied for these films in order to determine both dispersion energy and oscillating energy, and the ratio of free carrier concentration/effective mass (N/m*) was determined optically. It was found that change in the composition of these films affects strongly …

An Investigation On Silar Deposited Cu_Xs Thin Films, Aykut Astam, Yunus Akaltun, Muhammet Yildirim

Turkish Journal of Physics

A copper sulfide thin film was deposited on glass substrate by successive ionic layer adsorption and reaction method at room temperature, using cupric sulfate and sodium sulfide aqueous solutions as precursors. The structural, surface morphological, optical, and electrical properties of the as-deposited film were investigated via X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, optical absorption, and d.c. 2-point probe methods. The film was found to be amorphous, dense, and uniform. Average atomic percentage of Cu:S in the as-deposited film was calculated as 63:37. The band gap energy of copper sulfide thin film was found to be 2.14 eV …

Nanoscale Thermoelectrics: A Study Of The Absolute Seebeck Coefficient Of Thin Films, Sarah J. Mason

Electronic Theses and Dissertations

The worlds demand for energy is ever increasing. Likewise, the environmental impact of climate change due generating that energy through combustion of fossil fuels is increasingly alarming. Due to these factors new sources of renewable energies are constantly being sought out. Thermoelectric devices have the ability to generate clean, renewable, energy out of waste heat. However promising that is, their inefficiency severely inhibits applicability and practical use. The usefulness of a thermoelectric material increases with the dimensionless quantity, ZT, where, Z = S²σ/κ, and S, σ, and κ are the Seebeck coefficient and electrical and thermal …

Polarization Of Bi2te3 Thin Film In A Floating-Gate Capacitor Structure, Hui Yuan, Kai Zhang, Haitao Li, Hao Zhu, John E. Bonevich, Helmut Baumgart, Curt A. Richter, Qiliang Li

Electrical & Computer Engineering Faculty Publications

Metal-Oxide-Semiconductor (MOS) capacitors with Bi₂Te₃ thin film sandwiched and embedded inside the oxide layer have been fabricated and studied. The capacitors exhibit ferroelectric-like hysteresis which is a result of the robust, reversible polarization of the Bi₂Te₃ thin film while the gate voltage sweeps. The temperature-dependent capacitance measurement indicates that the activation energy is about 0.33 eV for separating the electron and hole pairs in the bulk of Bi₂Te₃, and driving them to either the top or bottom surface of the thin film. Because of the fast polarization speed, potentially excellent …

Physical Analysis Of Vo2 Films Grown By Atomic Layer Deposition And Rf Magnetron Sputtering, Madhavi Tangirala, Kai Zhang, David Nminibapiel, Venkateswara Pallem, Christian Dussarrat, Wei Cao, Thomas N. Adam, Corbet S. Johnson, Hani E. Elsayed-Ali, Helmut Baumgart

Electrical & Computer Engineering Faculty Publications

Among the many vanadium suboxides and different stoichiometries, VO₂ has received considerable attention due to its remarkable metal-insulator transition (MIT) behavior, which causes a significant reversible change in its electrical and optical properties occurring across the phase transition at 67°C. The initially amorphous VO₂ thin films were fabricated by the emerging, Atomic Layer Deposition (ALD) technique with (tetrakis[ethylmethylamino]vanadium) {V(NEtMe)₄} as precursor and H₂O vapor as oxidation agent. For benchmarking we have also used the RF Magnetron Sputtering technique to deposit metallic vanadium thin films, which were later oxidized during furnace annealing. Post annealing of …

Adsorption-Controlled Growth Of Bivo4 By Molecular-Beam Epitaxy, D. A. Hillsberry, D. A. Tenne

Physics Faculty Publications and Presentations

Single-phase epitaxial films of the monoclinic polymorph of BiVO₄ were synthesized by reactive molecular-beam epitaxy under adsorption-controlled conditions. The BiVO₄ films were grown on (001) yttria-stabilized cubic zirconia (YSZ) substrates. Four-circle x-ray diffraction, scanning transmission electron microscopy (STEM), and Raman spectroscopy confirm the epitaxial growth of monoclinic BiVO₄ with an atomically abrupt interface and orientation relationship (001)_BiVO4 ∥ (001)_YSZ with [100]_BiVO4 ∥ [100]_YSZ. Spectroscopic ellipsometry, STEM electron energy loss spectroscopy (STEM-EELS), and x-ray absorption spectroscopy indicate that the films have a direct band gap of 2.5 ± 0.1 eV.

The Impact Of Growth Conditions On Cubic Znmgo Ultraviolet Sensors, Ryan Boutwell

Electronic Theses and Dissertations

Cubic Zn1-xMgxO (c-Zn1-xMgxO) thin films have opened the deep ultraviolet (DUV) spectrum to exploration by oxide optoelectronic devices. These extraordinary films are readily wet-etch-able, have inversion symmetric lattices, and are made of common and safe constituents. They also host a number of new exciting experimental and theoretical challenges. Here, the relation between growth conditions of the c-Zn1-xMgxO film and performance of fabricated ultraviolet (UV) sensors is investigated. Plasma-Enhanced Molecular Beam Epitaxy was used to grow Zn1-xMgxO thin films and formation conditions were explored by varying the growth temperature, Mg source flux, oxygen flow rate, and radio-frequency (RF) power coupled into …

Origin Of The Low Frequency Radiation Emitted By Radiative Polaritons Excited By Infrared Radiation In Planar La2o3 Films, Anita J. Vincent-Johnson, Yosep Schwab, Harkirat S. Mann, Mathieu Francoeur, James S. Hammonds Jr., Giovanna Scarel

Department of Physics and Astronomy - Faculty Scholarship

Upon excitation in thin oxide films by infrared radiation, radiative polaritons are formed with complex angular frequency ω, according to the theory of Kliewer and Fuchs (1966 Phys. Rev. 150 573). We show that radiative polaritons leak radiation with frequency ωi to the space surrounding the oxide film. The frequency ωi is the imaginary part of ω. The effects of the presence of the radiation leaked out at frequency ωi are observed experimentally and numerically in the infrared spectra of La2O3 films on silicon upon excitation by infrared radiation of the 0TH type radiative polariton. The frequency ωi is found …

Structural, Optical And Electrical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Abhilash Kongu

Open Access Theses & Dissertations

Hafnium oxide (HfO2) has emerged as the most promising high-k dielectric for Metal-Oxide-Semiconductor (MOS) devices and has been highlighted as the most suitable dielectric materials to replace silicon oxide because of its comprehensive performance. In the present research, yttrium-doped HfO2 (YDH) thin films were fabricated using RF magnetron sputter deposition onto Si (100) and quartz with a variable thickness. Cross-sectional scanning electron microscopy coupled with Filmetrics revealed that film thickness values range from 700 A° to 7500 A°. Electrical properties such as AC Resistivity and current-voltage (I-V) characteristics of YDH films were studied. YDH films that were relatively thin (<1500 A°) crystallized in monoclinic phase while thicker films crystallized in cubic phase. The band gap (Eg) of the films was calculated from the optical measurements. The band gap was found to be ∼5.60 eV for monoclinic while it is ∼6.05 eV for cubic phase of YDH films. Frequency dependence of the electrical resistivity (ρac) and the total conductivity of the films were measured. Resistivity decreased (by three orders of magnitude) with increasing frequency from 100 Hz to 1 MHz, attributed due to the hopping mechanism in YDH films. Whereas, while ρac∼1Ω-m at low frequencies (100 Hz), it decreased to ∼ 104 Ω-cm at higher frequencies (1 MHz). Aluminum (Al) metal electrodes were deposited to fabricate a thin film capacitor with YDH layer as dielectric film thereby employing Al-YDH-Si capacitor structure. The results indicate that the capacitance of the films decrease with increasing film thickness. A detailed analysis of the electrical characteristics of YDH films is presented.

Applications Of High Throughput (Combinatorial) Methodologies To Electronic, Magnetic, Optical, And Energy-Related Materials, Martin L. Green, Ichiro Takeuchi, Jason R. Hattrick-Simpers

Faculty Publications

High throughput (combinatorial) materials science methodology is a relatively new research paradigm that offers the promise of rapid and efficient materials screening, optimization, and discovery. The paradigm started in the pharmaceutical industry but was rapidly adopted to accelerate materials research in a wide variety of areas. High throughput experiments are characterized by synthesis of a “library” sample that contains the materials variation of interest (typically composition), and rapid and localized measurement schemes that result in massive data sets. Because the data are collected at the same time on the same “library” sample, they can be highly uniform with respect to …

Ruco To Extend The Scalability Of Ultra-Thin Direct Plate Liners, Daniel Verne Greenslit

Legacy Theses & Dissertations (2009 - 2024)

In traditional semiconductor technology a sputtered copper seed layer is used to improve the adhesion, microstucture, and electromigration characteristics of electrochemically deposited (ECD) copper. The seed layer is deposited on top of a Ta/TaN stack. The Ta layer acts as an adhesion and nucleation layer for the copper seed and the TaN serves as a diffusion barrier for the Cu. As the line widths continue to shrink, scaling each of these layers becomes more difficult. It would be advantageous for the interconnect to be composed of as much copper as possible, transitioning from the traditional liner seed stack to a …

Investigation Of Nbnx Thin Films And Nanoparticles Grown By Pulsed Laser Deposition And Thermal Diffusion, Ashraf Hassan Farha

Electrical & Computer Engineering Theses & Dissertations

Niobium nitride films (NbNx) were grown on Nb and Si (100) substrates using pulsed laser deposition (PLD), laser heating, and thermal diffusion methods. Niobium nitride films were deposited on Nb substrates using PLD with a Q-switched Nd: YAG laser (λ = 1064 nm, 40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, different nitrogen background pressures and deposition temperatures. The effect of changing PLD parameters for films done by PLD was studied. The seen observations establish guidelines for adjusting the laser parameters to achieve the desired morphology and phase of the grown NbNx films.

When the …

Thin Films Of Carbon Nanotubes And Nanotube/Polymer Composites, Anthony D. Willey

Theses and Dissertations

A method is described for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-Methyl-2-pyrrolidone or N-Cyclohexyl-2-pyrrolidone and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent quickly evaporated, leaving a thin film of randomly oriented nanotubes. Film thickness was controlled by the spray time and ranged between 200-500 nm, with RMS roughness of about 40 nm. Also described is a method for creating thin (300 nm) conductive freestanding nanotube/polymer composite films by infiltrating sprayed nanotube films with polyimide.