Matching Items (52)
Description
Complex perovskite materials, including Ba(Zn1/3Ta2/3)O3 (BZT), are commonly used to make resonators and filters in communication systems because of their low dielectric loss and high-quality factors (Q). Transition metal additives are introduced (i.e., Ni2+, Co2+, Mn2+) to act as sintering agents and tune their temperature coefficient to zero or near-zero. However, losses in these commercial dielectric materials at cryogenic temperatures increase markedly due to spin-excitation resulting from the presence of paramagnetic defects. Applying a large magnetic field (e.g., 5 Tesla) quenches these losses and has allowed the study of other loss mechanisms present at low temperatures. Work was performed on Fe3+ doped LaAlO3. At high magnetic fields, the residual losses versus temperature plots exhibit Debye peaks at ~40 K, ~75 K, and ~215 K temperature and can be tentatively associated with defect reactions O_i^x+V_O^x→O_i^'+V_O^•, Fe_Al^x+V_Al^"→Fe_Al^'+V_Al^' and Al_i^x+Al_i^(••)→〖2Al〗_i^•, respectively. Peaks in the loss tangent versus temperature graph of Zn-deficient BZT indicate a higher concentration of defects and appear to result from conduction losses.Guided by the knowledge gained from this study, a systematic study to develop high-performance microwave materials for ultra-high performance at cryogenic temperatures was performed. To this end, the production and characterization of perovskite materials that were either undoped or contained non-paramagnetic additives were carried out. Synthesis of BZT ceramic with over 98% theoretical density was obtained using B2O3 or BaZrO3 additives. At 4 K, the highest Q x f product of 283,000 GHz was recorded for 5% BaZrO3 doped BZT.
A portable, inexpensive open-air spectrometer was designed, built, and tested to make the electron paramagnetic resonance (EPR) technique more accessible for high-school and university lab instruction. In this design, the sample is placed near a dielectric resonator and does not need to be enclosed in a cavity, as is used in commercial EPR spectrometers. Permanent magnets used produce fields up to 1500 G, enabling EPR measurements up to 3 GHz.
ContributorsGajare, Siddhesh Girish (Author) / Newman, Nathan (Thesis advisor) / Alford, Terry (Committee member) / Tongay, Sefaattin (Committee member) / Chamberlin, Ralph (Committee member) / Arizona State University (Publisher)
Created2022
Description
Diamond as a wide-bandgap (WBG) semiconductor material has distinct advantages for power electronics applications over Si and other WBG materials due to its high critical electric field (> 10 MV/cm), high electron and hole mobility (??=4500 cm2/V-s, ??=3800 cm2/V-s), high thermal conductivity (~22 W/cm-K) and large bandgap (5.47 eV). Owing to its remarkable properties, the application space of WBG materials has widened into areas requiring very high current, operating voltage and temperature. Remarkable progress has been made in demonstrating high breakdown voltage (>10 kV), ultra-high current density (> 100 kA/cm2) and ultra-high temperature (~1000oC) diamond devices, giving further evidence of diamond’s huge potential. However, despite the great success, fabricated diamond devices have not yet delivered diamond’s true potential. Some of the main reasons are high dopant activation energies, substantial bulk defect and trap densities, high contact resistance, and high leakage currents. A lack of complete understanding of the diamond specific device physics also impedes the progress in correct design approaches. The main three research focuses of this work are high power, high frequency and high temperature. Through the design, fabrication, testing, analysis and modeling of diamond p-i-n and Schottky diodes a milestone in diamond research is achieved and gain important theoretical understanding. In particular, a record highest current density in diamond diodes of ~116 kA/cm2 is demonstrated, RF characterization of diamond diodes is performed from 0.1 GHz to 25 GHz and diamond diodes are successfully tested in extreme environments of 500oC and ~93 bar of CO2 pressure. Theoretical models are constructed analytically and inii
Silvaco ATLAS including incomplete ionization and hopping mobility to explain space charge limited current phenomenon, effects of traps and Mott-Gurney dominated diode ???. A new interpretation of the Baliga figure of merit for WBG materials is also formulated and a new cubic relationship between ??? and breakdown voltage is established. Through Silvaco ATLAS modeling, predictions on the power limitation of diamond diodes in receiver-protector circuits is made and a range of self-heating effects is established. Poole-Frenkel emission and hopping conduction models are also utilized to analyze high temperature (500oC) leakage behavior of diamond diodes. Finally, diamond JFET simulations are performed and designs are proposed for high temperature – extreme environment applications.
ContributorsSurdi, Harshad (Author) / Goodnick, Stephen M (Thesis advisor) / Nemanich, Robert J (Committee member) / Thornton, Trevor J (Committee member) / Lyons, James R (Committee member) / Arizona State University (Publisher)
Created2022
Description
In this dissertation, atomic layer processing and surface characterization techniques were used to investigate surface conditions of wide band gap materials, gallium nitride (GaN) and gallium oxide (Ga2O3). These studies largely focused on mitigation and removal of defect formation induced by ions used in conventional plasma-based dry etching techniques. Band bending measured by x-ray photoelectron spectroscopy (XPS) was used to characterize charge compensation at the surface of GaN (0001) and determine densities of charged surface states produced by dry etching. Mitigation and removal of these dry-etch induced defects was investigated by varying inductively coupled plasma (ICP) etching conditions, performing thermal and plasma-based treatments, and development of a novel low-damage, self-limiting atomic layer etching (ALE) process to remove damaged material. Atomic layer deposition (ALD) and ALE techniques were developed for Ga2O3 using trimethylgallium (TMG). Ga2O3 was deposited by ALD on Si using TMG and O2 plasma with a growth rate of 1.0 ± 0.1 Å/cycle. Ga2O3 films were then etched using HF and TMG using a fully thermal ALE process with an etch rate of 0.9 ± Å/cycle. O2 plasma oxidation of GaN for surface conversion to Ga2O3 was investigated as a pathway for ALE of GaN using HF and TMG. This process was characterized using XPS, in situ multi-wavelength ellipsometry, and transmission electron microscopy. This study indicated that the etch rate was lower than anticipated, which was attributed to crystallinity of the converted surface oxide on GaN (0001).
ContributorsHatch, Kevin Andrew (Author) / Nemanich, Robert J (Thesis advisor) / Ponce, Fernando A (Committee member) / Smith, David J (Committee member) / Zhao, Yuji (Committee member) / Arizona State University (Publisher)
Created2021
Description
In this dissertation, the surface interactions of fluorine were studied during atomic layer deposition (ALD) and atomic layer etching (ALE) of wide band gap materials. To enable this research two high vacuum reactors were designed and constructed for thermal and plasma enhanced ALD and ALE, and they were equipped for in-situ process monitoring. Fluorine surface interactions were first studied in a comparison of thermal and plasma enhanced ALD (TALD and PEALD) of AlF3 thin films prepared using hydrogen fluoride (HF), trimethylaluminum (TMA), and H2-plasma. The ALD AlF3 films were compared ¬in-situ using ellipsometry and X-ray photoelectron spectroscopy (XPS). Ellipsometry showed a growth rate of 1.1 Å/ cycle and 0.7 Å/ cycle, at 100°C, for the TALD and PEALD AlF3 processes, respectively. XPS indicated the presence of Al-rich clusters within the PEALD film. The formation of the Al-rich clusters is thought to originate during the H2-plasma step of the PEALD process. The Al-rich clusters were not detected in the TALD AlF3 films. This study provided valuable insight on the role of fluorine in an ALD process.
Reactive ion etching is a common dry chemical etch process for fabricating GaN devices. However, the use of ions can induce various defects, which can degrade device performance. The development of low-damage post etch processes are essential for mitigating plasma induced damage. As such, two multistep ALE methods were implemented for GaN based on oxidation, fluorination, and ligand exchange. First, GaN surfaces were oxidized using either water vapor or O2-plasma exposures to produce a thin oxide layer. The oxide layer was addressed using alternating exposures of HF and TMG, which etch Ga2O3 films. Each ALE process was characterized using in-situ using ellipsometry and XPS and ex-situ transmission electron microscopy (TEM). XPS indicated F and O impurities remained on the etched surfaces. Ellipsometry and TEM showed a slight reduction in thickness. The very low ALE rate was interpreted as the inability of the Ga2O3 ALE process to fluorinate the ordered surface oxide on GaN (0001).
Overall, these results indicate HF is effective for the ALD of metal fluorides and the ALE of metal oxides.
ContributorsMessina, Daniel C (Author) / Nemanich, Robert J (Thesis advisor) / Goodnick, Stephen (Committee member) / Ponce, Fernando A (Committee member) / Smith, David (Committee member) / Arizona State University (Publisher)
Created2021
Description
This thesis examines the interpretations derived from the Kac Ring Model, and the adding of a modification to the original model via “kick backs,” which can be interpreted to represent time reversals in the individual Kac rings. The results of this modification are analyzed, and their implications explored. There are three main parts to this thesis. Part 1 is a literature review which explains the working principles of the original Kac ring and explores its numerous applications. Part 2 describes the software and the theoretical & computational methodology used to implement the model and gather data. Part 3 analyzes the data gathered and makes a conclusion about its implications. There is an appendix included which contains some figures from Part 3 in a larger size, as it wasn’t possible to make the figures bigger within the text due to formatting.
ContributorsGavrilov, Alexander (Author) / Sukharev, Maxim (Thesis director) / Chamberlin, Ralph (Committee member) / Peng, Xihong (Committee member) / Barrett, The Honors College (Contributor) / College of Integrative Sciences and Arts (Contributor) / Department of Information Systems (Contributor)
Created2022-05
Description
We describe the fabrication and characterization of magnesium diboride (MgB2) thin films for applications in superconducting devices. MgB2 shows great potential as a superconducting thin-film material due to its high transition temperature (Tc ≅ 39 K) and its level of nonlinear kinetic inductance that could enable a large current-controlled phase shift for accessibility to higher frequencies (0.5 – 3 THz). Compared to other high-temperature superconductors like YBa2Cu3O7 (YBCO), FeSe, and BaFe2As2 that require complex deposition techniques and have intricate crystal structures, MgB2 stands out due to its simple synthesis process and suitability for thin-film fabrication. We measure Coplanar Waveguide (CPW) and inverted microstrip MgB2 resonators that yield an internal quality factor of up to 15,000 at 4.2 K. By DC-biasing 3-μm wide CPW and inverted microstrip transmission lines, we demonstrate current-tunable phase-delays between 0 and 2π radians, showcasing the nonlinear kinetic inductance in MgB2. Understanding the total loss and nonlinear kinetic inductance of MgB2 allows for the design and realization of THz frequency superconducting devices, which are crucial for astrophysics and quantum sensors. MgB2 thin films find applications in Hot Electron Bolometers (HEBs), Thermal Kinetic Inductance Detectors (TKIDs), THz Traveling Wave Parametric Amplifiers (TWPAs), and THz frequency multipliers.
ContributorsBell, Christina (Author) / Mauskopf, Philip (Thesis director) / Chamberlin, Ralph (Committee member) / Cunnane, Daniel (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor)
Created2024-05
Description
Millimeter wave technologies have various applications in many science and engineering disciplines, from astronomy and chemistry to medicine and security. The superconducting circuit technology, in particular mm-wave, is one of the most appealing candidates due to their extremely low loss, near quantum-limited noise performance, and scalable fabrication. Two main immediate applications of these devices are in astronomical instrumentation and quantum computing and sensing. The kinetic inductance caused by the inertia of cooper pairs in thin-film superconductors dominates over the geometric inductance of the superconducting circuit. The nonlinear response of the kinetic inductance to an applied field or current provides a Kerr-like medium. This nonlinear platform can be used for mixing processes, parametric gain, and anharmonic resonance. In this thesis, I present the development of an mm-wave superconducting on-chip Fourier transform spectrometer (SOFTS) based on a nonlinear kinetic inductance of superconducting thin films. The circuit elements of the SOFTS device include a quadrature hybrid and current-controllable superconducting transmission lines in an inverted microstrip geometry. Another similar device explored here is a kinetic inductance traveling wave parametric amplifier (KI-TWPA) with wide instantaneous bandwidth, quantum noise limited performance, and high dynamic range as a candidate for the readout of cryogenic detectors and superconducting qubits. I report four-wave mixing gain measurements of ~ 30 dB from 0.2 - 5 GHz in KI-TWPAs made of capacitively shunted microstrip lines. I show that the gain can be tuned over the above-mentioned frequency range by changing the pump tone frequency. I also discuss the measured gain (~ 6 dB) of a prototype mm-wave KI-TWPA in the 75 - 100 GHz frequency range. Finally, I present, for the first time, the concept and simulation of a kinetic inductance qubit I named Kineticon. The qubit exploits the nonlinearity of the kinetic inductance of a very thin nanowire connecting two capacitive pads with a resonant frequency of ~ 96 GHz. the qubit is embedded in an mm-wave aluminum cavity. I show that mm-wave anharmonic microstrip resonators made of NbTiN have quality factors > 60,000. These measurements are promising for implementing high-quality factor resonators and qubits in the mm-wave regime.
ContributorsFaramarzi, Farzad (Author) / Mauskopf, Philip (Thesis advisor) / Day, Peter (Committee member) / Chamberlin, Ralph (Committee member) / Terrano, William (Committee member) / Arizona State University (Publisher)
Created2023
Description
We implemented the well-known Ising model in one dimension as a computer program and simulated its behavior with four algorithms: (i) the seminal Metropolis algorithm; (ii) the microcanonical algorithm described by Creutz in 1983; (iii) a variation on Creutz’s time-reversible algorithm allowing for bonds between spins to change dynamically; and (iv) a combination of the latter two algorithms in a manner reflecting the different timescales on which these two processes occur (“freezing” the bonds in place for part of the simulation). All variations on Creutz’s algorithm were symmetrical in time, and thus reversible. The first three algorithms all favored low-energy states of the spin lattice and generated the Boltzmann energy distribution after reaching thermal equilibrium, as expected, while the last algorithm broke from the Boltzmann distribution while the bonds were “frozen.” The interpretation of this result as a net increase to the system’s total entropy is consistent with the second law of thermodynamics, which leads to the relationship between maximum entropy and the Boltzmann distribution.
ContributorsLewis, Aiden (Author) / Chamberlin, Ralph (Thesis director) / Beckstein, Oliver (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor)
Created2023-05
Description
Seeking an upper limit of the Neutron Electric Dipole Moment (nEDM) is a test of charge-parity (CP) violation beyond the Standard Model. The present experimentally tested nEDM upper limit is 3x10^(26) e cm. An experiment to be performed at the Oak Ridge National Lab Spallation Neutron Source (SNS) facility seeks to reach the 3x10^(28) e cm limit. The experiment is designed to probe for a dependence of the neutron's Larmor precession frequency on an applied electric eld. The experiment will use polarized helium-3
(3He) as a comagnetometer, polarization analyzer, and detector.
Systematic influences on the nEDM measurement investigated in this thesis include (a) room temperature measurements on polarized 3He in a measurement cell made from the same materials as the nEDM experiment, (b) research and development of the Superconducting QUantum Interference Devices (SQUID) which will be used in the nEDM experiment, (c) design contributions for an experiment with nearly all the same conditions as will be present in the nEDM experiment, and (d) scintillation studies in superfluid helium II generated from alpha particles which are fundamentally similar to the nEDM scintillation process. The result of this work are steps toward achievement of a new upper limit for the nEDM experiment at the SNS facility.
(3He) as a comagnetometer, polarization analyzer, and detector.
Systematic influences on the nEDM measurement investigated in this thesis include (a) room temperature measurements on polarized 3He in a measurement cell made from the same materials as the nEDM experiment, (b) research and development of the Superconducting QUantum Interference Devices (SQUID) which will be used in the nEDM experiment, (c) design contributions for an experiment with nearly all the same conditions as will be present in the nEDM experiment, and (d) scintillation studies in superfluid helium II generated from alpha particles which are fundamentally similar to the nEDM scintillation process. The result of this work are steps toward achievement of a new upper limit for the nEDM experiment at the SNS facility.
ContributorsDipert, Robert (Author) / Alarcon, Ricardo (Thesis advisor) / Chamberlin, Ralph (Committee member) / Golub, Robert (Committee member) / Chen, Tingyong (Committee member) / Schmidt, Kevin (Committee member) / Arizona State University (Publisher)
Created2019
Description
Measurements of the response of superconducting nanowire single photon detector (SNSPD) devices to changes in various forms of input power can be used for characterization of the devices and for probing device-level physics. Two niobium nitride (NbN) superconducting nanowires developed for use as SNSPD devices are embedded as the inductive (L) component in resonant inductor/capacitor (LC) circuits coupled to a microwave transmission line. The capacitors are low loss commercial chip capacitors which limit the internal quality factor of the resonators to approximately $Qi = 170$. The resonator quality factor, approximately $Qr = 23$, is dominated by the coupling to the feedline and limits the detection bandwidth to on the order of 1MHz. In our experiments with this first generation device, we measure the response of the SNSPD devices to changes in thermal and optical power in both the time domain and the frequency domain. Additionally, we explore the non-linear response of the devices to an applied bias current. For these nanowires, we find that the band-gap energy is $\Delta_0 \approx 1.1$meV and that the density of states at the Fermi energy is $N_0 \sim 10^{10}$/eV/$\mu$m$^3$.
We present the results of experimentation with a superconducting nanowire that can be operated in two detection modes: i) as a kinetic inductance detector (KID) or ii) as a single photon detector (SPD). When operated as a KID mode in linear mode, the detectors are AC-biased with tones at their resonant frequencies of 45.85 and 91.81MHz. When operated as an SPD in Geiger mode, the resonators are DC biased through cryogenic bias tees and each photon produces a sharp voltage step followed by a ringdown signal at the resonant frequency of the detector. We show that a high AC bias in KID mode is inferior for photon counting experiments compared to operation in a DC-biased SPD mode due to the small fraction of time spent near the critical current with an AC bias. We find a photon count rate of $\Gamma_{KID} = 150~$photons/s/mA in a critically biased KID mode and a photon count rate of $\Gamma_{SPD} = 10^6~$photons/s/mA in SPD mode.
This dissertation additionally presents simulations of a DC-biased, frequency-multiplexed readout of SNSPD devices in Advanced Design System (ADS), LTspice, and Sonnet. A multiplexing factor of 100 is achievable with a total count rate of $>5$MHz. This readout could enable a 10000-pixel array for astronomy or quantum communications. Finally, we present a prototype array design based on lumped element components. An early implementation of the array is presented with 16 pixels in the frequency range of 74.9 to 161MHz. We find good agreement between simulation and experimental data in both the time domain and the frequency domain and present modifications for future versions of the array.
We present the results of experimentation with a superconducting nanowire that can be operated in two detection modes: i) as a kinetic inductance detector (KID) or ii) as a single photon detector (SPD). When operated as a KID mode in linear mode, the detectors are AC-biased with tones at their resonant frequencies of 45.85 and 91.81MHz. When operated as an SPD in Geiger mode, the resonators are DC biased through cryogenic bias tees and each photon produces a sharp voltage step followed by a ringdown signal at the resonant frequency of the detector. We show that a high AC bias in KID mode is inferior for photon counting experiments compared to operation in a DC-biased SPD mode due to the small fraction of time spent near the critical current with an AC bias. We find a photon count rate of $\Gamma_{KID} = 150~$photons/s/mA in a critically biased KID mode and a photon count rate of $\Gamma_{SPD} = 10^6~$photons/s/mA in SPD mode.
This dissertation additionally presents simulations of a DC-biased, frequency-multiplexed readout of SNSPD devices in Advanced Design System (ADS), LTspice, and Sonnet. A multiplexing factor of 100 is achievable with a total count rate of $>5$MHz. This readout could enable a 10000-pixel array for astronomy or quantum communications. Finally, we present a prototype array design based on lumped element components. An early implementation of the array is presented with 16 pixels in the frequency range of 74.9 to 161MHz. We find good agreement between simulation and experimental data in both the time domain and the frequency domain and present modifications for future versions of the array.
ContributorsSchroeder, Edward, Ph.D (Author) / Mauskopf, Philip (Thesis advisor) / Chamberlin, Ralph (Committee member) / Lindsay, Stuart (Committee member) / Newman, Nathan (Committee member) / Easson, Damien (Committee member) / Arizona State University (Publisher)
Created2018