Physics Commons^™

Experimental Studies Of Electrical Resistivity Behavior Of Cu, Zn And Co Along Their Melting Boundaries: Implications For Heat Flux At Earth’S Inner Core Boundary, Innocent Chinweikpe Ezenwa

Electronic Thesis and Dissertation Repository

Abstract

The electrical resistivity of high purity Cu, Zn and Co has been measured at pressures (P) up to 5GPa and at temperatures (T) in the liquid phase. The electrical resistivity of solid state Nb was also measured up to 5GPa and ~1900K. All measurements were made in a large volume cubic anvil press. Using two thermocouples placed at opposite ends of the sample wire, serving as temperature probes as well as resistance leads, a four-wire technique resistivity measurement was employed along with a polarity switch. Post-experiment compositional analyses were carried out on an electron microprobe.

The expected resistivity decrease …

Enhanced Metallic Properties Of Srruo3 Thin Films Via Kinetically Controlled Pulsed Laser Epitaxy, Justin K. Thompson, J. Nichols, S. Lee, S. Ryee, John H. Gruenewald, John G. Connell, Maryam Souri, J. M. Johnson, J. Hwang, M. J. Han, H. N. Lee, D. -W. Kim, Sung S. Ambrose Seo

Physics and Astronomy Faculty Publications

Metal electrodes are a universal element of all electronic devices. Conducting SrRuO₃ (SRO) epitaxial thin films have been extensively used as electrodes in complex-oxide heterostructures due to good lattice mismatches with perovskite substrates. However, when compared to SRO single crystals, SRO thin films have shown reduced conductivity and Curie temperatures (T_C), which can lead to higher Joule heating and energy loss in the devices. Here, we report that high-quality SRO thin films can be synthesized by controlling the plume dynamics and growth rate of pulsed laser epitaxy (PLE) with real-time optical spectroscopic monitoring. The SRO thin …

Enhanced Magnetism In Dy And Tb At Extreme Pressure, Jinhyuk Lim

Arts & Sciences Electronic Theses and Dissertations

At ambient pressure all lanthanide metals order magnetically at temperatures at or below ambient. The magnetic ordering is known to result from the indirect exchange interaction between localized 4f magnetic moments mediated by the surrounding conduction electrons, the so-called Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. With the RKKY interaction the magnetic ordering temperature To is expected to be proportional to the de Gennes factor which is a function of the Landé g factor gJ and the total angular momentum J. For example, Gd has the highest value of To, 292 K, at ambient pressure as it has the largest de Gennes factor of …

Magnetoresistance Characteristics In Individual Fe3O4 Single Crystal Nanowire, K. M. Reddy, Nitin P. Padture, Alex Punnoose, Charles Hanna

Physics Faculty Publications and Presentations

We report on the magnetoresistance (MR) and electron transport measurements observed on asingle crystal magnetite nanowire prepared using a hydrothermal synthesis method. High-resolution electron microscopy revealed the single crystal magnetite nanowires with 80–120 nm thickness and up to 8 μm in length. Magnetic measurements showed the typical Verwey transition around 120 K with a 100 Oe room temperature coercivity and 45 emu/g saturationmagnetization, which are comparable to bulk magnetite. Electrical resistance measurements in 5-300 K temperature range were performed by scanning gate voltage and varying appliedmagnetic field. Electrical resistivity of the nanowire was found to be around 5 × …

Investigation Of Cdznte Crystal Defects Using Scanning Probe Microscopy, Goutam Koley, J. Liu, K. C. Mandal

Krishna C. Mandal

No abstract provided.

Investigation Of Cdznte Crystal Defects Using Scanning Probe Microscopy, Goutam Koley, J. Liu, K. C. Mandal

Krishna C. Mandal

No abstract provided.

Investigation Of Cdznte Crystal Defects Using Scanning Probe Microscopy, Goutam Koley, J. Liu, K. C. Mandal

Krishna C. Mandal

No abstract provided.

Electrostatic Force Microscopy And Electrical Isolation Of Etched Few-Layer Graphene Nano-Domains, D. Patrick Hunley, Abhishek Sundararajan, Mathias J. Boland, Douglas R. Strachan

Physics and Astronomy Faculty Publications

Nanostructured bi-layer graphene samples formed through catalytic etching are investigated with electrostatic force microscopy. The measurements and supporting computations show a variation in the microscopy signal for different nano-domains that are indicative of changes in capacitive coupling related to their small sizes. Abrupt capacitance variations detected across etch tracks indicates that the nano-domains have strong electrical isolation between them. Comparison of the measurements to a resistor-capacitor model indicates that the resistance between two bi-layer graphene regions separated by an approximately 10 nm wide etch track is greater than about 1×10¹² Ω with a corresponding gap resistivity greater than about …

Non-Fermi Liquid Transport And "Universal" Ratios In Quantum Griffiths Phases, David Nozadze, Thomas Vojta

Physics Faculty Research & Creative Works

We use the semi-classical Boltzmann equation to investigate transport properties such as electrical resistivity, thermal resistivity, thermopower, and the Peltier coefficient of disordered metals close to an antiferromagnetic quantum phase transition. In the quantum Griffiths phase, the electrons are scattered by spin-fluctuations in the rare regions. This leads to singular temperature dependencies not just at the quantum critical point, but in the entire Griffiths phase. We show that the resulting non-universal power-laws in transport properties are controlled by the same Griffiths exponent λ which governs the thermodynamics. λ takes the value zero at the quantum critical point and increases throughout …

Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers

Physics Faculty Publications

Growth of Ga-doped ZnO by pulsed laser deposition at 200 °C in an ambient of Ar and H₂produces a resistivity of 1.5 × 10⁻⁴ Ω-cm, stable to 500 °C. The resistivity can be further reduced to 1.2 × 10⁻⁴ Ω-cm by annealing on Zn foil, which reduces the compensating Zn-vacancy acceptor concentration N_A to 5 × 10¹⁹ cm⁻³, only 3% of the Ga-donor concentration N_D of 1.6 × 10²¹ cm⁻³, with N_D and N_A determined from a degenerate mobility theory. The plasmon-resonance wavelength is only 1060 …

Structure And Electrical Properties Of Lanthanum Doped Bi_2sr_2ca_{2-X}La_Xcu_3o_{10+ \Delta} Superconductor, Kareem Jasim

Turkish Journal of Physics

In this work we studied the effect of La-doping on phase purity, crystal structure and electrical resistivity of Bi_2Sr_2Ca_2Cu_3O_{10+\delta} superconductor, synthesized by usual solid state reaction method. The X-ray florescence (XRF) show the stoichiometry of samples and X-ray diffraction (XRD) analysis showed the change of structure from orthorhombic to tetragonal by increasing La doping. It was found that the change of lanthanum concentrations of all our samples produce a change in the oxygen content, the ratio of lattice parameters c/a and mass density \rho_m. Electrical resistivity, using the four-probe technique, was used to find the critical temperature T_c and to …

Highly Conductive Zno Grown By Pulsed Laser Deposition In Pure Ar, Robin C. Scott, Kevin D. Leedy, Burhan Bayraktaroglu, David C. Look, Yong-Hang Zhang

Physics Faculty Publications

Ga-doped ZnO was deposited by pulsed laser deposition at 200 °C on SiO₂/Si, Al₂O₃, or quartz in 10 mTorr of pure Ar. The as-grown, bulk resistivity at 300 K is 1.8×10⁻⁴ Ω cm, three-times lower than that of films deposited at 200 °C in 10 mTorr of O₂ followed by an anneal at 400 °C in forming gas. Furthermore, depth uniformity of the electrical properties is much improved. Mobility analysis shows that this excellent resistivity is mostly due to an increase in donor concentration, rather than a decrease in acceptor concentration. Optical …

Tunneling Electroresistance In Ferroelectric Tunnel Junctions With A Composite Barrier, M. Ye. Zhuravlev, Yong Wang, S. Maekawa, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Tunneling electroresistance (TER) effect is the change in the electrical resistance of a ferroelectric tunnel junction (FTJ) associated with polarization reversal in the ferroelectric barrier layer. Here we predict that a FTJ with a composite barrier that combines a functional ferroelectric film and a thin layer of a nonpolar dielectric can exhibit a significantly enhanced TER. Due to the change in the electrostatic potential with polarization reversal, the nonpolar dielectric barrier acts as a switch that changes its barrier height from a low to high value. The predicted values of TER are giant and indicate that the resistance of the …

Temperature And Electric Field Dependence Of Conduction In Low-Density Polyethylene, John R. Dennison, Jerilyn Brunson

All Physics Faculty Publications

A traditional constant voltage conductivity test method was used to measure how the conductivity of highly insulating low-density polyethylene (LDPE) polymer films depends on applied electric field, repeated and prolonged electric field exposure, and sample temperature. The strength of the applied voltage was varied to determine the electric field dependence. At low electric field, the resistivity was measured from cryogenic temperatures to well above the glass transition temperature. Comparisons were made with a variety of models of the conduction mechanisms common in insulators, including transient polarization and diffusion and steady-state thermally activated hopping conductivity and variable range hopping conductivity, to …

Investigation Of Cdznte Crystal Defects Using Scanning Probe Microscopy, Goutam Koley, J. Liu, K. C. Mandal

Faculty Publications

No abstract provided.

Competition Between Ferromagnetic Metallic And Paramagnetic Insulating Phases In Manganites, G. Li, H. D. Zhou, S. J. Feng, Xiaojuan Fan, X. G. Li, Z. D. Wang

Physics Faculty Research

La_0.67Ca_0.33Mn_1−xCu_xO₃(x=0 and 0.15) epitaxial thin films were grown on the (100) LaAlO₃ substrates, and the temperature dependence of their resistivity was measured in magnetic fields up to 12 T by a four-probe technique. We found that the competition between the ferromagnetic metallic (FM) and paramagnetic insulating (PI) phases plays an important role in the observed colossal magnetoresistance(CMR) effect. Based on a scenario that the doped manganites approximately consist of phase-separated FM and PI regions, a simple phenomenological model was proposed to describe the CMR effect. Using this model, we …

Behavior Of Grain Boundary Resistivity In Metals Predicted By A Two-Dimensional Model, Rand Dannenberg, Alexander H. King

Alexander H. King

The behavior of a model for the specific grain boundary resistivity in metallic bamboo conductor lines is developed and compared to other theoretical treatments, and to experiment. The grain boundary is modeled as an array of scatterers on a plane. The scatterers are called “vacancy-ion” complexes, in which the vacancy represents the boundary free volume, and the ion is an atom adjacent to the vacancy. Three cases are investigated, that of noninterfering scatterers, a continuum of interfering scatterers, and discrete interfering scatterers. The approximations used lead to a specific grain boundary resistivity ∼10−16 Ω m2 for aluminum, in agreement with …

Resistivity, Thermopower And The Correlation To Infrared Active Vibrations Of Mn1.56co0.96ni0.48o4 Spinel Films Sputtered In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor

Alexander H. King

Mn1.56Co0.96Ni0.48O4 spinel was sputter deposited using a series of oxygen partial pressures. Electrical resistivity versus temperature and thermopower versus temperature measurements at each oxygen partial pressure were made. The variations of the thermopower and resistivity with oxygen partial pressure are consistent with a change in the ratio of Mn3+ to Mn4+ cations, which occurs due to changes of oxygen content of the material. The weak temperature dependence of the thermopower indicates small polaron hopping is the charge transport mechanism. Combining the models of Mott and Schnakenberg to analyze the transport data, we find that the Debye temperature (or frequency) is …

Low‐Temperature Phase Diagram Of Ybbipt, R. Movshovich, A. Lacerda, Paul C. Canfield, J. D. Thompson, Z. Fisk

Paul C. Canfield

Resistivity measurements are reported on the cubic heavy‐fermion compound YbBiPt at ambient and hydrostatic pressures to ≊19 kbar and in magnetic fields to 1 T. The phase transition at T c =0.4 K is identified by a sharp rise in resistivity. That feature is used to build low‐temperature H‐T and P‐Tphase diagrams. The phase boundary in the H‐T plane follows the weak‐coupling BCS expression remarkably well from T c to T c /4, while small hydrostatic pressure of ≊1 kbar suppresses the low‐temperature phase entirely. These effects of hydrostatic pressure and magnetic field on the phase transition are consistent with …

Magnetism And Heavy Fermion‐Like Behavior In The Rbipt Series, Paul C. Canfield, J. D. Thompson, W. P. Beyermann, A. Lacerda, M. F. Hundley, E. Peterson, Z. Fisk, H. R. Ott

Paul C. Canfield

Members of the RBiPt (R=Ce–Lu with the exceptions of Pm and Eu) series have been grown as single crystals.Magnetic susceptibility and electrical resistance have been measured on all members of the series, and specific heatmeasurements have been performed on representatives. The high temperature resistance uniformly changes from that of a small‐gap semiconductor or semimetal seen in NdBiPt to that of a heavy‐fermion metal seen in YbBiPt, which shows a linear coefficient of specific heat at low temperatures of 8 J/K2 mole. Further, the lighter rare earth members show an unusually sharp increase in their resistance associated with antiferromagnetic ordering at …