2008 Condensed Matter and LASER Physics REU/RET Projects

Austin Stafford, Linfield College, McMinnville, OR (Advisor: Dr. Alan Craig)

Silicon Nanoparticle Mass by Milliken Oil Drop Experiment

This experiment is meant to find the mass to charge ratio of silicon nanoparticles to confirm the expected particles sizes. The experiment is designed similarly to the Milliken oil drop experiment with the expectation that a laser will allow the particles to fluoresce so they can be detected by a ccd camera. The silicon particles tend to maintain a neutral charge. To induce a charge, the particles were bombarded with x-rays in the hope that an electron would be ejected. With the experiment still unfinished, the methods are being adjusted to better obtain results.

Alyssa McComas, Transylvania University, Lexington, KY (Advisor: Dr. Richard Smith)

Effect of aluminum on oxidation resistance of Co/Mn thin films for SOFC interconnects

A Co/Mn thin film, designed for SOFC interconnects, was doped with aluminum and tested for oxidation resistance alongside an undoped film. Both samples were annealed at 500^˚C for increasing amounts of time up to 64 hours. Measurements for oxidation were taken using Rutherford Backscattering Spectroscopy (RBS). The experimental data were fitted using the SIMNRA program. From this data, the oxygen weight gain over time was plotted for both samples. It was found that the Al-containing sample was less oxidized during the time tested.

Christopher S. Wolfe, Southern Illinois University Carbondale (Advisor: Yves Idzerda)

Magnetic Anisotropy in Galfenol Thin Films

The goal of this project was to investigate the feasibility of using the magneto-optic Kerr effect (MOKE), which involves measuring the rotation of the plane of polarization of linearly polarized light as a function of applied magnetic field for different orientations of the samples, as a fast and easy way to obtain the magnetic anisotropy constant of single-crystal Iron-Gallium alloy (Galfenol) films. Galfenol (Fe_100-xGa_x) films, have high tensile strength and magneto-elastic properties which give them potential for applications in magnetic transducers and even acoustic sensors [P.R. Downey and A.B. Flatau. J. Appl. Phys. 97, 10R505 (2005)]. The magnetic anisotropy constant can be used to further obtain the magneto-elastic constant of the films, which can then be compared to bulk material values. Results show the method is possible, but potentially not as fast or accurate as was expected.

Brian Swarthout, Bozeman High School, Bozeman, MT (Advisor: Dr. Richard Smith)

Atomic Structure of Vanadium on Al(100) using RBS/c and LEED

The epitaxial growth of thin V layers on the Al(100) surface has been investigated using Rutherford back scattering (RBS), and channeling (RBS/c), and low energy electron diffraction (LEED), for V coverages from 0 to 17 monolayers.  Measurements of the backscattered ions from Al and V show that the first few monolayers of V displace Al atoms from their equilibrium positions or form an alloy of Al/V.  LEED indicates that after approximately 6 monolayers of V deposition, V begins to form a periodic structure.

Robbie Gill, Berry College, Mt. Berry, GA (Advisor: Hugo Schmidt)

Effects of Sintering Atmosphere on Solid Oxide Fuel Cell Electrolyte Material

The goal of this project is to determine the effects of sintering atmosphere on Ba(Zr_0.8Y_0.2)O₃ ceramic material, which is an electronic insulator and ionic conductor. Samples were prepared and sintered under four different atmospheric conditions: in Air, in 4 % Hydrogen balanced Argon, in Nitrogen, and in Argon. Three characterization techniques, X-Ray Diffraction, Scanning Electron Microscopy, and Impedance Spectroscopy, were utilized to examine the properties of each sample. Impedance data was fit to an accepted model with respect to grain interior, grain boundary, and electrical contacts. The presentation includes descriptions of materials synthesis, experimental methods, and data analysis.

Andrew Rice, Bethel University, MN (Advisors: Ariana de Campos and John Neumeier)

Electrical Resistivity Measurements of LaTiO_3.41 and SrNbO_3.41

The goal of this project was to study the electrical resistivity of the highly anisotropic, quasi one-dimensional materials LaTiO_3.41 and SrNbO_3.41. Single crystals of these compounds were grown using an optical image furnace. Room temperature electrical resistance of LaTiO_3.41 and SrNbO_3.41 was measured using the 4-probe method. Electrical resistivity was determined using Montgomery’s method. Electric resistance as a function of temperature was measured using a Physical Properties Measurement System from 2 K to 300 K. The anisotropic electrical resistivities for numerous crystals were determined. The results will be discussed.

Nathan Haydon, Montana State University, Bozeman, MT (Advisor: Dr. Randall Babbitt)

Decoherence

The transition from the quantum to the classical world has been a matter of debate since quantum mechanics inception. Recently, the phenomenon of decoherence has been invoked to explain part of this transition. Decoherence brings to the forefront the idea that quantum systems are not closed but open systems, constantly interacting with their environment and surroundings. The result of decoherence is the natural suppression of interference terms, thereby bringing the system one step closer to the classical states we come to expect from the everyday world. In this project we study the nature of decoherence and the factors that play a role. We begin by focusing on the theoretical approaches used to analyze decoherence and then apply what we have learned to models of simple, two-level coupled atoms. Finally, we conclude with results and paths for further study.

Max Lifson, Dartmouth College, Hanover, NH (Advisor: Dr. Stephen Sofie)

Effects of Nickel Oxide Sintering Aid in Micro and Nano Yttria Stabilized Zirconia Powders

The effect of low-level NiO additions in Yttria-Stabilized Zirconia (YSZ) was examined to provide a means to tailor the sintering behavior of both fully and partially stabilized YSZ.   Commercial YSZ powders (8 mol% and 3 mol%) of micro and nano scale were mixed with 0.1, 0.5, and 1.0 mol% nickel oxide by solid state mixing.  The resultant pellets were measured before and after sintering from 1200°C to 1400°C with a 1 hour sintering dwell. While the un-doped nano-grade powders obtained a higher percent density than the micro-grade powders, they were not as responsive to the nickel oxide as a sintering aid.  Micro 8YSZ and 3YSZ powders with small amounts of Ni showed a great increase in densification at 1300°C for one hour, a much lower temperature and shorter dwell than standard heating procedures. Using dilatometry, the onset and rate of densification were determined.  Additionally, activation energies for all powder compositions were derived and confirmed that the additions of nickel oxide decreased the activation energy for the sintering process while providing a qualitative means to determine optimal dopant quantity. Characterization of the microstructure was performed by Scanning Electron Microscopy to obtain the grain size. It was interesting to note that the grain size was largely not affected.  Additionally, the effects of nickel oxide on electrical conductivity by electronic impedance spectroscopy have revealed that small additions of NiO decreased the grain boundary resistance contribution. Results indicate that NiO dopants are particularly effective for promoting early densification of micro size scale YSZ powders meeting the performance of nano scale powders with characteristics that are particularly beneficial for soil oxide fuel cell development.

Erich Beuerman, Montana State University (Advisor: Dr. Aleks Rebane)

Measurement of Solvatochromic Shifts of Rhodamine Dyes: Steps towards Improved Understanding of Two-Photon Absorption Properties

Current two-photon absorption (2PA) models are limited in their ability to explain the asymmetry between linear and 2PA spectra of strongly fluorescent molecules. The ratio of vibronic-transition peak and electronic-transition peak has been observed to be much greater in 2PA than linear absorption. We are in the process of developing a model that would explain the discrepancy quantum mechanically. To verify this theory, several experimental parameters must be measured; among which are solvatocrhromic shifts, molecular radii, fluorescence anisotropy, and fluorescence lifetime of several Rhodamine and Rhodamine-like dyes. These parameters are useful in calculating the change in dipole moment between ground and excited states, which is an integral part of our new 2PA model. Methods used to obtain and calculate these parameters will be discussed.