2007REU

2007 REU/RET Participants in Condensed Matter and LASER Physics

Joseph Bari, St. Olaf College, Northfield, MN; Research Advisor - Dr. Richard Smith

Interdifusion of Metallic Bilayers - With evolving technology, we are now able to grow layered structures that are only nanometers thick. For most practical applications the films must be flat on an atomic scale with abrupt interfaces that are at least thinner than the films making up the structure. Various film deposition techniques are used, but none of them are designed to prevent interdiffusion at the metal-metal interface. Dr. Guille Bozzolo, from the Ohio Aerospace Institute, has developed a model based upon calculated binary formation energies to predict suitable interlayer materials for specific interfaces. For the Iron-Aluminum interface, useful in computing, the model predicts that both Titanium and Vanadium will be adequate. Previous work has shown that Ti is a suitable interlayer material, but doubts remain about the use of V. It has also been observed that the amount of interdiffusion at the interface depends on whether the Al or the transition metal is deposited first. In general, they found that interface width is larger when the transition metal is deposited on the Al film. We will study interdiffusion for several interfaces in sputtered bilayers and then test the effectiveness of the V interlayer for these films. Films will be deposited using the rf/dc sputtering chamber located in the Electrical Engineering department as Montana State University. The samples will be analyzed with Rutherford backscattering (RBS) and X-ray reflectivity (XRR).

Ann Deml, University of Wisconsin - River Falls; Research Advisors - Drs. Carlos dos Santos and John Neumeier

Quasi-One Dimensionality in SrNbO_3.41 and LaTiO_3.41 Compounds - Prior research conducted by Dr. John Neumeier’s group [1,2] has shown Li_0.9Mo₆O₁₇ to possess interesting electrical transport properties. Li_0.9Mo₆O₁₇ is an example of a quasi-one dimensional (quasi-1D) compound, a material that exhibits exceptional conductivity along a single crystallographic axis. Furthermore, the Li_0.9Mo₆O₁₇ compound is believed to be the best example of a Luttinger Liquid [3], a theoretical model of the interacting electrons in a 1D compound. To gain a fundamental understanding of the transport properties of such quasi-1D compounds, two additional compounds, SrNbO_3.41 and LaTiO_3.41, will be studied. These compounds were chosen for their exceptionally high anisotropic behavior, significant differences in behavior along each crystallographic axis, and because previous results suggest the existence of superconducting properties in the compounds. Samples of each compound will be prepared by compacting powder into rods, utilizing an optical image furnace to grow crystals, and then extracting large crystals for study. Characterization of the crystals will be performed by Laue diffraction and X-ray powder diffraction. Resistivity as a function of temperature will be measured down to 0.3K with a Physical Properties Measurement System using a He-3 system in order to study the anisotropic behaviors of the compounds. The data obtained for SrNbO_3.41 and LaTiO_3.41 will be compared with previous results from Li_0.9Mo₆O₁₇ which indicate that disorder plays an important role in the existence of superconductivity in low-dimensional compounds. Superconductivity in the SrNbO_3.41 and LaTiO_3.41 compounds will also be sought.

[1] C. A. M. dos Santos, B. D. White, Yi-Kuo Yu, J. J. Neumeier, and J.A. Souza, accepted to appear in Phys. Rev. Lett. (Jul/2007).
[2] C. A. M. dos Santos, M. S. da Luz, Yi-Kuo Yu, J. J. Neumeier, J. Moreno, and B. D. White, submitted to Phys. Rev. Lett.
[3] F. Wang, J. V. Alvarez, S.-K. Mo, J. W. Allen, G.-H. Gweon, J. He, R. Jin, D. Mandrus, and H. Höchst, Phys. Rev. Lett. 95, 196403 (2006).

Mary Keany, Maui Community College, Kahului, Hawaii; Research Advisor - Dr. Recep Avci

Visco-Elastic Response of Live Bacteria - The purpose of this project is to determine quantitatively and reliably the visco-elastic response of a live bacteria using a well characterized Atomic Force Microscope (AFM) tip. A large part of the time will be spent learning how to operate the AFM in both air and liquid. This includes imaging, taking force curves and taking force volume data. Because the goal will be to obtain force volume data of live bacteria, emphasis will be on acquiring such data in liquid. For accurate results the AFM tips must be characterized and the spring constant and tip diameters determined. Spring constants will be determined by thermal excitation of cantilevers and the use of a purchased, well calibrated cantilever standard. AFM tip diameters will be determined by imaging of gold particles of known size. Data will be analyzed using the MatLab code written by Muhammedin Deliorman and spring constant and tip diameter determined. When the AFM tips have been well characterized, force-volume data will be taken of live bacteria that have been immobilized with the help of Dr. Zhiyong (Jahson) Suo. This data will also be analyzed by the MatLab code developed by Muhammedin to determine the visco-elastic response.

Alanna Keith, University of North Dakota; Research Advisor - Dr. Hugo Schmidt

Comparing Synthesis Routes of Materials for Solid Oxide Fuel Cells - This project deals with Solid Oxide Fuel Cells, or SOFC. We will synthesize Ba(Zr_0.8-xCe_xY_0.2)O_^3-δ powder (where x is 0.4) that will be sintered into ceramic using two methods. The first is the normal method using LiF as a sintering aid. The second will utilize an Infra-Red Imaging Furnace (IRIF), which should be much quicker and produce a higher quality sample. The properties of the two ceramics will then be compared. Eventually, the goal is to make ceramics with x varying from 0.0 to 0.4 to determine which compound offers the best balance between stability and conductivity. Higher amounts of Zirconium increase stability and decrease conductivity, while Cerium increases conductivity but decreases stability.

Stephanie Keith, University of North Dakota; Research Advisors - Drs. Mikhail Drobijev and Aleks Rebane

Building Proteins for Applications in Laser Physics - This project deals with the isolation of a fluorescent protein and analysis of its optical properties. The appropriate gene will be introduced into E. coli, after which a bacteria will express the gene and build the protein. Much of the synthesis will entail determination of the optimal conditions for protein production and purification of the protein. Finally, using tunable lasers, the two-photon absorption spectra of the protein will be measured.

Brandon May, Skidmore College, Saratoga Springs, NY; Research Advisor - Dr. Alan Craig

Modelocked Laser Construction and Applications - This project includes planning and budgeting to establish an optical fiber modelocked laser capability with flexibility for intracavity experimentation. In addition, the plan conceives use of the output pulse train to seed a supercontinuum source. Engineering the optimal fiber laser design, including selection of fiber dopant (and concomitant emission wavelength), is underway. Final selection and evaluation of construction, characterization, operation, and cost risk factors might indicate purchase of the basic modelocked fiber laser in lieu of lab assembly. In the case of lab assembly, the project will include design, specification and purchase of components, bench top assembly, and characterization and optimization with the anticipated goal of sub-picosecond modelocked pulse train emission. In the case that purchase of a modelocked laser is indicated, external components will be acquired to construct a fiber amplifier, a supercontinuum fiber source, and a frequency doubler to provide a spectroscopic source with wavelength selectivity across the visible range.

Anna Tapio, College of St. Benedict, St. Joseph, MN; Research Advisors - Dr. Pete Roos and Dr. Randall Babbitt

Single-Mode Nd:YAG Laser As Remote Sensor for Methamphetamine Detection - Methamphetamine, or meth, labs grow in population as the demand for the drug increases. Detecting these labs is difficult. Dr. Roos’ past research in laser pulse optical interactions provides insight to meth detection using remote sensing. The production of meth emits certain chemicals, and thus molecules, into the atmosphere. A single-mode laser that interacts with these molecules, detecting the manufacture of this drug based on light detection and ranging (LIDAR). The goal of the first step in this research, and the work I conduct, is to make a monoblock Neodymium:YAG laser single-mode, or lase at one wavelength. Injection seeding a multi-mode Nd:YAG laser with the wavelength of a seed laser will stimulate the Nd:YAG to lase at the injected wavelength. Currently, I have been working on developing the seed laser needed to produce the single-mode Nd:YAG laser. In later steps, the research bases detection specifically on differential absorption lidar (DIAL). Different molecules absorb different frequencies, creating unique frequency signatures for each molecule. As a result, DIAL uses two wavelengths to identify the chemical composition of the atmosphere. The wavelength, or frequency, of the Nd:YAG laser is set so that a molecule emitted during the production of meth absorbs it. The second laser is used only for comparison. A difference between the signals of the two wavelengths will appear if the molecule is present in the atmosphere. From this comparison, detection of methamphetamine can occur.

Cherie Turner, University of Missouri - Rolla; Research Advisor - Dr. Stephen Sofie

Synthesis of Materials for More Efficient Fuel Cell Anodes - The anode component of solid oxide fuel cells (SOFC) is made up of two sections: the bulk anode, and the active anode. The bulk anode supports the function of the active anode, ideally both mechanically and electrically, but has no direct impact on the fuel cell. By studying the bulk anode, the ideal thickness of the active anode may be discovered, allowing the production of more efficient fuel cells. In this project I will be synthesizing, calcining, fabricating, and sintering some possible compositions to be used as a bulk anode. The focus will be on lanthanum chromite compositions, which are ionically insulating, but electrically conducting. Zirconium titanate compositions, which are insulating both ionically and electrically, will also be considered if time allows. The bulk anodes will be tested for phase purity using XRD, and for thermal expansion using dilatometry, as well as studying the thermal behavior and microstructure using TGA and SEM analysis.

2007 RET Participants

Suzie Flentie, Lewistown Junior High School; Advisor - Dr. Yves Idzerda

(1) Solid Oxide Fuel Cell Research - This project will involve the development of optimization tests to determine the most efficient ratio of nitrogen to hydrogen versus air to produce constant power in the solid oxide fuel cell. The fuel cell’s anode is yttrium stabilized zirconium with nickel oxide and the cathode is LSMO (lanthanum strontium manganese oxide). These fuel cells are also being tested for hydrogen sulfide poisoning.

(2) Educational Projects Related to Fuel Cells - An additional component of this summer's work is the development of Fuel-Cell related activities for the junior-high classroom. This includes the development of an understanding of the basic chemistry involved with the electrolysis process of splitting water into hydrogen and oxygen and how hydrogen can then be used as a fuel source. An electrolysis device will be constructed using PVC for the main body and NaCl instead of NaOH for ionization (the former is less corrosive). This device will be used for classroom instruction and experimentation. A teaching unit will be developed to help students correlate the electrolysis process with an understanding of the polymer electrolyte fuel cell, its main parts and the process necessary for the production of electricity. A dismantle able fuel cell, miniature fuel cell car and fuel cell animations will be used to clarify these concepts for students. These teaching materials will include specific lesson plans that can be easily used by other teachers and posters which depict the concepts, standards and skills involved with each project.

Sarah Hall, Baker Prairie Middle School, Canby, Or; Advisor - Dr. Hugo Schmidt

(1) Solid Oxide Fuel Cell Research – The project goal is to determine a consistent and simple method to produce high purity Ba(Zr_0.8-xCe_xY_0.2)0_3-δ of very small particle size. The ideal balance of reactants produces a stable proton conducting membrane with high proton conductivity. Although Zr and Ce are both good proton conductors, differences in their molecular behavior affect the membrane. Zirconium is a weaker proton conductor than Ce, but does not decay in steam or CO₂. Cerium does decay in steam and CO₂, but is a better proton conductor than Zr. I am working with REU and graduate students to find the optimal Zr and Ce concentration. The powder’s purity is tested using X-ray diffraction analysis. Optically sintered (using an optical image furnace) and kiln sintered samples will be analyzed for grain size distribution. Electronic conductivity will be tested using impedance spectroscopy, and hydrogen permeation testing will be used to test protonic conductivity. Samples with even grain size, high protonic conductivity, and low electronic conductivity are desired.

(2) Curriculum Goal- Incorporate basic fuel cell technology in the middle school classroom. I am working to develop an affordable chemical reaction that illustrates the production of a proton conducting substance. My lesson plans will be combined with those of other RET participants to produce a comprehensive fuel cell unit.