Lestes Tikalus, N. Sp. and Other Odonata from Guatemala

Author Institution: Department of Zoology, Oberlin Colleg

Letter from Edward J. Kormondy to Madeleine Giguere

Letter from Edward J. Kormonday, Provost at the University of Maine Portland-Gorham, to Madeleine Giguère thanking her for her contributions to the 1980 Core Curriculum Report and outlining the next actions.https://digitalcommons.usm.maine.edu/giguere-usm-career/1026/thumbnail.jp

Catalogue of the Odonata of Michigan

http://deepblue.lib.umich.edu/bitstream/2027.42/56348/1/MP104.pd

A Second Experiment in Self-Instruction in General Biology

Author Institution: Department of Biology, Oberlin College, Oberlin, OhioA study was made in 1964 of the effectiveness of college-level independent study of basic Mendelian genetics using a programed text as compared to a conventional text and both compared to traditional lecture-textbook approach. Covariance analysis of preand post-tests demonstrated a significant difference in mean gain scores of the programed text group over the other two; no significant difference was observed between the independent study-traditional text group and the lecture-text group, nor between freshmen and upperclassmen in any of the three groups

The systematics of Tetragoneuria, based on ecological, life history, and morphological evidence (Odonata: Corduliidae)

http://deepblue.lib.umich.edu/bitstream/2027.42/56351/1/MP107.pd

Oxide materials at the two-dimensional limit

Emergent phenomena in transition metal oxide films are receiving considerable attention with the development of techniques for the preparation of well-controlled oxide surfaces. On the macroscopic scale, such display novel physics phenomena including superconductivity, magnetism, ferroelectricity, and more. On the nanometer scale, the properties of epitaxial interfaces are further impacted by strain, band alignment, and crystal imperfections that may affect the long-range as well as the short-range order. Furthermore, symmetry lowering at the interface creates entirely new environments that are not accessible in the bulk environment. Thus, thin-film oxide materials are increasingly important in many applications. My work focuses on epitaxial oxides of the perovskite, spinel, and rocksalt structure and covers two main phenomena: (1) the two-dimensional electron gas at epitaxial oxide interfaces, and (2) thin epitaxial electro-optic oxides. Because polar oxides are of prominent interest as a mechanism for the formation of the two-dimensional electron gas, I start with a study of polar semiconductor Co₃O₄. Ellipsometry reveals a direct band gap of 0.75 eV, and magnetic measurements show the signature of antiferromagnetic ordering at 49 K, higher than the typical bulk value. Next, I look closer at the role of defects by studying the highly conducting layer at the crystalline [gamma]-alumina/SrTiO₃ (STO) interface which is attributed to oxygen vacancies. Annealing in oxygen is found to reduce the carrier density and turn a conductive sample into an insulator. Building upon these results, I show that even at room temperature, out-diffusion of oxygen from SrTiO₃ during epitaxy of highly spin-split semiconductor EuO epitaxy creates a highly conductive layer of oxygen vacancies on the SrTiO₃ side of the interface. The films are ferromagnetic with a Curie temperature of 70 K and display giant magnetoresistance below the transition temperature. Leveraging this approach offers an as-yet unexplored route to seamlessly integrate ferromagnetism and the oxide two-dimensional electron gas for the development of novel nano-oxide spintronic devices. The large effective Pockels coefficient for high-quality epitaxial BaTiO₃ (BTO) films on Si distinguishes BaTiO₃ as a highly promising material for integrated silicon nanophotonics. However, the linear electro-optic effect in BaTiO₃ thin films determined in previous experiments clearly shows deteriorated properties compared to bulk BTO crystals. First, I study BaTiO₃ films of varied thickness in order to quantify the Pockels coefficient with respect to crystalline orientation. As a next step, I report on the strong dependence of the Pockels effect in BaTiO₃ thin films on their microstructure, and provide guidelines on how to engineer thin films with strong electro-optic response. The 25× enhancement of the Pockels coefficient indicates a promising route to increase the performance of nonlinear oxides in the two-dimensional limit for the development of novel hybrid silicon photonic platform.Physic

High yield assembly and electron transport investigation of semiconducting-rich local-gated carbon nanotube field effect transistors

Single-walled carbon nanotubes (SWNTs) are ideal for use in nanoelectronic devices because of their high current density, mobility and subthreshold swing. However, assembly methods must be developed to reproducibly align all-semiconducting SWNTs at specific locations with individually addressable gates for future integrated circuits. We show high yield assembly of local-gated semiconducting SWNTs assembled via AC-dielectrophoresis (DEP). Using individual local gates and scaling the gate oxide shows faster switching behavior and lower power consumption. The devices were assembled by DEP between prefabricated Pd source and drain electrodes with a thin Al/Al2O3 gate in the middle, and the electrical characteristics were measured before anneal and after anneal. Detailed electron transport investigations on the devices show that 99% display good FET behavior, with an average threshold voltage of 1V, subthreshold swing as low as 140 mV/dec, and on/off current ratio as high as 8x105. Assembly yield can also be increased to 85% by considering devices where 2-5 SWNT bridge the gap between source and drain electrode. To examine the characteristics of devices bridged by more than one SWNT, similar electron transport measurements were taken for 35 devices with electrodes bridged by 2-3 SWNT and 13 devices connected by 4-5 SWNT. This high yield directed assembly of local-gated SWNT-FETs via DEP may facilitate large scale fabrication of CMOS compatible nanoelectronic devices

Experiment in Self-Instruction in General Biology

Author Institution: Department of Biology and Department of Psychology, Oberlin College, Oberlin, Ohi

A general approach for high yield fabrication of CMOS compatible all semiconducting carbon nanotube field effect transistors

We report strategies of achieving both high assembly yield of carbon nanotubes at selected position of the circuit via dielectrophoresis (DEP) and field effect transistor (FET) yield using semiconducting enriched single walled carbon nanotube (s-SWNT) aqueous solution. When the DEP parameters were optimized for the assembly of individual s-SWNT, 97% of the devices show FET behavior with a maximum mobility of 210 cm2/Vs, on-off current ratio ~ 106 and on conductance up to 3 {\mu}S, however with an assembly yield of only 33%. As the DEP parameters were optimized so that 1-5 s-SWNTs are connected per electrode pair, the assembly yield was almost 90% with ~ 90% of these assembled devices demonstrating FET behavior. Further optimization gives an assembly yield of 100% with up to 10 SWNT/site, however with a reduced FET yield of 59%. Improved FET performance including higher current on-off ratio and high switching speed were obtained by integrating a local Al2O3 gate to the device. Our 90% FET with 90% assembly yield is the highest reported so far for carbon nanotube devices. Our study provides a pathway which could become a general approach for the high yield fabrication of CMOS compatible carbon nanotube FETs.Comment: 20 pages, 6 figure