Bulletin of the American Physical Society
2013 Annual Meeting of the California-Nevada Section of the APS
Volume 58, Number 14
Friday–Saturday, November 1–2, 2013; Rohnert Park, California
Session C2: Material Science |
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Chair: Sergey Savrasov, University of California, Davis Room: Darwin 29 |
Friday, November 1, 2013 2:00PM - 2:12PM |
C2.00001: Al-doping of ZnO (AZO) via Electrochemical Deposition: An Exploration of Optoelectronic Applications Stephan Jackowski, Hongtao Shi Zinc Oxide (ZnO) is a semiconductor of group II-VI with numerous applications due to its wide band gap, good transparency, high electron mobility, and low cost. Tuning the band gap via doping enables an array of applications, specifically in optoelectronics. A 1:1 solution of zinc nitrate hexahydrate and hexamethylenetetramine (HMT) was used in an electrochemical deposition of ZnO on silicon substrates. After introducing aluminum nitrate to the solution and varying deposition parameters, characterization techniques including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy were implemented to quantify film properties. [Preview Abstract] |
Friday, November 1, 2013 2:12PM - 2:24PM |
C2.00002: Observed Effects on the Optical Properties of Mg-doped ZnO Thin Films Produced via Electrochemical Deposition Jordan Sperry, Hongtao Shi, Esther Unti Zinc oxide (ZnO) is a semiconductor that has been studied extensively due to its ideal optical properties for applications in optoelectronics. This is due to its relatively large band gap of 3.37 eV and high exciton energy at room temperature. Using high-cost, cutting-edge techniques such as pulsed laser deposition (PLD) and metal organic vapor phase epitaxy (VPE), the band gap of Mg-doped ZnO alloys can be further tuned to as high as 7.8 eV, giving the material even more potential for deep UV applications. Here we report the growth and characterization of Mg-doped ZnO samples onto substrates such as Si, Al, and ITO, using a low-cost, low-temperature electrochemical method in solutions containing zinc nitrate hexahydrate and hexamethylenetetramine (HMT). By tuning various parameters in the growth process, such as the voltage, current density, growth time, and Mg concentration we were able to alter the ratio of Mg incorporated into the samples, and consequently shift the UV emission peak of the alloyed samples. [Preview Abstract] |
Friday, November 1, 2013 2:24PM - 2:36PM |
C2.00003: A DFT Study of Tetragonal Rocksalt Copper Monoxide: A Proxy Structure for Understanding HTSC in the Copper Oxide Perovskites Paul Grant Copper monoxide does not naturally crystallize in face-centered cubic rocksalt symmetry. It has been shown such may result from Jahn-Teller degeneracies which are relieved by distortion into monoclinic tenorite. It has been found possible to ``force epitaxially'' grow 4-5 layers of fcc tetragonal CuO on suitable perovskite substrates A ``c/a-axis'' elongation of roughly 1.3 -- 1.4 stabilizes the ground state. What is paramount is that fcc tetragonal CuO contains the essential feature of all high temperature superconducting copper oxide perovskites without the complicating inclusion of ``3$^{\mathrm{rd}}$ elements,'' and thus provides a simple ``proxy'' to understand the origin of high-Tc. We report using density-functional-theory towards this end. We add charge to the relevant Cu-O bond states, compensated by background ``jellium'' to simulate doping. We introduce an empirical screening of coulomb repulsion and present our results, suggesting electron-phonon coupling underlies HTSC, in the phase diagram context of the ``Great Quantum Conundrum (Nature, 2011).'' [Preview Abstract] |
Friday, November 1, 2013 2:36PM - 2:48PM |
C2.00004: Effect of Gold Roughness on Growth of Copper Phthalocyanine Kevin Cano, Joshua Corona, Carlos Garcia, Thomas Gredig Metallo-phthalocyanine-based thin films have found diverse applications, in field-effect transistors, gas sensors, and photovoltaic devices. The device performance and electrical properties depend on the orientation of the planar molecule with respect to the substrate. It had been previously found that the molecular plane adheres parallel to a metallic surface, whereas the metal-centers attach to themselves on insulating substrates forming a standing configuration. Here, the effect of gold roughness is examined using atomic force microscopy (AFM) and x-ray diffraction (XRD). Samples were co-deposited at room temperature with 20~nm of CuPc ensuring equal conditions. The Au roughness was varied by depositing it either onto Cr or Si and by modifying the Au thickness from 12~nm to 50~nm. The change in thickness for the Au/Si substrates affected a change in the roughness of the CuPc, which changed from 5.8~nm to 2.3~nm. Crystallo-graphic peaks from the x-ray diffraction showed a crystalline peak of 13.0~\AA~at 6.8$^{\circ}$ for all samples. The surface morphology and grain size, however, was unaffected. [Preview Abstract] |
Friday, November 1, 2013 2:48PM - 3:00PM |
C2.00005: Improved Synthesis of Bechgaard Salts Jacob Lewis, Jeremy Qualls Many advances in material science are often impeded by sample quality. This is especially true for low dimensional organic conductors where low lying ground states can be completely masked by poor sample quality. The purpose of our work is to increase the sample quality of a set of materials that had previously been heavily studied to gain access to a region thought inaccessible. In this work our target systems are the Bechgaard Salts (TMTSF)$_{2}$ClO$_{4}$ and (TMTSF)$_{2}$PF$_{6}$. These systems have very interesting behaviors that occur at helium base temperatures and continue to be the topics of many research groups and publications. The nature of the transport mechanism and formation of density waves at low temperatures are of great interest but these states are fragile. A single x-ray crystallographic measurement will introduce enough defects that the low temperature ground states never form. We are looking at three target areas of growth including proper exclusion of water, reduction of vibrations, and continuous availability of electrolytes during growth. In this talk we will discuss what advances we have made and what kind of ground state behavior we are hoping to find. [Preview Abstract] |
Friday, November 1, 2013 3:00PM - 3:12PM |
C2.00006: Atomic Force Microscopy (AFM) of Ion - Irradiated Cadmium Zinc Telluride Crystals Madhusudhan Goundla Cadmium Zinc Telluride (CZT) is considered a good candidate material for radiation detectors However, current technology has difficulties in growing large dimension single crystals. Also, leakage (dark) currents along grain boundaries and device surface are still a big issue. In this study, we used AFM to study the changes to the surface topography of CZT crystals irradiated with Pt ions at 180 keV and 1.6x10$^{11}$ ions/cm$^{2}$. The initial CZT sample is prepared by polishing and baseline AFM topographic images are taken, monitoring the values for the average roughness and root mean square. The CZT sample is then treated by etching with 2\% bromine methanol (BM), followed by average roughness and root mean square AFM measurements. Next, the sample is irradiated with Pt ions and measured with AFM. The results show that the surface after irradiation has a smaller roughness and fewer morphology features than before irradiation. Current-voltage electrical measurements were also taken at each preparation stage and correlated with the AFM results. Finally, the CZT sample was assembled into a radiation detector device and its performance was tested. [Preview Abstract] |
Friday, November 1, 2013 3:12PM - 3:24PM |
C2.00007: SESAME -- A third generation light source for the Middle Ease and a model project for other regions Herman Winick Modeled on CERN, under the auspices of UNESCO, Bahrain, Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, Palestinian Authority, and Turkey are constructing a light source in Jordan. SESAME is on track to start commissioning in late 2015. UNESCO became the umbrella organization for SESAME at its Executive Board 164th session, May 2002. The following comments about SESAME were made by this board: ``a quintessential UNESCO project combining capacity building with vital peace-building through science'' and ``a model project for other regions.'' The history and present status of SESAME will be presented. Now that SESAME is well underway, other regions (e.g.; Africa and Central Asia) are welcomed to join SESAME as a first step in developing similar projects. see: \\[4pt] http://www.sciencediplomacy.org/perspective/2012/synchrotron-light-and-middle-east \\[0pt] http://mag.digitalpc.co.uk/fvx/iop/esrf/sesamebrochure/ \\[0pt] http://www.bbc.co.uk/news/world-middle-east-20492294 \\[0pt] http://mag.digitalpc.co.uk/fvx/iop/esrf/sesamepeople/ \\[0pt] http://europa.eu/rapid/press-release\textunderscore IP-13-468\textunderscore en.htm?locale$=$en www.sesame.org.jo [Preview Abstract] |
Friday, November 1, 2013 3:24PM - 3:36PM |
C2.00008: Clean Water Collection Daniel Ryan, Jeremy Qualls An estimated 780 million people lack access to an improved water source and more than 3 million die every year due to water related diseases. This talk takes a hard look at new emerging air to water collection technologies and development of new water collection devices at SSU. We are attempting to develop a solar refrigeration system based on a single adsorption cycle, utilizing methanol and activated carbon. Our calculations predict that a square meter solar adsorption collection system should be able to produce 1-5 liters of water per night. The system would be able to serve as a point source for clean water and require little to no maintenance at relative low cost. Current prototypes will be discussed as well as progress that we have made towards maximizing the condensation stage of water collection. Ultimately, the design must be robust, scalable, and environmentally friendly. [Preview Abstract] |
Friday, November 1, 2013 3:36PM - 3:48PM |
C2.00009: Coexistence of Spin Density Wave and Superconducting States in Bechgaard Salts Jeremy Qualls The electronic ground states of Bechgaard salts have been heavily studied since they were discovered over thirty years ago. These quasi-one dimensional organic conductors can display superconductivity, density waves, and metallic states. Many of these states are easily modified or revealed by the application of external magnetic field or hydrostatic pressure. Recent experiments by multiple investigators have begun to paint a picture of regimes where various states can coexist. Of great interest is how a spin density wave can be a precursor or competitor of the superconducting state. (TMTSF)2ClO4 and (TMTSF)2PF6 have been synthesized and investigated towards additional evidence to understand the coexistence of spin-density waves and superconductivity. A general picture will be painted, unifying data over the last twenty years showing a clear coexistence of multiple spin density waves and spin density waves with the superconducting state within these materials. [Preview Abstract] |
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