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2000 MRS Spring Meeting

作者： Ong, Eddie W. Mossman, Kenneth Ramakrishna, B.L. Pizziconi, Vincent B. Glaunsinger, William S. Patrick, Eric Vishwanath, Prashanth Allagadda, Kranti Tan, Terence Razdan, Anshuman Center for Solid State Science Arizona State University Tempe AZ Dept. of Chemistry and Biochemistry Arizona State University Tempe AZ Dept. of Plant Biology Arizona State University Tempe AZ Dept. of Chemical Bio- and Materials Engineering Arizona State University AZ PRISM Arizona State University AZ

ISBN: (纸本)1558995420

The Interactive Nano-Visualization for science and engineering Education (IN-VSEE) project at Arizona state University (ASU) has developed a remotely operable scanning probe microscope (SPM), a visualization gallery of images, and a number of educational modules with materials themes. It exploits the incredible potential of materials science for teaching at the high school and college level about fundamental concepts that cross traditionally separated disciplines. The packing of spheres is a topic that is ideal for linking together the different science and engineering disciplines because of the ubiquity and relevance of spheres in the materials world and the universality of the rules that govern their packing over a large range of sizes. Students can perform a number of discovery-based learning activities, over the web by simultaneously using IN-VSEE's web-accessible module (e.g., The Music of Spheres) and by accessing the remotely-operable SPM for experimenting with nanosphere samples that they prepare. With these resources students can pose materials questions and are empowered to design their experiments to increase their understanding of real materials. The fundamental concepts (e.g., packing geometry, density, surface composition, long-range/short-range ordering, intermolecular forces, etc.) they learn through these materials science experiments are applicable to many other curricular, research, and technology areas. © 2000 materials Research Society.

关键词： engineering education

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Novel Cubic ZnxMg1−xO Epitaxial Heterostructures on Si (100) Substrates

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MRS Online Proceedings Library 2001年第1期639卷 3531-3538页

作者： Kvit, A. Narayan, J. Sharma, A. K. Jin, C. Muth, J. F. Teng, C. W. Holland, O. W. NSF Center for Advanced Materials and Smart Structures Department of Materials Science and Engineering North Carolina State University Raleigh USA Department of Electrical and Computer Engineering North Carolina State University Raleigh USA Solid State Division Oak Ridge National Laboratory Oak Ridge USA

We have synthesized new cubic phase of ZnxMg1−xO alloy, which can be grown epitaxially on MgO (100) by lattice-matching epitaxy, and on Si (100) substrate by our domainmatching epitaxy for integration with silicon microelectronic devices. Cubic ZnxMg1−xO films on MgO (100) and Si (100) substrates were grown using a rotating target in a single chamber “insitu” pulsed-laser deposition system. Integration of ZnxMg1−xO films with silicon was accomplished via titanium nitride (TiN) buffer layers where four lattice constants of TiN match with three of the silicon during epitaxial growth via domain epitaxy. Rutherford backscattering/ion channeling techniques were used to determine chemical composition and crystalline quality of the films for x = 0.0-0.18. Detailed X-ray diffraction and transmission electron microscopy studies confirmed the epitaxial nature of ZnMgO/MgO (100) and ZnMgO/TiN/Si (100) heterostructures, and showed the formation of the Mg2−xZnxTiO4 spinel at the interface with TiN. Using optical transmission measurements, the band gap of cubic Zn0.18Mg0.82O film was estimated to be approximately 6.7 eV. The potential use of these alloys for optical devices in the ultraviolet range is discussed.

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Phase Separation in Multiple ZnO/Cubic- MgxZn1−xO Superlattice Heterostructures Observed Via High Resolution Transmission Electron Microscopy

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MRS Online Proceedings Library 2001年第1期639卷 6501-6506页

作者： Kvit, A. Dusher, G. Sharma, A. K. Jin, C. Narayan, J. Muth, J. Teng, C.W NSF Center for Advanced Materials and Smart Structures Department of Materials Science and Engineering North Carolina State University Raleigh USA Solid State Division Oak Ridge National Laboratory Oak Ridge USA Department of Electrical and Computer Engineering North Carolina State University Raleigh USA

We have synthesized ZnMgO alloy of wurtzite (Mg content equals to 0.0=0.34) and cubic (Zn content equals to 0.0- 0.18) phases using nonequilibrium pulsed laser deposition method. Epitaxial films of ZnMgO wurtzite structure have been grown on (0001) sapphire substrates. Using JEOL-2010 field-emission transmission electron microscope equipped with STEM and Gatan image filter, we can perform atomic structure, STEM-Z, electron energy loss spectroscopy and imaging simultaneously. Such studies on the ZnO/MgZnO superlattices provide first direct evidence of phase-separation in the range 3 nm.

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Dynamical properties of Au from tight-binding molecular-dynamics simulations

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Physical Review B 2001年第19期63卷 195101-195101页

作者： F. Kirchhoff M. J. Mehl N. I. Papanicolaou D. A. Papaconstantopoulos F. S. Khan Department of Electrical Engineering Ohio State University Columbus Ohio 43210 Center for Computational Materials Science Naval Research Laboratory Washington DC 20375-5000 Department of Physics Solid State Division University of Ioannina P.O. Box 1186 GR-45110 Ioannina Greece

We studied the dynamical properties of Au using our previously developed tight-binding method. Phonon-dispersion and density-of-states curves at T=0 K were determined by computing the dynamical matrix using a supercell approach. In addition, we performed molecular-dynamics simulations at various temperatures to obtain the temperature dependence of the lattice constant and of the atomic mean-square displacement, as well as the phonon density-of-states and phonon-dispersion curves at finite temperature. We further tested the transferability of the model to different atomic environments by simulating liquid gold. Whenever possible, we compared these results to experimental values.

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Phase contrast of spherical magnetic particles

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Journal of Microscopy 2001年第1期194卷

作者： M. DE GRAEF N. T. NUHFER M. R. McCARTNEY Department of Materials Science and Engineering Carnegie Mellon University Pittsburgh PA 15213-3890 U.S.A. Center for Solid State Science Arizona State University Tempe AZ 85287 U.S.A.

This paper derives analytical expressions for the magnetic and electrostatic phase shifts of a plane electron wave upon traversing a spherical, uniformly magnetized particle with a non-zero mean inner potential. The Aharonov—Bohm phase shift is represented in terms of dimensionless parameters. Standard Foucault and Fresnel Lorentz image simulations are presented for a range of particle sizes and saturation inductions. We discuss the detection limits of the Lorentz techniques and compare them with the sensitivity of the electron holography method. We conclude the paper with experimental holography results for nanocrystalline cobalt particles; the observed phase changes are in good agreement with the analytical predictions.

关键词： Lorentz microscopy magnetic particles electron holography

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Phase Breaking as a Probe of the Intrinsic Level Spectrum of Open Quantum Dots

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physica status solidi (b) 2001年第1期204卷

作者： J. P. Bird H. Linke J. Cooper A. P. Micolich D. K. Ferry R. Akis Y. Ochiai R. P. Taylor R. Newburry P. Omling Y. Aoyagi T. Sugano Center for Solid State Electronics Research Arizona State University Tempe AZ 85287-6206 USA Department of Solid State Physics Lund University Box 118 S-22100 Lund Sweden Nanoelectronic Materials Laboratory Frontier Research Program RIKEN 2-1 Hirosawa Wako Saitama 351-01 Japan School of Physics University of New South Wales Sydney 2052 Australia Department of Materials Science Chiba University 1-33 Yayoi-cho Inage-ku Chiba 263 Japan

We measure the dependence of the phase breaking time on temperature and on dc voltage in ballistic split-gate quantum dots, the lead openings of which are defined by means of quantum point contacts. Estimates for the phase breaking time are obtained by studying the high-field evolution of the reproducible fluctuations, observed in the low-temperature magneto-conductance of the devices, and from the quenching of quantum interference induced by the dc bias. Varying either temperature or dc bias, a saturation of the phase breaking time is observed for sufficiently low values of these parameters. The energy scale at which the saturation onsets is found to be comparable to the average spacing of discrete levels within the quantum dot, indicative of a crossover to zero-dimensional phase breaking. Based on these observations, we suggest that studies of electron phase coherence may provide a powerful probe of the intrinsic eigenspectra of open quantum dots.

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Phase breaking and energy relaxation in open quantum-dot arrays

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Physical Review B 2000年第23期62卷 15356-15356页

作者： C. Prasad D. K. Ferry A. Shailos M. Elhassan J. P. Bird L.-H. Lin N. Aoki Y. Ochiai K. Ishibashi Y. Aoyagi Department of Electrical Engineering and Center for Solid State Electronics Research Arizona State University Tempe Arizona 85287-5706 Department of Materials Science Chiba University 1-33 Yayoi Inage Chiba 236-8522 Japan Semiconductor Laboratory RIKEN 2-1 Hirosawa Wako Saitama 351-0198 Japan

We study both the phase-breaking and the energy-relaxation times as a function of both temperature and bias current in arrays of coupled, open quantum dots. These times show a saturation at low temperature, and a decay at higher temperatures. Importantly, the variations of sample resistance as a function of temperature and current cannot be used to infer the electron temperature at a given bias current, which suggests that the energy relaxation process is likely to be phonon based.

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Hydrolysis of biodegradable polymers by superoxide ions

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Journal of Polymer science 2000年第18期37卷

作者： K. H. Lee C. Y. Won C. C. Chu Ivan Gitsov Fiber Science Program Department of Textile and Apparel and Biomedical Engineering Program Cornell University Ithaca NY 14853-4401 Department of Chemistry State University of New York College of Environmental Science and Forestry Syracuse NY 13210 Cornell Center for Materials Research and Department of Chemistry and Chemical Biology Cornell University Ithaca NY 14853-1301

The objective of this study was to examine the reactivity of superoxide ion as an oxygen nucleophile towards biodegradable biomaterials having an aliphatic polyester structure, such as poly( D , L -Lactide) (PDLLA). The changes in molecular weights and thermal properties of PDLLA were studied as a function of the superoxide ion concentration, hydrolysis time, and hydrolysis temperature. The superoxide ion induced fragmentation of PDLLA yielded a mixture of various species with different chain length. A combined size exclusion chromatography (SEC) method with a chemical tagging by phenyl isocyanate revealed that the structure of the oligomer species with the lowest molecular weight formed in the superoxide ion induced degradation mixture was linear. The significant reduction in T g was consistent with the significant reduction in the molecular weight of PDLLA. The linear low molecular fragments (dimers and trimers) in the reaction mixture could act as an internal plasticizers to enhance the T g reduction by increasing the free volume of chain ends. The relationship of T g with molecular weight of PDLLA followed the general theory of Fox–Flory. The mechanism of simple hydrolysis of ester by superoxide ion proposed by Forrester et al. was modified to interpret the data obtained from the synthetic biodegradable polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3558–3567, 1999

关键词： superoxide ion biodegradable polymers hydrolysis polylactide degradation

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Microstructure Of Tin Ohmic Contacts On N-Gan

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Microscopy and Microanalysis 1999年第S2期5卷 130-131页

作者： Bailey, GW Jerome, WG McKernan, S Mansfield, JF Price, RL Liu, R-J R. W.Carpenter, R. W.Carpenter Kim, M J Science and Engineering of Materials Program and Center of Solid State Science Arizona Satte University Tempe AZ 85287-1704

GaN is a direct, wide band -gap semiconductor (Eg=3.4 eV) which has a potential application in electronic and optical devices including UV-emitting lasers and bright p-n junction GaN light emitting diodes. In order to attain optimum device performance, it is necessary to develop lowresistance, thermally stable and uniform ohmic *** this study, the TiN/GaN contact synthesis and examination of contact performance were conducted at North Carolina state University. Si-doped n-GaN films were grown on 6H-SiC substrates via MOVPE with an A1N buffer layer. The TiN films were deposited in an ion-beam assisted, UHV electron-beam evaporation system. TiN growth was performed at a substrate temperature of 350 °C and a nitrogen pressure of about 2×10-4torr. The deposition rate was 1- 1.5 nm/min. The TiN contacts deposited on (0001) n-GaN were ohmic with high resistivity in the as-deposited condition, but the resistivity decreased sharply in response to annealing. The TiN/GaN interface was examined by transmission electron microscopy to provide correlations between changes in microstructure and electrical behavior.

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Abstract

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Journal of Chemical sciences 2000年第3期112卷 339-438页

作者： M. M. Balakrishnarajan Eluvathingal D Jemmis Sayan Gupta Shyamalava Mazumdar Pulakesh Mukherjee Tim Machonkin Jennifer L Dubois Adam P Cole Britt Hedman Keith O Hodgson Edward I Solomon T. D. P. Stack Herbert W Roesky P. T. Manoharan Sujoy Baitalik Kamalaksha Nag Sabyasachi Sarkar Ram Seshadri Claudia Felser John F Nixon Kattesh V Katti Nagavarakishore Pillarsetty Hideo Kamei Upasana Bora Mihir K. Chaudhuri Sidhartha S. Dhar Dipak Kalita B. N. Anand A. Ramanan Prasun Roy T. Duraisamy Sanjeev Sharma P. Ayyappan B. D. Gupta V. Vijai Kanth Veena Singh Eringathodi Suresh Kamla Boopalan Raksh Vir Jasra Mohan Madhav Bhadbhade G. A. Naganagowda K. V. Ramanathan V. Gayathri N. M. Nanjegowda P. Sengupta S. Ghosh Manish Bhattacharjee Shamayita Sen Gupta Riya Datta C. V. Sastri D. Easwaramoorthy Athi Lakshmi L. Giribabu B. G. Maiya P. Rabindra Reddy M. Radhika K. Florence Nightingale R. Srinivasan R. Venkatesan T. M. Rajendiran P. Sambasiva Rao P. Bhavana P. Bhyrappa M. Ravikanth Sudha Kumaraswamy Praveen Kommana G. Padmaja K. C. Kumara Swamy B. Mondal S. Chakraborty G. K. Lahiri Manabendra Ray Lawrence Que Anubhav Saxena N. Sampriya A. S. Brar Ravi Shankar B. B. Sahoo G. Panday A. A. Wasthi S. M. S. Chauhan Parvesh Wadhwani Deb Kumar Bandyopadhyay Ratna Bandyopadhyay Sudeb Biswas Ramgopal Bhattacharyya Vishwas Johis Dilip Kotkar Vinit S. Pathak V. Swayambhunathan Prashant Kamat Amitava Das Pushpito K. Ghosh Rajeev Gupta Rabindranath Mukherjee M. G. Walawalkar Sushanta K. Pal Anu Krishnan A. G. Samuelson Puspendu K. Das G. Anantharaman Kanhayalal Baheti R. Murugavel Gunjan Garg Ashok K. Ganguli M. Suresh A. V. Prasadarao S. Neeraj Srinivasan Natarajan C. N. R. Rao P. V. Vanitha P. N. Santhosh G. Girish Kumar N. Munichandraiah T. V. V. Ramakrishna Anil J. Elias Ashwani Vij Kajal Krishna Rajak Sankar Prasad Rath Sujit Dutta P. K. Bhattacharya P. Natarajan P. Paul T. Dhanasekaran H. Prakash N. Mangayarkarasi P. S. Zacharias A. Srinivasan Simi K Pushpan V. G. Anand T. K. Chandrashekar Punam Tripathi Abhigyan Som Parimal K. Bhar School of Chemistry University of Hyderabad Hyderabad India Department of Chemical Sciences Tata Institute of Fundamental Research Mumbai India Department of Chemistry Stanford University Stanford USA Stanford Synchrotron Radiation Laboratory SLAC Stanford USA University of Gottingen Gottingen Germany RSIC Indian Institute of Technology Chennai India Department of Inorganic Chemistry Indian Association for the Cultivation of Science Jadavpur Calcutta India Department of Chemistry Indian Institute of Technology Kanpur India Institut für Anorganische Chemie und Analytische Chemie Johannes Gutenberg-Universität Mainz Germany Solid State and Structural Chemistry Unit Indian Institute of Science Bangalore India School of Chemistry Physics and Environmental Science University of Sussex Brighton England Radiopharmaceutical Sciences Institute Departments of Radiology University of Missouri Columbia USA Radiopharmaceutical Sciences Institute Departments of Research Reactor University of Missouri Columbia USA Radiopharmaceutical Sciences Institute Departments of Chemistry University of Missouri Columbia USA Department of Surgery Aichi-Gakuin University Hospital Nagoya Japan Department of Chemistry Indian Institute of Technology Guwahati India Department of Chemistry Panjab University Chandigarh India Department of Chemistry Indian Institute of Technology New Delhi India Silicates and Catalysis Division Central Salt and Marine Chemicals Research Institute Bhavnagar India Sophisticated Instruments Facility Indian Institute of Science Bangalore India Department of Chemistry Central College Campus Bangalore University Bangalore India Department of Inorganic Chemistry Indian Association for the Cultivation of Science Calcutta India Department of Chemistry Indian Institute of Technology Kharagpur India Department of Chemistry Osmania University Hyderabad India Department of Chemistry Pondicherry University Pondicherry India Department of Chemistry I

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