8 results
Chemical Characterization, Structural Features, and Thermal Behavior of Sodium and Hydrogen Octosilicate
- G. Borbély, H. K. Beyer, H. G. Karge, W. Schwieger, A. Brandt, K.-H. Bergk
-
- Journal:
- Clays and Clay Minerals / Volume 39 / Issue 5 / October 1991
- Published online by Cambridge University Press:
- 02 April 2024, pp. 490-497
-
- Article
- Export citation
-
The chemical composition and the thermal behavior of sodium and hydrogen octosilicate was studied by chemical and thermal analysis, infrared (IR), magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray diffractometry. Both compounds are layer silicates with basal spacings of 11.10 and 7.38 Å, respectively. In both forms the ratio of Q4 silicon (connected via oxygen bridges with four silicon atoms) to Q3 silicon (connected with only three other Si atoms) is 1. At least a small part of the Q4 silicon can be substituted by aluminum. Elimination of water coordinated to the cations in sodium octosilicate results in a concomitant structural collapse. Replacement of the sodium ions by protons affects the atomic arrangement in the sheets only to a minor degree, but results in a decrease of the periodicity along the crystallographic c axis. Upon heat treatment an endothermal structural rearrangement occurs at about 360 K as revealed by significant changes of the IR and 29Si MAS-NMR spectra. Reexchange with Na ions largely, but not completely, restores the structure of the parent octosilicate.
The X-ray diffraction pattern of sodium octosilicate was indexed in the monoclinic system with a = 7.345 Å, b = 12.74 Å, c = 11.25 Å and β = 99.3°. Based on conclusions drawn from the results of the present study, the X-ray pattern of hydrogen octosilicate was tentatively indexed in the monoclinic system with a = 7.345 Å, b = 12.74 Å, c = 8.51 Å and β = 119.8°.
Contributors
-
- By Mitchell Aboulafia, Frederick Adams, Marilyn McCord Adams, Robert M. Adams, Laird Addis, James W. Allard, David Allison, William P. Alston, Karl Ameriks, C. Anthony Anderson, David Leech Anderson, Lanier Anderson, Roger Ariew, David Armstrong, Denis G. Arnold, E. J. Ashworth, Margaret Atherton, Robin Attfield, Bruce Aune, Edward Wilson Averill, Jody Azzouni, Kent Bach, Andrew Bailey, Lynne Rudder Baker, Thomas R. Baldwin, Jon Barwise, George Bealer, William Bechtel, Lawrence C. Becker, Mark A. Bedau, Ernst Behler, José A. Benardete, Ermanno Bencivenga, Jan Berg, Michael Bergmann, Robert L. Bernasconi, Sven Bernecker, Bernard Berofsky, Rod Bertolet, Charles J. Beyer, Christian Beyer, Joseph Bien, Joseph Bien, Peg Birmingham, Ivan Boh, James Bohman, Daniel Bonevac, Laurence BonJour, William J. Bouwsma, Raymond D. Bradley, Myles Brand, Richard B. Brandt, Michael E. Bratman, Stephen E. Braude, Daniel Breazeale, Angela Breitenbach, Jason Bridges, David O. Brink, Gordon G. Brittan, Justin Broackes, Dan W. Brock, Aaron Bronfman, Jeffrey E. Brower, Bartosz Brozek, Anthony Brueckner, Jeffrey Bub, Lara Buchak, Otavio Bueno, Ann E. Bumpus, Robert W. Burch, John Burgess, Arthur W. Burks, Panayot Butchvarov, Robert E. Butts, Marina Bykova, Patrick Byrne, David Carr, Noël Carroll, Edward S. Casey, Victor Caston, Victor Caston, Albert Casullo, Robert L. Causey, Alan K. L. Chan, Ruth Chang, Deen K. Chatterjee, Andrew Chignell, Roderick M. Chisholm, Kelly J. Clark, E. J. Coffman, Robin Collins, Brian P. Copenhaver, John Corcoran, John Cottingham, Roger Crisp, Frederick J. Crosson, Antonio S. Cua, Phillip D. Cummins, Martin Curd, Adam Cureton, Andrew Cutrofello, Stephen Darwall, Paul Sheldon Davies, Wayne A. Davis, Timothy Joseph Day, Claudio de Almeida, Mario De Caro, Mario De Caro, John Deigh, C. F. Delaney, Daniel C. Dennett, Michael R. DePaul, Michael Detlefsen, Daniel Trent Devereux, Philip E. Devine, John M. Dillon, Martin C. Dillon, Robert DiSalle, Mary Domski, Alan Donagan, Paul Draper, Fred Dretske, Mircea Dumitru, Wilhelm Dupré, Gerald Dworkin, John Earman, Ellery Eells, Catherine Z. Elgin, Berent Enç, Ronald P. Endicott, Edward Erwin, John Etchemendy, C. Stephen Evans, Susan L. Feagin, Solomon Feferman, Richard Feldman, Arthur Fine, Maurice A. Finocchiaro, William FitzPatrick, Richard E. Flathman, Gvozden Flego, Richard Foley, Graeme Forbes, Rainer Forst, Malcolm R. Forster, Daniel Fouke, Patrick Francken, Samuel Freeman, Elizabeth Fricker, Miranda Fricker, Michael Friedman, Michael Fuerstein, Richard A. Fumerton, Alan Gabbey, Pieranna Garavaso, Daniel Garber, Jorge L. A. Garcia, Robert K. Garcia, Don Garrett, Philip Gasper, Gerald Gaus, Berys Gaut, Bernard Gert, Roger F. Gibson, Cody Gilmore, Carl Ginet, Alan H. Goldman, Alvin I. Goldman, Alfonso Gömez-Lobo, Lenn E. Goodman, Robert M. Gordon, Stefan Gosepath, Jorge J. E. Gracia, Daniel W. Graham, George A. Graham, Peter J. Graham, Richard E. Grandy, I. Grattan-Guinness, John Greco, Philip T. Grier, Nicholas Griffin, Nicholas Griffin, David A. Griffiths, Paul J. Griffiths, Stephen R. Grimm, Charles L. Griswold, Charles B. Guignon, Pete A. Y. Gunter, Dimitri Gutas, Gary Gutting, Paul Guyer, Kwame Gyekye, Oscar A. Haac, Raul Hakli, Raul Hakli, Michael Hallett, Edward C. Halper, Jean Hampton, R. James Hankinson, K. R. Hanley, Russell Hardin, Robert M. Harnish, William Harper, David Harrah, Kevin Hart, Ali Hasan, William Hasker, John Haugeland, Roger Hausheer, William Heald, Peter Heath, Richard Heck, John F. Heil, Vincent F. Hendricks, Stephen Hetherington, Francis Heylighen, Kathleen Marie Higgins, Risto Hilpinen, Harold T. Hodes, Joshua Hoffman, Alan Holland, Robert L. Holmes, Richard Holton, Brad W. Hooker, Terence E. Horgan, Tamara Horowitz, Paul Horwich, Vittorio Hösle, Paul Hoβfeld, Daniel Howard-Snyder, Frances Howard-Snyder, Anne Hudson, Deal W. Hudson, Carl A. Huffman, David L. Hull, Patricia Huntington, Thomas Hurka, Paul Hurley, Rosalind Hursthouse, Guillermo Hurtado, Ronald E. Hustwit, Sarah Hutton, Jonathan Jenkins Ichikawa, Harry A. Ide, David Ingram, Philip J. Ivanhoe, Alfred L. Ivry, Frank Jackson, Dale Jacquette, Joseph Jedwab, Richard Jeffrey, David Alan Johnson, Edward Johnson, Mark D. Jordan, Richard Joyce, Hwa Yol Jung, Robert Hillary Kane, Tomis Kapitan, Jacquelyn Ann K. Kegley, James A. Keller, Ralph Kennedy, Sergei Khoruzhii, Jaegwon Kim, Yersu Kim, Nathan L. King, Patricia Kitcher, Peter D. Klein, E. D. Klemke, Virginia Klenk, George L. Kline, Christian Klotz, Simo Knuuttila, Joseph J. Kockelmans, Konstantin Kolenda, Sebastian Tomasz Kołodziejczyk, Isaac Kramnick, Richard Kraut, Fred Kroon, Manfred Kuehn, Steven T. Kuhn, Henry E. Kyburg, John Lachs, Jennifer Lackey, Stephen E. Lahey, Andrea Lavazza, Thomas H. Leahey, Joo Heung Lee, Keith Lehrer, Dorothy Leland, Noah M. Lemos, Ernest LePore, Sarah-Jane Leslie, Isaac Levi, Andrew Levine, Alan E. Lewis, Daniel E. Little, Shu-hsien Liu, Shu-hsien Liu, Alan K. L. Chan, Brian Loar, Lawrence B. Lombard, John Longeway, Dominic McIver Lopes, Michael J. Loux, E. J. Lowe, Steven Luper, Eugene C. Luschei, William G. Lycan, David Lyons, David Macarthur, Danielle Macbeth, Scott MacDonald, Jacob L. Mackey, Louis H. Mackey, Penelope Mackie, Edward H. Madden, Penelope Maddy, G. B. Madison, Bernd Magnus, Pekka Mäkelä, Rudolf A. Makkreel, David Manley, William E. Mann (W.E.M.), Vladimir Marchenkov, Peter Markie, Jean-Pierre Marquis, Ausonio Marras, Mike W. Martin, A. P. Martinich, William L. McBride, David McCabe, Storrs McCall, Hugh J. McCann, Robert N. McCauley, John J. McDermott, Sarah McGrath, Ralph McInerny, Daniel J. McKaughan, Thomas McKay, Michael McKinsey, Brian P. McLaughlin, Ernan McMullin, Anthonie Meijers, Jack W. Meiland, William Jason Melanson, Alfred R. Mele, Joseph R. Mendola, Christopher Menzel, Michael J. Meyer, Christian B. Miller, David W. Miller, Peter Millican, Robert N. Minor, Phillip Mitsis, James A. Montmarquet, Michael S. Moore, Tim Moore, Benjamin Morison, Donald R. Morrison, Stephen J. Morse, Paul K. Moser, Alexander P. D. Mourelatos, Ian Mueller, James Bernard Murphy, Mark C. Murphy, Steven Nadler, Jan Narveson, Alan Nelson, Jerome Neu, Samuel Newlands, Kai Nielsen, Ilkka Niiniluoto, Carlos G. Noreña, Calvin G. Normore, David Fate Norton, Nikolaj Nottelmann, Donald Nute, David S. Oderberg, Steve Odin, Michael O’Rourke, Willard G. Oxtoby, Heinz Paetzold, George S. Pappas, Anthony J. Parel, Lydia Patton, R. P. Peerenboom, Francis Jeffry Pelletier, Adriaan T. Peperzak, Derk Pereboom, Jaroslav Peregrin, Glen Pettigrove, Philip Pettit, Edmund L. Pincoffs, Andrew Pinsent, Robert B. Pippin, Alvin Plantinga, Louis P. Pojman, Richard H. Popkin, John F. Post, Carl J. Posy, William J. Prior, Richard Purtill, Michael Quante, Philip L. Quinn, Philip L. Quinn, Elizabeth S. Radcliffe, Diana Raffman, Gerard Raulet, Stephen L. Read, Andrews Reath, Andrew Reisner, Nicholas Rescher, Henry S. Richardson, Robert C. Richardson, Thomas Ricketts, Wayne D. Riggs, Mark Roberts, Robert C. Roberts, Luke Robinson, Alexander Rosenberg, Gary Rosenkranz, Bernice Glatzer Rosenthal, Adina L. Roskies, William L. Rowe, T. M. Rudavsky, Michael Ruse, Bruce Russell, Lilly-Marlene Russow, Dan Ryder, R. M. Sainsbury, Joseph Salerno, Nathan Salmon, Wesley C. Salmon, Constantine Sandis, David H. Sanford, Marco Santambrogio, David Sapire, Ruth A. Saunders, Geoffrey Sayre-McCord, Charles Sayward, James P. Scanlan, Richard Schacht, Tamar Schapiro, Frederick F. Schmitt, Jerome B. Schneewind, Calvin O. Schrag, Alan D. Schrift, George F. Schumm, Jean-Loup Seban, David N. Sedley, Kenneth Seeskin, Krister Segerberg, Charlene Haddock Seigfried, Dennis M. Senchuk, James F. Sennett, William Lad Sessions, Stewart Shapiro, Tommie Shelby, Donald W. Sherburne, Christopher Shields, Roger A. Shiner, Sydney Shoemaker, Robert K. Shope, Kwong-loi Shun, Wilfried Sieg, A. John Simmons, Robert L. Simon, Marcus G. Singer, Georgette Sinkler, Walter Sinnott-Armstrong, Matti T. Sintonen, Lawrence Sklar, Brian Skyrms, Robert C. Sleigh, Michael Anthony Slote, Hans Sluga, Barry Smith, Michael Smith, Robin Smith, Robert Sokolowski, Robert C. Solomon, Marta Soniewicka, Philip Soper, Ernest Sosa, Nicholas Southwood, Paul Vincent Spade, T. L. S. Sprigge, Eric O. Springsted, George J. Stack, Rebecca Stangl, Jason Stanley, Florian Steinberger, Sören Stenlund, Christopher Stephens, James P. Sterba, Josef Stern, Matthias Steup, M. A. Stewart, Leopold Stubenberg, Edith Dudley Sulla, Frederick Suppe, Jere Paul Surber, David George Sussman, Sigrún Svavarsdóttir, Zeno G. Swijtink, Richard Swinburne, Charles C. Taliaferro, Robert B. Talisse, John Tasioulas, Paul Teller, Larry S. Temkin, Mark Textor, H. S. Thayer, Peter Thielke, Alan Thomas, Amie L. Thomasson, Katherine Thomson-Jones, Joshua C. Thurow, Vzalerie Tiberius, Terrence N. Tice, Paul Tidman, Mark C. Timmons, William Tolhurst, James E. Tomberlin, Rosemarie Tong, Lawrence Torcello, Kelly Trogdon, J. D. Trout, Robert E. Tully, Raimo Tuomela, John Turri, Martin M. Tweedale, Thomas Uebel, Jennifer Uleman, James Van Cleve, Harry van der Linden, Peter van Inwagen, Bryan W. Van Norden, René van Woudenberg, Donald Phillip Verene, Samantha Vice, Thomas Vinci, Donald Wayne Viney, Barbara Von Eckardt, Peter B. M. Vranas, Steven J. Wagner, William J. Wainwright, Paul E. Walker, Robert E. Wall, Craig Walton, Douglas Walton, Eric Watkins, Richard A. Watson, Michael V. Wedin, Rudolph H. Weingartner, Paul Weirich, Paul J. Weithman, Carl Wellman, Howard Wettstein, Samuel C. Wheeler, Stephen A. White, Jennifer Whiting, Edward R. Wierenga, Michael Williams, Fred Wilson, W. Kent Wilson, Kenneth P. Winkler, John F. Wippel, Jan Woleński, Allan B. Wolter, Nicholas P. Wolterstorff, Rega Wood, W. Jay Wood, Paul Woodruff, Alison Wylie, Gideon Yaffe, Takashi Yagisawa, Yutaka Yamamoto, Keith E. Yandell, Xiaomei Yang, Dean Zimmerman, Günter Zoller, Catherine Zuckert, Michael Zuckert, Jack A. Zupko (J.A.Z.)
- Edited by Robert Audi, University of Notre Dame, Indiana
-
- Book:
- The Cambridge Dictionary of Philosophy
- Published online:
- 05 August 2015
- Print publication:
- 27 April 2015, pp ix-xxx
-
- Chapter
- Export citation
Contributors
-
- By Lenard A. Adler, Pinky Agarwal, Rehan Ahmed, Jagga Rao Alluri, Fawaz Al-Mufti, Samuel Alperin, Michael Amoashiy, Michael Andary, David J. Anschel, Padmaja Aradhya, Vandana Aspen, Esther Baldinger, Jee Bang, George D. Baquis, John J. Barry, Jason J. S. Barton, Julius Bazan, Amanda R. Bedford, Marlene Behrmann, Lourdes Bello-Espinosa, Ajay Berdia, Alan R. Berger, Mark Beyer, Don C. Bienfang, Kevin M. Biglan, Thomas M. Boes, Paul W. Brazis, Jonathan L. Brisman, Jeffrey A. Brown, Scott E. Brown, Ryan R. Byrne, Rina Caprarella, Casey A. Chamberlain, Wan-Tsu W. Chang, Grace M. Charles, Jasvinder Chawla, David Clark, Todd J. Cohen, Joe Colombo, Howard Crystal, Vladimir Dadashev, Sarita B. Dave, Jean Robert Desrouleaux, Richard L. Doty, Robert Duarte, Jeffrey S. Durmer, Christyn M. Edmundson, Eric R. Eggenberger, Steven Ender, Noam Epstein, Alberto J. Espay, Alan B. Ettinger, Niloofar (Nelly) Faghani, Amtul Farheen, Edward Firouztale, Rod Foroozan, Anne L. Foundas, David Elliot Friedman, Deborah I. Friedman, Steven J. Frucht, Oded Gerber, Tal Gilboa, Martin Gizzi, Teneille G. Gofton, Louis J. Goodrich, Malcolm H. Gottesman, Varda Gross-Tsur, Deepak Grover, David A. Gudis, John J. Halperin, Maxim D. Hammer, Andrew R. Harrison, L. Anne Hayman, Galen V. Henderson, Steven Herskovitz, Caitlin Hoffman, Laryssa A. Huryn, Andres M. Kanner, Gary P. Kaplan, Bashar Katirji, Kenneth R. Kaufman, Annie Killoran, Nina Kirz, Gad E. Klein, Danielle G. Koby, Christopher P. Kogut, W. Curt LaFrance, Patrick J.M. Lavin, Susan W. Law, James L. Levenson, Richard B. Lipton, Glenn Lopate, Daniel J. Luciano, Reema Maindiratta, Robert M. Mallery, Georgios Manousakis, Alan Mazurek, Luis J. Mejico, Dragana Micic, Ali Mokhtarzadeh, Walter J. Molofsky, Heather E. Moss, Mark L. Moster, Manpreet Multani, Siddhartha Nadkarni, George C. Newman, Rolla Nuoman, Paul A. Nyquist, Gaia Donata Oggioni, Odi Oguh, Denis Ostrovskiy, Kristina Y. Pao, Juwen Park, Anastas F. Pass, Victoria S. Pelak, Jeffrey Peterson, John Pile-Spellman, Misha L. Pless, Gregory M. Pontone, Aparna M. Prabhu, Michael T. Pulley, Philip Ragone, Prajwal Rajappa, Venkat Ramani, Sindhu Ramchandren, Ritesh A. Ramdhani, Ramses Ribot, Heidi D. Riney, Diana Rojas-Soto, Michael Ronthal, Daniel M. Rosenbaum, David B. Rosenfield, Durga Roy, Michael J. Ruckenstein, Max C. Rudansky, Eva Sahay, Friedhelm Sandbrink, Jade S. Schiffman, Angela Scicutella, Maroun T. Semaan, Robert C. Sergott, Aashit K. Shah, David M. Shaw, Amit M. Shelat, Claire A. Sheldon, Anant M. Shenoy, Yelizaveta Sher, Jessica A. Shields, Tanya Simuni, Rajpaul Singh, Eric E. Smouha, David Solomon, Mehri Songhorian, Steven A. Sparr, Egilius L. H. Spierings, Eve G. Spratt, Beth Stein, S.H. Subramony, Rosa Ana Tang, Cara Tannenbaum, Hakan Tekeli, Amanda J. Thompson, Michael J. Thorpy, Matthew J. Thurtell, Pedro J. Torrico, Ira M. Turner, Scott Uretsky, Ruth H. Walker, Deborah M. Weisbrot, Michael A. Williams, Jacques Winter, Randall J. Wright, Jay Elliot Yasen, Shicong Ye, G. Bryan Young, Huiying Yu, Ryan J. Zehnder
- Edited by Alan B. Ettinger, Albert Einstein College of Medicine, New York, Deborah M. Weisbrot, State University of New York, Stony Brook
-
- Book:
- Neurologic Differential Diagnosis
- Published online:
- 05 June 2014
- Print publication:
- 17 April 2014, pp xi-xx
-
- Chapter
- Export citation
Contributors
-
- By Dag Aarsland, Angelo Antonini, Liana G. Apostolova, Marek Balaz, Roger A. Barker, Oscar Bernal-Pacheco, Mona K. Beyer, Başar Bilgiç, Daniel J. Burdick, Jessica Calleo, K. Ray Chaudhuri, Jeffrey Cummings, Turi O. Dalaker, Christine Daniels, Kathy Dujardin, Sheila R. Eichenseer, Murat Emre, Hubert H. Fernandez, Adam Gerstenecker, Christopher G. Goetz, Haşmet A. Hanağası, Kristina Røkenes Karlsen, Jaime Kulisevsky, Albert F. G. Leentjens, James B. Leverenz, Irene Litvan, Elisabet Londos, Laura Marsh, Saül Martínez-Horta, Pablo Martinez-Martin, Benjamin T. Mast, Brit Mollenhauer, Pouya Movahed, Agneta Nordberg, Javier Pagonabarraga, Irena Rektorova, Per Svenningsson, Alexander I. Tröster, Carolina Villa-Bonomo, Jens Volkmann, Ryan R. Walsh, Daniel Weintraub, Caroline H. Williams-Gray, Henrik Zetterberg
- Edited by Dag Aarsland, Jeffrey Cummings, Daniel Weintraub, University of Pennsylvania, K. Ray Chaudhuri
-
- Book:
- Neuropsychiatric and Cognitive Changes in Parkinson's Disease and Related Movement Disorders
- Published online:
- 05 August 2013
- Print publication:
- 29 August 2013, pp vii-x
-
- Chapter
- Export citation
Quantitative Analysis of Chemical Composition Using HAADF-STEM in a JEOL 2200FS
- R Fritz, A Beyer, W Stolz, K Müller, M Schowalter, A Rosenauer, I Häusler, H Kirmse, A Mogilatenko, H Kirmse, W Neumann, K Volz
-
- Journal:
- Microscopy and Microanalysis / Volume 17 / Issue S2 / July 2011
- Published online by Cambridge University Press:
- 08 April 2017, pp. 1410-1411
- Print publication:
- July 2011
-
- Article
-
- You have access Access
- Export citation
-
Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.
Characterization and Integration in Cu Damascene Structures of AURORA, an Inorganic Low-k Dielectric
- R. A. Donaton, B. Coenegrachts, E. Sleeckx, M. Schaekers, G. Sophie, N. Matsuki, M. R. Baklanov, H. Struyf, M. Lepage, S. Vanhaelemeersch, G. Beyer, M. Stucchi, D. De Roest, K. Maex
-
- Journal:
- MRS Online Proceedings Library Archive / Volume 612 / 2000
- Published online by Cambridge University Press:
- 17 March 2011, D5.14.1
- Print publication:
- 2000
-
- Article
- Export citation
-
AURORA films, which have a Si-O-Si network with –CH3 terminations, were characterized and integrated into Cu single damascene structures. The relatively low carbon concentration (∼ 20%) and the very small pore size (∼ 0.6 nm) found could be advantageous during integration of AURORA. Integration of AURORA into Cu single damascene structures was successfully achieved. Suitable resist strip processes, which are critical for Si-O-C type materials, were developed, resulting in trenches with satisfactory profiles. After a complete single damascene process, a interline dielectric constant value of 2.7 was found for line spacing down to 0.25 µm.
Optical and structural analysis of Ge quantum dots embedded in strained Si quantum wells grown on patterned substrates
- A. Beyer, E. Müller, H. Sigg, S. Stutz, C. David, D. Grützmacher, K. Ensslin
-
- Journal:
- MRS Online Proceedings Library Archive / Volume 638 / 2000
- Published online by Cambridge University Press:
- 17 March 2011, F14.8.1
- Print publication:
- 2000
-
- Article
- Export citation
-
Germanium quantum dots embedded in silicon have been used in the past to improve the opto-electronic properties of Si based materials. The idea is to overcome the limitation of the indirect band gap of Si by a strong localization of the carriers in quantum dots. However, the Ge quantum dots provide a strong carrier confinement only for the holes, the electrons are only weakly confined in the Si. In this study we embedded the Ge quantum dots in strained Si quantum wells grown on relaxed SiGe buffer layers. The strained Si quantum wells provide a confinement of the electrons in the vicinity of the Ge dots.
The structures were deposited on planar as well as on patterned substrates by molecular beam epitaxy. The structural and optical properties of the samples were analyzed using high resolution cross sectional transmission electron microscopy (TEM) as well as low temperature photoluminescence. The size of the mesa structures have been used as experimental parameter. Relaxed buffer layers grown on line shaped mesa structures show a strongly reduced dislocation density. Consequently the deep luminescence attributed to dislocations in the buffer layers is strongly reduced and pronounced photoluminescence of the quantum structures grown on top of the buffer layers can be observed.
Endohedral Metallofullerenes: Isolation and Characterization
- H. C. Dorn, S. Stevenson, P. Burbank, Z. Sun, T. Glass, K. Harich, P. H. M. Van Loosdrecht, R. D. Johnson, R. Beyers, J. R. Salem, M. S. De Vries, C. S. Yannoni, C. H. Kiang, D. S. Bethune
-
- Journal:
- MRS Online Proceedings Library Archive / Volume 359 / 1994
- Published online by Cambridge University Press:
- 15 February 2011, 123
- Print publication:
- 1994
-
- Article
- Export citation
-
Since the initial discovery of fullerenes nearly a decade ago [1], material scientists have focused attention on the possibility of encapsulating one or more metal atoms inside these spheroidal carbon frames. The experimental realization of macroscopic quantities of endohedral metallofullerenes (Am@C2n, n=30-55) in the early 1990's has heightened interest in developing this new class of tunable materials with possible electronic and/or optical applications [2,3]. They have been characterized by a number of spectroscopic techniques, for example, scanning tunneling microscope [4,5], EXAFS [6,7] and x-ray diffraction and electron microscopy [8]. However, low production yields and purification difficulties have hampered the development of this new class of materials. The soluble product distribution usually consists of high levels of the empty-caged fullerenes C60, C70, C84 and decreasing levels of the higher fullerenes, while the endohedral metallofullerene fraction usually constitutes less than 1% of the total soluble yield. Furthermore, the endohedral metallofullerene fraction consists of molecules with different numbers of metal atoms encapsulated (m=1-3), cage sizes (C2n) and isomers of the same mass (e.g., Er2@C82). The purification process is further complicated by the chemical reactivity of several endohedral metallofullerenes [9] in aerobic environments. For several years, we have been involved in a collaborative effort to develop methodology for detection, isolation, and characterization of endohedral metallofullerenes. The focus of the present study is on fullerenes encapsulating metals from Group II1b, (Sc@C2n, Y@C2n, and La@C2n) and the lanthanide series metal (Er@C2n).