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Relevance of Threading Dislocations for the Thermal Oxidation of GaN (0001)
- Maria Reiner, Christian Koller, Kurt Pekoll, Rudolf Pietschnig, Clemens Ostermaier
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1792 / 2015
- Published online by Cambridge University Press:
- 01 June 2015, mrss15-2133138
- Print publication:
- 2015
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The influence of threading dislocations (TDs) on the dry thermal oxidation of c-plane gallium nitride (GaN) is investigated for oxidation temperatures above 800°C. The transformation of GaN to gallium oxide (Ga2O3) is preferably found at TDs and grain boundaries, showing enhanced vertical oxidation, compared to defect free surface sites. Therefore, the increase in surface roughness commonly obtained upon oxidation is explained by an inhomogeneous chemical reactivity associated with those crystal defects. Additionally, annealing in an N2 atmosphere showed that also decomposition is favored at such chemically reactive spots. Comparison between decomposition and oxidation suggests that at temperatures above 950°C, the Ga2O3 formation is supported by the decomposition of GaN and subsequent oxidation of the metallic gallium.
The science of EChO
- Giovanna Tinetti, James Y-K. Cho, Caitlin A. Griffith, Olivier Grasset, Lee Grenfell, Tristan Guillot, Tommi T. Koskinen, Julianne I. Moses, David Pinfield, Jonathan Tennyson, Marcell Tessenyi, Robin Wordsworth, Alan Aylward, Roy van Boekel, Angioletta Coradini, Therese Encrenaz, Ignas Snellen, Maria R. Zapatero-Osorio, Jeroen Bouwman, Vincent Coudé du Foresto, Mercedes Lopez-Morales, Ingo Mueller-Wodarg, Enric Pallé, Franck Selsis, Alessandro Sozzetti, Jean-Philippe Beaulieu, Thomas Henning, Michael Meyer, Giuseppina Micela, Ignasi Ribas, Daphne Stam, Mark Swain, Oliver Krause, Marc Ollivier, Emanuele Pace, Bruce Swinyard, Peter A.R. Ade, Nick Achilleos, Alberto Adriani, Craig B. Agnor, Cristina Afonso, Carlos Allende Prieto, Gaspar Bakos, Robert J. Barber, Michael Barlow, Peter Bernath, Bruno Bézard, Pascal Bordé, Linda R. Brown, Arnaud Cassan, Céline Cavarroc, Angela Ciaravella, Charles Cockell, Athéna Coustenis, Camilla Danielski, Leen Decin, Remco De Kok, Olivier Demangeon, Pieter Deroo, Peter Doel, Pierre Drossart, Leigh N. Fletcher, Matteo Focardi, Francois Forget, Steve Fossey, Pascal Fouqué, James Frith, Marina Galand, Patrick Gaulme, Jonay I. González Hernández, Davide Grassi, Matt J. Griffin, Ulrich Grözinger, Manuel Guedel, Pactrick Guio, Olivier Hainaut, Robert Hargreaves, Peter H. Hauschildt, Kevin Heng, David Heyrovsky, Ricardo Hueso, Pat Irwin, Lisa Kaltenegger, Patrick Kervella, David Kipping, Geza Kovacs, Antonino La Barbera, Helmut Lammer, Emmanuel Lellouch, Giuseppe Leto, Mercedes Lopez Morales, Miguel A. Lopez Valverde, Manuel Lopez-Puertas, Christophe Lovi, Antonio Maggio, Jean-Pierre Maillard, Jesus Maldonado Prado, Jean-Baptiste Marquette, Francisco J. Martin-Torres, Pierre Maxted, Steve Miller, Sergio Molinari, David Montes, Amaya Moro-Martin, Olivier Mousis, Napoléon Nguyen Tuong, Richard Nelson, Glenn S. Orton, Eric Pantin, Enzo Pascale, Stefano Pezzuto, Ennio Poretti, Raman Prinja, Loredana Prisinzano, Jean-Michel Réess, Ansgar Reiners, Benjamin Samuel, Jorge Sanz Forcada, Dimitar Sasselov, Giorgio Savini, Bruno Sicardy, Alan Smith, Lars Stixrude, Giovanni Strazzulla, Gautam Vasisht, Sandrine Vinatier, Serena Viti, Ingo Waldmann, Glenn J. White, Thomas Widemann, Roger Yelle, Yuk Yung, Sergey Yurchenko
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- Journal:
- Proceedings of the International Astronomical Union / Volume 6 / Issue S276 / October 2010
- Published online by Cambridge University Press:
- 10 November 2011, pp. 359-370
- Print publication:
- October 2010
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The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?
In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.
The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.
EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.