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5. Acceptor-oxygen defects in silicon

Author

De Guzman, Joyce Ann T., Markevich, Vladimir P., Hawkins, Ian D., Coutinho, José, Ayedh, Hussein M., Binns, Jeff, Abrosimov, Nikolay V., Lastovskii, Stanislau B., Crowe, Iain F., Halsall, Matthew P., Peaker, Anthony R., University of Manchester, University of Aveiro, Department of Electronics and Nanoengineering, Nexcel Electronic Technology, Leibniz Institute for Crystal Growth, Belarusian Academy of Sciences, Aalto-yliopisto, and Aalto University

Abstract

Funding Information: We would like to thank EPSRC (UK) for funding this work via Grant No. EP/TO25131/1. J.A.T. de Guzman would like to thank the Government of the Philippines through the Department of Science and Technology (DOST) for her PhD funding. J.C. acknowledges the support of the i3N projects, Ref. Nos. UIDB/ 50025/2020 and UIDP/50025/2020, financed by the Fundação para a Ciência e a Tecnologia in Portugal. Publisher Copyright: © 2021 Author(s). It is well established that boron reacts with two oxygen atoms in Czochralski-grown silicon (Cz-Si) to form a defect, which is responsible for the dominant light-induced degradation (LID) in solar cells made from Cz-Si:B material. The detrimental effect of LID has stimulated a move by solar cell manufacturers to the use of silicon with other group-III dopants, particularly with gallium. Cz-Si:Ga is immune to the BO-type LID. The information available in the literature on the interactions of oxygen with either Al, Ga, or In impurities in Si is limited. We use ab initio modeling and junction spectroscopy techniques to study a family of defects with unusual electronic properties, which have been detected in Cz-Si samples doped with different shallow acceptor species. We have carried out detailed measurements of the temperature dependencies of hole emission rate, equilibrium occupancy, and hole capture kinetics for the traps observed in differently doped p-type Cz-Si samples. It is found from the analysis of the changes in magnitude of the deep-level-transient signals with temperature that the equilibrium occupancy function of the traps is characteristic for a defect with negative-U properties in all the samples. The positions of the E(-/+) occupancy level of the defects are very close in differently doped samples, E(-/+) = E-v + (0.31 & PLUSMN; 0.01) eV. It is argued that the oxygen dimer interacts with group-III atoms in silicon and these interactions result in the formation of A(s)O(2) complexes (A is either B, Al, Ga, or In atom) with very similar electronic properties.& nbsp;(c) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Published
2021

6. Indium-Doped Silicon for Solar Cells—Light-Induced Degradation and Deep-Level Traps

Author

Anthony R. Peaker, Hussein M. Ayedh, Robert J. Falster, Jeff Binns, Matthew P. Halsall, Vladimir P. Markevich, Nikolay V. Abrosimov, Iain F. Crowe, José Coutinho, I. D. Hawkins, Joyce Ann T. De Guzman, University of Manchester, Department of Electronics and Nanoengineering, University of Aveiro, Nexcel Electronic Technology, Leibniz Institute for Crystal Growth, Aalto-yliopisto, and Aalto University

Subjects
Materials science, Silicon, Deep level, light-induced degradation, business.industry, ResearchInstitutes_Networks_Beacons/photon_science_institute, Doping, chemistry.chemical_element, Surfaces and Interfaces, Photon Science Institute, Condensed Matter Physics, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, chemistry, oxygen recombination enhanced reactions, solar cells, Materials Chemistry, Light induced, Optoelectronics, Degradation (geology), indium-doped silicon, Electrical and Electronic Engineering, business, Indium
Abstract

Funding Information: The authors would like to thank EPSRC (UK) for funding this work via grant EP/TO25131/1. J.A.T.D.G. would like to thank the Government of the Philippines through the Department of Science and Technology (DOST) for her Ph.D. funding. J.C. is thankful for the support of the i3N projects, Refs. UIDB/50025/2020 and UIDP/50025/2020, financed by the Fundação para a Ciência e a Tecnologia in Portugal. Publisher Copyright: © 2021 The Authors. physica status solidi (a) applications and materials science published by Wiley-VCH GmbH Indium-doped silicon is considered a possible p-type material for solar cells to avoid light-induced degradation (LID), which occurs in cells made from boron-doped Czochralski (Cz) silicon. Herein, the defect reactions associated with indium-related LID are examined and a deep donor is detected, which is attributed to a negative-U defect believed to be InsO2. In the presence of minority carriers or above bandgap light, the deep donor transforms to a shallow acceptor. An analogous transformation in boron-doped material is related to the BsO2 defect that is a precursor of the center responsible for BO LID. The electronic properties of InsO2 are determined and compared to those of the BsO2 defect. Structures of the BsO2 and InsO2 defects in different charges states are found using first-principles modeling. The results of the modeling can explain both the similarities and the differences between the BsO2 and InsO2 properties.

Published
2021
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18. Influence of slip on the Plateau-Rayleigh instability on a fibre

Author

Sabrina Haefner, Oliver Bäumchen, Thomas Salez, Elie Raphaël, Karin Jacobs, Kari Dalnoki-Veress, Robert D. Peters, Joshua D. McGraw, Michael Benzaquen, Gulliver (UMR 7083), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Leibniz Institute for Crystal Growth, and Leibniz Institute

Subjects
Materials science, General Physics and Astronomy, FOS: Physical sciences, 02 engineering and technology, Slip (materials science), engineering.material, Condensed Matter - Soft Condensed Matter, Bioinformatics, 01 natural sciences, Instability, General Biochemistry, Genetics and Molecular Biology, Article, 010305 fluids & plasmas, Plasma physics, Physics::Fluid Dynamics, Coating, Fluid dynamics, Physics - Chemical Physics, 0103 physical sciences, Boundary value problem, Growth rate, Physics - Biological Physics, ComputingMilieux_MISCELLANEOUS, Chemical Physics (physics.chem-ph), [PHYS]Physics [physics], Multidisciplinary, Plateau–Rayleigh instability, Liquid layer, Fluid Dynamics (physics.flu-dyn), General Chemistry, Mechanics, Physics - Fluid Dynamics, 021001 nanoscience & nanotechnology, Condensed Matter::Soft Condensed Matter, Wavelength, Biological Physics (physics.bio-ph), engineering, Soft Condensed Matter (cond-mat.soft), 0210 nano-technology
Abstract

The Plateau–Rayleigh instability of a liquid column underlies a variety of fascinating phenomena that can be observed in everyday life. In contrast to the case of a free liquid cylinder, describing the evolution of a liquid layer on a solid fibre requires consideration of the solid–liquid interface. Here we revisit the Plateau–Rayleigh instability of a liquid coating a fibre by varying the hydrodynamic boundary condition at the fibre–liquid interface, from no slip to slip. Although the wavelength is not sensitive to the solid–liquid interface, we find that the growth rate of the undulations strongly depends on the hydrodynamic boundary condition. The experiments are in excellent agreement with a new thin-film theory incorporating slip, thus providing an original, quantitative and robust tool to measure slip lengths., A thin liquid coating on a fibre can break up into droplets due to the Plateau–Rayleigh instability, as for instance on a spider web. Here, Haefner et al. show that the growth rate of the droplet undulations strongly depends on the fibre–liquid boundary condition and slip accelerates the instability.

Published
2020
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19. TiSrantisite

Author

Karjalainen, Antti, Prozheeva, Vera, Makkonen, Ilja, Guguschev, Christo, Markurt, Toni, Bickermann, Matthias, Tuomisto, Filip, Antimatter and Nuclear Engineering, University of Helsinki, Leibniz Institute for Crystal Growth, Department of Applied Physics, Aalto-yliopisto, and Aalto University

Abstract

We present a systematic study of the positron lifetime as a function of measurement temperature in strontium titanate (SrTiO3) single crystals grown in different conditions and by different synthesis methods. We combine our experimental results with state-of-the-art theoretical calculations of positron annihilation parameters. We find that the essentially omnipresent 180-190 ps lifetime component is most likely the Ti Sr antisite defect, possibly coupled with one or more oxygen vacancies, supporting the importance of the Ti Sr antisite related defects in SrTiO3.

Published
2020

20. Ti-A nd Fe-related charge transition levels in β-Ga 2 O 3

Author

Lasse Vines, Zbigniew Galazka, Walter E. Meyer, Joel B. Varley, Christian Zimmermann, Klaus Irmscher, F.D. Auret, Antti Karjalainen, Ymir Kalmann Frodason, Abraham W. Barnard, University of Oslo, University of Pretoria, Lawrence Livermore National Laboratory, Leibniz Institute for Crystal Growth, Department of Applied Physics, Aalto-yliopisto, and Aalto University

Subjects
010302 applied physics, Materials science, Deep-level transient spectroscopy, Physics and Astronomy (miscellaneous), chemistry.chemical_element, Charge (physics), 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Hybrid functional, Secondary ion mass spectrometry, Crystallography, chemistry, Octahedron, 0103 physical sciences, Atom, Gallium, 0210 nano-technology, Transient spectroscopy
Abstract

Deep-level transient spectroscopy measurements on β-Ga 2 O 3 crystals reveal the presence of three defect signatures labeled E 2 a, E 2 b, and E 3 with activation energies at around 0.66 eV, 0.73 eV, and 0.95 eV below the conduction band edge. Using secondary ion mass spectrometry, a correlation between the defect concentration associated with E 3 and the Ti concentration present in the samples was found. Particularly, it is found that E 3 is the dominant Ti-related defect in β-Ga 2 O 3 and is associated with a single Ti atom. This finding is further corroborated by hybrid functional calculations that predict Ti substituting on an octahedral Ga site, denoted as Ti GaII, to be a good candidate for E 3. Moreover, the deep level transient spectroscopy results show that the level previously labeled E 2 and attributed to Fe substituting on a gallium site (Fe Ga) consists of two overlapping signatures labeled E 2 a and E 2 b. We tentatively assign E 2 a and E 2 b to Fe substituting for Ga on a tetrahedral or an octahedral site, respectively.

Published
2020

21. Ga vacancies and electrical compensation in β-Ga 2 O 3 thin films studied with positron annihilation spectroscopy

Author

Vera Prozheeva, Filip Tuomisto, Antti Karjalainen, Günter Wagner, Ilja Makkonen, M. Baldini, Rogers, David J., Teherani, Ferechteh H., Look, David C., Department of Applied Physics, Antimatter and Nuclear Engineering, Leibniz Institute for Crystal Growth, Aalto-yliopisto, and Aalto University

Subjects
Materials science, Positron annihilation spectroscopy, Vacancy, ta114, Doping, Analytical chemistry, Chemical vapor deposition, Conductivity, Positron, Gallium oxide, Vacancy defect, Metalorganic vapour phase epitaxy, Defect, Thin film, Compensation
Abstract

We have applied positron annihilation spectroscopy to study vacancy-type defects in unintentionally doped and Si and Sn doped β-Ga 2 O 3 homoepitaxial thin films grown by metal-organic chemical vapor deposition (MOCVD). We detect Ga vacancy related defects at high concentrations in semi-insulating and highly resistive material, while conductive (ntype) material exhibits very low Ga vacancy concentrations. These findings show that Ga vacancies can act as efficient electrical compensators for n-type conductivity, but their concentrations can be suppressed by controlling the growth environment, leading to efficient n-type doping. We also note the strong anisotropy of the positron annihilation signals and give recommendation for presenting positron data obtained in β-Ga 2 O 3 .

Published
2019

22. Incorporation and effects of impurities in different growth zones within basic ammonothermal GaN

Author

Shuji Nakamura, Sakari Sintonen, Siddha Pimputkar, James S. Speck, Pyry Kivisaari, Sami Suihkonen, Tobias Schulz, Leibniz Institute for Crystal Growth, Department of Neuroscience and Biomedical Engineering, University of California Santa Barbara, Department of Micro and Nanosciences, Aalto-yliopisto, and Aalto University

Subjects
Photoluminescence, Materials science, Silicon, Analytical chemistry, chemistry.chemical_element, 02 engineering and technology, 01 natural sciences, Inorganic Chemistry, Crystal, Lattice constant, Impurity, B1. Nitrides, 0103 physical sciences, Materials Chemistry, Fourier transform infrared spectroscopy, A2. Single crystal growth, 010302 applied physics, ta114, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Secondary ion mass spectrometry, A2. Ammonothermal crystal growth, chemistry, Limiting oxygen concentration, B1. Bulk GaN, 0210 nano-technology, A1. Impurities
Abstract

The ammonothermal method is one of the most promising candidates for large-scale bulk GaN growth due to its scalability and high crystalline quality. However, emphasis needs to be put on understanding the incorporation and effects of impurities during growth. This article discusses how impurities are incorporated in different growth zones in basic ammonothermal GaN, and how they affect the structural, electrical and optical properties of the grown crystal. The influence of growth time on the impurity incorporation is also studied. We measure the oxygen, silicon, and carbon impurity concentrations using secondary ion mass spectrometry, and measure their effect on the lattice constant by high resolution x-ray diffraction (HR-XRD). We determine the resulting free carrier concentration by spatially resolved Fourier transform infrared spectroscopy and study the optical properties by spatially resolved low-temperature photoluminescence. We find that oxygen is incorporated preferentially in different growth regions and its incorporation efficiency depends on the growth direction. The oxygen concentration varies from 6.3×1020 cm-3 for growth on the 112-2 planes to 2.2×1019 cm-3 for growth on the (0001) planes, while silicon and carbon concentration variation is negligible. This results in a large variation in impurity concentration over a small length scale, which causes significant differences in the strain within the boule, as determined by HR-XRD on selected areas. The impurity concentration variation induces large differences in the free carrier concentration, and directly affects the photoluminescence intensity.

Published
2016

23. Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

Author

Timea Csengeri, Stefan Heyminck, S. F. Wampfler, Rolf Güsten, A. I. Gómez-Ruiz, Friedrich Wyrowski, Helmut Wiesemeyer, Karl Jacobs, Antoine Gusdorf, G. Pineau des Forêts, Karl M. Menten, Claudio Codella, Lars E. Kristensen, M. A. Requena-Torres, Silvia Leurini, D. R. Flower, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Division for Submm Technologies, Max-Planck-Institut für Radioastronomie (MPIFR), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Leibniz Institute for Crystal Growth, Leibniz Institute, Danish Meat Research Institute (DMRI), École normale supérieure - Paris (ENS Paris), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP)

Subjects
Astrochemistry, 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, 7. Clean energy, 0103 physical sciences, Protostar, 010303 astronomy & astrophysics, Hyperfine structure, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Line (formation), Physics, formation [stars], Stratospheric Observatory for Infrared Astronomy, astrochemistry, jets and outflows [ISM], ISM [infrared], Astronomy and Astrophysics, individual objects: Cep A [ISM], Astrophysics - Astrophysics of Galaxies, Redshift, Shock (mechanics), kinematics and dynamics [ISM], [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA)
Abstract

OH is a key molecule in H2O chemistry, a valuable tool for probing physical conditions, and an important contributor to the cooling of shock regions. OH participates in the re-distribution of energy from the protostar towards the surrounding ISM. Our aim is to assess the origin of the OH emission from the Cepheus A massive star-forming region and to constrain the physical conditions prevailing in the emitting gas. We thus want to probe the processes at work during the formation of massive stars. We present spectrally resolved observations of OH towards the outflows of Cepheus A with the GREAT spectrometer onboard the SOFIA telescope. Three triplets were observed at 1834.7 GHz, 1837.8 GHz, and 2514.3 GHz (163.4, 163.1, and 119.2 microns), at angular resolutions of 16.3", 16.3", and 11.9", respectively. We present the CO (16-15) spectrum at the same position. We compared the integrated intensities in the redshifted wings to shock models. The two triplets near 163 microns are detected in emission with blending hyperfine structure unresolved. Their profiles and that of CO can be fitted by a combination of 2 or 3 Gaussians. The observed 119.2 microns triplet is seen in absorption, since its blending hyperfine structure is unresolved, but with three line-of-sight components and a blueshifted emission wing consistent with that of the other lines. The OH line wings are similar to those of CO, suggesting that they emanate from the same shocked structure. Under this common origin assumption, the observations fall within the model predictions and within the range of use of our model only if we consider that four shock structures are caught in our beam. Our comparisons suggest that the observations might be consistently fitted by a J-type model with nH > 1e5 cm-3, v > 20 km/s, and with a filling factor of ~1. Such a high density is generally found in shocks associated to high-mass protostars., 10 pages, 7 figures, 5 tables

Published
2015
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24. Spectroscopically resolved far-IR observations of the massive star-forming region G5.89-0.39

Author

Heiko Richter, O. Ricken, Helmut Wiesemeyer, Rolf Güsten, Antoine Gusdorf, Karl M. Menten, Maryvonne Gerin, Friedrich Wyrowski, K. Jacobs, Silvia Leurini, Heinz-Wilhelm Hübers, François Levrier, Max-Planck-Institut für Radioastronomie (MPIFR), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Division for Submm Technologies, Leibniz Institute for Crystal Growth, Leibniz Institute, and École normale supérieure - Paris (ENS-PSL)

Subjects
010504 meteorology & atmospheric sciences, Flux, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, Spectral line, Luminosity, terahertz, 0103 physical sciences, Spectral resolution, Sternentstehung, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Line (formation), Physics, Line-of-sight, interstellares Medium, Astronomy and Astrophysics, Ferninfrarot, Astrophysics - Astrophysics of Galaxies, 13. Climate action, Space and Planetary Science, Excited state, Astrophysics of Galaxies (astro-ph.GA), [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], SOFIA
Abstract

The fine-structure line of [OI] at 63micron is an important diagnostic tool in different fields of astrophysics. However, our knowledge of this line relies on observations with low spectral resolution, and the real contribution of each component (PDR, jet) in complex environment of star-forming regions (SFRs) is poorly understood. We investigate the contribution of jet and PDR emission, and of absorption to the [OI]63micron line towards the ultra-compact H{\sc ii} region G5.89--0.39 and study its far-IR line luminosity in different velocity regimes through [OI], [CII], CO, OH, and H2O. We mapped G5.89--0.39 in [OI] and in CO(16--15) with the GREAT receiver onboard SOFIA. We observed the central position of the source in the OH^2\Pi_{3/2}, J=5/2\toJ=3/2 and ^2\Pi_{1/2}, J=3/2\toJ=1/2 lines. These data were complemented with APEX CO(6-5) and CO(7-6) and HIFI maps and single-pointing observations in [CII], H2O, and HF. The [OI] spectra in G5.89--0.39 are severely contaminated by absorptions from the envelope and from different clouds along the line of sight. Emission is detected only at HV, clearly associated with the compact north-south outflows traced by extremely HV low-J CO. The mass-loss rate and energetics of derived from [OI] agree well with estimates from CO, suggesting that the molecular outflows in G5.89--0.39 are driven by the jet system seen in [OI]. The far-IR line luminosity of G5.89--0.39 is dominated by [OI] at HV; the second coolant in this velocity regime is CO, while [CII], OH and H2O are minor contributors to the cooling in the outflow. Our study shows the importance of spectroscopically resolved data of [OI]63micron for using this line as diagnostic of SFRs. While this was not possible until now, the GREAT receiver onboard SOFIA has recently opened the possibility of detailed studies of this line to investigate its potential for probing different environments., Comment: A&A in press

Published
2015
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25. Detection of interstellar oxidaniumyl: Abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334

Author

C. Joblin, A. Di Giorgio, Olivier Berné, Sylvie Cabrit, Carsten Dominik, S. Pacheco, Paul F. Goldsmith, Charlotte Vastel, H. W. Yorke, Pieter Dieleman, G. Melnick, S.-L. Quin, F. F. S. van der Tak, M. Salez, Nathan R. Crockett, Sandrine Bottinelli, Andrew I. Harris, Doug Johnstone, Patrick W. Morris, Asunción Fuente, Juergen Stutzki, Frank Helmich, Claudio Codella, Sébastien Maret, David A. Neufeld, P. Saraceno, Neil Trappe, Adam Walters, Jonas Zmuidzinas, Robert Simon, Javier R. Goicoechea, C. McCoey, Tom Bell, Pierre Encrenaz, T. Jacq, M. H. D. van der Wiel, D. C. Lis, Carsten Kramer, Simon Bruderer, Pierre Hily-Blant, R. Plume, J. A. Murphy, F. Boulanger, A. Lorenzani, Karl Jacobs, Peter Schilke, Serena Viti, Mihkel Kama, S. Wang, N. Whyborn, Arnold O. Benz, Alain Baudry, Jesús Martín-Pintado, A. C. A. Boogert, Thomas G. Phillips, Stephan Schlemmer, Peter G. Martin, Martin Emprechtinger, K. Demyk, Milena Benedettini, Rolf Güsten, Edwin A. Bergin, Volker Ossenkopf, R. Rizzo, Audrey Coutens, Paola Caselli, D. Teyssier, Valentine Wakelam, Bhaswati Mookerjea, Shanshan Yu, Thomas F. Giesen, N. Crimier, Emmanuel Caux, Karl Schuster, Brunella Nisini, A. Bacman, C. Leinz, Alain Klotz, Claudia Comito, Markus Röllig, Cecilia Ceccarelli, M. Melchior, William D. Langer, A. G. G. M. Tielens, John C. Pearson, F. Daniel, Maryvonne Gerin, José Cernicharo, Geoffrey A. Blake, Holger S. P. Müller, Bertrand Lefloch, S. D. Lord, T. Klein, Karl M. Menten, Berengere Parise, E. Herbst, Marie-Lise Dubernet, Michel Perault, L. Pagani, Edith Falgarone, Claudine Kahane, Laboratoire Univers et Théories (LUTH (UMR_8102)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), SRON Netherlands Institute for Space Research (SRON), California Institute of Technology (CALTECH), Univ Cologne, Inst Phys 1, D-50937 Cologne, Germany, Univ Cologne, Inst Phys 1, Max Planck Institute for Radio Astronomy, Max-Planck-Institut für Extraterrestrische Physik (MPE), Department of Astronomy [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), FORMATION STELLAIRE 2010, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), Institute of Astronomy [ETH Zürich], Department of Physics [ETH Zürich] (D-PHYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich)-Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Laboratoire Optimisation de la Conception et Ingénierie de l'Environnement (LOCIE), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Univ Toulouse UPS, Ctr Etud Spatiale Rayonnements, F-31062 Toulouse 9, France, Centre Etud Spatiale Rayonnements Toulouse, CNRS INSU, UMR 5187, F-31028 Toulouse 4, France, UMR 5187 Toulouse, Ctr Astrobiol CSIC INTA, Lab Astrofis Mol, Madrid 28850, Spain, Ctr Astrobiol CSIC INTA, Lab Astrofis Mol, Madrid, École normale supérieure - Paris (ENS Paris), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Cahill Center for Astronomy and Astrophysics, Laboratoire de Radioastronomie (LRA), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), foreign laboratories (FL), CERN [Genève], Ohio State Univ, Dept Phys, Columbus, OH 43210 USA, Ohio State University [Columbus] (OSU), Ohio State Univ, Dept Astron & Chem, Columbus, OH 43210 USA, Leibniz Institute for Crystal Growth, Leibniz Institute, Natl Res Council Canada, Herzberg Inst Astrophys, Victoria, BC V9E 2E7 Canada, Natl Res Council Canada, Herzberg Inst Astrophys, Victoria, Max-Planck-Institut für Radioastronomie (MPIFR), Observatoire de Haute-Provence (OHP), Institut Pythéas (OSU PYTHEAS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), Laboratoire de Modélisation Multi-échelles des Combustibles (LM2C), Service d'Etudes de Simulation du Comportement du combustibles (SESC), Département d'Etudes des Combustibles (DEC), CEA-Direction de l'Energie Nucléaire (CEA-DEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction de l'Energie Nucléaire (CEA-DEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, KOSMA, I. Physikalisches Institut, Universität zu Köln, CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA, CALTECH, Ctr Infrared Proc & Anal, Pasadena, Osservatorio di Astrofisica di Roma (OAR), Department of Physics and Astronomy [Calgary], University of Calgary, Istituto di Fisica dello Spazio Interplanetario (IFSI), Consiglio Nazionale delle Ricerche (CNR), Helmholtz zentrum für Schwerionenforschung GmbH (GSI), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Laboratoire de Didactique André Revuz (LDAR (EA_4434)), Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Université Paris Diderot - Paris 7 (UPD7)-Université d'Artois (UA), AMOR 2010, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Low Energy Astrophysics (API, FNWI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), I. Physikalisches Institut [Köln], Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Université Paris sciences et lettres (PSL), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Smithsonian Institution-Harvard University [Cambridge], INAF - Osservatorio Astronomico di Roma (OAR), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Universität zu Köln = University of Cologne, Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Universiteit Leiden, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Harvard University-Smithsonian Institution, Infrared Processing and Analysis Center (IPAC), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Université d'Artois (UA)-Université Paris Diderot - Paris 7 (UPD7)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12), Astronomy, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])

Subjects
Experimental Physics, molecular data, Continuum (design consultancy), Rotational transition, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, LASER MAGNETIC-RESONANCE, 01 natural sciences, ISM: clouds, Spectral line, ISM: abundances, 0103 physical sciences, ABSORPTION, Absorption (electromagnetic radiation), 010303 astronomy & astrophysics, Hyperfine structure, Astrophysics::Galaxy Astrophysics, QB, Line (formation), Physics, Range (particle radiation), SPECTROSCOPY, IDENTIFICATION, 010308 nuclear & particles physics, astrochemistry, NGC-6334, OH, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, ISM: molecules, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], COMET-KOHOUTEK, Space and Planetary Science, GROUND-STATE, Astrophysics of Galaxies (astro-ph.GA), Outflow, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], EMISSION, ROTATIONAL SPECTRUM, line: identification
Abstract

We identify a prominent absorption feature at 1115 GHz, detected in first HIFI spectra towards high-mass star-forming regions, and interpret its astrophysical origin. The characteristic hyperfine pattern of the H2O+ ground-state rotational transition, and the lack of other known low-energy transitions in this frequency range, identifies the feature as H2O+ absorption against the dust continuum background and allows us to derive the velocity profile of the absorbing gas. By comparing this velocity profile with velocity profiles of other tracers in the DR21 star-forming region, we constrain the frequency of the transition and the conditions for its formation. In DR21, the velocity distribution of H2O+ matches that of the [CII] line at 158\mu\m and of OH cm-wave absorption, both stemming from the hot and dense clump surfaces facing the HII-region and dynamically affected by the blister outflow. Diffuse foreground gas dominates the absorption towards Sgr B2. The integrated intensity of the absorption line allows us to derive lower limits to the H2O+ column density of 7.2e12 cm^-2 in NGC 6334, 2.3e13 cm^-2 in DR21, and 1.1e15 cm^-2 in Sgr B2., Comment: Accepted for publication in A&A

Published
2010
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26. Low-temperature chemical bath deposition of crystalline ZnO

Author

D. V. Balitsky, Philippe Papet, Pascale Armand, K. Jacobs, Leibniz Institute for Crystal Growth, Leibniz Institute, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Inorganic chemistry, Hydrothermal growth, Crystal growth, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Hydrothermal circulation, nanocrystals, Zinc oxide, Hydrothermal synthesis, General Materials Science, Solubility, ComputingMilieux_MISCELLANEOUS, Aqueous solution, Chemistry, Substrate (chemistry), General Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, chemical bath deposition, Nanocrystal, Chemical engineering, 0210 nano-technology, Chemical bath deposition
Abstract

ZnO crystals can be grown from alkaline aqueous solution not only by the standard hydrothermal technique at temperatures between 350 °C and 400 °C, but also by chemical bath deposition (CBD) at temperatures below 100 °C. In the presence of ZnO and ScAlMgO4 (SCAM) substrates almost all ZnO deposits on the substrate, with different habits, however. Under optimized conditions even homoepitaxial layers can be obtained, while rod-like structures are obtained on SCAM substrates. The chemistry and the driving forces behind the two processes are considered in detail and the temperature dependence of the solution composition has been calculated. The driving force for the ZnO crystal growth in the standard hydrothermal technique is the difference in the ZnO solubility in alkaline solutions at different temperatures. In contrast, the driving force for the chemical bath deposition of ZnO at low temperatures is the decay of zinc ion complex molecules with increasing temperature.

Published
2010
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27. The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI)

Author

Brian Jackson, B. Kopf, R. Bieber, R. Güsten, A. M. di Giorgio, J. A. Stern, Holger S. P. Müller, B. J. van Leeuwen, G. S. Liu, R. Orfei, Neal R. Erickson, R. Lai, B. Delforges, Wolfgang Wild, Christian Leinz, O. Coeur-Joly, J. Desbat, David Teyssier, S. D. Lord, Karl Jacobs, Bruce Bumble, Lorene Samoska, M. Rataj, R. H. Lin, Dominicus Kester, M. Salez, X. Tielens, Alexandre Karpov, Paolo Saraceno, K. Edwards, R. Huisman, A. Megej, K. F. Schuster, Michel Fich, L. Dubbeldam, Serguei Cherednichenko, H. Golstein, Christian Monstein, J. A. Murphy, C. van Baaren, Victor Belitsky, P. Planesas, E. Natale, Michael Olberg, Lorenzo Piazzo, T. Peacock, Martin Eggens, Emmanuel Caux, W. A. Hatch, Neil Trappe, Hubregt J. Visser, Herbert Zirath, Jaap Evers, S. Phillip-May, Alain Maestrini, Hamid Javadi, Jacob Kooi, Th. de Graauw, F. Schmülling, E. C. Honingh, C. McCoey, J. C. Pearson, W. Luinge, I. Lopez-Fernandez, W. M. Laauwen, M. Michalska, Bengt Larsson, S. Wulff, John Gill, René Liseau, Volker Ossenkopf, Colin Borys, B. Kruizenga, Rafael Teipen, C. Kramer, A. Cros, H. Goulooze, P. Cais, W. Nowosielski, Goutam Chattopadhyay, M. Stokroos, Rafael Bachiller, F. Zwart, C. Gal, Piotr Orleanski, J. Kawamura, H. Smit, O. Siebertz, H. Aarts, Francesco Nuzzolo, L. Meinsma, Jonas Zmuidzinas, R. Assendorp, D. A. Beintema, H. van de Stadt, Jesús Martín-Pintado, G. de Lange, Ryszard Szczerba, Erich Schlecht, R. Higgins, Christophe Risacher, Patrick W. Morris, H. Jacobs, Christopher Jarchow, Willem Jellema, Pieter Dieleman, Todd Gaier, B. Franke, J. Stutzki, Imran Mehdi, Th. Klein, Harald Franz Arno Merkel, T. Finn, M. Justen, P.R. Wesselius, M. Ciechanowicz, T. M. Klapwijk, Hans-Joachim Wunsch, C. Comito, P. Zaal, Erik L. Kollberg, C. Diez-Gonzalez, T. den Boggende, John Ward, Jian-Rong Gao, Pasquale Cerulli-Irelli, C. Kasemann, T. Kuhn, Frank Helmich, K. Wildeman, Henry G. LeDuc, L. Ravera, Frank Maiwald, Y. Delorme, D. Moratschke, F. Schlöder, J. M. Krieg, M. Olbrich, A. Marston, Juan Daniel Gallego, P.-P. Kooiman, E. Steinmetz, T. Gunsing, A. Naber, M. Melchior, Geert Keizer, M. Schultz, I. Peron, S. Gauffre, C. K. Wafelbakker, N. Whyborn, M. Krause, T. Tils, Alexander Loose, A. de Jonge, Pieter R. Roelfsema, Rudolf Schieder, M. Caris, S. Glenz, A. Barcia, W. Baechtold, Paul Hartogh, R. Shipman, Adwin Boogert, Arnold O. Benz, Thomas G. Phillips, California Institute of Technology (CALTECH), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Université Sciences et Technologies - Bordeaux 1, Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology [Gothenburg, Sweden], Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Dept Pathol & Microbiol, Université de Montréal (UdeM)-Faculté de médecine vétérinaire, Leibniz Institute for Crystal Growth, Leibniz Institute, Technische Universität Darmstadt (TU Darmstadt), Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster (WWU), Institute of Molecular Medicine and Cell Research (ZBMZ), University of Freiburg [Freiburg], Onsala Space Observatory, Chalmers University of Technology [Göteborg], ESO, European Southern Observatory (ESO), Istituto di Fisica dello Spazio Interplanetario (IFSI), Consiglio Nazionale delle Ricerche (CNR), Max Planck Institute for Meteorology (MPI-M), Institut für Chemie und Dynamik der Geosphäre - Troposphäre (ICG-2), Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association-Helmholtz-Gemeinschaft = Helmholtz Association, Herschel Science Center [Madrid], European Space Astronomy Centre (ESAC), European Space Agency (ESA)-European Space Agency (ESA), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), École normale supérieure - Paris (ENS-PSL), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Technische Universität Darmstadt - Technical University of Darmstadt (TU Darmstadt), Westfälische Wilhelms-Universität Münster = University of Münster (WWU), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), TNO Industrie en Techniek, and Astronomy

Subjects
Experimental Physics, Local oscillator, Observatories, Orbits, general [Submillimeter], 01 natural sciences, 7. Clean energy, spectroscopic [Techniques], law.invention, Far infrared, Spectrographs, law, spectrographs [Instrumentation], 010303 astronomy & astrophysics, instrumentation: spectrographs, Physics, Spectrometers, submillimeter: general, Bolometers, Correlators, methods: observational, infrared: general, Heterodyne, Frequency band, Submillimeter: generals, Instantaneous phase, Radio spectrum, Optics, Mixers (machinery), 0103 physical sciences, Frequency bands, observational [Methods], 010306 general physics, Remote sensing, techniques: spectroscopic, Spectrometer, business.industry, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Bolometer, generals [Submillimeter], Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Launching, general [Infrared], Space and Planetary Science, Heterodyning, Instruments, business
Abstract

International audience; Aims: This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods: The instrument is a set of 7 heterodyne receivers that are electronically tuneable, covering 480-1250 GHz with SIS mixers and the 1410-1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s-1. Results: After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Published
2010
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29. Low-temperature Hydrothermal Growth of ZnO nanocrystals and epitaxial layers

Author

Balitsky, Denis, Jacobs, K., Gogova, D., Schulz, D., Klimm, D., Papet, Philippe, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Leibniz Institute for Crystal Growth, and Leibniz Institute

Subjects
crystal growth, ZnO, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.INOR]Chemical Sciences/Inorganic chemistry
Abstract

ZnO crystals can be grown from alkaline hydrous solutions at temperatures between 100 oC and 200 oC. Here, the driving force is obviously an increase in temperature, leading to the destruction of soluble complex Zn containing cations. Without the presence of a substrate, ZnO nanocrystals in a great morphological variety are grown. The presence of an almost lattice-matched substrate leads to the preferred deposition of ZnO on this substrate. ZnO nanorods that are mostly aligned parallel, but also agglomerates of such nanocrystals are grown. Under optimum conditions even epitaxial layers of ZnO can be obtained.

Published
2008

30. Charge-Controlled Energy Optimization of the Reconstruction of Semiconductor Surfaces: sp 3 - sp 2 Transformation of Stoichiometric GaN(0001) Surface to (4 × 4) Pattern.

Author

Strak P, Miller W, and Krukowski S

Abstract

It was demonstrated by ab initio calculations that energy optimization in the reconstruction of semiconductor surfaces is controlled by the global charge balance. The charge control was discovered during simulations of the influence of heavy doping in the GaN bulk, which changes sp 3 to sp 2 ratio in the reconstruction of stoichiometric GaN(0001), i.e., a Ga-polar surface. Thus, the reconstruction is not limited to the charge in the surface only; it can be affected by the charge in the bulk. The discovered new reconstruction of the GaN(0001) surface is (4 × 4), which is different from the previously reported (2 × 1) pattern. The undoped GaN reconstruction is surface charge controlled; accordingly, (3/8) top-layer Ga atoms remain in a standard position with sp 3 hybridized bonding, while the remaining (5/8) top-layer Ga atoms are shifted into the plane of N atoms with sp 2 hybridized bonding. The change in the charge balance caused by doping in the bulk leads to a change or disappearance of the reconstruction pattern.

Published
2024
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31. Scintillation and radioluminescence mechanism in β-Ga 2 O 3 semiconducting single crystals.

Author

Wojtowicz AJ, Witkowski ME, Drozdowski W, Makowski M, and Galazka Z

Abstract

In this paper, we present the results of experiments on samples of β-Ga 2 O 3 single crystals under a project aimed at assessing and improving the scintillation performance of this material by studying scintillation and radioluminescence mechanism and its limitations. In addition to standard experiments, such as scintillation light yields and time profiles, radio-, and thermoluminescence, we developed and tested a new and promising two-beam experiment, in which a sample is excited by an X-ray beam and additionally stimulated by an IR laser diode. Fe and Mg doping compensate for the inherent n-type conductivity of β-Ga 2 O 3 to obtain semi-insulating single crystals for large-area substrates and wafers. At the same time, residual Fe and Ir are ubiquitous uncontrolled impurities leached from the Ir crucibles used to grow large bulk crystals by the Czochralski method. For these experiments, we selected four samples cut from the Czochralski grown 2-cm diameter β-Ga 2 O 3 single crystal boules; one with a reduced Fe content, two unintentionally Fe- and Ir-doped (UID) with lower and higher Fe content, and one doped with Mg. We find that steady-state radioluminescence spectra measured at temperatures between 10 and 350 K are dominated by the UV emission peaking at about 350-370 nm. Unfortunately, even for the best sample with a reduced Fe-content, the intensity of this emission drops precipitously with the temperature down to about 10 % at 300 K. From the two-beam experiments, we conclude that recombination via inadvertent Fe impurity involving three charge states (2+, 3+, and 4+) may reduce a steady-state UV emission of β-Ga 2 O 3 under X-ray excitation by as much as 60-70 %, one-third to one-half of which is due to the recombination (specific for Fe-doped β-Ga 2 O 3 ) involving the 4+ and 3+ charge states of Fe and the remaining 50-70 % being due to a more familiar route typical of other oxides, involving the 2+ and 3+ charge states of Fe. These losses are at higher temperatures enhanced by a thermally activated redistribution of self-trapped holes (STHs). In addition, the trapping of electrons by Fe and holes by Mg, Fe, and Ir may be responsible for scintillation light loss and reduction of the zero-time amplitude essential for the fast timing scintillation applications. Despite indirect evidence of competitive recombination in β-Ga 2 O 3 involving a deep Ir 3+/4+ donor level, we could not quantitatively assess losses of the UV steady state radioluminescence light due to the inadvertent Ir impurity., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Published
2023
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32. Role of Metal Vacancies in the Mechanism of Thermal Degradation of InGaN Quantum Wells.

Author

Smalc-Koziorowska J, Grzanka E, Lachowski A, Hrytsak R, Grabowski M, Grzanka S, Kret S, Czernecki R, Turski H, Marona L, Markurt T, Schulz T, Albrecht M, and Leszczynski M

Abstract

In this work, we study the thermal degradation of In-rich In x Ga 1- x N quantum wells (QWs) and propose explanation of its origin based on the diffusion of metal vacancies. The structural transformation of the In x Ga 1- x N QWs is initiated by the formation of small initial voids created due to agglomeration of metal vacancies diffusing from the layers beneath the QW. The presence of voids in the QW relaxes the mismatch stress in the vicinity of the void and drives In atoms to diffuse to the relaxed void surroundings. The void walls enriched in In atoms are prone for thermal decomposition, what leads to a subsequent disintegration of the surrounding lattice. The phases observed in the degraded areas of QWs contain voids partly filled with crystalline In and amorphous material, surrounded by the rim of high In-content In x Ga 1- x N or pure InN; the remaining QW between the voids contains residual amount of In. In the case of the In x Ga 1- x N QWs deposited on the GaN layer doped to n-type or on unintentionally doped GaN, we observe a preferential degradation of the first grown QW, while doping of the underlying GaN layer with Mg prevents the degradation of the closest In x Ga 1- x N QW. The reduction in the metal vacancy concentration in the In x Ga 1- x N QWs and their surroundings is crucial for making them more resistant to thermal degradation.

Published
2021
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33. Single-photon emission from isolated monolayer islands of InGaN.

Author

Sun X, Wang P, Wang T, Chen L, Chen Z, Gao K, Aoki T, Li M, Zhang J, Schulz T, Albrecht M, Ge W, Arakawa Y, Shen B, Holmes M, and Wang X

Abstract

We identify and characterize a novel type of quantum emitter formed from InGaN monolayer islands grown using molecular beam epitaxy and further isolated via the fabrication of an array of nanopillar structures. Detailed optical analysis of the characteristic emission spectrum from the monolayer islands is performed, and the main transmission is shown to act as a bright, stable, and fast single-photon emitter with a wavelength of ~400 nm., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© The Author(s) 2020.)

Published
2020
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34. Transport Properties and Finite Size Effects in β-Ga 2 O 3 Thin Films.

Author

Ahrling R, Boy J, Handwerg M, Chiatti O, Mitdank R, Wagner G, Galazka Z, and Fischer SF

Abstract

Thin films of the wide band gap semiconductor β-Ga 2 O 3 have a high potential for applications in transparent electronics and high power devices. However, the role of interfaces remains to be explored. Here, we report on fundamental limits of transport properties in thin films. The conductivities, Hall densities and mobilities in thin homoepitaxially MOVPE grown (100)-orientated β-Ga 2 O 3 films were measured as a function of temperature and film thickness. At room temperature, the electron mobilities ((115 ± 10) cm 2 /Vs) in thicker films (>150 nm) are comparable to the best of bulk. However, the mobility is strongly reduced by more than two orders of magnitude with decreasing film thickness ((5.5 ± 0.5) cm 2 /Vs for a 28 nm thin film). We find that the commonly applied classical Fuchs-Sondheimer model does not explain sufficiently the contribution of electron scattering at the film surfaces. Instead, by applying an electron wave model by Bergmann, a contribution to the mobility suppression due to the large de Broglie wavelength in β-Ga 2 O 3 is proposed as a limiting quantum mechanical size effect.

Published
2019
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35. Ferroelectric monoclinic phases in strained K 0.70 Na 0.30 NbO 3 thin films promoting selective surface acoustic wave propagation.

Author

von Helden L, Schmidbauer M, Liang S, Hanke M, Wördenweber R, and Schwarzkopf J

Abstract

We present a detailed analysis of the ferroelectric domain structure of K 0.70 Na 0.30 NbO 3 thin films on (110) TbScO 3 grown by metal-organic chemical vapor deposition. Upon piezoresponse force microscopy and nanofocus x-ray diffraction measurements we derive a domain model revealing monoclinic M C domains. The complex domain pattern is formed out of four co-existing in-plane orientations of the shearing direction of the monoclinic unit cell resulting in four types of superdomains each being composed of well-ordered stripe domains. Finally, we present surface acoustic wave (SAW) experiments that exhibit extraordinary signal intensities given the low thickness of the tested film. Moreover, the SAW propagation is found to occur selectively along the identified shearing directions.

Published
2018
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36. Electrical and optical properties of epitaxial binary and ternary GeTe-Sb 2 Te 3 alloys.

Author

Boschker JE, Lü X, Bragaglia V, Wang R, Grahn HT, and Calarco R

Abstract

Phase change materials such as pseudobinary GeTe-Sb 2 Te 3 (GST) alloys are an essential part of existing and emerging technologies. Here, we investigate the electrical and optical properties of epitaxial phase change materials: α-GeTe, Ge 2 Sb 2 Te5 (GST225), and Sb 2 Te 3 . Temperature-dependent Hall measurements reveal a reduction of the hole concentration with increasing temperature in Sb 2 Te 3 that is attributed to lattice expansion, resulting in a non-linear increase of the resistivity that is also observed in GST225. Fourier transform infrared spectroscopy at room temperature demonstrates the presence of electronic states within the energy gap for α-GeTe and GST225. We conclude that these electronic states are due to vacancy clusters inside these two materials. The obtained results shed new light on the fundamental properties of phase change materials such as the high dielectric constant and persistent photoconductivity and have the potential to be included in device simulations.

Published
2018
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37. Hierarchy and scaling behavior of multi-rank domain patterns in ferroelectric K 0.9 Na 0.1 NbO 3 strained films.

Author

Braun D, Schmidbauer M, Hanke M, and Schwarzkopf J

Abstract

The formation process of a ferroelectric multi-rank domain pattern in the thickness range of 7-52 nm is investigated for monoclinic K 0.9 Na 0.1 NbO 3 strained epitaxial films on (110) NdScO 3 substrates. Although the elastic strain energy density is degenerated for two pseudocubic orientations, a distinctive hierarchy of domain evolution is observed with exclusive in-plane a 1 a 2 domains for very thin films and the retarded onset of a ferroelectric M C phase at larger film thickness. This is accompanied by a thickness dependent transformation from stripe domains to a herringbone pattern and, eventually, for the thickest film, to a checkerboard-like structure. These transformations in the domain arrangement and width are correlated to energetic aspects as depolarization field and anisotropic strain relaxation in the film. While for the M C domains plastic strain relaxation is throughout observed, the a 1 a 2 domains show a two-step strain relaxation mechanism starting with an in-plane elastic shearing, which is followed by plastic lattice relaxation. Our results highlight a pathway for engineering and patterning of periodic ferroelectric domain structures.

Published
2018
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38. Bulk Single Crystal-Like Structural and Magnetic Characteristics of Epitaxial Spinel Ferrite Thin Films with Elimination of Antiphase Boundaries.

Author

Singh AV, Khodadadi B, Mohammadi JB, Keshavarz S, Mewes T, Negi DS, Datta R, Galazka Z, Uecker R, and Gupta A

Abstract

Spinel ferrite NiFe 2 O 4 thin films have been grown on three isostructural substrates, MgAl 2 O 4 , MgGa 2 O 4 , and CoGa 2 O 4 using pulsed laser deposition. These substrates have lattice mismatches of 3.1%, 0.8%, and 0.2%, respectively, with NiFe 2 O 4 . As expected, the films grown on MgAl 2 O 4 substrate show the presence of the antiphase boundary defects. However, no antiphase boundaries (APBs) are observed for films grown on near-lattice-matched substrates MgGa 2 O 4 and CoGa 2 O 4 . This demonstrates that by using isostructural and lattice-matched substrates, the formation of APBs can be avoided in NiFe 2 O 4 thin films. Consequently, static and dynamic magnetic properties comparable with the bulk can be realized. Initial results indicate similar improvements in film quality and magnetic properties due to the elimination of APBs in other members of the spinel ferrite family, such as Fe 3 O 4 and CoFe 2 O 4 , which have similar crystallographic structure and lattice constants as NiFe 2 O 4 ., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2017
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39. Strain engineering of monoclinic domains in K x Na 1-x NbO 3 epitaxial layers: a pathway to enhanced piezoelectric properties.

Author

Schmidbauer M, Braun D, Markurt T, Hanke M, and Schwarzkopf J

Abstract

A novel concept to obtain a ferroelectric material with enhanced piezoelectric properties is proposed. This approach is based on the combination of two pathways: (i) the evolution of a ferroelectric monoclinic phase and, (ii) the coexistence of different types of ferroelectric domains leading to polarization discontinuities at the domain walls. Each of these pathways enables polarization rotation in the material which is responsible for giant piezoelectricity. Targeted incorporation of anisotropic epitaxial lattice strain is used to implement this approach. The feasibility of our concept is demonstrated for K 0.9 Na 0.1 NbO 3 epitaxial layers grown on NdScO 3 substrates where the coexistence of (100) pc and (001) pc pseudocubic oriented monoclinic domains is experimentally verified. This coexistence results in a complex periodic domain pattern with alternating emergence of ferroelectric in-plane a 1 a 2 and inclined M C monoclinic phases, which differ in the direction of the electrical polarization vector. Our approach opens the possibility to exploit ferroelectric properties in both vertical and lateral directions and to achieve enhanced piezoelectric properties in lead-free material caused by singularities at the domains walls.

Published
2017
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40. Exciton emission of quasi-2D InGaN in GaN matrix grown by molecular beam epitaxy.

Author

Ma D, Rong X, Zheng X, Wang W, Wang P, Schulz T, Albrecht M, Metzner S, Müller M, August O, Bertram F, Christen J, Jin P, Li M, Zhang J, Yang X, Xu F, Qin Z, Ge W, Shen B, and Wang X

Abstract

We investigate the emission from confined excitons in the structure of a single-monolayer-thick quasi-two-dimensional (quasi-2D) In x Ga 1-x N layer inserted in GaN matrix. This quasi-2D InGaN layer was successfully achieved by molecular beam epitaxy (MBE), and an excellent in-plane uniformity in this layer was confirmed by cathodoluminescence mapping study. The carrier dynamics have also been investigated by time-resolved and excitation-power-dependent photoluminescence, proving that the recombination occurs via confined excitons within the ultrathin quasi-2D InGaN layer even at high temperature up to ~220 K due to the enhanced exciton binding energy. This work indicates that such structure affords an interesting opportunity for developing high-performance photonic devices.

Published
2017
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41. Melt growth and properties of bulk BaSnO 3 single crystals.

Author

Galazka Z, Uecker R, Irmscher K, Klimm D, Bertram R, Kwasniewski A, Naumann M, Schewski R, Pietsch M, Juda U, Fiedler A, Albrecht M, Ganschow S, Markurt T, Guguschev C, and Bickermann M

Abstract

We present the first-time growth of bulk BaSnO 3 single crystals from the melt by direct solidification, their basic electrical and optical properties as well as their structural quality. Our measurement of the melting point (MP) of BaSnO 3 amounts to 1855 °C  ±  25 K. At this temperature an intensive decomposition and non-stoichiometric evaporation takes place as the partial pressure of SnO(g) is about 90 times higher than that of BaO(g). X ray powder diffraction identified only the BaSnO 3 perovskite phase, while narrow rocking curves having a full width at half maximum of 26 arcsec and etch pit densities below 10 6 cm -2 confirm a high degree of structural perfection of the single crystals. In this respect they surpass the structural properties of those single crystals that were reported in the literature. The electrical conductivity of nominally undoped crystals depends on the growth conditions and ranges from insulating to medium n-type conductivity. After post-growth annealing in an oxidizing atmosphere undoped crystals are generally insulating. Doping the crystals with lanthanum during growth results in a high n-type conductivity. For a La doping concentration of 0.123 wt.% we measured an electron concentration of 3.3  ×  10 19 cm -3 and an electron mobility of 219 cm 2 V -1 s -1 . Based on optical absorption measurements we determined an energy of 3.17  ±  0.04 eV at 5 K and of 2.99  ±  0.04 eV at 297 K for the indirect band gap of BaSnO 3 .

Published
2017
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42. Contactless processing of SiGe-melts in EML under reduced gravity.

Author

Luo Y, Damaschke B, Schneider S, Lohöfer G, Abrosimov N, Czupalla M, and Samwer K

Abstract

The processing of semiconductors based on electromagnetic levitation is a challenge, because this kind of materials shows a poor electrical conductivity. Here, we report the results of measurements of the thermophysical properties obtained recently from highly doped semiconductors Si 1- x Ge x under microgravity conditions in the framework of parabola flight campaigns. Due to the limited time of about 20 s of microgravity especially Ge-rich samples with low melting temperatures were investigated. The measurements were performed contactlessly by video techniques with subsequent digital image processing. Linear and volume thermal expansion coefficients were measured hereby from image data. An anomaly of volume changes near the solidus temperature is visible. Viscosity and surface tension were determined by the oscillating drop technique using optic and electronic data. It was observed that the alloying of Si into Ge increases the surface tension of the melts. The viscosity is following an Arrhenius equation and shows a crossover temperature which separates simple liquid at high temperatures from cooperative liquid at low temperatures.

Published
2016
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43. High-Output-Power Ultraviolet Light Source from Quasi-2D GaN Quantum Structure.

Author

Rong X, Wang X, Ivanov SV, Jiang X, Chen G, Wang P, Wang W, He C, Wang T, Schulz T, Albrecht M, Jmerik VN, Toropov AA, Ratnikov VV, Kozlovsky VI, Martovitsky VP, Jin P, Xu F, Yang X, Qin Z, Ge W, Shi J, and Shen B

Abstract

Quasi-2D GaN layers inserted in an AlGaN matrix are proposed as a novel active region to develop a high-output-power UV light source. Such a structure is successfully achieved by precise control in molecular beam epitaxy and shows an amazing output power of ≈160 mW at 285 nm with a pulsed electron-beam excitation. This device is promising and competitive in non-line-of-sight communications or the sterilization field., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2016
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44. Surface effects of vapour-liquid-solid driven Bi surface droplets formed during molecular-beam-epitaxy of GaAsBi.

Author

Steele JA, Lewis RA, Horvat J, Nancarrow MJ, Henini M, Fan D, Mazur YI, Schmidbauer M, Ware ME, Yu SQ, and Salamo GJ

Abstract

Herein we investigate a (001)-oriented GaAs1-xBix/GaAs structure possessing Bi surface droplets capable of catalysing the formation of nanostructures during Bi-rich growth, through the vapour-liquid-solid mechanism. Specifically, self-aligned "nanotracks" are found to exist trailing the Bi droplets on the sample surface. Through cross-sectional high-resolution transmission electron microscopy the nanotracks are revealed to in fact be elevated above surface by the formation of a subsurface planar nanowire, a structure initiated mid-way through the molecular-beam-epitaxy growth and embedded into the epilayer, via epitaxial overgrowth. Electron microscopy studies also yield the morphological, structural, and chemical properties of the nanostructures. Through a combination of Bi determination methods the compositional profile of the film is shown to be graded and inhomogeneous. Furthermore, the coherent and pure zincblende phase property of the film is detailed. Optical characterisation of features on the sample surface is carried out using polarised micro-Raman and micro-photoluminescence spectroscopies. The important light producing properties of the surface nanostructures are investigated through pump intensity-dependent micro-PL measurements, whereby relatively large local inhomogeneities are revealed to exist on the epitaxial surface for important optical parameters. We conclude that such surface effects must be considered when designing and fabricating optical devices based on GaAsBi alloys.

Published
2016
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45. Strain Control of Fermiology and Many-Body Interactions in Two-Dimensional Ruthenates.

Author

Burganov B, Adamo C, Mulder A, Uchida M, King PD, Harter JW, Shai DE, Gibbs AS, Mackenzie AP, Uecker R, Bruetzam M, Beasley MR, Fennie CJ, Schlom DG, and Shen KM

Abstract

Here we demonstrate how the Fermi surface topology and quantum many-body interactions can be manipulated via epitaxial strain in the spin-triplet superconductor Sr_{2}RuO_{4} and its isoelectronic counterpart Ba_{2}RuO_{4} using oxide molecular beam epitaxy, in situ angle-resolved photoemission spectroscopy, and transport measurements. Near the topological transition of the γ Fermi surface sheet, we observe clear signatures of critical fluctuations, while the quasiparticle mass enhancement is found to increase rapidly and monotonically with increasing Ru-O bond distance. Our work demonstrates the possibilities for using epitaxial strain as a disorder-free means of manipulating emergent properties, many-body interactions, and potentially the superconductivity in correlated materials.

Published
2016
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46. Three dimensional analysis of the composition in solid alloys by variable probe in scanning transmission electron microscopy.

Author

Rotunno E, Albrecht M, Markurt T, Remmele T, and Grillo V

Abstract

This paper reports on a novel approach to quantitatively reconstruct the column by column composition and the 3D distribution of guest atoms inside a host matrix by scanning transmission electron microscopy high angle annular dark field technique. We propose a new mathematical framework that allows to jointly analyze the information from a set of experiments with variable beam convergence and/or defocus. Our scheme allows to reconstruct the atomic distribution along the imaged columns from the measured intensity, for any dependence of the probe intensity on the depth. It is therefore well suited to incorporate channeling effects that are usually neglected in other approaches. As a case study, we focus here on the systematic variation of the beam convergence that permits to set the maximum of the channeling oscillations at different depths. We aim here to define the reliability and the limitation of this technique by the application of the method to accurate dynamic simulations in the case of the InGaN alloy., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Published
2014
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47. Electronic materials with a wide band gap: recent developments.

Author

Klimm D

Abstract

The development of semiconductor electronics is reviewed briefly, beginning with the development of germanium devices (band gap E g = 0.66 eV) after World War II. A tendency towards alternative materials with wider band gaps quickly became apparent, starting with silicon (E g = 1.12 eV). This improved the signal-to-noise ratio for classical electronic applications. Both semiconductors have a tetrahedral coordination, and by isoelectronic alternative replacement of Ge or Si with carbon or various anions and cations, other semiconductors with wider E g were obtained. These are transparent to visible light and belong to the group of wide band gap semiconductors. Nowadays, some nitrides, especially GaN and AlN, are the most important materials for optical emission in the ultraviolet and blue regions. Oxide crystals, such as ZnO and β-Ga2O3, offer similarly good electronic properties but still suffer from significant difficulties in obtaining stable and technologically adequate p-type conductivity.

Published
2014
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48. Blocking growth by an electrically active subsurface layer: the effect of Si as an antisurfactant in the growth of GaN.

Author

Markurt T, Lymperakis L, Neugebauer J, Drechsel P, Stauss P, Schulz T, Remmele T, Grillo V, Rotunno E, and Albrecht M

Abstract

Combining aberration corrected high resolution transmission electron microscopy and density functional theory calculations we propose an explanation of the antisurfactant effect of Si in GaN growth. We identify the atomic structure of a Si delta-doped layer (commonly called SiN(x) mask) as a SiGaN(3) monolayer that resembles a √3×√3 R30° surface reconstruction containing one Si atom, one Ga atom, and a Ga vacancy (V(Ga)) in its unit cell. Our density functional theory calculations show that GaN growth on top of this SiGaN(3) layer is inhibited by forming an energetically unfavorable electrical dipole moment that increases with layer thickness and that is caused by charge transfer between cation dangling bonds at the surface to V(Ga) bound at subsurface sites.

Published
2013
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49. High-precision absolute lattice parameter determination of SrTiO3, DyScO3 and NdGaO3 single crystals.

Author

Schmidbauer M, Kwasniewski A, and Schwarzkopf J

Abstract

The lattice parameters of three perovskite-related oxides have been measured with high precision at room temperature. An accuracy of the order of 10(-5) has been achieved by applying a sophisticated high-resolution X-ray diffraction technique which is based on the modified Bond method. The results on cubic SrTiO(3) [a = 3.905268 (98) Å], orthorhombic DyScO(3) [a = 5.442417 (54), b = 5.719357 (52) and c = 7.904326 (98) Å], and orthorhombic NdGaO(3) [a = 5.428410 (54), b = 5.498407 (55) and c = 7.708878 (95) Å] are discussed in view of possible systematic errors as well as non-stoichiometry in the crystals., (© 2012 International Union of Crystallography)

Published
2012
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50. Evolution of cellular structures during Ge 1-x Si x single-crystal growth by means of a modified phase-field method.

Author

Miller W, Rasin I, and Stock D

Subjects
Anisotropy, Copper chemistry, Materials Testing, Models, Biological, Nickel chemistry, Polymers chemistry, Thermodynamics, Biophysics methods, Crystallization, Germanium chemistry, Silicon chemistry
Abstract

We have studied the evolution of cellular structures in Ge 1-x Si x single-crystal growth as a function of process parameters. Because these structures are much larger than those occurring during the solidification of metals, we developed a modified phase-field method, which is able to handle these structure within reasonable computer times using the real material parameters. The model has been tested for computing equilibrium shapes of crystals, dendritic growth, and cellular growth of Ni x Cu 1-x. We also performed classical molecular dynamics calculations in order to compute the diffusion coefficients of Si and Ge in melts of various compositions.

Published
2010
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