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Author |
Mikhailova, D.; Kuratieva, N.N.; Utsumi, Y.; Tsirlin, A.A.; Abakumov, A.M.; Schmidt, M.; Oswald, S.; Fuess, H.; Ehrenberg, H. |
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Title |
Composition-dependent charge transfer and phase separation in the V1-xRexO2 solid solution |
Type |
A1 Journal article |
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Year  |
2017 |
Publication |
Journal of the Chemical Society : Dalton transactions |
Abbreviated Journal |
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Volume |
46 |
Issue |
5 |
Pages |
1606-1617 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
The substitution of vanadium in vanadium dioxide VO2 influences the critical temperatures of structural and metal-to-insulator transitions in different ways depending on the valence of the dopant. Rhenium adopts valence states between + 4 and + 7 in an octahedral oxygen surrounding and is particularly interesting in this context. Structural investigation of V1-xRexO2 solid solutions (0.01 <= x <= 0.30) between 80 and 1200 K using synchrotron X-ray powder diffraction revealed only two polymorphs that resemble VO2: the low-temperature monoclinic MoO2-type form (space group P2(1)/c), and the tetragonal rutile-like form (space group P4(2)/mnm). However, for compositions with 0.03 < x <= 0.15 a phase separation in the solid solution was observed below 1000 K upon cooling down from 1200 K, giving rise to two isostructural phases with slightly different lattice parameters. This is reflected in the appearance of two metal-toinsulator transition temperatures detected by magnetization and specific heat measurements. Comprehensive X-ray photoelectron spectroscopy studies showed that an increased amount of Re leads to a change in the Re valence state from solely Re6+ at a low doping level (<= 3 at% Re) via mixed-valence states Re4+/Re6+ for at least 0.03 < x <= 0.10, up to nearly pure Re4+ in V0.70Re0.30O2. Thus, compositions V1-xRexO2 with only one valence state of Re in the material (Re6+ or Re4+) can be obtained as a single phase, while intermediate compositions are subjected to a phase separation, presumably due to different valence states of Re. |
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Place of Publication |
London |
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Wos |
000395442700030 |
Publication Date |
2016-12-24 |
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Abbreviated Series Title |
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Series Issue |
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Edition |
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ISSN |
0300-9246; 1477-9226; 1472-7773 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.029 |
Times cited |
1 |
Open Access |
Not_Open_Access |
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Notes |
; The authors are indebted to Dr G. Auffermann (Max Planck Institute for Chemical Physics of Solids, Dresden, Germany) for performing the ICP-OES analyses. This research has received a partial funding from the BMBF, project grant number 03SF0477B (DESIREE). AT acknowledges financial support from Federal Ministry for Education and Research under Sofja Kovalevksaya Award of Alexander von Humboldt Foundation. AMA is grateful to the Russian Science Foundation (grant 14-13-00680) for financial support. ; |
Approved |
Most recent IF: NA |
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Call Number |
UA @ lucian @ c:irua:142580 |
Serial |
4642 |
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Author |
Nistor, L.; Buschmann, V.; Ralchenko, V.; Dinca, G.; Vlasov, I.; van Landuyt, J.; Fuess, H. |
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Title |
Microstructural characterization of diamond films deposited on c-BN crystals |
Type |
A1 Journal article |
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Year |
2000 |
Publication |
Diamond and related materials
T2 – 10th European Conference on Diamond, Diamond-Like Materials, Nitrides, and Silicon Carbide (Diamond 1999), SEP 12-17, 1999, PRAGUE, CZECH REPUBLIC |
Abbreviated Journal |
Diam Relat Mater |
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Volume |
9 |
Issue |
3-6 |
Pages |
269-273 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
The morphology and structure of diamond films, deposited on cubic boron nitride (c-BN) crystals by microwave-plasma-enhanced chemical vapor deposition, is studied by high-resolution scanning electron microscopy and micro-Raman spectroscopy. The c-BN crystals, with sizes of 200 to 350 mu m and grown by a high-temperature/high-pressure technique, were embedded in a copper holder, and used as substrates in deposition runs of 15 min to 5 h. The nucleation centers for diamond appear as well-shaped cuboctahedral crystallites, having diameters of approximately 100 nm. With increasing deposition time the diamond crystallites grew larger, forming islands on the c-BN faces. In some cases, epitaxial growth was observed on the (111) c-BN faces where coalesced particles gave rise to very smooth regions. A number of diamond crystals with peculiar shapes are observed, such as a pseudo five-fold symmetry due to multiple twinning. Moreover, both randomly distributed carbon tubes, about 100 nn in diameter and 1 mu m in length, and spherically shaped features are observed in samples prepared under the typical conditions of diamond deposition, this effect being ascribed to the influence of plasma-sputtered copper contamination. Quite unusual diamond crystals with a deep, pyramidal-shaped hole in the middle grew on the copper substrate between the c-BN crystals. (C) 2000 Elsevier Science S.A. All rights reserved. |
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Place of Publication |
Amsterdam |
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Wos |
000087382400009 |
Publication Date |
2002-07-26 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0925-9635; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.561 |
Times cited |
9 |
Open Access |
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Notes |
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Approved |
Most recent IF: 2.561; 2000 IF: 1.591 |
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Call Number |
UA @ lucian @ c:irua:102877 |
Serial |
2041 |
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Author |
Buschmann, V.; Rodewald, M.; Fuess, H.; Van Tendeloo, G.; Schäffer, C. |
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Title |
High resolution electron microscopy study of molecular beam epitaxy grown CoSi2/Si1-xGex/Si(100) heterostructurs |
Type |
A1 Journal article |
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Year |
1999 |
Publication |
Journal of applied physics |
Abbreviated Journal |
J Appl Phys |
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Volume |
85 |
Issue |
4 |
Pages |
2119-2123 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Two CoSi2/Si1-xGex/Si(100) heterostructures, with different Ge content, made by molecular beam epitaxy are characterized by high resolution electron microscopy. In general, the interface between the CoSi2 thin film and the Si1-xGex layer is of a high structural quality and the strained Si1-xGex layer exhibits few defects. For both samples, different interface structures are present, although the dominant interfacial configuration is similar to the unreconstructed interface present at the CoSi2/Si(100) interface. Only occasionally (2x1) reconstructed interface regions are found which are just a few nanometers in length. Phenomena such as Ge segregation and the introduction of defects are also observed in the Si1-xGex layer. We attribute the minimal presence of the reconstructed interface to both the (2x8):Si1-xGex(100) surface reconstruction and the Ge segregation that takes place. (C) 1999 American Institute of Physics. [S0021-8979(99)02104-0]. |
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Publisher |
American Institute of Physics |
Place of Publication |
New York, N.Y. |
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Wos |
000078403000017 |
Publication Date |
2002-07-26 |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0021-8979; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.068 |
Times cited |
6 |
Open Access |
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Notes |
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Approved |
Most recent IF: 2.068; 1999 IF: 2.275 |
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Call Number |
UA @ lucian @ c:irua:103977 |
Serial |
1455 |
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Author |
Buschmann, V.; Rodewald, M.; Fuess, H.; Van Tendeloo, G.; Schaffer, C. |
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Title |
Hetero-epitaxial growth of CoSi2 thin films on Si(100) : template effects and epitaxial orientations |
Type |
A1 Journal article |
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Year |
1998 |
Publication |
Journal of crystal growth |
Abbreviated Journal |
J Cryst Growth |
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Volume |
191 |
Issue |
3 |
Pages |
430-438 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
This HREM investigation focuses on the influence of point defects on the final epitaxial relation and atomic interface configuration in a CoSi2/Si(1 0 0) heterostructure. A two-step SPE-MBE grown CoSi2/Si(1 0 0) system is used and, by altering the number of deposited Co monolayers in the template layer, the point defect behavior is studied. We propose a film growth model in which the knowledge about the reconstructed (2 x 1) : Si(1 0 0) surface, the point defect behavior in the presence of an interface, especially a silicide interface, the migration of point defects through a lattice by formation of [1 0 0]-split interstitial (dumbbell) atomic configurations, and a new type of extended defect configurations in diamond type materials will all amalgamate. (C) 1998 Published by Elsevier Science B.V. All rights reserved. |
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Publisher |
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Place of Publication |
Amsterdam |
Editor |
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Language |
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Wos |
000075032500017 |
Publication Date |
2002-07-25 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0022-0248; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
1.751 |
Times cited |
6 |
Open Access |
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Notes |
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Approved |
Most recent IF: 1.751; 1998 IF: 1.307 |
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Call Number |
UA @ lucian @ c:irua:102930 |
Serial |
1418 |
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