ANNUAL REPORT - MTA SzFKI

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Raman spectroscopy is widely used for the characterization of these materials. However it is rather difficult to obtain specific information on the bonding configuration of only the grain boundaries from Raman spectra of NCD thin films. These spectra give averaged information about the bonding configuration of all carbon atoms falling into the excitation volume being a part of the diamond crystallites or the surrounding amorphous matrix. Additionally the resonance enhancement of the scattering in the amorphous matrix causes the intense bands of this phase to overlap the scattering contribution of such minor parts of the structure, like the grain boundaries. To overcome these difficulties and to obtain information on the bonding configuration in grain boundaries from the Raman spectrum of NCD films we have lowered the excitation volume so that the excitation took place only on a few crystallites. Additionally the excitation energy was shifted in order to decrease the resonant Raman scattering. This way the characteristic vibrations from grain boundaries of NCD thin films of different grain size were detected successfully (Fig. 1) and identified as characteristic bands of aromatic hydrocarbons and sp 3 CH 2 groups. A100 Intensity [a.u.] A100 A50 Intensity [a.u.] A50 A40 A40 A25 A25 800 1000 1200 1400 1600 1800 2000 Raman shift [cm -1 ] 800 1000 1200 1400 1600 1800 2000 Raman shift [cm -1 ] Fig. 1. 488 nm (a) and 785 nm (b) excited Raman spectra of ultra-nanocrystalline diamond films of different grain size: A25, A40, A50 and A100 samples have grain sizes between 3-50 nm, 50-100 nm, 100-150 and 200-300 nm respectively. The above described method cannot be used for UNCD films having grain sizes below 50 nm, since excitation beam diameter is limited by the diffraction. In the case of these layers we have used Surface Enhanced Raman Scattering (SERS) to detect characteristic vibrations from grain boundaries. Putting SERS-active gold nanoparticles (average size is 20 nm) in contact with the UNCD film, the excitation volume from where the SERS signal arises is limited to a few tens nm surrounding of these nanoparticles. As a result, we were able to detect characteristic vibrations of the grain boundaries of UNCD thin films too. 66
Intensity [a.u.] SERS NR 800 1000 1200 1400 1600 1800 2000 Raman shift [cm -1 ] Fig.2. Comparison of the normal (NR) and surface enhanced (SERS) spectra measured on the A25 sample. The detailed analysis of the spectra measured on the same UNCD sample showed also that the position and the intensity of some of the observed peaks varies when measuring in different points of the surface. Statistical analysis was performed on more than 100 spectra recorded in different points of the sample. The most frequent peaks and corresponding structural units were determined. Our results show that the Raman scattering with nearinfrared excitation is highly sensitive to smallest differences in the structure and it allows the detection and determination of the Raman peaks arising from definite regions of the sample. E-Mail: Aladár Czitrovszky czi@szfki.hu, czitrovszky@sunserv.kfki.hu Miklós Füle fule@szfki.hu Péter Gál gal@szfki.hu Péter Jani pjani@sunserv.kfki.hu Árpád Kiss kissa@szfki.hu Margit Koós koos@szfki.hu Sándor Lakó lako@szfki.hu Attila Nagy anagy@szfki.hu Dániel Oszetzky odani@szfki.hu Sára Tóth tothsara@szfki.hu Lénárd Vámos vamos@szfki.hu Miklós Veres vm@szfki.hu Grants and international cooperations NKFP-3A/089 NKFP- 3A/071 National Research and Development Program, Environmental Pollution of the Atmosphere (Coordinator: A. Czitrovszky, 2004- 2007) National Researh and Development Program, Nanotechnology II (sub-coordinator: A. Czitrovszky, 2004-2007) OTKA T-043359 Preparation and complex characterization of carbon based nanocomposites (M. Koós, 2005-2007) GVOP-3.1.1. No 0403/3.0, DIADEM (in cooperation with Budapest Technical University) (A. Czitrovszky, 2005-2007) GVOP-3.1.1. No 0259/3.0 Photo-catalytic decomposition of pollutants (in cooperation with the University of Szeged (A. Czitrovszky, 2005-2007) 67
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ANNUAL REPORT 2007 RESEARCH INSTITU
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Dear Reader, It is my pleasure to h
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Key figures Permanent staff of the
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A. STRONGLY CORRELATED SYSTEMS J. S
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presented detailed study should hel
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B. COMPLEX SYSTEMS F. Iglói, R. Ju
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B.3. B.4. B.5. B.6. B.7. B.8. B.9.
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the α2 reconstruction increases on
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Page 24 and 25: See also H.6. and nanostructured Pd
Page 26 and 27: Ab initio structure solution. — I
Page 28 and 29: ESA PECS 98021 Phase field modeling
Page 30 and 31: Conference proceedings E.17. Oszlá
Page 32 and 33: Fig. 1. ns-EC to s-EC transition in
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Page 38 and 39: H. METAL PHYSICS K. Tompa, I. Bakon
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Page 42 and 43: I. METALLURGY AND MAGNETISM L.K. Va
Page 44 and 45: temperature profile increases the s
Page 46 and 47: I.13 Kane * SN, Khinchi * SS, Gercs
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Page 56 and 57: László Temleitner temla@szfki.hu
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Page 100 and 101: CONFERENCES ⎯ Electrochemistry se
Page 102: TABLE of CONTENTS PREFACE 1 KEY FIG
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