Annual Report 2012 - Latvijas Universitātes Cietvielu fizikas institūts

More documents

Recommendations

Info

APPLICATION IMPEDANCE SPECTROSCOPY TO STUDY ZINC AND NICKEL FERRITES A. Lusis, A.Sutka*, G. Mezinskis* *) Institute of Silicate Materials, Riga Technical University, For characterization of gas sensor material, synthesized by sol-gel auto combustion method the impedance spectroscopy were employed as well as to sdudy: • Electric and dielectric properties of nanostructured stoichiometric and excess-iron Ni–Zn ferrites, • Properties of Ni–Zn ferrite thin films deposited using spray pyrolysis, • Influence of iron non-stoichiometry on spinel zinc ferrite gas sensing properties, • An alternative method to modify the sensitivity of p-type NiFe2O4 gas sensor. High DC resistivity and low dielectric losses of thin Ni1−xZnxFe2O4 films are explained by mixed n-p conductivity and nanograin structure of spray pyrolysis deposited coatings which are changing with the ratio of Ni/Zn.It has been shown that the DC resistivity, dielectric loss and optical band gap of deposited films are influenced by the zinc content. It was found that the sensors cooled with lower rate exhibited better sensing performance, due to increase of resistance. The influence of zinc ion concentration to the NiFe2O4 p-type semiconductor gas sensing characteristics is demonstrated. The change of sensitivity is deeply related to formation of small amount of the Fe2+ in compositions consisting zinc ion during sintering and surface conductance effects resulting with change type of conductivity for Ni-Zn ferrites. The impedance spectroscopy distinguishes influence on gas-sensing measurements different volatile organic compounds (VOCs) which were used as testing gases.The impedance spectroscopy helped to identify the contribution of the different sensing layer elements to the conduction. Laboratory of EXAFS Spectroscopy REVERSE MONTE CARLO MODELING OF THERMAL DISORDER IN CRYSTALLINE MATERIALS FROM EXAFS SPECTRA J. Timoshenko, A. Kuzmin, J. Purans In this work we propose the improved Reverse Monte Carlo (RMC) scheme for the analysis of the EXAFS spectra. In our approach, the difference between theoretical and experiment EXAFS signals is minimized during the RMC simulation simultaneously in k and R spaces by using the modified Morlet continuous wavelet transform of the EXAFS signal. Besides, to improve convergence during the simulation, we use slowly reducing “temperature” parameter in the Metropolis algorithm (the socalled simulated annealing method). 130
Fig.1. Upper panel: 4 × 4 ×4 supercell (128 atoms), used in the RMC simulations of crystalline germanium; model Ge K-edge EXAFS signal (dots) and EXAFS signal, obtained in RMC simulations (solid line). Bottom panel: WT moduli for model EXAFS signal and for difference between model and RMC EXAFS signals. The use of the method is demonstrated on the example of the EXAFS spectra analysis for the model system and experimental data for crystalline germanium and rhenium trioxide. It is shown that the method allows one to reconstruct the 3D atomic structure of the compound taking into account the thermal disorder and to obtain the distributions of distances and bond angles describing the local structure around the absorber. Also the uncorrelated (MSD) and correlated (MSRD) thermal vibration amplitudes can be recovered with reasonable accuracy. The obtained results for Ge and ReO 3 are in good agreement with that previously found by conventional EXAFS analysis and molecular dynamics simulations. PROBING THE OXYGEN VACANCY DISTRIBUTION IN RESISTIVE SWITCHING Fe-SrTiO 3 METAL-INSULATOR-METAL STRUCTURES BY MICRO-X-RAY ABSORPTION NEAR EDGE STRUCTURE Ch. Lenser, 1,2 A. Kuzmin, J. Purans, A. Kalinko, R. Waser, 1,2,3 R. Dittmann 1,2 1 Peter Grunberg Institute, Forschungszentrum Julich, Julich, Germany 2 Julich-Aachen Research Alliance, Germany 3 Institut fur Werkstoffe der Elektrotechnik, RWTH Aachen, Aachen, Germany Binary and ternary metal oxides as emergent materials for non-volatile memory applications are receiving an increasing amount of scientific attention due to the promising scalability, retention and switching characteristics of this material class. The key role of oxygen non-stoichiometry and oxygen-deficient oxide-phases as the underlying mechanism of the resistance change has been recognized for many different oxide systems. It is becoming widely accepted that the resistance switching process in SrTiO3 is related to the movement of oxygen vacancies and the associated electron doping. The mechanism of electroforming in Pt/Fe:SrTiO3/Nb:SrTiO3 MIM-structures proposes the local bypassing of the interfacial Schottky-type barrier by oxygen deficient filaments forming along extended defects. It is assumed that the films are already oxygen deficient after deposition. While this model is well supported by the electrical behaviour of the devices, direct experimental observation of the oxygen deficiency and the formation of the conducting filament has so far been reported for a few polycristalline, binary oxides, but not for single crystalline thin films of complex oxides. 131
Page 1 and 2:
Institute of Solid State Physics Un
Page 3 and 4:
CONTENTS Introduction 4 Department
Page 5 and 6:
ORGANIZATIONAL STUCTURE OF THE ISSP
Page 7 and 8:
The annual report summarizes the re
Page 9 and 10:
The main source for international f
Page 11 and 12:
lector at the Faculty of Physics an
Page 13 and 14:
the samples having different phase
Page 15 and 16:
LABORATORY OF MAGNETIC RESONANCE SP
Page 17 and 18:
Scientific publications 1. U. Rogul
Page 19 and 20:
Main investigations and results ALU
Page 21 and 22:
Lectures on Conferences 28 th LU Sc
Page 23 and 24:
Main Results LASER CRYSTALLIZATION
Page 25 and 26:
CONTROLLED MANIPULATION AND MECHANI
Page 27 and 28:
DEPARTMENT OF FERROELECTRICS Head o
Page 29 and 30:
Belorussia 1. Institute of solid st
Page 31 and 32:
Density and dielectric properties f
Page 33 and 34:
CONCENTRATION AND THERMAL PHASE TRA
Page 35 and 36:
Latvia; SSPA ”Scientific-Practica
Page 37 and 38:
• Δ T εmax : Mn>Co>Fe>Cu~Ni •
Page 39 and 40:
Li x Na 1-x Ta y Nb 1-y O 3 Solid S
Page 41 and 42:
34. А.И. Бурханов, И.Е.
Page 43 and 44:
16. Š. Svirskas, M. Ivanov, Š. Ba
Page 45 and 46:
45. С.Н. Каллаев, А.Р.
Page 47 and 48:
LABORATORY OF VISUAL PERCEPTION Hea
Page 49 and 50:
in terms of colour coordinate dispe
Page 51 and 52:
4. R.Truksa, S.Fomins, M.Ozolins, "
Page 53 and 54:
Scientific visits abroad 1. Dr. hab
Page 55 and 56:
experimental data. We focused on th
Page 57 and 58:
GB1 with oxygen vacancy revealed th
Page 59 and 60:
Fig. 4. The thermodynamic stability
Page 61 and 62:
a supercell model was used, and the
Page 63 and 64:
a) b) l [110] d [110] (001) Fig. 9.
Page 65 and 66:
Drain CNT Source Drain GNR Source 5
Page 67 and 68:
The oxygen incorporation energy for
Page 69 and 70:
such as high thermal stability, ver
Page 71 and 72:
STATISTICAL ANALYSIS AND CELLULAR A
Page 73 and 74:
REGIONS OF AZIMUTHAL INSTABILITY IN
Page 75 and 76:
25. A. Gopejenko, Yu.F. Zhukovskii,
Page 77 and 78:
15. S. Piskunov and E. Spohr, "SrTi
Page 79 and 80: 43. P. Merzlakov, G. Zvejnieks, V.N
Page 81 and 82: XII. Annual Monitory Meeting of Eur
Page 83 and 84: 91. L. Shirmane, A.I. Popov, V. Pan
Page 85 and 86: 115. A.I. Popov, J. Zimmermann, V.
Page 87 and 88: Estonia Institute of Physics, Tartu
Page 89 and 90: 5. Grigorjeva L., Jankoviča D., Sm
Page 91 and 92: LABORATORY OF AMORPHOUS MATERIALS S
Page 93 and 94: Main results ABSORPTION AND LUMINES
Page 95 and 96: LUMINESCENCE OF FUSED AND UNFUSED B
Page 97 and 98: enables sensitive and selective det
Page 99 and 100: LABORATORY OF OPTICAL RECORDING Hea
Page 101 and 102: HOLOGRAPHIC LITHOGRAPHY IN AMORPHOU
Page 103 and 104: 5. U.Gertners, J.Teteris, The impac
Page 105 and 106: 24. J.Aleksejeva, J.Teteris, A.Tokm
Page 107 and 108: Israel Technion, Haifa (Dr.S.Stolya
Page 109 and 110: 3. A. Rusakova, J. Maniks, K. Schwa
Page 111 and 112: • Investigation of energetic stru
Page 113 and 114: Scheme 2 Synthesis of indane-1,3-di
Page 115 and 116: The synthesized compounds ZWK-1, DW
Page 117 and 118: 7. A. Vembris, K. Pudzs, I. Muzikan
Page 119 and 120: 20. A. Vembris, K. Pudzs, I. Muzika
Page 121 and 122: • Ion transfer problems related t
Page 123 and 124: 13. SIA „EMU PRIM”, 14. JSC „
Page 125 and 126: Main results Laboratory of Solid St
Page 127 and 128: Flax and Hemp Fiber Functionalizati
Page 129: CHARACTERIZATION OF LiFePO4/C COMPO
Page 133 and 134: Fig.1. Left panel: Schematic view o
Page 135 and 136: Titania with anatase structure is i
Page 137 and 138: RESEARCH OF CATHODE MATERIALS FOR L
Page 139 and 140: 17. T Dizhbite, J Ponomarenko, A An
Page 141 and 142: 6. J. Kleperis, B. Sloka, J. Dimant
Page 143 and 144: 33. P. Lesnicenoks, A. Sivars, L. G
Page 145 and 146: France 1. Institute Laue-Langevin,
Page 147 and 148: different neutron orbits (11/2[615]
Page 149 and 150: LABORATORY OF ELECTRONIC ENGINEERIN
Page 151 and 152: 2. For JSC Augstsprieguma tīkls an
Page 153 and 154: 4. By orders of several organizatio
Page 155: Partners: Fonons Ltd, Riga Technica
show all

Annual Report 2012 - Latvijas Universitātes Cietvielu fizikas institūts

Create successful ePaper yourself

Delete template?

Save as template?