«ANNUAL REPORT Riga 2012 Annual Report 2011, Institute of Solid State Physics, University of Latvia. Editor: A.Krumins. Composed matter: A.Muratova. ...»
18. J.Teteris, J.Aleksejeva, U.Gertners, Photoinduced mass transport in amorphous chalcogenide and organic polymer films, 24th Intern. Conf. on Amorphous and Nanocrystalline Semiconductors (ICANS24), Nara, Japan, 21-26 August, 2011, Book of abstracts, p. 38.
19. U.Gertners, J.Aleksejeva, J.Teteris,, Photo-induced structural transformations in chalcogenide vitreous semiconductors, 24th Intern. Conf. on Amorphous and Nanocrystalline Semiconductors (ICANS24), Nara, Japan, 21-26 August, 2011, Book of abstracts, p. 143.
20. J.Aleksejeva, A.Gerbreders, U.Gertners, M.Reinfelde, J.Teteris, Polarization and Surface Relief Gratings in Disperse Red1 Doped Polyurethane Thin Films, 24th Intern. Conf. on Amorphous and Nanocrystalline Semiconductors (ICANS24), Nara, Japan, 21-26 August, 2011, Book of abstracts, p. 169.
21. A.Gerbreders, Photosensitive Polyurethanes for Optical Record, The 7th Intern. Conf. on Photonics, Devices and Systems (Photonics Prague 2011), Prague, Czech Republic, August 24-26, 2011, Book of abstracts, p.94.
22. U.Gertners, Direct Photo-Induced Surface-Relief Formation in Thin Layers of Chalcogenide Vitreous Semiconductors, The 13th Intern. Conf.”Advanced materials and technologies”, Palanga, Lithuania, 27-31 August, 2011, Book of abstracts, p.46.
23. J.Aleksejeva, A.Gerbreders, J.Teteris, Surface relief and polarization grating formation in azo-dye containingpolymer films, Intern. Conf.”Advanced optical materials and devices” (AOMD-7), Vilnius, Lithuania, August 28-31, 2011, Book of abstracts, p. 10.
24. J.Teteris, Photoinduced mass transport in organic and inorganic polymers, Intern.
Conf.”Advanced optical materials and devices” (AOMD-7), Vilnius, Lithuania, August 28-31, 2011, Book of abstracts, p. 11.
25. A.Gerbreders, J.Aleksejeva, J.Teteris, Azo-polyurethane polymers for optical record, Intern. Conf.”Advanced optical materials and devices” (AOMD-7), Vilnius, Lithuania, August 28-31, 2011, Book of abstracts, p. 21.
26. V.Kolbjonoks, V.Gerbreders, J.Teteris, Fabrication of gratings on chalcogenide As-S-Se thin films using electron beam, Intern. Conf.”Advanced optical materials and devices” (AOMD-7), Vilnius, Lithuania, August 28-31, 2011, Book of abstracts, p. 23.
27. V. Kolbjonoks, V.Gerbreders, J.Teteris, A.Bulanov, E.Tamanis, Electron beam lithography on As-S-Se films, 8th Intern Conf. “HoloExpo-2011”, 29 September- 01 October 2011, Proc. p.410-412.
28. M.Reinfelde, J.Teteris, Surface structuring by direct holographic recording, 8th Intern Conf. “HoloExpo-2011”, 29 September- 01 October 2011, Proc. p.219-223.
29. J.Teteris, Photoinduced mass transport in organic and inorganic polymers, V Ukrainian scientific Conf. on physics of semiconductors (USCPS-5), Uzhgorod, Ukraine, 9-15 October 2011,
Research Area and Main Problems Laboratory is a joint between colleagues in institute and department of Otometry and vision science of the University. Most of Department’s Master thesis have been accomplished due to collaboration between units. All representatives of laboratory research staff and PhD students are members of department lecturers. The Optometry Master’s program of the University has been established and is functioning to a large extent based on integration of research and study. The leading academic colleagues conduct research, also engaging students in scientific work. In 2011 more than 15 Bachelor’s and 12 Master’s thesis have been completed under supervision of laboratory researchers.
Research in laboratory is focused on following problems:
Visual evoked potentials related to visual perception;
• Aberrations of the eye and its impact on visual perception and retinal image quality;
• Color vision in visual perception and elaboration of new color vision tests;
• Aging and its impact on visual perception;
• Visual perception in road safety and new retroreflective materials;
• Kinematics of the Eye in describing cognitive processes;
• Vision in light scattering conditions, stray light and vision impairment;
• Subjective fixation disparity affected by dynamic asymmetry, resting vergence, and nonius bias.
Scientiffic staff Prof. Ivars Lacis Prof. Maris Ozolins Asoc.prof. Gunta Krumina Dr. phys. Gatis Ikaunieks Dr.phys. Sergejs Fomins PhD students MSc. Varis Karitans MSc. Aiga Svede MSc. Ieva Timrote MSc. Evita Kassaliete Master student BSc. Anete Pausus
Estonia Tallin Health care college, Department of Optometry, (MSc. Vootele Tamme) France Laboratoire Regional des Ponts et Chaussees de Clermont-Ferrand (Dr. M. Colomb) Germany Institut fur Arbeitsphysiologie an der Universitat Dortmund (Dr. Wolfgang Jaschinski) Russia Pavlov Institute of Physiology of Russian Academy of Sciences, Laboratory of Motion Physiology (Dr. V.A. Lyakhovetskii)
1. Svede A, Hoormann J, Jainta S, Jaschinski W. (2011). Subjective fixation disparity affected by dynamic asymmetry, resting vergence, and nonius bias. Invest Ophthalmol Vis Sci., 52(7), 4356-4361.
2. K. Luse, M. Ozolins, V. Karitans, I. Jekabsone "Effect of position of retroreflective signs on recognition of pedestrian in reduced visibility conditions". Abstr. Int.Conf.
„DOC`2011”, Riga, p. 26 (2011).
3. S.Fomins, M.Ozoliņš, G.Krūmiņa, I.Lācis „Analysis of Rabkin Color Deficiency test under different illumination.” Abstr. Int.Conf. „Functional Materials and Nanotechnologies FMNT– 2011”, Riga, p.101 (2011).
4. M. Ozolinsh, I. Martín, D. Lauva, and V. Karitans „Howard-Dolman test at different opponent colour stimuli.” Journal of Modern Optics, iFirst published on: 18 March 2011, DOI: 10.1080/09500340.2011.559313
5. E. Skutele, V. Karitans "Producing of ray tracing aberrometer for studying wavefront deformations". Abstr. Int.Conf. „DOC`2011”, Riga, p. 70 (2011).
Research Area and Main Problems The research interests of the Laboratory of Wide Band Gap Materials are focused on spectral characterization of compounds formed from the III-V group elements such as AlN, h-BN, AlGaN and some related materials such as Al2O3. Recently it was shown that optical properties of nitride compounds are prospective for its application as new UV light and visible light emitters (Watanabe, Taniguchi), besides, features of AlN could rate it among materials available for UV light dosimetry (our results). Presently different forms of these materials are synthesized including a bulk material and its nanostructured forms and it is also known that their optical properties could be different. Our interests are largely focussed on revealing of the difference between the optical properties of the bulk material and its nanostructured forms. The spectral investigations performed in our laboratory are based on luminescence studies (photoluminescence (PL) and its excitation (PLE) spectra within a wide temperature range between 8 K and 300 K), optically stimulated luminescence (OSL) and thermo-luminescence (TL)) including also optical absorption. This complex can give essential information about the defects and optical properties of the material, containing revealing of light-induced processes, luminescence mechanisms, energy accumulation and its release mechanisms. These problems could be prevalently related to the fundamental physics. In the field of innovations the interests are focussed on application of materials mentioned above for elaboration of new luminescent materials for energy saving compact luminescent light sources. Part of investigations was performed together with the collaboration partners from abroad.
Latvia Institute of Inorganic Chemistry, Riga TU (Prof. J.Grabis) Institute of Solid State Physics, University of Latvia USA Wake Forest University, Department of Physics, Winston-Salem (Prof. R.T. Williams, Dr.
U.Burak) Taiwan Center of Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan (Prof. LiChyong Chen) Lithuania Institute of Applied Research, Department of Semiconductor Optoelectronics, Vilnius University, Vilnius, Lithuania (Prof. K. Jarasiunas)
Photoluminescence was studied in six samples of Al2O3 nanopowders produced from the same initial material by calcination in the 800-1400 ºC temperature range. At temperature around 1200 ºC phase transition in aluminum oxide lattice occurs; the samples produced at temperatures up to 1200 contain mainly δ phase, while those obtained at 1400 ºC contain pure α phase. In all studied samples of nominally pure aluminum oxide nanopowders photoluminescence is observed in red-infrared spectral range and determined by trace level concentrations of uncontrolled impurities. It was found that phase transition is accompanied with modification of the emission spectrum: a broad diffuse band centered around 750 nm presumably ascribed to emission of Fe3+ ions is characteristic for photoluminescence of the samples of δ phase, while narrow band emission of Mn4+ is observed in the samples of α phase. Aside from that emission of Cr3+ ion is observed in all studied samples with the difference that intensity, position and shape of emission bands are characteristic either to transient forms or to α phase of aluminum oxide. Switching of the active luminescence centers in the samples of the same composition with phase transition is tentatively explained by change of the crystal field symmetry affecting probability of electron transitions in impurity centers.
These studies were performed within a support of European project ERAF 2010/0253/2DP / 18.104.22.168.0/10/APIA/VIAA/079.
Photoluminescence (PL) spectra of h-BN powder and multi-wall BN nanotubes were investigated within a wide spectral region from 8 K up to 300 K. A similarity of complex luminescence spectra was found for both the BN nanotubes and bulk h-BN powder. Two main predominant luminescence bands at 320 nm and 400 nm were established. Complex spectral investigations including luminescence and its kinetics measurements allow reveal luminescence mechanisms and defect structure forming luminescence centers.
On basis of investigations mentioned above Valdis Korsaks has worked out his PhD Thesis.
LOW TEMPETATURE LUMINESCENCE OF AlN
L.Trinkler, B. Berzina, J.Grigorjeva Photoluminescence of AlN ceramics and macro and nanopowders were investigated within a wide spectral range from 8 K up to 300 K in order to reveal the luminescence mechanisms and luminescence centers useful for elaboration of new white light sources. These studies were performed within a support of European project ERAF 2010/0253/2DP / 22.214.171.124.0/10/APIA/VIAA/079.
Ternary compound AlGaN consists of two wide band gap components AlN and GaN with different band gaps Eg (6,2 eV and 3,2 eV, respectively) forming solid solution with common Eg depending on reciprocal concentration of Al and Ga atoms in material. Therefore, variation of concentration of Al and Ga components in Al1-xGaxN allows obtain material with variable band gap corresponding to wide spectral range of ultraviolet light providing its application in light emitting devices.
Spectral characterization of synthesized materials (nanorods and thin layers) synthesized at Taiwan National University was performed. The luminescence spectra were measured within wide temperature range from 8 K up to 300 K under sample excitation with laser light pulses at 266 nm and 310 nm. It was found that the exciton related luminescence band is observed within the spectral range of 320 nm – 400 nm and location of its maximum depends on value x characterizing the Al1-xGaxN material.
These studies were performed within a support of Mutual Funds Taiwan-Latvia-Lithuania Cooperation Project: “One-dimensional Nanostructures of Ternary AlGaN and metal dopedZinc Oxide with Tunable Bandgaps: Growth, Characterization and Optical Properties”
1. L.Trinkler, B.Berzina, D.Jakimovica, J.Grabis, I.Steins “Peculiarities of photoluminescence of Al2O3 bulk and nanosize powders at low temperature”. Optical materials, 33 (2011), 817-822. doi:10.1016/j.optmat.2010.12.020
2. L.Trinkler and B.Berzina “Luminescence properties in AlN ceramics and its potential application for solid state dosimetry”. (pp. 59-82) A chapter in book Advances in Ceramics Characterization, 82 Raw Materials, Processing, Properties, Degradation and Healing. ISBN 978-953-307-504-4, 370 pages, Publisher: InTech, Croatia, August 2011 http://www.intechopen.com/articles/show/title/luminescence-properties-of-aln-ceramics-andits-potential-application-for-solid-state-dosimetry
3. V. Korsaks, B. Berzina, L. Trinklere. “Low temperature 450 nm luminescence of hexagonal boron nitride”. Latvian Journal of Physics and Technical Sciences N1 (2011) 55-60.
27th LU Scientific Conference of Institute of Solid State Physics, University of Latvia, February 14 - 16, 2011, Riga, Latvia
1. J.Grigorjeva, V.Korsaks, L.Trinkler, B.Berzina. “Low temperature luminescence of AlN powders”. Book of Abstracts, 2011, p.54.
2. Z. Jevsjutina, L.Trinkler and B.Berzina. “Dependence of Al2O3 luminescence on temperature and grain size”. Book of Abstracts, 2011 p. 55.
International Conference FM&NT; Functional materials and nanotechnologies 2011;
Institute of Solid State Physics University of Latvia April 5 – 8, Riga
3. B.Berzina, V.Korsaks, L.Trinkler and J.Grigorjeva. “Defect luminescence of III group element nitrides and hBN”, FM&NT Abstact book, p.45, Riga, 2011.
4. L.Trinkler, B.Berzina, Z.Jevsjutina, J.Grabis and I.Steins. „Photoluminescence of Al2O3 nanopowders of different phases”, FM&NT Abstact book, p.103, Riga, 2011.
International Conference on New Diamond and Nano Carbons NDNC 2011, May 16 – 20, 2011, Matsue, Japan
5. V.Korsaks, B.Berzina and L.Trinkler. „Defect luminescence of hBN: bulk powder and multiwall nanotubes”, NDNC 2011, Abstract book, p.100, Matsue, Japan, 2011.
9th International Conference on Nitride Semiconductors ICNS-9, 10 – 15 July 2011, Glasgow, UK