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«ANNUAL REPORT Riga 2012 Annual Report 2011, Institute of Solid State Physics, University of Latvia. Editor: A.Krumins. Composed matter: A.Muratova. ...»

-- [ Page 19 ] --

During the past 10 years, research in the field of optical materials based on amorphous chalcogenide semiconductors has made significant advances. Much of this research is driven by applied interest and this field of research is extremely broad and active. The use of amorphous chalcogenide thin films in holography and lithography has probably only just begun, but already produced some promising results.

The main functional principles and practical application of amorphous chalcogenide photoresists for production of the embossed rainbow holograms and holographic optical elements are discused. The laser interference lithography is used as a low-cost method for the exposure of large surfaces with regular patterns like subwavelength-gratings and microsieves.

The regular features with the sizes of about 50 nm and less can be fabricated by this method.

The Bragg reflection gratings were recorded and studied in amorphous As2S3 and As-S-Se films. Amorphous chalcogenide thin films are thought to be one of the potential materials for all-optical integrated circuits for the optical communication systems due to their excellent infrared transparency, large nonlinear refractive index, and low phonon energies. The possibility to use the amorphous chalcogenide films as a media for holographic recording, processing and storage of information with high density is discussed.

–  –  –

The recording of the surface-relief and refractive index modulated gratings with a period of 0.15 – 1.0 μm was performed by solid immersion holographic method. The grating period for two intersecting light beams in a coupling prism with refractive index n can be expressed as Λ=λ0/2 n sinθ, where λ0 is the wavelength of laser light in vacuum, n is refractive index of the prism and θ is the half-angle between the laser beams inside the prism.

The right angle prisms with n= 1.5 – 2.6 were used. Amorphous As-S-Se based photoresist with refractive index n1=3.2 at 0.488 μm was used for the recording of surface-relief gratings.

After recording, wet etching of the photoresist was performed to obtain a surface-relief grating. The grating period and profile were measured by AFM. If the recording was performed in air (n=1) and the angle between the beams was equal to 90o, a grating with a period of 0.345 μm was obtained. If the intersection of the laser beams is performed in a prism with a refractive index of 1.75, a grating period of 0.197 μm was obtained. The application of a prism as an immersion medium decreases the period of the recorded grating n times. The transmission, reflection and polarization properties of the subwavelength transmission gratings in As2S3 amorphous films were studied. The angular selectivity of holographic recording in amorphous chalcogenide thin films has been improved significantly by a decrease of grating period.

SURFACE RELIEF FORMATION DURING HOLOGRAPHIC RECORDING

–  –  –

The key element for the production of surface-relief holographic optical elements is photoresist or light sensitive material. Changes of the chemical properties induced in resist material by light or e-beam exposure enable the surface relief structuring by wet or dry etching. Therefore this process includes two steps: recording and development by etching.

Recently a number of organic and inorganic materials have been studied for direct surface relief formation during the exposure process by a light or e-beam. It is very promising for practical application enabling the possibility to simplify technology of the surface patterning.

In this research the study of direct holographic recording of the surface-relief gratings on amorphous As-S and As-S-Se films has been presented from the side of light polarization.

Because of direct surface relief formation, efficiency of the relief formation also depends on softening temperature of the sample what in this case is about 1700C. Results have shown that the surface relief formation efficiency is many times larger in case of extra softening by additional incoherent light during recording. The mechanism of the direct recording of surface relief on amorphous chalcogenide films based on the photoinduced plasticity has been discussed.

NANOSTUCTURED SURFACES FOR OPTICAL ANTIREFLECTION

–  –  –

The demand for optically antireflective layers during last years has increased.

Particularly such high demand is in the branches where large surfaces will be covered (greenhouses, solar cells etc.) At present work we show the results obtained for surface patterning consisting of nano-structural elements smaller than incident light wavelength. The decreasing of light reflection for such structures results from light diffraction on above mentioned structures. Nanostructured antireflective elements are formed by holographic recording in chalcogenide photoresist. The next step is electrochemical growing of Ni shim used as a stamp for printing of nanostructures into organic polymer – laminate which can be pasted on glass surface. Nano-relief surface are transferred into transparent polymer films by hot embossing at 100-1200C or UV curing.

The nanostructures with a sizes less than 100 nm were fabricated by immersion holography in amorphous chalcogenids, organic azobenzol and photopolymer films. For recording UV CW lasers with 325nm wavelength (He-Cd laser) and 266nm (frequency doubler pumped by Verdi-8 laser 532 nm radiation) and visible region lasers (442 and 532 nm) were used. The conventional photoresist technology and as well as direct relief fabrication method - surface relief formation in amorphous films during the holographic recording were used. For holographic grating forming was used Two-beam holographic setup for 1D, and three- and more beams holographic setup with possibility to change polarization state for each beam for 2D structural element recording were used.





Optical properties of nanostructures as transmission, reflection, diffraction efficiency and their spectral dependences were studied. The form and size of nanostructures were studied by AFM.

–  –  –

Preparation method and optical properties of spiropyran and polymer composite thin films was studied. Polyvinyl acetate, polymethylmetacrylate and copolymer of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) were used as base for composite.

The transmission spectra of composites were measured before and after illumination by laser beams with different wavelengths. Transmission of composite film of merocianine form was measured by laser beam wavelength 532 nm in dependence on beam intensity.

The holographic recording of diffraction gratings was performed by different laser lines (325, 532 nm). During recording the diffraction efficiency was measured in transmission mode. The profiles of the gratings area were analyzed by AFM microscope.

Scientific Publications

1. J.Teteris, J.Aleksejeva and U.Gertners, Photoinduced mass transport in soft materials, IOP Conf.Series: Materials Science and Engineering 23 (2011) 012002.

2. J.Aleksejeva, A.Gerbreders, U.Gertners, M.Reinfelde and J.Teteris, Polarization holographic recording in Disperse Red 1 doped polyurethane polymer film, IOP Conf.Series: Materials Science and Engineering 23 (2011) 012006.

3. U.Gertners, Photoinduced mass transfer in chalcogenides, IOP Conf.Series: Materials Science and Engineering 23 (2011) 012007.

4. J.Teteris, U.Gertners and M.Reinfelde, Photoinduced mass transfer in As2S3 films, PSS(c) 8 (2011) 2780-4.

5. J.Aleksejeva, J.Teteris, Ultraviolet holographic recording in photopolymers, PSS(c) 8 (2011) 2850-3.

6. V. Kolbjonoks, V.Gerbreders, J.Teteris. A.Bulanovs, Amorphous As-S-Se semiconductor thin films for holography and lithography, Proc.SPIE 8074 (2011) 80740U.

7. Bulanovs A., Gerbreders V., Kirilovs G., Teteris J., Investigations of As-S-Se thin films for use as inorganic photoresist for digital image-matrix holography, Central European Journ. of Physics, 9 (2011) 1327-1333.

8. V. Kolbjonoks, V.Gerbreders, J.Teteris, A.Bulanov, E.Tamanis, Electron beam lithography on As-S-Se films, Proc. of 8th Intern Conf. “HoloExpo-2011”, 29 September- 01 October 2011, p.410-412.

9. M.Reinfelde, J.Teteris, Surface structuring by direct holographic recording, Proc. of 8th Intern Conf. “HoloExpo-2011”, 29 September- 01 October 2011, p.219-223.

10. U.Gertners, J.Teteris, Light intensity and its polarization relation to the photo-induced mass movement in thin layers of chalcogenide vitreous semiconductors. JOAM, 13 (2011) 1462-6.

11. A.Gerbreders, J.Aleksejeva, U.Gertners, J.Teteris, The synthesis of different variants of azo-polyerethane polymers for optical recording. JOAM, 13 (2011) 1559-62.

12. J.Aleksejeva, A.Gerbreders, M.Reinfelde, J.Teteris, Polarization holographic recording in azo-benzene doped polyurethane polymer films. JOAM, 13 (2011) 1577M.Reinfelde, J.Teteris, Surface relief and polarization holographic grating formation in amorphous As-S-Se films. JOAM, 13 (2011) 1531-3.

14. J.Aleksejeva, A.Gerbreders, M.Reinfelde, J.Teteris, Photoinduced birefringence in azo-dye doped polyurethane, Latv.Journ.Phys.Tech.Sc. Nr.4 (2011) 4-15.

15. A.Gerbreders, J.Aleksejeva, J.Teteris, Photosensitive polyurethanes for optical record, Pros.SPIE, vol.8306 (2011) 83061A-7.

Lectures on Conferences

1. E.Palčevskis, M.Reinfelde, J.Teteris, Optiskais ieraksts nanodaļiņu suspensijās (Optical recording in nanoparticle suspensions), LU CFI 27. zinātniskā konference, Rīga,

2011.gada 14.-16.februāris, 27th Scientific Conference of the Institute of Solid State Physics, University of Latvia, February 14-16, 2011, Book of Abstracts, p.58.

2. A.Aleksejeva, J.Teteris, Vektorhologrammu ieraksts organiskajos azo-polimēros (Recording of vector holograms in organic azo-polymers), LU CFI 27. zinātniskā konference, Rīga, 2011.gada 14.-16.februāris, 27th Scientific Conference of the Institute of Solid State Physics, University of Latvia, February 14-16, 2011, Book of Abstracts, p.87.

3. U.Gertners, Foto-inducētā masas pārbīde halkogenīdos (Photo-induced mass transfer in chalcogenides), LU CFI 27. zinātniskā konference, Rīga, 2011.gada 14.-16.februāris, 27th Scientific Conference of the Institute of Solid State Physics, University of Latvia, February 14-16, 2011, Book of Abstracts, p.86.

4. A.Gerbreders, Poliuretānu un azo-savienojumu polimēru sintēze optiskam ierakstam (The synthesis of polyurathane and azo-compound polymer for optical record), LU CFI 27.

zinātniskā konference, Rīga, 2011.gada 14.-16.februāris, 27th Scientific Conference of the Institute of Solid State Physics, University of Latvia, February 14-16, 2011, Book of Abstracts, p.57.

5. M.Reinfelde, Hologrāfiskā ieraksta atkarība no 632.8 nm lāzeru staru polarizācijas (Dependence of holographic recording on polarisation of 632.8 nm wave beam), LU CFI

27. zinātniskā konference, Rīga, 2011.gada 14.-16.februāris, 27th Scientific Conference of the Institute of Solid State Physics, University of Latvia, February 14-16, 2011, Book of Abstracts, p.59.

6. J.Aleksejeva, A.Gerbreders, U.Gertners, M.Reinfelde and J.Teteris, Polarization Holographic Recording in Disperse Red1 Doped Polyurethane Polymer Film., Intern.

Conf. TM&NT (Functional materials and nanotechnologies 2011, Riga, Latvia, April 5-8, 2011, Book of abstracts,. p.108.

7. J.Teteris, J.Aleksejeva, U.Gertners, Photoinduced mass transfer in soft materials, Intern.

Conf. TM&NT (Functional materials and nanotechnologies 2011, Riga, Latvia, April 5-8, 2011, Book of abstracts,. p.62.

8. A.Trukhin, K.Golant, J.Teteris, Luminescence in GeO2-SiO2 Films Fabricated by SPCVD, Intern. Conf. TM&NT (Functional materials and nanotechnologies 2011, Riga, Latvia, April 5-8, 2011, Book of abstracts,. p.91.

9. U.Gertners and J.Teteris, Photo-Induced Mass Transport in Chalcogenides, Intern. Conf.

TM&NT (Functional materials and nanotechnologies 2011, Riga, Latvia, April 5-8, 2011, Book of abstracts,. p.110.

10. A.Gerbreders, J.Aleksejeva, J.Teteris, The Synthesis if Different Azo-Polyurethane Polymers for Optical Record. Intern. Conf. TM&NT (Functional materials and nanotechnologies 2011, Riga, Latvia, April 5-8, 2011, Book of abstracts,. p.152.

11. J.Aleksejeva, A.Gerbreders, M.Reinfelde, J.Teteris, Photoinduced birefringence in azodye doped polyurethane, International Young Scientist Conference “Developments in Optics and Communications 2011”, Riga, Latvia, April 23-25, 2011, Book of abstracts, p.

60.

12. U. Gertners, J.Teteris, Light intensity and its polarization relation to the photo-induced mass movement in thin layers of chalcogenide vitreous semiconductors, 5th Intern.Conf.

on Amorphous and Nanostructured Chalcogenides (ANC-5), Bucharest, Romania, June 26-July 1, 2011, Book of abstracts, p. 35.

13. J.Teteris, Photoinduced mass transport in amorphous chalcogenide and organic polymer films, 5th Intern.Conf. on Amorphous and Nanostructured Chalcogenides (ANC-5), Bucharest, Romania, June 26-July 1, 2011, Book of abstracts, p. 7.

14. M.Reinfelde, J.Teteris, Surface relief and polarization holographic grating formation in amorphous As-S-Se films, 5th Intern.Conf. on Amorphous and Nanostructured Chalcogenides (ANC-5), Bucharest, Romania, June 26-July 1, 2011, Book of abstracts, p.

37.

15. J.Aleksejeva, A.Gerbreders, U. Gertners, M.Reinfelde, J.Teteris, Polarization holographic recording in azo-benzene doped polyurethane polymer films, 5th Intern.Conf. on Amorphous and Nanostructured Chalcogenides (ANC-5), Bucharest, Romania, June 26July 1, 2011, Book of abstracts, p. 40.

16. A.Gerbreders, J.Aleksejeva, J.Teteris, The synthesis of different variants of azopolyurethane polymers for optical record, 5th Intern.Conf. on Amorphous and Nanostructured Chalcogenides (ANC-5), Bucharest, Romania, June 26-July 1, 2011, Book of abstracts, p. 45.

17. J.Teteris, J.Aleksejeva, E.Laizane, Photo-induced mass transport in azobenzene containing organic polymers, The 12th European Conf. on Organized Films (ECOF 12), Sheffield, United Kingdom, 17-20 July, 2011, Book of abstracts, p. 52.



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