A. Gerbreders

Holographic recording in polymer composites of organic photochromes and chalcogenides

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 the surface-relief formation technology. In this report the method of preparation of thin polymer-chalcogenide and polymer-azobenzene composite films is described, and some features of photoinduced changes of optical properties and holographic recording of these materials are studied. Films of composites were obtained from solution of arsenic sulphide, Disperse red 1 and polymers in organic solvents. The solution was spread on glass substrate and dried. The dry film thickness was in the range of 3-10 μm, with different correlation of arsenic sulphide, Disperse red 1 and polymers. The absorption spectres of these films was studied and described. The holographic recording of diffraction gratings was performed by different laser lines (442, 532 nm). During recording the diffraction efficiency was measured simultaneously in transmission and reflection mode. The profiles of the gratings and expositing area were analyzed by AFM microscope. Microanalysis of exposed and unexposed films showed a difference in chemical composition that can be explained by transfer of matter under the action of light.

Optical properties of the low-molecular amorphous azochromophores and their application in holography

The films based on the low-molecular amorphous azochromophore 2-(3-(4-((4- (Ethyl(2-(trityloxy)ethyl)amino)phenyl)diazenyl)styryl)-5,5-dimethylcyclohex-2-enylidene) malononitrile (IWK-2M) were prepared. The optical properties of the material, such as transmittance and reflection spectra of the film, sensitivity to polarization holographic recording by two wavelengths (405 and 532 nm) were studied. The direct relief formation during the polarization holographic recording was explored, relief depth dependence on exposure and record beam intensity was investigated. The holographic matrix on this material base was produced without chemical etching process; the replication of holographic image was performed.

Optical Properties of Composite Films Based on Copper Chloride in PMMA Matrix

The composite lms based on PMMA, CuCl2 and photoinitiator were prepared.Transmission spectra of the lms with and without photoinitiator were measured. The holo-graphic gratings were recorded, the sensitivity of the lms and surface structure of gratingswere studied. Microanalysis of the lms was performed in di erent part of structure elementsof grating.

Photosensitive properties of composite films based on copper chloride in polymer matrix

The composite films based on PMMA and CuCl2 were prepared. Transmission spectra of the films before and after illumination by different laser lines (405, 448, 456 nm) were measured. The reversible character of the composite photosensitivity was fixed. The phenomenon of direct surface relief formation after laser beam illumination of composite films was described. The holographic gratings were recorded by different exposure (200 – 500 J/cm2) in the films with different concentration (8 and 20 wt. %) of copper salt. The film sensitivity dependence on polymer molecular weight was studied. Surface relief of the gratings was measured by AFM.

ZnO-nanostructure-based electrochemical sensor: Effect of nanostructure morphology on the sensing of heavy metal ions

ZnO nanostructures are promising candidates for use in sensors, especially in electrochemical sensors and biosensors, due to their unique physical and chemical properties, as well as sensitivity and selectivity to several types of contamination, including heavy metal ions. In this work, using the hydrothermal method, nanostructures of ZnO were synthesized in four different morphologies: nanorods, nanoneedles, nanotubes and nanoplates. To determine the peculiarities of adsorption for each morphology, a series of electrochemical measurements were carried out using these nanostructured ZnO coatings on the working electrodes, using aqueous solutions of Pb(NO3)2 and Cd(NO3)2 as analytes with different concentrations. It was found that the sensitivity of the resulting electrochemical sensors depends on the morphology of the ZnO nanostructures: the best results were achieved in the case of porous nanostructures (nanotubes and nanoplates), whereas the lowest sensitivity corresponded to ZnO nanorods with a large diameter (i.e., low surface-to-volume ratio). The efficiency of sedimentation is also related to the electronegativity of adsorbate: it has been shown that all observed ZnO morphologies exhibited significantly higher sensitivity in detecting lead ions compared to cadmium ions.

STRUCTURAL CHANGES IN PULSED LASER ABLATED CuInSe2 COMPOUND STRUKTURĀLĀS IZMAIŅAS IMPULSA LĀZERA ABLĒTAJĀ CuInSe2 SAVIENOJUMĀ

Abstract CuInSe2 (CISe) compound was produced by high-temperature synthesis. After mechanical milling, the average CISe particle size decreased to 10μm. The authors study structural changes of the compound after ablation in liquid by a 1064 nm pulsed laser. The SEM examination indicated the presence of spherical particles with the average size of ~ 450 nm. A nonlinear relationship was established between the laser radiation dose and the quantity of spherical particles. The XRD analysis has shown an improvement in the CISe crystalline structure and the absence of significant changes in its stoichiometry. The 3 μm thick experimental CISe samples were screen-printed on planar Ni electrodes, and improvement also was revealed in their photosensitivity. The conclusion is that the pulsed-laser ablation can be applied to chalcopyrite structures like CISe without destruction of their initial properties. Kopsavilkums Darba autori apskata impulsa lāzera ablācijas pielietojuma iespēju CuInSe2 savienojumam. Eksperimentu gaitā tika konstatēts, ka ablācijas procesā CuInSe2 vidē veidojas sfēriskas formas daļiņas, kuru izmēri ir atkarīgi no lāzera starojuma parametriem un no vides īpašībām. Apstarotā materiāla analīze uzrādīja CuInSe2 struktūras kvalitātes uzlabojumus, kā arī gaismjūtības palielināšanos par 8%, salīdzinājumā ar neapstarotu materiālu. Darba rezultāti liecina par to, ka, mainot lāzera starojuma parametrus, ir iespējams uzlabot CuInSe2 savienojumu, nesagraujot tā darba īpašības. Aprakstītās eksperimentālās metodes un tehnoloģijas sniedz plašu darbības lauku tālākiem pētījumiem šajā jomā.

Direct Surface Relief Formation in Polymer Films

Due to active development of nanoelectronics, the studies of methods of nanorelief surface formation in different materials, in particular polymers are very important. Organic polymer films in consequence of their dielectric and optical properties have been used as basis of these devices. In this paper, the possibility of UV optical record and electron beam lithography in different type of polymeric films was studied. Mechanisms of molecular structure changes: photoisomerization, destruction, cross-linking and oxidation have been discussed. The results of UV illumination of polyurethanes, polyacrylates, and some block-copolymers were described. The element analysis of polybutadiene block copolymer was performed before and after UV illumination, and the changes in optical transmission spectra of the polymer film were measured. The resolution of electron beam lithography on polymeric films also was studied.

UV optical record and electron beam lithography in polymer films

Possibility of UV optical record and electron beam lithography in different type of organic polymer films was studied. Mechanisms of molecular structure changes: photoisomerization, destruction, cross-linking and oxidation have been discussed. The results of UV illumination of polyurethanes, polyacrilates, and some block-copolymers are described. The element analysis of polyisoprene block copolymer was performed before and after UV illumination, and the changes in transmission spectra of the polymer film were measured. The resolution of electron beam lithography on polymer films was studied. In the polyisoprene block copolymer film the oxidation polymerization was ascertain at UV-illumination.

Photoinduced Birefringence in Azo-Dye Doped Polyurethane

Photoinduced Birefringence in Azo-Dye Doped Polyurethane In this report we describe a photoinduced birefringence in disperse red (DR1) azo-dye doped polyurethane films. DR1 dye molecules in these films are chemically bound with the polyurethane polymers main chain. Under laser radiation the DR1 molecules experience the isomerization process; as a result, the dipole moment of such a molecule changes and they align in the presence of electric field. Photo-birefringence was induced by linearly polarized laser radiation (532 nm, 448 nm, 375 nm and 632.8 nm) in the films with various concentrations of DR1 dye. The photo-induced birefringence (PIBR) Δn was measured at 634 nm wavelength, and its dependences on the pumping beam wavelength and intensity were evaluated. The Δn relaxation was studied both in the dark and under light illumi-nation. In DR1-doped polyurethane films the holographic recording was performed using laser light radiation (532 nm). The profile of surface relief grating (SRG) was studied using AFM. The relationship between SRG formation and PIBR is discussed. Fotoinducētā Dubultlaušana Azo-krāsvielas Saturošā Poliuretānā Kopsavilkums Šajā darbā mēs apskatam fotoinducētu dubultlaušanu azo-krāsvielu Disperse Red 1 (DR1) saturošu poliuretāna plēvītēs. DR1 molekulas šajās plēvītēs ir ķīmiski saistītas ar poliuretāna galveno ķēdi. Gaismas ietekmē DR1 molekulas piedzīvo isomerizācijas procesu, kā rezultātā izmainās molekulas dipola moments un mole-kula novietojas perpendikulāri gaismas elektriskajam laukam. Fotodubultlaušana tika ierosināta ar lineāri polarizētu lāzera starojumu ar 532 nm, 448 nm, 375 nm un 632.8 nm viļņa garumu plēvītēs ar dažādu DR1 krāsvielas koncentrāciju. Fotoinducētā dubultlaušana mērīta pie 634 nm viļņa garu-ma un noteikta tās atkarība no ierosinošā stara viļņa garuma un intensitātes. Relaksācijas process pētīts, plēvīti apgaismojot ar lāzera starojumu, kā arī uzgla-bājot to tumsā. DR1 saturošajā poliuretānā tika veikts hologrāfiskais ieraksts. Šim nolūkam izmantoja lāzeru ar 532 nm viļņa garumu. Virsmas reljefa režgis pētīts ar Atom-spēka mikroskopu. Analizēta sakarība starp virsmas reljefa veidošanos un foto-infudēto dubultlaušanu.