| SM ISO690:2012|
PAIUK, Oleksandr; MESHALKIN, Alexei; BOIARINOV, Yu.; PRISĂCAR, Alexandra; ROBU, Stefan; ACHIMOVA, Elena; STRONSKI, Alexander. Holographic gratings recording in carbazole-containing polymer thin films. In: Materials Science and Condensed Matter Physics. Editia a 7-a, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, p. 255.
|Materials Science and Condensed Matter Physics
Editia a 7-a, 2014
Conferința "Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 16-19 septembrie 2014
Carbazolic compounds have attracted wide interest due to their potential applications in such areas as optical data storage and information processing. There has been a widespread interest in carbazole-containing polymers as effective charge-transport elements in photorefractive and photoconductive materials in electrophotography, xerography, electroluminescent, and photovoltaic devices. The host carbazol-containing polymer material is expected to possess good photorefractive, photoconductive, and/or photochemical properties for hologram recording. In this work polyepoxypropilcarbazole (PEPC) was studied as media for holographic recording. The polymer was synthesized as the host polymer matrix and iodoform CHI3 was used as the photosensitizing dye. As the pure polymer material is only sensitive in the UV spectral range its sensitivity should be shifted to the type of recording laser region. To shift the spectral sensitivity to the blue region of spectrum the sensitizing dye such as iodoform CHI3 has been introduced into the samples. The dependence of photosensitivity of the deposited films on the content of iodoform CHI3 was studied earlier, where it was established that the optimum concentration of the iodoform was 10 mass%. Thin polymer films with thickness 1.3 m were prepared from homogeneous polymer solution in toluene by spin coating procedure using spin-coater “SGS Spincoat G3P-8”. Film thickness was determined using the modified interferometric measurement based on MII-4 interference microscope and AFM microscopy. With the purpose of firmly assessing the nature of the synthesized material, a detailed characterization by IR, UV-VIS and Raman spectroscopy was applied. 473 nm 100 mW DPSS laser was used for holographic characterization. Diffraction gratings were recorded on such polymer films by keeping during gratings recording beam ratio as 1:1 and spatial frequency as 1000 lines/mm. After recording of grating wet selective chemical treatment was applied for relief formation. Etching treatment was controlled by the consequent diffraction efficiency measurement in transmission mode at 633 nm wavelength. The carbon tetrachloride was chosen as etching agent. Variation of the diffraction efficiency with recording and etching time was studied. After recording and before selective etching the diffraction efficiency (η) of all samples was less than 0.1%. After chemical etching due to relief formation the diffraction efficiency was increased up to 18%. Diffraction efficiency of etching polymer films as depended on etching time is shown in Table. Sample composition Etching time, s 5 10 15 20 PEPC 5% 10% 18% 15% On exposing to the interference pattern, the CHI3 molecules get excited and electron transfer takes place between carbazole ring and CHI3. This reaction produce carbazole radical and this radical initiates the polymerization reaction. Polymerization takes place at the region of constructive interference and as a result this polymerization (crosslinking) contribute to the structurization of copolymer. This structurization takes place without significant change of the refractive index and transmittance of film (as was mentioned above the diffraction efficiency in this case is less than 0.1%) which leads to the hidden grating formation. The grating formation can be revealed only by wet selective etching.