CPPP 23 P Optical properties of amorphous (As2S1.5Se1.5)0.99:Sn0.01 thin films
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IASENIUC, Oxana, ANDRIESH, Andrei, ABASHKIN, A.. CPPP 23 P Optical properties of amorphous (As2S1.5Se1.5)0.99:Sn0.01 thin films. In: Materials Science and Condensed Matter Physics, 13-17 septembrie 2010, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2010, Editia 5, p. 150.
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Materials Science and Condensed Matter Physics
Editia 5, 2010
Conferința "Materials Science and Condensed Matter Physics"
Chișinău, Moldova, 13-17 septembrie 2010

CPPP 23 P Optical properties of amorphous (As2S1.5Se1.5)0.99:Sn0.01 thin films


Pag. 150-150

Iaseniuc Oxana, Andriesh Andrei, Abashkin A.
 
Institute of Applied Physics
 
Disponibil în IBN: 16 aprilie 2021


Rezumat

Thin films of chalcogenide glasses are currently a subject of systematic research because they manifest strong photo- and thermally-induced properties that offer the possibility of using amorphous chalcogenides for high-density information storage, high-resolution display devices, fabrication of diffractive optics such as Bragg gratings elements, inorganic photo-resists, and different holographic patterns. In this context the most studied compositions are As2S3 and As2Se3 . It is known, that the As-S system has lower photosensitivity then As-Se system, but As-S-Se system possess maximum phase shift in infrared that makes them attractive candidates for some important technological applications. Special interest for the using of chalcogenide amorphous films is connected with their metal doping, which alter optical, photoelectrical and photochemical properties of the host material. Of special interest is doping with tin because doping of chalcogenide films by tin assist in stabilizing the glassy matrix increases the refractive index and photosensitivity [1,2,3], the band gap decrease with increasing of tin concentration and the maximum modifications of the refractive index under the light irradiation Δn (Δn=0.20) occur for the composition Sb2Se3:Sn0.01 [4]. In the present paper the photoinduced transformations in thin films (As2S1.5Se1.5)1-х:Snх (х=0.01 ат.%) were studied, and the optical constants (refractive index n, photoinduced change of refractive index Δn, change of optical band gap Eg opt, the absorption coefficient α and extinction coefficient k) have been calculated. This bulk material was prepared by conventional melt-quenching technique from elements heated together in an evacuated silica ampoule (at T=900ºС during about 30h). Thin films (thicknesses 0.28; 0.34; 0.45μms) were prepared by thermal evaporation during 30s-90s. The sample thicknesses were measured by interferometer Linnik. The chemical composition of the deposited films was checked using EnergyDispersive X-ray Spectroscopy. The optical transmission spectra at normal incidence were obtained over the 300-800 nm wavelength spectral regions by a double-beam computer-controlled spectrophotometer Specord UV VIS before and after exposure. In the present work the envelope method for the calculating the optical constants suggested by Swanepoel and Tauc, which based on the extremes of the interference fringes of the obtained spectra, has been applied. Chalcogenide thin films were exposed by quartz halogen lamp with an IR filter (λ = 400-700 nm), UV lamp with a filter (λmax = 330 nm), Nd: YAG laser (λ = 532 nm) and He-Ne laser (λ = 633 nm). The relatively higher sensitivity was shown to Nd: YAG laser and halogen lamp. The influence of the light exposure on the optical transmission was examined after Nd: YAG laser illumination of the samples during 5min, 10min, and 30min. As a result of illumination the optical absorption edge shifts to longer wavelengths. Results of calculation of optical constants of thin films (As2S1.5 Se1.5)0.99:Sn0.01 showed that before illumination: n = 2.52 ± 0.02 (at λ = 700 nm of transmission spectra); Eg opt = 2.16 ± 0.01 eV. And after light exposition the results are: n = 2.62 ± 0.02 (at λ = 700 nm of transmission spectra); Eg opt = 2.09 ± 0.01 eV; Δ Eg opt = 0.07 ± 0.01 eV; Δn = 0.10 ± 0.02. Such large changes in refractive index and a small shift of the optical absorption edge allows to use this material in the form of thin films for fabrication of diffractive elements and channel waveguides recording.