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The present paper is concerned with investigations of photosensitive properties of As-S thin layers. Spectral dependence of the refraction index n of variously treated (virgin, exposed, annealed) samples was estimated from optical transmission in the spectral region 400 - 2500 nm. The n energy dependence of variously treated samples was fitted by the Wemple-DiDomenico dispersion relationship and used to estimate the single-oscillator model parameters. It was found, that exposure, as well as annealing leads to the increase in n values over the all investigated spectral region. Compositional dependencies of single-oscillator model parameter Ed (dispersion energy), optical dielectric constant e(0) show maximum at stoichiometric composition As40-S60 and, possibly, weak maximum at As28.6S71.4 composition. Composition evolution of the intensity of bands in Raman spectra corresponding to the As rich and S rich molecular fragments is in agreement with compositional changes of Ed and optical dielectric constant. Changes of the parameters of the single-oscillator model induced by treatment are discussed on the base of photo- and thermally-induced structural changes and are consistent with topological models and models that claim a degree of chemical ordering. Such photoinduced structural changes provide good etching selectivity of As-S layers in amine based solvents. Surface relief patterns that were fabricated have good surface quality. Diffraction efficiency values of holographic diffraction gratings obtained on the base of As100-XSX layers consisted 60 - 70%.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A bond-conversion model for the photostructural changes in the photoluminescence and Raman spectra is proposed. The essential role in this model belongs to lone-pair electrons of chalcogen atoms, which are optically convert into bonding ones, leading to the structure reconstruction.

The present paper deals with an investigation of the image formation properties of As40Se60 thin layers and their application for the production of diffractive optical elements. Thin layers (0.5 - 5 micrometers ) were deposited by the vacuum thermal evaporation and exposed by a Xe-lamp or annealed at 150 degree(s)C. The spectral dependence of the index of refraction, n, of variously treated samples was obtained using Swanepoel method and the single-oscillator model parameters ((epsilon) , Eo, Ed) were estimated. Photo- and thermally induced changes of n, (epsilon) , Eo and Ed induced by exposure or by annealing are discussed on the basis of photo- and thermally induced structural changes, which were directly confirmed by Raman spectroscopy. Such photostructural changes provide good etching selectivity of unexposed and exposed parts of As40Se60 layers in amine based solutions. This provides possibility for the fabrication of surface-relief patterns. The sensitivity of As40Se60 layers has been found to be approximately 10 cm2/J. Holographic diffraction gratings were produced by the Ar and/or HeNe laser exposure. Diffraction efficiency values of holographic gratings achieved approximately 90% for the polarized light. The results obtained show that As40Se60 inorganic resists can be used for the production of holographic diffraction gratings.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The results of investigations of photostimulated phenomena in As 40 S 40 Se 20 thin films with the help of optical methods are presented in this paper. Raman spectra, optical constants in the transparency region of as- evaporated, exposed and annealed films were obtained. The As 40 S 40 Se 20 thin films have shown good etching selectivity in amine based (in particular, nonaqueous solutions based on triethylamine) etching solutions.

Reversible changes of the Raman spectra by the cycle of band-gap laser irradiation and annialing (storing in the dark) has been observed for amorphous Ge 20 S 80 thin films for the first time. The observed changes in the region of stretch vibrations of the chalcogenide atoms is direct evidence for the occurrence of gross structural changes in local bonding configuration caused by optical irradiation. It has been shown that under the laser irradiation the bonding tendency of the chalcogenide atoms is to form rings rather than chains, i.e. the cis-conformation is preferred over trans-conformation.