The comparative analysis of the calculated and experimental Raman spectra of non‐crystalline As2S3, Bi2S3 and Sb2S3 films (i.e. with exchanging As to Sb, Bi) obtained by flash evaporation on glassy and silicon substrates was performed. The spectra were interpreted and analysed using the results of molecular modelling and ab initio calculations. The structural models used for calculations include both basic building blocks and other types of atomic clusters known for As‐S, Bi‐S, and Sb‐S binary systems. The influence of atomic substitution on the nanostructure of flash evaporated As(Sb,Bi)2S3 films were investigated, observed photo‐induced phenomena and related peculiarities were analysed using results of ab initio calculations and discussed in detail. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

As-deposited, annealed, and in situ As2S3 nanolayers, illuminated by blue (405 nm) and red (650 nm) laser light, were studied using synchrotron radiation photoelectron spectroscopy and DFT electronic structure calculations. Changes in composition and local atomic coordination occurring in the irradiated region of As2S3 films were monitored by analysis of As 3d and S 2p core levels. These studies show that both the thermal treatment and the red laser illumination of As2S3 nanolayers decrease the concentration of homopolar (As-As and S-S) bonds. From the other hand, an increasing concentration of As-rich structural units (s.u.) with a homopolar As-As bond was observed under in situ blue laser illumination of As2S3 nanolayers. Molecular orbital energies were calculated for different As- and S-centered s.u. and used for the interpretation of the core levels and valence band spectra. The surface local structure of the As2S3 nanolayers and its photoinduced transformation are discussed in detail.

No abstract

The super-bandgap laser irradiation of the in situ prepared As-S chalcogenide films was found to cause drastic structural transformations and unexpected selective diffusion processes, leading to As enrichment on the nanolayer surface. Excitation energy dependent synchrotron radiation photoelectron spectroscopy showed complete reversibility of the molecular transformations and selective laser-driven mass transport during “laser irradiation”-“thermal annealing” cycles. Molecular modeling and density functional theory calculations performed on As-rich cage-like clusters built from basic structural units indicate that the underlying microscopic mechanism of laser induced transformations is connected with the realgar-pararealgar transition in the As-S structure. The detected changes in surface composition as well as the related local and molecular structural transformations are analyzed and a model is proposed and discussed in detail. It is suggested that the formation of a concentration gradient is a result of bond cleavage and molecular reorientation during transformations and anisotropic molecular diffusion.

AsxS100-x (x = 40, 45, 50) thin films top surface nanolayers affected by green (532 nm) diode laser illumination have been studied by high-resolution X-ray photoelectron spectroscopy, Raman spectroscopy, optical spectroscopy, and surface profilometry. It is shown that the composition of obtained films depends not only on the composition of the source material but as well on the composition of the vapor during the evaporation process. Near-bandgap laser light decreases both As–As and S–S homopolar bonds in films, obtained from thermal evaporation of the As40S60 and As50S50 glasses. Although As45S55 composition demonstrates increasing of As–As bonds despite to the partial disappearance of S–S bonds, for explanation of this phenomenon Raman investigations has also been performed. It is shown that As4S3 structural units (s.u.) responsible for the observed effect. Laser light induced surface topology of the As45S55 film has been recorded by 2D profilometer.