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We have investigated photoinduced effects in as-deposited Ge 40−x Sb x Se 60 (x = 8, 15, and 20) films via in situ measurements of transmission spectra for wavelengths λ = 500 to 950 nm. The absorption coefficient increases initially, indicating the photodarkening (PD) effect, which rapidly saturates in tens of seconds. Then the absorption coefficient starts decreasing representing photobleaching (PB). The evolution of PD and PB can be described by stretched exponential function, yielding the time constants for the changes in absorption coefficients. The kinetics of PD is faster than that of PB. The coexistence of PB and PD suggests that the Sb and Ge based structural units of Ge-Sb-Se films respond to bandgap radiation independently. The structural origins of the observed opposing photoinduced effects are discussed. [ABSTRACT FROM AUTHOR]

Laser heating of chalcogenide glasses has successfully produced rotating lattice single crystals through a solid-solid transformation. To better understand the nature of complex, orientation-dependent lattice rotation, we designed heat profiles of the continuous wave laser by beam shaping, fabricated larger Sb2S3 crystal dots in Sb2S3 glass, and investigated the lattice rotation where the crystal could grow in all radial directions under a circular thermal gradient. The results show that the rate of lattice rotation is highly anisotropic and depends on crystallographic direction. The nature of this rotation is the same in crystals of different orientation relative to the surface. The growth directions that align with the slip planes show the highest rate of rotation and the rotation rate gradually decreases away from this direction. Additionally, the presence of multiple growth directions results in a complicated rotation system. We suggest that the growth front influences the density of dislocations introduced during growth under confinement and thus affects the lattice rotation rate in these crystals. [ABSTRACT FROM AUTHOR]

Laser heating can be used to produce single crystal architectures in glass with a lattice that rotates at a constant rate. Such metamaterials can offer properties that are disallowed by conventional crystal structures. To establish the mechanism of this lattice rotation, we used transmission electron microscopy (TEM) to directly observe and characterize dislocations in Sb 2 S 3 crystal lines fabricated in Sb-S-I glass as a model system. The lattice rotation calculated from the density and Burgers vectors of edge dislocations agrees with lattice rotation values experimentally determined by electron backscatter diffraction (EBSD) and selected area diffraction patterns (SADP). These results provide the first direct proof of the dislocation mechanism of lattice rotation in rotating lattice single (RLS) crystals, and very likely other forms of growth actuated bending, twisting and noncrystallographic branching as seen in spherulites. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Photoinduced expansion is a special property of chalcogenide glasses, which makes them useful for various applications in photonics. A clear understanding of the kinetics and the topography of photoinduced effects is fundamental to improve potential applications. A detailed study on bulk glass is performed using in situ Atomic Force Microscope measurements. The corresponding expected thermal contribution is obtained by numerical simulation using Finite Elemental Analysis method. The results show a significant difference between the dynamics of metastable/permanent and transitory effects, with the permanent photoexpansion being much larger in magnitude and slower in kinetics than the transient or reversible changes. The former effect is of athermal origin. However, the dynamic response of the latter is similar to that expected from thermoelastic expansion, suggesting a close correlation between the two effects, which remains to be established. Image 1 • Thermal and athermal contributions for the dynamics of the laser induced effects in A s 2 S 3 bulk glass. • In situ laser-induced surface deformation measurement by Atomic Force Microscopy. • Numerical determination of the thermal contribution for the transient part of photoexpansion. [ABSTRACT FROM AUTHOR]

Abstract Chalcogenide glass – silver heterostructures are candidates for photoresist and diffractive optical applications. To optimize their processing, we report the kinetics of Ag photo-dissolution in As 2 S 3 matrix using in-situ optical transmission/reflection measurements and real time atomic force microscopy (AFM) imaging under optical illumination. The results indicate that photo-dissolution occurs in three stages with the extent and kinetics of each stage depending strongly on Ag film thickness. By contrast, the photo-dissolution is found to be independent of As 2 S 3 matrix thickness. The extent of three stages also depends strongly on the laser dose and can be reduced to two stages at higher laser fluence. A comparative study of two oppositely stacked sample configurations: As 2 S 3 /Ag/glass and Ag/As 2 S 3 /glass show that the heterostructures respond differently to light illumination. For the former, Ag dissolves completely into As 2 S 3 matrix at a faster rate than for the latter case. The origin of this difference is established by energy dispersive X-ray spectroscopy and AFM measurements. Highlights • We resolve three different stages of Ag photo-dissolution in As 2 S 3 matrix. • The kinetics and extent of each stage depend strongly on Ag film thickness and laser fluence. • Ag photo-dissolution is found to be independent of As 2 S 3 matrix film thickness. • The sequence of Ag and As 2 S 3 films within stacked heterostructure strongly affects Ag photo-dissolution. • In situ AFM imaging shows real time evolution of morphological changes resulting from Ag dissolution into As 2 S 3 matrix [ABSTRACT FROM AUTHOR]

Abstract: The use of high resolution X-ray photoelectron spectroscopy to study chalcogenide glass thin films is analyzed. It is shown that the method is an effective tool to explore different chemical environments in the films and control chemical composition of the surface. Examples of the method applications such as kinetics study of induced silver dissolution in the thin films and investigation of oxidation on the surface of the thin film are presented. Limitations of the method are shown on the example of photoinduced structural transformations in chalcogenide glass thin films. [Copyright &y& Elsevier]

Abstract: Changes of electronic and atomic structure during silver photodissolution in As2S3 thin film are studied using a combination of high-resolution X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) methods. It is shown that the photodiffusion process starts already under the influence of Al Kα and synchrotron X-ray probe radiations, forming a highly disordered metastable structure. Concurrent irradiation with UV/VIS light leads to the formation of a stable uniform ternary phase. The mechanisms of structural transformations and final chemical products are proposed. The influence of surface oxidation on the structure of Ag/As2S3 bilayer is also investigated. [Copyright &y& Elsevier]