Evolution of surface relief gratings in As20Se80 amorphous chalcogenide films under laser illumination

• Published in: Journal of non-crystalline solids Vol. 588; p. 121611
• Main Authors: Kaganovskii, Yu, Freilikher, V., Rosenbluh, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2022
• Subjects: Amorphous chalcogenide films; Diffusion; Light induced mass transport; Surface profile variation; Amorphous chalcogenide films; Surface profile variation; 66.30.h; 60.80.Fe; Diffusion; 81.05.Ge; Light induced mass transport; 81.65.Cf
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2022.121611

•Profile evolution depends on the period of surface relief gratings.•Profile variation occurs by diffusion driven by capillary and electrostatic forces.•Competition between driven forces defines flattening or growth of grating amplitudes.•Data on profile variation allows measuring photo-induced diffusion coefficients Variation of grating amplitudes on a surface of amorphous chalcogenide films (ACF) As20Se80 has been studied under illumination by a band-gap light with the purpose to understand mechanism of photo-induced (PI) mass transfer. After holographic recording of surface relief gratings (SRGs) of various periods Λ (from 3 to 15 µm) they were illuminated by a diode laser (λ = 660 nm) and their profile variation was analyzed using optical microscopy, atomic force microscopy, light scattering, and optical profilometry. The SRGs with Λ < 8 µm exponentially flattened with time of illumination, whereas amplitudes of the SRGs with Λ > 8 µm exponentially grew. Theoretical analysis of the kinetics of PI mass transfer shows that the SRG profile variation occurs by bulk diffusion of As and Se atoms as a result of competition between capillary forces and electrostatic forces created by redistribution of electrons and holes generated by light. Our theory predicts both flattening and growth of the SRG amplitudes under uniform light illumination. The PI diffusion coefficients have been estimated both from the flattening kinetics of the SRG amplitude and from its growth and found to be in good agreement with the theory. It is also observed that the profile evolution is accompanied by dewetting of ACFs and roughening of the initial SRGs.