Laser Recording in Chalcogenide Glass Films: Driving Forces and Kinetics of the Mass Transfer

Abstract

Herein, precision recording of indented dots and lines in As10Se90 and As2S3 chalcogenide glass films by a focused laser beam is demonstrated and the kinetics and mechanisms of mass transfer under illumination are studied. Due to inhomogeneous intensity distribution and local heating of the film at the focal point, the beam at rest produces an indentation whose depth increases with time and laser power. Illumination by a moving beam leads to formation of groves whose morphology depends on the beam speed and power. At low light intensities, formation of the indentations occurs in the solid phase, due to photoinduced radial diffusion of the film constituents coupled with electrons and holes created by light. The two main driving forces present are: 1) a lateral steady‐state electric field formed due to different mobilities of electrons and holes and 2) driving force of thermodiffusion (Soret effect). At high light intensities, formation of the indentations and grooves occurs with the participation of a liquid phase, with an additional mechanism of viscous flow caused by a gradient in surface tension. However, the contribution of viscous flow mechanism is small compared with diffusion mass transfer. Calculated profiles of the indentations and grooves are in a good agreement with experimental data.

Insight into the photoinduced phenomena in ternary Ge-Sb-Se sputtered thin films

“…Such change is coming from a mutual polymerization of defective entities resulting in ordered structures via homo-to heteropolar bond conversion [1]. The excitation generates the charged radiation defects followed by recombination-induced bond rearrangements due to the diffusion of atoms [21]. Although the photoexcited states have not yet been proven experimentally [22], their existence leading to an increased short-and mediumrange order [23] is generally accepted explanation of irreversible changes in different properties including absorption edge shift.…”