Athermal Photoelectronic Effects in Non-Crystalline Chalcogenides: Current Status and Beyond

Abstract

Dedicated to Prof. George N. Papatheodorou on the occasion of his 80 th birthday.

Raman evidence for the oxidation of amorphous As2(SexS1–x)3 film surfaces under visible light

“…Photoinduced mass transport upon illumination at λ exc , P exc , and duration values of the same order was earlier reported for amorphous arsenic chalcogenides, revealing the formation of similar pits in the laser spot with depth up to 500-600 nm as well as noticeable protrusions with lateral size up to several micrometers [4, 13-15, 28, 43]. Despite a temptation to ascribe the drastic changes of the amorphous film surface to illumination-induced heating, the formation of the pit and the surrounding circular protrusion are generally attributed to a nonthermal mechanism related to photosoftening (photofluidisation) [1,3,4,28,43]. Local structural changes in amorphous chalcogenides upon illumination are considered as relaxation events in the vicinity of the atom having absorbed a photon.…”

“…Although at the microscopic level the material structure is constantly changed with perpetual bond breaking and rearrangement, at the macroscopic level it is in a 'saturated' dynamic state with constant physical characteristics. A variety of acts of formation, changing, and vanishing of local and collective energy barriers occurring under illumination lead to multiple local fluidisation events [3,44,45]. The photofluidisation is revealed as a drastic decrease of the material viscosity and a strongly enhanced diffusion under intense illumination.…”

“…Amorphous arsenic chalcogenides are extensively studied due to a variety of photostructural effects resulting in drastic changes of their properties under illumination by light of appropriate energy, intensity, and polarization [1][2][3][4]. The photoinduced effects make these materials suitable for applications in all-optical switching [5,6], waveguides [7], memory devices [8], holographic gratings [6], microstructured optical fibres [9], photoresists [10], substrates for surface-enhanced Raman scattering (SERS) [11], etc.…”