Nanoplasmonics and surface enhanced spectroscopy

Impact of surface plasmon polaritons on photostimulated diffusion in light-sensitive Ag–As4Ge30S66 structures.
Indutnyi I. Z., Mynko V. I., Sopinskyy M. V., Danko V. A. and Lytvyn P. M.
V. Lashkaryov Institute of Semiconductor Physics Natl. Acad. of Sci. of Ukraine. 45 Prospect Nauky, 03028 Kyiv, Ukraine.  
E-mail: indutnyy@isp.kiev.ua 

A surface plasmon polariton (SPP), or surface plasma wave, is an electromagnetic wave that propagates along the interface between a metal and dielectric material. SPPs are characterized by localization of the electromagnetic field near the interface, where electromagnetic field strength is much higher than that of the exciting radiation. In the previous study [1], we observed the acceleration of photostimulated diffusion of silver into the As2S3 film under the action of the SPP field excited at the interface between the profiled surface of the silver layer (in the form of a diffraction grating) and the As2S3 layer. However, photosensitive structures that use germanium chalcogenide films (or ternary compounds based on germanium chalcogenides with low arsenic content) are of greater practical interest. Therefore, in this work, we studied the effect of SPP excitation on the photostimulated diffusion of silver in Ag-As4Ge30S66 structures with thin (5 –13 nm) chalcogenide layers.
Gratings with a period of a = 519 nm and modulation depth of h/a ≈ 0.037 (where h is the grating depth) were formed on chalcogenide photoresist films by interference lithography, covered with 80 nm thick opaque aluminum film, and then with 85 nm thick silver film. A layer of As4Ge30S66 was deposited on the surface of the silver grating by thermal evaporation in a vacuum. Photostimulated changes in this structure were registered by measuring the angular dependences of the specular reflection (Rp) of 632.8 nm wavelength p-polarized light. It was found that, as a result of exposure, the “degradation” (broadening, increase in reflection at the minimum) of the Rp angular dependence minimum (SPP resonance) occurs faster when samples are irradiated with SPP excitation. This observation indicates the 6x acceleration of the photostimulated diffusion process in this structure under the plasmon field action.

1.	Ivan Indutnyi, Viktor Mynko, Mykola Sopinskyy, Petro Lytvyn, Impact of Surface Plasmon Polaritons on Silver Photodiffusion into As2S3 Film // Plasmonics. – 2021. – 16, №1. – P. 181 – 188.