CC BY
20LM-O-23
Morphological and phase modifications of amorphous Ge2Sb2Te5 thin films on dielectric substrate induced by femtosecond laser
irradiation
A.V. Kolchin1, S.V. Zabotnov1, D.V. Orlov1, D.V. Shuleiko1, L.A. Golovan1, D.E. Presnov1, T.P. Kamenskayd, P.I. Lazarenko2, T.S. Kunkel3, S.A. Kozyukhin4, P.K.
Kashkarov15
1-M.V. LomonosovMoscow State University, Moscow, Russia 2-National Research University of Electronic Technology Zelenograd, Russia
3-Moscow Institute of Physics and Technology, Dolgoprudniy, Russia 4-N.S. Kurnakov Institute of General and Inorganic Chemistry, Moscow, Russia 5-National Research Center «Kurchatov Institute», Moscow, Russia
Chalcogenide quasi-binary alloys such as Ge2Sb2Tes (GST225) are represented as a basic material for non-volatile and rewritable memory applications, as well as reconfigurable nanophotonical devices [1 Femtosecond laser irradiation of amorphous GST225 thin films on conductive substrates possess both reversible phase switching and for mation of surface gratings with wavelength period [2]. However, similar investigations haven't been provided with such samples on dielectric substrates. It is necessary to demonstrate easy integration of formed ripples to all-dielectric nanophotonical devices. Amorphous GST225 thin films with thicknesses 130 nm were deposited by magnetron sputtering on oxidized silicon substrate. The samples were subsequently treated by femtosecond laser pulses ( 1250 nm, 135 fs, 10 Hz, 0.1 J/cm2) at the scanning mode (laser pulses per spot Ns from 3 to 750). Scanning electron (SEM) and atomic-force microscopies (AFM) techniques revealed formation of so-called laser-induced periodic surface structures (LIPSS) since Ns=150. The observed grain ridges are ordered with period 120 0-1300 nm and directed orthogonally to the incident laser polarization. Such structural properties may emerge surface plasmon-polariton excitation during intensive photoinduction of free charge carriers [3]. Sipe-Drude theory simulations confirm this hypot hesis [4]. In turn, wide broadband from 110 to 180 cm1 at the Raman spectra show amorphous structure of initial samples The line 125 cm-1 increases with the pulse number growth from N1=3 to Ns=15. It indicates driven transitior to metastable face-centered cubic (fcc) crystalline phase [5]. For the greater Ns (from 30 to 750) values the line 125 cm-1 decreases. Such behavior may correspond to possible re-amorphization [2]. The research was supported by RFBR (grant № 20-32-90111).
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