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Journal of Materials Science: Materials in Electronics, vol.36, no.27, 2025 (SCI-Expanded)
Amorphous Ge20Te80, Sb40Te60, and Ge20SbxTe80-x (x = 1, 2, 5, 10) compounds were synthesized and deposited as thin films (40–80 nm) on glass substrates via thermal evaporation under high vacuum (10–5 Torr). Their structural characteristics were examined using X-ray diffraction, scanning electron microscopy, and atomic-force microscopy. Applying the void–cluster model, the quasi-period of density fluctuations (r), correlation length (L), and packing fraction (L/r) were estimated from the first sharp diffraction peak in the XRD patterns. Partial substitution of Te by Sb in Ge20Te80 led to a reduction in L and L/r, indicating increase in structural disorder. Raman spectroscopy revealed vibrational modes associated with short-range ordering in Ge20Te80 and Sb40Te60, aiding interpretation of Ge20SbₓTe80₋ₓ films. In Ge20Te80, dominant Raman peaks at 121.5 and 139 cm−1 were assigned to GeTe₄₋nGen (n = 0, 1) tetrahedra, while bands at 154–159 cm−1 and 174–177 cm−1 corresponded to Te chains and defective octahedral units. For Sb40Te60 films, peaks at 124.5 and 142 cm−1 were attributed to Sb–Te vibrations in pyramidal SbTe₃ units and distorted octahedral Sb coordination. Additional peaks at 97 and 152 cm−1 were associated with Te–Te bonds, while the band at 113.5 cm−1 corresponds to Sb–Te stretching modes. The Raman intensity at 121.5, 139 and 157 cm−1 in Ge20SbxTe80-x exhibits a non-monotonic dependence on Sb concentration, reaching a maximum at x = 2. A low- frequency boson peak (< 100 cm−1) observed in Sb40Te60 suggests a high density of low-energy vibrational states, characteristic of disordered structure.