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Evolution of Low‐Frequency Vibrational Modes in Ultrathin GeSbTe Films
Author(s) -
Zallo Eugenio,
Dragoni Daniele,
Zaytseva Yuliya,
Cecchi Stefano,
Borgardt Nikolai I.,
Bernasconi Marco,
Calarco Raffaella
Publication year - 2021
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.202000434
Subject(s) - raman spectroscopy , materials science , van der waals force , epitaxy , lamella (surface anatomy) , molecular vibration , molecular beam epitaxy , density functional theory , spectroscopy , molecular physics , layer (electronics) , optoelectronics , chemical physics , optics , nanotechnology , chemistry , computational chemistry , molecule , physics , organic chemistry , quantum mechanics , composite material
GeSbTe (GST) phase‐change alloys feature layered crystalline structures made of lamellae separated by van der Waals (vdW) gaps. This work sheds light on the dependence of interlamellae interactions at the vdW gap on film thickness of GST alloys as probed by vibrational spectroscopy. Molecular beam epitaxy is used for designing GST layers down to a single lamella. By combining density‐functional theory and Raman spectroscopy, a direct and simple method is demonstrated to identify the thickness of the GST film. The shift of the vibrational modes is studied as a function of the layer size, and the low‐frequency range opens up a new route to probe the number of lamellae for different GST compositions. Comparison between experimental and theoretical Raman spectra highlights the precision growth control obtained by the epitaxial technique.