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.

中文翻译：

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超薄GeSbTe薄膜中的低频振动模式的演变

GeSbTe（GST）相变合金具有层状晶体结构，该结构由由范德华（vdW）缝隙隔开的薄片制成。这项工作揭示了vdW间隙处的层间相互作用对GST合金膜厚的依赖性，这是通过振动光谱法进行探测的。分子束外延用于设计GST层直至单个薄片。通过结合密度泛函理论和拉曼光谱，证明了直接简单的方法来识别GST膜的厚度。研究了振动模式随层大小的变化，低频范围开辟了一条新的途径来探究不同GST成分的薄片数量。实验和理论拉曼光谱之间的比较突出了通过外延技术获得的精确生长控制。