Electronic Properties and Stacking Ordering in Layered GeTe-Rich (GeTe)m(Sb2Te3)n

In this work, a study of the structural and electronic properties of epitaxial GeTe-rich (GeTe)m(Sb2Te3)nalloys grown on Si substrate by molecular beam epitaxy is presented, with particular focus on the effects of annealing at increasing temperatures. The samples, displaying a lamellar structure stabilized by epitaxy, were investigated by X-ray diffraction and X-ray photoemission spectroscopy after heating in ultra-high vacuum. The combined use of these techniques, supported by density functional theory calculations, reveals compositional and structural changes induced by annealing, clarifying how the rearrangement of residual defects influences the stacking order of the epilayers. These results provide key insights into the vacancy ordering of GeTe-rich (GeTe)m(Sb2Te3)n, which are particularly relevant not only for memory applications but also in light of the recent discovery of (GeTe)m(Sb2Te3)nferroelectricity.