Atomic‐Scale Epitaxy for Tailoring Crystalline GeSbTe Alloys Into Bidimensional Phases

In this study, we establish an accurate growth diagram—describing the phase, composition, and atomic stacking of Ge-Sb-Te alloys (GST)—that can be used as a prediction tool for thin film deposition. This framework for epitaxy at the atomic scale allows for designing tailored crystalline GST phases with precise atomic layer stacking configurations. By leveraging insights into phase stability, we optimize growth conditions to achieve high-quality, bidimensional GST structures of different compositions (Ge2Sb2Te5, Ge3Sb2Te6, and Ge1Sb2Te4) and phases (ordered-cubic and trigonal). Moreover, we examine the influence of structural anisotropies and interface effects on the low-temperature magneto-transport properties. The orientational ordering of the vacancy layers and their evolution into van der Waals gaps alters the electrical conduction dramatically, plausibly also in the presence of the topological surface states and their coupling with the bulk states. In addition, we examine the reversible transition between two stable resistance states in a memory cell for the GST precisely tailored by the growth using Molecular Beam Epitaxy (MBE). Its textured structure favors low power consumption, making it a promising candidate for phase-change memory technology.