High-stability van der Waals structures of GeTe/Sb${}_2$Te${}_3$ superlattices for 100× increased durability phase-change memory (PCM) by low-temperature atomic layer deposition

The superlattices phase-change memory (SL-PCM), based on GeTe/Sb${}_2$Te${}_3$ superlattices (SLs), garners considerable attention within the academic community owing to its exceptional electrical properties. While the exact mechanism remains a topic of ongoing debate, researchers widely acknowledge that the presence of van der Waals (vdW) gap structures within SLs plays a pivotal role. However, the formation of vertical nanoparticles (VNPs) from the random orientation of Sb${}_2$Te${}_3$ and the substantial intermixing between GeTe and Sb${}_2$Te${}_3$ due to high-temperature fabrication processes leads to pronounced elemental intermixing during electrical operations, causing a loss of SLs properties. This investigation uses atomic layer deposition techniques, specifically Sb-atomic seed layer and periodic quintuple layers stacking, to address issues from random orientation Sb${}_2$Te${}_3$ grains and anomalous VNPs. This approach yields Sb${}_2$Te${}_3$ crystalline films with a high-stability vdW gap structures. By leveraging these films, SLs with a preferred crystallographic orientation at a notable low temperature of 90 °C are successfully fabricated. The optimized SLs exhibit remarkable structural stability and mitigate alloy phase emergence during electrical operations, resulting in a 100-fold enhancement in device durability. This work advances reliable SL-PCM understanding and implementation, propelling this memory technology into the next generation. (© 2024 Wiley‐VCH GmbH)