Encoding multistate charge order and chirality in endotaxial heterostructures

High-density phase change memory (PCM) storage is proposed for materials with multiple intermediate resistance states, which have been observed in 1T-TaS2 due to charge density wave (CDW) phase transitions. However, the metastability responsible for this behavior makes the presence of multistate switching unpredictable in TaS2 devices. Here, we demonstrate the fabrication of nanothick verti-lateral H-TaS2/1T-TaS2 heterostructures in which the number of endotaxial metallic H-TaS2 monolayers dictates the number of resistance transitions in 1T-TaS2 lamellae near room temperature. Further, we also observe optically active heterochirality in the CDW superlattice structure, which is modulated in concert with the resistivity steps, and we show how strain engineering can be used to nucleate these polytype conversions. This work positions the principle of endotaxial heterostructures as a promising conceptual framework for reliable, non-volatile, and multi-level switching of structure, chirality, and resistance. Phase transitions in charge density wave materials could be useful for memory and electronic device applications. Here, the authors correlate the temperature-driven transitions in the electrical and optical properties of H-TaS2/1T-TaS2 heterostructures to the number of endotaxial metallic H-TaS2 monolayers.

Automated summary

In this study, researchers demonstrate high-density phase change memory based on phase transition materials. By fabricating H-TaS2/1T-TaS2 heterostructures, they observe optically active heterochirality and correlate it with resistivity steps in the CDW superlattice structure. They also show the role of strain engineering in promoting multi-level switching.