Reversible Crystalline‐Crystalline Transitions in Chalcogenide Phase‐Change Materials

Abstract Phase‐change random access memory (PCRAM) is one of the most technologically mature candidates for next‐generation non‐volatile memory and is currently at the forefront of artificial intelligence and neuromorphic computing. Traditional PCRAM exploits the typical phase transition and electrical/optical contrast between non‐crystalline and crystalline states of chalcogenide phase‐change materials (PCMs). Currently, traditional PCRAM faces challenges that vastly hinder further memory optimization, for example, the high‐power consumption, significant resistance drift, and the contradictory nature between crystallization speed and thermal stability, nearly all of them are related to the non‐crystalline state of PCMs. In this respect, a reversible crystalline‐to‐crystalline phase transition can solve the above problems. This review delves into the atomic structures and switching mechanisms of the emerging atypical crystalline‐to‐crystalline transitions, and the understanding of the thermodynamic and kinetic features. Ultimately, an outlook is provided on the future opportunities that atypical all‐crystalline phase transitions offer for the development of a novel PCRAM, along with the key challenges that remain to be addressed.