Metal–insulator transition in ScxSb2Te3 phase-change memory alloys

The scandium doped antimony tellurides (ScxSb2Te3), as promising phase-change memory materials, possess the merits of ultrafast crystallization speed and ultralow resistance drift, of the amorphous phases, ensuring the development of cache-type universal memory and high-accuracy computing chip. There is keenness to further explore the annealing effect in the crystalline ScxSb2Te3 phases to seek a potential metal–insulator transition (MIT) in electrical conduction, by which more intermediate resistance states of superior stability can be generated to enhance the programming contrast and accuracy. In this work, we have identified the metastable rock salt ScxSb2Te3 as an Anderson-type insulator and verified that the MIT occurs in its stable rhombohedral grains when lattice vacancies are highly ordered into the van der Waals-like gaps. The Sc dopant can exert profound influence on retarding the vacancy-ordering procedure, even completely prohibiting the MIT for the Sc-rich compounds. Our work suggests that tuning Sc content in ScxSb2Te3 alloys provides a simple route to engineer the material microstructures and electrical properties for the desired memory and computing performances.