Phase-change random access memory is a promising technique to realize universal memory and neuromorphic computing, where the demand for robust multibit programming drives exploration for high-accuracy resistance control in memory cells. Here in Sc x Sb 2 Te 3 phase-change material films, we demonstrate thickness-independent conductance evolution, presenting an unprecedently low resistance−drift coefficient in the range of ∼10 −4 −10 −3 , ∼3−2 orders of magnitude lower compared to conventional Ge 2 Sb 2 Te 5 . By atom probe tomography and ab initio simulations, we unveiled that nanoscale chemical inhomogeneity and constrained Peierls distortion together suppress structural relaxation, rendering an almost invariant electronic band structure and thereby the ultralow resistance drift of Sc x Sb 2 Te 3 films upon aging. Associated with subnanosecond crystallization speed, Sc x Sb 2 Te 3 serves as the most appropriate candidate for developing high-accuracy cache-type computing chips. KEYWORDS: Sc x Sb 2 Te 3 phase-change materials, atom probe tomography, chemical heterogeneity, resistance drift

Ovonic threshold switching in chalcogenide glasses is a crucial physical phenomenon behind state-of-the-art memory chip technologies. Binary tellurides are one of the emerging candidates that deliver excellent properties, notably the large driving current and fast accessing speed, for volatile selector applications; however, the underlying switching mechanism remains poorly understood. To tackle this issue, we targeted the prototypical boron tellurides, further elevating the selector performances. Via ab initio simulating the electronic excitation process in the amorphous boron tellurides, we observed reversible semiconductor-metal transitions that can reflect the switching principles of the selectors. The transient switching in conductance originates from fine structural tunings, namely, the changes of constraint surrounding the big boron clusters and conversions between covalent and hypervalent bonding schemes throughout the entire tellurium network. Our work provides much-needed atomistic insight into the ovonic threshold switching mechanisms that may enlighten the material design to enable superior selector devices.