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The relatively slow set speed and poor cycle endurance of typical phase change memories constrain their ambitious goal of replacing all memories in complex hierarchical memory systems. Here, we demonstrate phase change memory devices based on In–Sb2Te3 (InST) with a size of 250 nm, showing the SET speed down to 1 ns and the excellent cycle endurance up to 3.6 × 108 times under 5 ns pulse operation. Doped In atoms occupy cation vacancy lattice positions in Sb2Te3, where they establish robust bonds with Te atoms and restore the lattice's integrity. Rapid crystallization is made possible by the great ability of the In rings to grasp the surrounding Te atoms and the high stability of the In–Te connection. In amorphous InST, lower concentrations of lone pair electrons and voids point to a more compact structure that contributes to good cycle durability by lowering the density difference between the crystalline and amorphous states. These findings provide a feasible candidate for completely replacing the DRAM. [ABSTRACT FROM AUTHOR]

The pressing need for data storage in the era of big data has driven the development of new storage technologies. As a prominent contender for next-generation memory, phase-change memory can effectively increase storage density through multilevel cell operation and can be applied to neuromorphic and in-memory computing. Herein, the structure and properties of Ta-doped MnTe thin films and their inherent correlations are systematically investigated. Amorphous MnTe thin films sequentially precipitated cubic MnTe 2 and hexagonal Te phases with increasing temperature, causing resistance changes. Ta doping inhibited phase segregation in the films and improved their thermal stability in the amorphous state. A phase-change memory cell based on a Ta 2.8% -MnTe thin film exhibited three stable resistive states with low resistive drift coefficients. The study findings reveal the possibility of regulating the two-step phase-change process in Ta-MnTe thin films, providing insight into the design of multilevel phase-change memory.

Phase-change memory (PCM) devices have great potential as multilevel memory cells and artificial synapses for neuromorphic computing hardware. However, their practical use is hampered by resistance drift, a phenomenon commonly attributed to structural relaxation or electronic mechanisms primarily in the context of bulk effects. In this study, we reevaluate the electrical manifestation of resistance drift in sub-100 nm Ge 2 Sb 2 Te 5 (GST) PCM devices, focusing on the contributions of bulk vs interface effects. We employ a combination of measurement techniques to elucidate the current transport mechanism and the electrical manifestation of resistance drift. Our steady-state temperature-dependent measurements reveal that resistance in these devices is predominantly influenced by their electrical contacts, with conduction occurring through thermionic emission (Schottky) at the contacts. Additionally, temporal current-voltage characterization allows us to link the resistance drift to a time-dependent increase in the Schottky barrier height. These findings provide valuable insights, pinpointing the primary contributor to resistance drift in PCM devices: the Schottky barrier height for hole injection at the interface. This underscores the significance of contacts (interface) in the electrical manifestation of drift in PCM devices.

As a non-volatile semiconductor memory technology, phase-change memory has a wide range of application prospects as a result of the excellent comprehensive performance. In this paper, multilayer thin films based on Sb 2 Te 3 material were designed and prepared by inserting the Sn 15 Sb 85 layer. The thermal and electrical properties of superlattice-like Sb 2 Te 3 /Sn 15 Sb 85 phase-change films can be adjusted by controlling the thickness ratio of Sb 2 Te 3 /Sn 15 Sb 85 . In comparison to the monolayer Sb 2 Te 3 film, the multilayer layer Sb 2 Te 3 /Sn 15 Sb 85 materials have a higher crystallization temperature, larger crystallization activation energy, and longer data lifetime, indicating the great improvement of thermal stability. The changes in the phase structure and vibrational modes of multilayer Sb 2 Te 3 /Sn 15 Sb 85 films were characterized by X-ray diffraction and Raman spectroscopy, respectively. The presence of Sn 15 Sb 85 layers restrains grain growth and refines the grain size. The multilayer Sb 2 Te 3 /Sn 15 Sb 85 films exhibit better surface flatness, smaller surface potential undulation, and lower thickness variations than single-layer Sb 2 Te 3 . Phase-change memory cells based on the [Sb 2 Te 3 (1 nm)/Sn 15 Sb 85 (9 nm)] 5 thin film has a lower threshold voltage (1.9 V) and threshold current (3.1 μA) compared to the Ge 2 Sb 2 Te 5 film. Meanwhile, the electrical heating model of a phase-change memory cell based on a [Sb 2 Te 3 (1 nm)/Sn 15 Sb 85 (9 nm)] 5 multilayer structure was established by multiphysics coupling analysis, proving the great improvement in heat transfer performance and efficiency. The experimental and theoretical studies confirm that the insertion of the Sn 15 Sb 85 layer can significantly improve the crystallization properties of Sb 2 Te 3 films, paving the way for optimizing the phase-change materials by regulating the microstructural parameters.

Controlled growth of semiconductor nanowires with atomic precision offers the potential to tune the material properties for integration into scalable functional devices. Despite significant progress in understanding the nanowire growth mechanism, definitive control over atomic positions of its constituents, structure, and morphology via self-assembly remains challenging. Here, we demonstrate an exquisite control over synthesis of cation-ordered nanoscale superstructures in Ge-Sb-Te nanowires with the ability to deterministically vary the nanowire growth direction, crystal facets, and periodicity of cation ordering by tuning the relative precursor flux during synthesis. Furthermore, the role of anisotropy on material properties in cation-ordered nanowire superstructures is illustrated by fabricating phase-change memory (PCM) devices, which show significantly different growth direction dependent amorphization current density. This level of control in synthesizing chemically ordered nanoscale superstructures holds potential to precisely modulate fundamental material properties such as the electronic and thermal transport, which may have implications for PCM, thermoelectrics, and other nanoelectronic devices.

Interface-influenced crystallization is crucial to understanding the nucleation- and growth-dominated crystallization mechanisms in phase-change materials (PCMs), but little is known. Here, we find that composition vacancy can reduce the interface energy by decreasing the coordinate number (CN) at the interface. Compared to growth-dominated GeTe, nucleation-dominated Ge 2 Sb 2 Te 5 (GST) exhibits composition vacancies in the (111) interface to saturate or stabilize the Te-terminated plane. Together, the experimental and computational results provide evidence that GST prefers (111) with reduced CN. Furthermore, the (8 - n ) bonding rule, rather than CN6, in the nuclei of both GeTe and GST results in lower interface energy, allowing crystallization to be observed at the simulation time in general PCMs. In comparison to GeTe, the reduced CN in the GST nuclei further decreases the interface energy, promoting faster nucleation. Our findings provide an approach to designing ultrafast phase-change memory through vacancy-stabilized interfaces.