Abstract
Sn-doped GeTe (SGT) nanowires (NWs) were investigated systematically for use in phase-change memory (PCM) applications. Composition and microstructure characterizations indicate that SGT with ∼3.0% Sn (SGT_3.0) NWs preserves the GeTe rhombohedral (R) structure, whereas SGT with a Sn content of ∼25.0% (SGT_25.0) NWs exhibits a cubic (C) structure. R–C structural conversion of SGT NWs is revealed with increasing Sn content. According to ab initio calculations, optimizing doping leads to a decrease in density of states near the Fermi level and reduces electrical conductivity, and thereby, SGT_3.0 is more applicable for PCM than SGT_25.0, which is attributed to Sn-induced structural change that brings about a diversity in the electrical properties. Experimentally, SGT_3.0 NWs have two significant threshold switchings and ideal high/low resistance ratio (∼105). Compared with undoped GeTe, SGT_3.0 NWs experience an increase in crystalline resistance, in agreement with our theoretical calculations, perfectly satisfying the requirement of low programming currents for PCM.
Highlights
Phase-change memory (PCM) has become one of the most promising types of non-volatile memory devices due to its higher stability, better scalability, faster switching, and lower power consumption, compared with traditional flash memory.1,2 The working mechanism of phase-change memory (PCM) is based on a reversible phase transition between the crystalline (SET state, low resistance) and amorphous states (RESET state, high resistance) of phase-change materials, corresponding to logic states “1” and “0,” respectively
According to ab initio calculations, optimizing doping leads to a decrease in density of states near the Fermi level and reduces electrical conductivity, and thereby, SGT_3.0 is more applicable for PCM than SGT_25.0, which is attributed to Sn-induced structural change that brings about a diversity in the electrical properties
The working mechanism of PCM is based on a reversible phase transition between the crystalline (SET state, low resistance) and amorphous states (RESET state, high resistance) of phase-change materials, corresponding to logic states “1” and “0,” respectively
Summary
Phase-change memory (PCM) has become one of the most promising types of non-volatile memory devices due to its higher stability, better scalability, faster switching, and lower power consumption, compared with traditional flash memory. The working mechanism of PCM is based on a reversible phase transition between the crystalline (SET state, low resistance) and amorphous states (RESET state, high resistance) of phase-change materials, corresponding to logic states “1” and “0,” respectively. Phase-change memory (PCM) has become one of the most promising types of non-volatile memory devices due to its higher stability, better scalability, faster switching, and lower power consumption, compared with traditional flash memory.. Its high melting point and relatively low electrical resistivity are disadvantageous to reduce the RESET current. N- and O-doped GeTe materials surprisingly exhibit higher crystalline resistance, they undergo instability during the crystallization process.. A bottom-up approach integrated with nanowires (NWs) has been emerging for scaling down the size of devices and assembly at the nanoscale, which can enable fast phase switching at very low power consumption.. Sn as a dopant was chosen to improve the performance of GeTe. Single-crystal Sn-doped GeTe (SGT) NWs were synthesized by a vapor transport method. The influences of Sn doping on the microstructure and electrical properties of SGT NWs were explored experimentally and theoretically
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