Abstract
Extending cycling endurance and suppressing programming noise of phase-change random-access memory (PCRAM) are the key challenges with respect to the development of nonvolatile working memory and high-accuracy neuromorphic computing devices. However, the large-scale atomic migration along electrical pulse direction in the unconstrained three-dimensional phase transitions of the phase-change materials (PCMs) induces big resistance fluctuations upon repeated programming and renders the classic PCRAM devices into premature failure with limited cycling endurance. Previous efforts of superlattice-like and superlattice PCM schemes cannot effectively resolve such issues. In this work, we demonstrated that, through fine-tuning the sputtering techniques, a phase-change heterostructure (PCH) of Sb2Te3/TiTe2 can be successfully constructed. In contrast to its superlattice-like counterpart with inferior crystal quality, the well-textured PCH architecture ensures the reliable (well-confined) two-dimensional phase transitions, promoting an ultralow-noise and long-life operation of the PCRAM devices. Our study thus provides a useful reference for better manufacturing the PCH architecture and further exploring the excellent device performances and other new physics.
Highlights
With the development of the Internet of Things, the exponentially growing demands in data processing and storage have imposed critical requirements on the energy efficiency and computing speed for data-centric tasks
Regarding the SLL films synthesized at room temperature, the sublayers are usually amorphous or have poor crystallinity (Chong et al, 2006; Lu et al, 2012; Chia Tan et al, 2013)
Similar situation was observed for the Sb2Te3/TiTe2 SLL samples, as well as the pure Sb2Te3 and TiTe2 films grown on SiO2 substrates (Supplementary Figure S1)
Summary
With the development of the Internet of Things, the exponentially growing demands in data processing and storage have imposed critical requirements on the energy efficiency and computing speed for data-centric tasks. Typical (mushroomor pillar-type) PCRAM devices execute three-dimensional (3D) phase transitions of GST film, where extensive cycles of highenergy/high-bias RESET (melting and amorphization) operation pulses trigger long-distance migrations of Sb (Ge) and Te elements in opposite (vertical) directions (Padilla et al, 2010; Xie et al, 2018), giving rise to the phase segregation and the formation of large voids near the bottom electrode This degrades the performing reliability and limits the endurance of massproduced GST devices to ∼109–1012 cycles (Yu and Chen, 2016; Xie et al, 2018), obstructing the implementation of PCRAM as nonvolatile working memory (with > ∼1016 cycles) for the deep modification of the von Neumann architecture (Wong and Salahuddin, 2015). The energy cutoff is 180 eV and the time step is 3 femtoseconds
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