Logic Computation in Phase Change Materials by Threshold and Memory Switching

Cassinerio, Marco; Ciocchini, Nicola; Ielmini, Daniele

doi:10.1002/adma.201301940

Cited by 144 publications

(104 citation statements)

References 31 publications

(54 reference statements)

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“…The voltage corresponding to the melting part of the pulse (first step) was chosen to obtain a given hot-spot temperature using equation (6). In this way, we can ensure that the size of the amorphous region initially created is almost identical at all ambient temperatures (Supplementary Note 3).…”

Section: Resultsmentioning

confidence: 99%

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Crystal growth within a phase change memory cell

2014

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In spite of the prominent role played by phase change materials in information technology, a detailed understanding of the central property of such materials, namely the phase change mechanism, is still lacking mostly because of difficulties associated with experimental measurements. Here, we measure the crystal growth velocity of a phase change material at both the nanometre length and the nanosecond timescale using phase-change memory cells. The material is studied in the technologically relevant melt-quenched phase and directly in the environment in which the phase change material is going to be used in the application. We present a consistent description of the temperature dependence of the crystal growth velocity in the glass and the super-cooled liquid up to the melting temperature.

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Section: Resultsmentioning

confidence: 99%

“…In particular, phase change memory (PCM) has recently emerged as the most promising new nonvolatile solid-state memory technology [1][2][3] . Phase-change materials are also being investigated as building blocks of neuromorphic computing hardware [4][5][6] .…”

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confidence: 99%

Crystal growth within a phase change memory cell

2014

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“…The length of the pulses was kept constant at 15 ns, and the time separation between them, where required, was maintained to be the same at 100 ns. The reference resistance levels, R ref , for the NOR and NAND, and NOT operations were chosen to be R = 0. operations in GST (10,11). It should be noted that this is also as short/shorter than those obtained for the cells in the nonpriming excitation scheme [of 5.0 V and (minimum) 1 ns] (SI Appendix, Figs.…”

Section: Significancementioning

confidence: 69%

“…Multiple operations in a logic device are currently best achieved using devices comprised of phase-change nonvolatile memory materials-based on the reversible and multilevel switching of a phase-change material (PCM) between crystalline and glassy states having a contrast in physical properties, e.g., electrical resistivity (8, 9)-which can perform more than three times the number of operations than can silicon-based logic devices (10,11). They also have the advantage of in-memory operation: the logical state is stored in a nonvolatile manner in the cell itself.…”

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confidence: 99%

“…They also have the advantage of in-memory operation: the logical state is stored in a nonvolatile manner in the cell itself. Multiple operations in phase-change-based logic devices have been achieved using crystallization; however, crystallization is a slow process and this approach can achieve mostly speeds of several hundreds of nanoseconds (10,11). A difficulty arises from the trade-off between increasing the speed of crystallization and, at the same time, extending the long-term (nonvolatile) stability of the initialized glassy state to avoid spontaneous crystallization causing corruption of the initial logic state (12).…”

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Ultrafast phase-change logic device driven by melting processes

Loke

Skelton

Wang

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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The ultrahigh demand for faster computers is currently tackled by traditional methods such as size scaling (for increasing the number of devices), but this is rapidly becoming almost impossible, due to physical and lithographic limitations. To boost the speed of computers without increasing the number of logic devices, one of the most feasible solutions is to increase the number of operations performed by a device, which is largely impossible to achieve using current silicon-based logic devices. Multiple operations in phase-change-based logic devices have been achieved using crystallization; however, they can achieve mostly speeds of several hundreds of nanoseconds. A difficulty also arises from the tradeoff between the speed of crystallization and long-term stability of the amorphous phase. We here instead control the process of melting through premelting disordering effects, while maintaining the superior advantage of phase-change-based logic devices over silicon-based logic devices. A melting speed of just 900 ps was achieved to perform multiple Boolean algebraic operations (e.g., NOR and NOT). Ab initio molecular-dynamics simulations and in situ electrical characterization revealed the origin (i.e., bond buckling of atoms) and kinetics (e.g., discontinuouslike behavior) of melting through premelting disordering, which were key to increasing the melting speeds. By a subtle investigation of the well-characterized phase-transition behavior, this simple method provides an elegant solution to boost significantly the speed of phase-change-based in-memory logic devices, thus paving the way for achieving computers that can perform computations approaching terahertz processing rates.computing | chalcogenides T he extremely high and ever-increasing demand for faster computers is currently addressed by traditional methods, such as miniaturization (to increase the number of devices), but this is rapidly becoming almost impossible, due to physical and lithographic constraints (1-4). The speed of computers is known to be determined almost solely by the performance of logic devices, i.e., their speed and number, which control most computations (or processes) in computers (5). Logic devices are mostly required to operate around 1 ns for achieving fast computations, and to transfer information between alternate devices, such as random-access memories, without delays (5). To increase the speed of computers without increasing the number of logic devices, one of the most feasible methods is to increase the number of operations performed by a device, which is largely unachievable using current silicon-based logic devices (6, 7).Multiple operations in a logic device are currently best achieved using devices comprised of phase-change nonvolatile memory materials-based on the reversible and multilevel switching of a phase-change material (PCM) between crystalline and glassy states having a contrast in physical properties, e.g., electrical resistivity (8, 9)-which can perform more than three times the number of operations than can s...

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