Article

Breaking the speed limits of phase-change memory.

Data Storage Institute, Agency for Science, Technology and Research (A*STAR), Singapore.
Science (impact factor: 31.2). 06/2012; 336(6088):1566-9. DOI:10.1126/science.1221561
Source: PubMed

ABSTRACT Phase-change random-access memory (PCRAM) is one of the leading candidates for next-generation data-storage devices, but the trade-off between crystallization (writing) speed and amorphous-phase stability (data retention) presents a key challenge. We control the crystallization kinetics of a phase-change material by applying a constant low voltage via prestructural ordering (incubation) effects. A crystallization speed of 500 picoseconds was achieved, as well as high-speed reversible switching using 500-picosecond pulses. Ab initio molecular dynamics simulations reveal the phase-change kinetics in PCRAM devices and the structural origin of the incubation-assisted increase in crystallization speed. This paves the way for achieving a broadly applicable memory device, capable of nonvolatile operations beyond gigahertz data-transfer rates.

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  • Article: Ultrafast synaptic events in a chalcogenide memristor.
    Yi Li, Yingpeng Zhong, Lei Xu, Jinjian Zhang, Xiaohua Xu, Huajun Sun, Xiangshui Miao
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    ABSTRACT: Compact and power-efficient plastic electronic synapses are of fundamental importance to overcoming the bottlenecks of developing a neuromorphic chip. Memristor is a strong contender among the various electronic synapses in existence today. However, the speeds of synaptic events are relatively slow in most attempts at emulating synapses due to the material-related mechanism. Here we revealed the intrinsic memristance of stoichiometric crystalline Ge2Sb2Te5 that originates from the charge trapping and releasing by the defects. The device resistance states, representing synaptic weights, were precisely modulated by 30 ns potentiating/depressing electrical pulses. We demonstrated four spike-timing-dependent plasticity (STDP) forms by applying programmed pre- and postsynaptic spiking pulse pairs in different time windows ranging from 50 ms down to 500 ns, the latter of which is 10(5) times faster than the speed of STDP in human brain. This study provides new opportunities for building ultrafast neuromorphic computing systems and surpassing Von Neumann architecture.
    Scientific Reports 04/2013; 3:1619.
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Keywords

Ab initio molecular dynamics simulations
 
amorphous-phase stability
 
applicable memory device
 
applying
 
capable
 
crystallization speed
 
gigahertz data-transfer rates
 
high-speed reversible switching
 
incubation-assisted increase
 
key challenge
 
leading candidates
 
next-generation data-storage devices
 
nonvolatile operations
 
paves
 
PCRAM devices
 
prestructural
 
structural origin
 

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