Sub-nanometer structural control delivers record-setting sub-nanosecond speed for phase-change memory

发布时间:2017-10-24 10:38:17

Sub-nanometer structural controldelivers record-setting

sub-nanosecond speed for phase-changememory

Wei Zhang1, Feng Rao2and Evan Ma1,3

1Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano), Xi’anJiaotong University, Xi’an 710049, China.

2State Key Laboratory of Functional Materials forInformatics, Shanghai Institute of Micro-system and Information Technology,Chinese Academy of Sciences, Shanghai 200050, China.

3Department of Materials Science and Engineering, Johns HopkinsUniversity, Baltimore, Maryland 21218, USA.

ema@jhu.edu


Abstract:


This talkdescribes an example of advancingmaterials performance from the nanoscale, the theme of research atCAMP-Nano. It shows a success story that exploitsthe advantages of metastable alloys for nanoelectronics, setting anunprecedented operation speed for memory and switch applications. Specifically, we have designed anew phase-change alloywithdrastically reduced crystal nucleationstochasticity to accomplish sub-nanosecond switchingfor cache-typephase-change random-access memory (PCRAM) technology.


Operationspeed is currently a key challenge in PCRAM technology, especially forachieving sub-nanosecond high-speed cache-memory. The limiting factor in thecommercialized PCRAM products is the writing speed (~currently several tens ofnanoseconds), which originates from the stochastic crystal nucleation duringthe crystallization of the Ge2Sb2Te5 glass.Here we demonstrate an alloying strategy that can speed up the crystallizationkinetics by orders of magnitude in phase-change memory glass. The newlydesigned chalcogenide compound enables a record high writing speed (as short as~700 picoseconds) in a large conventional PCRAM device, with no requirement forpre-programming or additional device design. This ultrafast crystallizationstems from the reduced stochasticity of nucleation via geometrically matchedand robust chemical bonds that stabilize crystal precursors in the glassystate, which are found via ab initiosimulations to exhibit long life-times. This discovery not only is a milestonethat paves the way for the development of universal memory using PCRAMtechnology to boost the working efficiency of computing systems, but also highlightsmaterials science principles in action, offering the insight to guide the alloydesign from atomic (bonding configurations and sub-critical nuclei) scale.


Brief bio of the speaker:

E. Ma did his undergraduatework at Tsinghua University and graduatework at Tsinghua University and Caltech, followed by postdoc sojourns at MITand University of Michigan. He is currently a professor in the Department ofMaterials Science and Engineering at Johns Hopkins University. Prof. Ma haspublished ~310 papers, with ~22,500 citations and h index=77 accordingto SCI (Web of Science), and~29,500 citations and h index=89, according to Google Scholar.Dr. Ma has presented ~127 invited talks at international conferences (and another ~85invited speeches at academic institutions). He is an elected Fellow of ASM, APS, and MRS. Dr. Mahas also been an adjunct professor (Qian Ren B) at Xi’an Jiaotong University since 2009. His current research interestsinclude amorphous metals (metallic glasses), chalcogenide phase-change alloysfor memory applications, strength/ductility and plasticitymechanisms of nanostructured metals, and insitu transmission electron microscopy of small-volume materials exposed to mechanical, thermaland environmental stimuli.


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