Understanding Structural Changes in Phase Change Memory Alloys
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0918-H04-01
Understanding Structural Changes in Phase Change Memory Alloys
Paul Fons1, Dale Brewe2, Ed Stern3,4, A. V. Kolobov1,5, and Junji Tominaga1 1
Center for Applied Near-Field Optics Research, National Institute of Advanced Industrial Science
and Technology, Higashi 1-1-1, Tsukuba Central 4, Tsukuba, Ibaraki, 305-8562, Japan 2
PNC-XOR, Advanced Light Source, Argonne National Laboratory, Bldg 435E sector 20, 9700 S.
Cass Ave., Argonne, Il, 60439 3
Physics Department, University of Washington, Box 351560, University of Washington, Seattle,
WA, 98195 4
PNC-XOR, Advanced Light Source, Argonne National Laboratory, Bldg 435E sector 20, 9700 S.
Cass Ave., Argonne, IL, 60439 5
Laboratoire de physicochimie de la matiere condensee, Universite Montpellier II, UMR CNRS
5617, Universite Montpellier II, Place Eugene Bataillon, Montlpellier Cedex 5, France
ABSTRACT In addition to their wide-spread application in the re-writable optical memory markets, phase-change memory alloys are also poised to take a prominent role in future non-volatile memory applications due to their potential for low-energy usage and indefinite cyclability compared with their silicon-based flash memory counterparts. In contrast with their widespread use, however, the details of the crystalline to amorphous switching process utilized for memory storage remain an active research topic with many details still lacking. Considering the conflicting requirements for high-speed switching, yet long term data storage integrity, a deeper understanding of these materials is essential for insightful application development. We have used x-ray absorption fine structure spectroscopy (XAFS), a technique equally suitable for amorphous and crystalline phases to elaborate details in structural changes in the phase-change process for a variety of phase-change alloys in static measurements. As the kinetics of the switching process are the linchpin for optimizing switching characteristics, we have recently initiated dynamic measurements of light -induced structural changes in Ge-Sb-Te (GST) alloys.
These
measurements have been carried out synchronously using both femtosecond and nanosecond laser pump pulses in conjunction with 100~ps x-ray pulses generated by an electron storage ring. By
synchronously triggering the laser with a variable sub-nanosecond delay, we have been able to use XAFS to probe details of the dynamics of the switching process. Preliminary results learned from this approach applied to GST alloys are presented. INTRODUCTION Although the concept of phase-change memory originates from the late 1960's [1], it has only been since the commercial success of chalcogenide-based optical phase change memory in the late 1990's that greater efforts has been directed to understanding their material and structural properties. In particular, compositions along the pseudobinary tie line GeTe-Sb2Te3, as typified by the composition, Ge2Sb2Te5, are now the focus of development efforts not only for optical disk storage (DVD-RAM), but also for use in electro
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