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Title: Nanoscale nuclei in phase change materials: Origin of different crystallization mechanisms of Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe

Phase change memory devices are based on the rapid and reversible amorphous-to-crystalline transformations of phase change materials, such as Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe. Since the maximum switching speed of these devices is typically limited by crystallization speed, understanding the crystallization process is of crucial importance. While Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe show very different crystallization mechanisms from their melt-quenched states, the nanostructural origin of this difference has not been clearly demonstrated. Here, we show that an amorphous state includes different sizes and number of nanoscale nuclei, after thermal treatment such as melt-quenching or furnace annealing is performed. We employ fluctuation transmission electron microscopy to detect nanoscale nuclei embedded in amorphous materials, and use a pump-probe laser technique and atomic force microscopy to study the kinetics of nucleation and growth. We confirm that melt-quenched amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} includes considerably larger and more quenched-in nuclei than its as-deposited state, while melt-quenched AgInSbTe does not, and explain this contrast by the different ratio between quenching time and nucleation time in these materials. In addition to providing insights to the crystallization process in these technologically important devices, this study presents experimental illustrations of temperature-dependence of nucleation rate and growthmore » speed, which was predicted by theory of phase transformation but rarely demonstrated.« less
Authors:
; ; ;  [1] ; ; ;  [2] ;  [2] ;  [3] ;  [4]
  1. Department of Materials Science and Engineering and the Coordinated Sciences Laboratory, University of Illinois at Urbana-Champaign, 1-109 Engineering Sciences Building, 1101 West Springfield Avenue, Urbana, Illinois 61801 (United States)
  2. IBM Research—Almaden, 650 Harry Rd., San Jose, California 95120 (United States)
  3. (United States)
  4. Department of Electrical and Computer Engineering and the Coordinated Sciences Laboratory, University of Illinois at Urbana-Champaign, 1406 West Green Street, Urbana, Illinois 61801 (United States)
Publication Date:
OSTI Identifier:
22278075
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 77 NANOSCIENCE AND NANOTECHNOLOGY; AMORPHOUS STATE; ANNEALING; ATOMIC FORCE MICROSCOPY; CRYSTALLIZATION; FLUCTUATIONS; GERMANIUM TELLURIDES; INDIUM ANTIMONIDES; MEMORY DEVICES; NANOSTRUCTURES; NUCLEATION; PHASE CHANGE MATERIALS; QUENCHING; SILVER TELLURIDES; TEMPERATURE DEPENDENCE; TRANSMISSION ELECTRON MICROSCOPY