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

Journal Article · Fri Feb 14 00:00:00 EST 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4865295· OSTI ID:22278075

Lee, Bong-Sub; Bogle, Stephanie N.; Darmawikarta, Kristof; Abelson, John R. ^[1]; Shelby, Robert M.; Retter, Charles T.; Burr, Geoffrey W. ^[2]; Raoux, Simone ^[2]; Bishop, Stephen G. ^[3]

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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. 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)

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 growth speed, which was predicted by theory of phase transformation but rarely demonstrated.

• OSTI ID: 22278075
• Journal Information: Journal of Applied Physics, Vol. 115, Issue 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

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