Phase transitions in Ge–Sb phase change materials

DOI PDF 7 Citations
  • Simone Raoux
    Almaden Research Center 1 IBM/Macronix PCRAM Joint Project, , San Jose, California 95120, USA
  • Cyril Cabral
    IBM T. J. Watson Research Center 2 , Yorktown Heights, New York 10598, USA
  • Lia Krusin-Elbaum
    IBM T. J. Watson Research Center 2 , Yorktown Heights, New York 10598, USA
  • Jean L. Jordan-Sweet
    IBM T. J. Watson Research Center 2 , Yorktown Heights, New York 10598, USA
  • Kumar Virwani
    Almaden Research Center 1 IBM/Macronix PCRAM Joint Project, , San Jose, California 95120, USA
  • Martina Hitzbleck
    Research Center Jülich 3 Institute for Bio- and Nanosystems, , 52425 Jülich, Germany
  • Martin Salinga
    RWTH University of Technology 4 1. Physikalisches Institut (1A), , 52056 Aachen, Germany
  • Anita Madan
    IBM Hudson Valley Research Park 5 , Hopewell Junction, New York 12533, USA
  • Teresa L. Pinto
    IBM Hudson Valley Research Park 5 , Hopewell Junction, New York 12533, USA

Bibliographic Information

Published
2009-03-15
DOI
  • 10.1063/1.3091271
Publisher
AIP Publishing

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<jats:p>Thin films of the phase change material Ge–Sb with Ge concentrations between 7.3 and 81.1 at. % were deposited by cosputtering from elemental targets. Their crystallization behavior was studied using time-resolved x-ray diffraction, Auger electron spectroscopy, differential scanning calorimetry, x-ray reflectivity, profilometry, optical reflectivity, and resistivity versus temperature measurements. It was found that the crystallization temperature increases with Ge content. Calculations of the glass transition temperature (which is a lower limit for the crystallization temperature Tx) also show an increase with Ge concentration closely tracking the measured values of Tx. For low Ge content samples, Sb x-ray diffraction peaks occurred during a heating ramp at lower temperature than Ge diffraction peaks. The appearance of Ge peaks is related to Ge precipitation and agglomeration. For Ge concentrations of 59.3 at. % and higher, Sb and Ge peaks occurred at the same temperature. Upon crystallization, film mass density and optical reflectivity increase as well as electrical contrast (ratio of resistivity in amorphous phase to crystalline phase) all showed a maximum for the eutectic alloy (14.5 at. % Ge). For the alloy with 59.3 at. % Ge there was very little change in any of these parameters, while the alloy with 81.1 at. % Ge behaved opposite to a typical phase change alloy and showed reduced mass density and reflectivity and increased resistivity.</jats:p>

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