Phase transitions in Ge-Sb phase change materials
- IBM/Macronix PCRAM Joint Project, Almaden Research Center, San Jose, California 95120 (United States)
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States)
- Institute for Bio- and Nanosystems, Research Center Juelich, 52425 Juelich (Germany)
- 1. Physikalisches Institut (1A), RWTH University of Technology, 52056 Aachen (Germany)
- IBM Hudson Valley Research Park, Hopewell Junction, New York 12533 (United States)
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 T{sub x}) also show an increase with Ge concentration closely tracking the measured values of T{sub x}. 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.
- OSTI ID:
- 21190110
- Journal Information:
- Journal of Applied Physics, Vol. 105, Issue 6; Other Information: DOI: 10.1063/1.3091271; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AGGLOMERATION
AMORPHOUS STATE
ANTIMONY ALLOYS
AUGER ELECTRON SPECTROSCOPY
CALORIMETRY
CRYSTALLIZATION
DEPOSITION
EUTECTICS
GERMANIUM ALLOYS
GLASS
HEATING
PHASE CHANGE MATERIALS
PRECIPITATION
REFLECTIVITY
SPUTTERING
TEMPERATURE MEASUREMENT
THIN FILMS
TIME RESOLUTION
TRANSITION TEMPERATURE
X-RAY DIFFRACTION