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Structural and Optical Properties of Amorphous Ge2Sb2Te5

Published online by Cambridge University Press:  01 February 2011

Heng Li ,
T. Ju ,
T. Herring ,
P. C. Taylor ,
D. L. Williamson ,
M. J. Nelson  and
C. E. Inglefield
Heng Li
Affiliation:
hengli@physics.utah.eduUniversity of UtahPhysicsSalt Lake City UT 84112United States
T. Ju
Affiliation:
jutong@physics.utah.edu, University of Utah, Physics, Salt Lake City, UT, 84112, United States
T. Herring
Affiliation:
herring@physics.utah.edu, University of Utah, Physics, Salt Lake City, UT, 84112, United States
P. C. Taylor
Affiliation:
pctaylor@mines.edu, Colorado School of Mines, Physics, Golden, CO, 80401, United States
D. L. Williamson
Affiliation:
dwilliam@mines.edu, Colorado School of Mines, Physics, Golden, CO, 80401, United States
M. J. Nelson
Affiliation:
mjnelson@weber.edu, Weber State University, Physics, Ogden, UT, 84408, United States
C. E. Inglefield
Affiliation:
cinglefield@weber.edu, Weber State University, Physics, Ogden, UT, 84408, United States
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Abstract

The optical and structural properties of amorphous sputtered films of Ge2Sb2Te5 depend strongly on the preparation conditions. Films grown at higher growth rates exhibit greater local strains as indicated by the slope of the optical absorption in the exponential “band-tail” region, but these films also incorporate smaller densities of oxygen impurities. At slower growth rates the band-tail slopes are sharper (smaller local strains) but there is greater oxygen incorporation. We will discuss several experiments that suggest that the local strain relief in the films grown at slower growth rates is due to a greater ability of the atoms to rearrange on the growing surface and not to increased oxygen incorporation. Small angle x-ray scattering experiments show that the films exhibit small elliptical “voids” with long axes perpendicular to the growing surface. The approximate dimensions of these voids are 3 × 20 nm. These films can be switched optically with little change in surface topography as measured by atomic force microscopy. Electron spin resonance measurements indicate that paramagnetic defects exist in some films but are either absent or below the detection limit (~ 1018 cm-3) in most films. The implications of these results for the switching mechanisms will be discussed.

Keywords

optical propertiesGesecondary ion mass spectroscopy (SIMS)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 918: Symposium H – Chalcogenide Alloys for Reconfigurable Electronics , 2006 , 0918-H02-05
Copyright
Copyright © Materials Research Society 2006

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References

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