In-situ crystallization of GeTe\GaSb phase change memory stacked films

Single and double layer phase change memory structures based on GeTe and GaSb thin films were deposited by pulsed laser deposition (PLD). Their crystallization behavior was studied using in-situ synchrotron techniques. Electrical resistance vs. temperature investigations, using the four points probe...

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Bibliographic Details
Published in:Journal of applied physics 2014-12, Vol.116 (23)
Main Authors: Velea, A., Borca, C. N., Socol, G., Galca, A. C., Grolimund, D., Popescu, M., van Bokhoven, J. A.
Format: Article
Language:English
Subjects:
ABSORPTION
ANNEALING
Antimony
Applied physics
ATOMS
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Computer memory
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Configurations
Crystal structure
Crystallinity
CRYSTALLIZATION
Diffusion layers
ELECTRIC CONDUCTIVITY
ENERGY BEAM DEPOSITION
FINE STRUCTURE
GALLIUM ANTIMONIDES
GERMANIUM TELLURIDES
LASER RADIATION
Lattice vacancies
Phase change
Phase transitions
Probe method (forecasting)
PULSED IRRADIATION
Pulsed laser deposition
Pulsed lasers
Temperature
TEMPERATURE RANGE 0400-1000 K
THIN FILMS
TRANSITION TEMPERATURE
VACANCIES
X ray absorption
X-RAY SPECTROSCOPY
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Summary:Single and double layer phase change memory structures based on GeTe and GaSb thin films were deposited by pulsed laser deposition (PLD). Their crystallization behavior was studied using in-situ synchrotron techniques. Electrical resistance vs. temperature investigations, using the four points probe method, showed transition temperatures of 138 °C and 198 °C for GeTe and GaSb single films, respectively. It was found that after GeTe crystallization in the stacked films, Ga atoms from the GaSb layer diffused in the vacancies of the GeTe crystalline structure. Therefore, the crystallization temperature of the Sb-rich GaSb layer is decreased by more than 30 °C. Furthermore, at 210 °C, the antimony excess from GaSb films crystallizes as a secondary phase. At higher annealing temperatures, the crystalline Sb phase increased on the expense of GaSb crystalline phase which was reduced. Extended X-ray absorption fine structure (EXAFS) measurements at the Ga and Ge K-edges revealed changes in their local atomic environments as a function of the annealing temperature. Simulations unveil a tetrahedral configuration in the amorphous state and octahedral configuration in the crystalline state for Ge atoms, while Ga is four-fold coordinated in both as-deposited and annealed samples.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4904741