Regensburg 2002 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 35: Hybride Systeme und neue Materialien

HL 35.4: Vortrag

Donnerstag, 14. März 2002, 12:45–13:00, H13

Crystallization kinetiks of Ge4Sb1Te5 — •Daniel Wamwangi, Njoroge Walter, and Wuttig Matthias — 1 Physikalisches Institut 1A RWTH Aachen, Sommerfeld Str.14 D-52056 Aachen.

Ge4Sb1Te5 is a promising candidate for rewritable optical data storage employing phase change recording, where the speed of crystallization limits the maximum the available data transfer rate. In this study the crystallization kinetics of sputtered Ge4Sb1Te5 thin films are correlated to the structural and density changes through temperature dependent sheet resistance measurements in conjuction with structural investigations employing X-ray diffraction (XRD) and X-ray reflectometry (XRR). Annealing of the Ge4Sb1Te5 films above the phase transition temperature shows a resistivity decrease from 200 Ωcm to 3.1· 10−3 Ωcm. The transition temperature is determined to about 180C and varied with heating rate. The rapid resistivity change corresponds to the structural transformation from an amorphous as-deposited state to a crystalline rock salt structure (a = 0.5974 ± 0.0002 nm). The activation energy for crystallisation, Ea is determined to 3.48 ± 0.12 eV by Kissinger’s analysis. Density values of 5.59 ±0.02 g/cm3 and 6.14 ±0.02 g/cm3 have been determined by XRR for the amorphous and crystalline phase, respectively. This corresponds to a density increase of 9.3% and a contraction of 9.1% in film thickness upon annealing. The growth of oxide layer is also observed to commence in the amorphous phase at 105C and saturates to 1.7 nm at 140C.

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