Influence of Sn doping upon the phase change characteristics of Ge2Sb2Te5

The influence of Sit doping upon the phase change characteristics of Ge2Sb2Te, alloys has been investigated using four-point-probe electrical resistance measurements, grazing incidence X-ray diffraction (XRD), X-ray reflectometry (XRR) and variable incident angle spectroscopic ellipsometry (VASE), a static tester and atomic force microscopy (AFM). For a Ge2Sb2Te, alloy doped with 4% Sit, two transition temperatures are observed in the temperature dependent sheet resistance measurements at 125 degreesC and 250 degreesC, respectively. The evolution of structures upon annealing, investigated by XRD, reveals that the first transition is caused by the crystallization of the amorphous film to a NaCl-type structure, while the second transition is related to the transition to a hexagonal structure. The density values of 6.02 +/- 0.05 g cm(-3), 6.38 +/- 0.05 g cm(-3) and 6.42 +/- 0.05 g cm(-3) are measured by XRR for the film in the amorphous, NaCl-type and hexagonal structure, respectively. Ultra-fast crystallization, which is correlated with a single NaCl-structure phase and the reduced activation barrier, is demonstrated. Sufficient optical contrast is exhibited and can be correlated with the density change upon crystallization. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.