Effects of excess Sb on crystallization of δ-phase SbTe binary thin films

The phase-change temperature and crystal structures of the delta-phase SbTe alloy for Sb contents of 64 at%, 72 at%, and 76 at% have been investigated. The delta-phase SbTe alloy has a rhombohedral crystal structure, and crystallization occurs in an extremely narrow temperature range of 140-145 degrees C compared with Sb40Te60. We have determined the relationship between the Sb content and the crystalline structure using X-ray diffraction and selected area electron diffraction. When the Sb content increases, the number of Sb layers stacked with Sb2Te3 in the unit cell increases, which results in the lowering of the activation energy for crystallization and a lower ovonic threshold voltage. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.