Homogeneous phase W-Ge-Te material with improved overall phase-change properties for future nonvolatile memory

Homogeneous phase W-Ge-Te material has been proposed and investigated for phase-change memory (PCM) applications. The crystallization temperature of GeTe is markedly improved by introducing W atoms. In the W-Ge-Te material, W atoms bonding to Ge and Te atoms serve as substitutional impurities. During the crystallization process, the diffusion of Ge and Te atoms is restricted by W atoms that have larger atomic mass, which further leads to more uniform crystallization of the material. W atoms serve as nucleation centers and attract the surrounding Ge and Te atoms, quickly building crystal grains. W-0.1(GeTe)(0.9) film has a 10-year data retention temperature of 225 degrees C and an ultrafast crystallization time of 3 ns. Specifically, W-0.1(GeTe)(0.9) film can withstand the Pb-free solder reflow temperature (260 degrees C) for 4.6 x 10(4) s. A voltage pulse of as little of 10 ns long can realize reversible operations for W-0.1(GeTe)(0.9)-based PCM devices. In addition, good endurance (5 x 10(5) cycles) has also been obtained for the cell. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.