Microscopic Local Bonding And Optically-Induced Switching For Ge(2)Sb(2)Te(5) Alloys: A Tale Of Four Pseudo-Binary And Three Binary Tie-Lines In Ge-Sb-Te Phase Field

Ge(2)Sb(2)Te(5) (GST-225) has emerged as an active medium for applications in reversible, ReWritable (RW) optical memory discs. Many studies have focused on the properties of this alloy, relative to the other GST compositions on tie-lines in the Ge-Sb-Te ternary phase field; (i) Sb(2)Te to GeTe(2): (ii) Sb(2)Te(3): to GeTe; (iii) GeSb to Te: and (iv) the truncated tie-line from GST-124 to Sb. This article focuses instead on the binary atomic join-lines, Te-Ge, Ge-Sb and Sb-Te, that comprise the perimeter of the Ge-Sb-Te ternary diagram. Three eutectic compositions, one on each perimeter segment: (i) Ge(12)Sb(88); (ii) Te(25)Sb(75); and (iii) Ge(17)Te(83) have been identified. Focussing on the significance of these eutectic compositions, and (i) building on previous publications from our group, and (ii) relying on two recently published articles, a new model for the RW properties of GST-22T has been proposed. Finally comparisons are made between GST and AIST RW films. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim