title: Understanding the phase-change mechanism of rewritable optical media.
abstract: Present-day multimedia strongly rely on rewritable phase-change optical memories. We demonstrate that, different from the current consensus, Ge(2)Sb(2)Te(5), the material of choice in DVD-RAM, does not possess the rocksalt structure but more likely consists of well-defined rigid building blocks that are randomly oriented in space consistent with cubic symmetry. Laser-induced amorphization results in drastic shortening of covalent bonds and a decrease in the mean-square relative displacement, demonstrating a substantial increase in the degree of short-range ordering, in sharp contrast to the amorphization of typical covalently bonded solids. This novel order-disorder transition is due to an umbrella-flip of Ge atoms from an octahedral position into a tetrahedral position without rupture of strong covalent bonds. It is this unique two-state nature of the transformation that ensures fast DVD performance and repeatable switching over ten million cycles.
authors.affiliation: Center for Applied Near-Field Optics Research, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Kolobov
authors.forename: Paul
authors.initials: P
authors.lastname: Fons
authors.forename: Anatoly I
authors.initials: AI
authors.lastname: Frenkel
authors.forename: Alexei L
authors.initials: AL
authors.lastname: Ankudinov
authors.forename: Junji
authors.initials: J
authors.lastname: Tominaga
authors.forename: Tomoya
authors.initials: T
authors.lastname: Uruga
mesh_terms: D000497:Alloys / Q000737:chemistry*; D000965:Antimony / Q000737:chemistry*; D003201:Computers; D005857:Germanium / Q000737:chemistry*; D008420:Manufactured Materials; D013059:Spectrum Analysis, Raman; D013691:Tellurium / Q000737:chemistry*
chemical_list: D000497:Alloys; D005857:Germanium; D000965:Antimony; D013691:Tellurium