Article abstract
Nature Materials 3, 703 - 708 (2004)
Published online: 12 September 2004 | doi:10.1038/nmat1215
Subject Category: Optical, photonic and optoelectronic materials
Understanding the phase-change mechanism of rewritable optical media
Alexander V. Kolobov1,5, Paul Fons1, Anatoly I. Frenkel2, Alexei L. Ankudinov3, Junji Tominaga1 & Tomoya Uruga4
Abstract
Present-day multimedia strongly rely on rewritable phase-change optical memories. We demonstrate that, different from the current consensus, Ge2Sb2Te5, 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.
- 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
- Department of Physics, Yeshiva University, 245 Lexington Avenue, New York, New York 10016, USA
- Department of Physics, Box 351560, University of Washington, Seattle, Washington 98195, USA
- SPring-8, Japan Synchrotron Radiation Research Institute, Mikazuki Hyogo 679-5198, Japan
- On leave from: A. F. Ioffe Physico-Technical Institute, 26 Polytechnicheskaya St., 194021 St Petersburg, Russia
Correspondence to: Alexander V. Kolobov1,5 e-mail: a.kolobov@aist.gp.jp
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