オペランド計測の最先端

[1603] Time-resolved optical effects in chalcogenide based phase-change materials

^○Paul Fons^1,2,3, Kirill Mitrofanov¹, Muneaki Hase^2,4, Alexander Kolobov^1,3, Junji Tominaga¹ (1.National Institute of Advanced Industrial Science & Technology, 2.RIKEN SPring-8 Center, 3.Japan Synchrotron Radiation Research Institute, 4.University of Tsukuba)

司会: 篠田弘造(東北大学)

キーワード：phase-change material、ultra-fast optical excitation、free-electron laser、time-resolved structural measurements

The presence of optically-induced structural changes in chalcogenide semiconductors has a long history with the first reports of optical-induced photodarkening in vitreous chalcogenides appearing at the end of the 1960s. Subsequent reports also indicated the possibility of athermal photoamorphization of differing chalcogenides such as As₅₀Se₅₀ and Se suggesting that photosensitivity is a characteristic of some chalcogenide-based materials. These characteristics take on additional meaning when the materials used in nonvolatile optical storage and a new generation of nonvolatile electrical memory are considered as chalcogenide-based materials play important roles in each. In particular, the compound Ge₂Te₂Te₅ is often considered as the prototypical phase-change memory alloy as it has enjoyed wide commercial success in the form of the nonvolatile optical storage media DVD-RAM and at the same time has served as the foundation of a new class of electrical storage phase-change random access memory which offers significant speed and lifetime improvements over charge-based flash storage. In phase-change materials information is stored in the form of structure and accessed by means of the very different electronic (reflectivity and transport properties) of the amorphous and crystalline phases. In this talk we will explore the effects of photo excitation on the structural and electronic properties of Ge₂Te₂Te₅ alloys by means of time-resolved structural measurements using pump-probe experiments with both synchrotron radiation at SPring-8 and the free-electron laser facility SACLA. Based upon data collected from these time-resolved experiments, structural and property changes induced in bonding and local structure by laser-based excitation will be discussed.