title: Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5.
abstract: Because of their robust switching capability, chalcogenide glass materials have been used for a wide range of applications, including optical storages devices. These phase transitions are achieved by laser irradiation via thermal processes. Recent studies have suggested the potential of nonthermal phase transitions in the chalcogenide glass material Ge2Sb2Te5 triggered by ultrashort optical pulses; however, a detailed understanding of the amorphization and damage mechanisms governed by nonthermal processes is still lacking. Here we performed ultrafast time-resolved electron diffraction and single-shot optical pump-probe measurements followed by femtosecond near-ultraviolet pulse irradiation to study the structural dynamics of polycrystalline Ge2Sb2Te5. The experimental results present a nonthermal crystal-to-amorphous phase transition of Ge2Sb2Te5 initiated by the displacements of Ge atoms. Above the fluence threshold, we found that the permanent amorphization caused by multi-displacement effects is accompanied by a partial hexagonal crystallization.
authors: Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan.|PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.
authors: Masaki
authors: M
authors: Hada
authors: Department of Physics, Graduate School of Engineering, Yokohama National University, Yokohama 240-8501, Japan.
authors: Wataru
authors: W
authors: Oba
authors: Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8562, Japan.
authors: Masashi
authors: M
authors: Kuwahara
authors: Department of Physics, Graduate School of Engineering, Yokohama National University, Yokohama 240-8501, Japan.
authors: Ikufumi
authors: I
authors: Katayama
authors: Graduate School of Science and Technology, Keio University, Yokohama 223-8522, Japan.
authors: Toshiharu
authors: T
authors: Saiki
authors: Department of Physics, Graduate School of Engineering, Yokohama National University, Yokohama 240-8501, Japan.
authors: Jun
authors: J
authors: Takeda
authors: Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan.|CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.
authors: Kazutaka G
authors: KG
authors: Nakamura