Initial Atomic Motion Immediately Following Femtosecond-Laser Excitation in Phase-Change Materials

E. Matsubara, S. Okada, T. Ichitsubo, T. Kawaguchi, A. Hirata, P. F. Guan, K. Tokuda, K. Tanimura, T. Matsunaga, M. W. Chen, and N. Yamada
Phys. Rev. Lett. 117, 135501 – Published 21 September 2016
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Abstract

Despite the fact that phase-change materials are widely used for data storage, no consensus exists on the unique mechanism of their ultrafast phase change and its accompanied large and rapid optical change. By using the pump-probe observation method combining a femtosecond optical laser and an x-ray free-electron laser, we substantiate experimentally that, in both GeTe and Ge2Sb2Te5 crystals, rattling motion of mainly Ge atoms takes place with keeping the off-center position just after femtosecond-optical-laser irradiation, which eventually leads to a higher symmetry or disordered state. This very initial rattling motion in the undistorted lattice can be related to instantaneous optical change due to the loss of resonant bonding that characterizes GeTe-based phase change materials. Based on the amorphous structure derived by first-principles molecular dynamics simulation, we infer a plausible ultrafast amorphization mechanism via nonmelting.

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  • Received 21 June 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.135501

© 2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsAtomic, Molecular & OpticalInterdisciplinary Physics

Authors & Affiliations

E. Matsubara1,*, S. Okada1, T. Ichitsubo1,†, T. Kawaguchi2, A. Hirata3,4, P. F. Guan5, K. Tokuda1, K. Tanimura6, T. Matsunaga2, M. W. Chen3,7, and N. Yamada1,‡

  • 1Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan
  • 2Office of Society-Academia Collaboration for Innovation, Kyoto University, Kyoto 611-0011, Japan
  • 3WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
  • 4Mathematics for Advanced Materials-OIL, AIST-Tohoku University, Sendai 980-8577, Japan
  • 5Beijing Computational Science Research Center , Beijing 100084, People’s Republic of China
  • 6The Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan
  • 7State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, People’s Republic of China

  • *matsubara.eiichiro.6z@kyoto-u.ac.jp
  • tichi@mtl.kyoto-u.ac.jp
  • yamada.noboru.4z@kyoto-u.ac.jp

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Issue

Vol. 117, Iss. 13 — 23 September 2016

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