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Success in Observing Persistent Covalent Bonding in Liquid Silicon (Press Release)

Release Date
10 Feb, 2012
  • BL08W (High Energy Inelastic Scattering)
- Results suggesting the existence of an unknown phase in silicon

Japan Aerospace Exploration Agency (JAXA)
The University of Tokyo
Japan Synchrotron Radiation Research Institute (JASRI)
Shibaura Institute of Technology

Scientists of JAXA have succeeded in clarifying the characteristic electron structure of liquid silicon for the first time in the world, jointly with scientists of Princeton University in the US, the University of Tokyo, Northeastern University in the US, JASRI, Shibaura Institute of Technology, and RIKEN. This was achieved by installing an electrostatic levitation furnace in SPring-8 and conducting an experiment to examine the electron structure of liquid silicon. This furnace was originally developed by JAXA to be mounted in the Japanese Experiment Module Kibo in the International Space Station. The results obtained were significant in that they indicate the improved functionality of silicon, a widely used functional material, which may lead to an increase in the productivity of semiconductor devices.

The achievements of this study were obtained by a research group led by the following scientists: Junpei Okada (Assistant Professor) and Takehiko Ishikawa (Professor) of JAXA; Yasuhiro Watanabe (Research Associate), Kaoru Kimura (Professor), and Susumu Nanao (Professor Emeritus) of the University of Tokyo; Dr. Patric Hoi-Land Sit of Princeton University; Dr. Bernardo Barbiellini Amidei and Arun Bansil (Professor) of Northeastern University; Yoshiharu Sakurai (Associate Chief Scientist) and Masayoshi Itou (Associate Senior Scientist) of JASRI; Tadahiko Masaki (Associate Professor) of Shibaura Institute of Technology; and Tetsuya Ishikawa (Director) of RIKEN SPring-8 Center. The results were published online in the American physics journal Physical Review Letters on 9 February 2012 prior to publication in the printed version on 10 February.

"Persistence of covalent bonding in liquid silicon probed by inelastic x-ray scattering"
J. T. Okada, P. H.-L. Sit, Y. Watanabe, Y. J. Wang, B. Barbiellini, T. Ishikawa, M. Itou, Y. Sakurai, A. Bansil, R. Ishikawa, M. Hamaishi, T. Masaki, P.-F. Paradis, K. Kimura, T. Ishikawa, and S. Nanao
Physical Review Letters, 108, Issue 6, published 8 February 2012



Fig. 1 (a) Crystal structure of solid silicon. Atoms are covalently bonded.
(b) Atomic arrangement of liquid silicon. Electrons were conventionally considered to move around randomly arranged atoms (metallic bonding).

Fig.2 Metal sphere levitated by electrostatic levitation method
Fig. 2 Metal sphere levitated by electrostatic levitation method

Arrows indicate the direction of SPring-8 synchrotron radiation X-rays used for Compton scattering experiments.

Fig.3 Atomic arrangement and electron distribution of liquid silicon clarified in this study
Fig.3 Atomic arrangement and electron distribution of liquid silicon clarified in this study

Yellow spheres represent silicon atoms, green spheres represent electron pairs that form a covalent bond, blue spheres represent electron pairs that form a metallic bond, and the red sphere represents an electron pair in the intermediate state between the covalent and metallic bonding.

For more information‚ please contact:
 Japan Aerospace Exploration Agency
 Institute of Space and Astronautical Science (ISAS)