Gravity-induced diffusion of isotope atoms in monoatomic solid Se

Mashimo, Tsutomu; Ono, Masao  ; Huang, X. S.*; Iguchi, Yusuke*; Okayasu, Satoru  ; Kobayashi, Katsura*; Nakamura, Eizo*

A strong gravitational field resulted in the gravity-induced diffusion (sedimentation) of isotope atoms in monoatomic solid Se. The layer crystalline morphology consisting of three zones of the fine-grained crystals, the long crystals and feather-shaped crystals grown parallel to gravity direction appeared in the specimen ultracentrifuged at 0.8-1 million G and at 190 C. Change in concentration ratio Se/Se of 0.8% was observed in the grown crystalline region. These results show an evidence for sedimentation of substitutional atoms in solid via self-diffusion, and suggest possibility of application to control of impurity and crystalline state as well as to isotope separation.