Formation of atomic-scale graded structure in Se-Te semiconductor under strong gravitational field

Huang, X. S.*; Ono, Masao  ; Ueno, Hideto*; Iguchi, Yusuke*; Tomita, Takeshi; Okayasu, Satoru  ; Mashimo, Tsutomu

A large linearly graded structure on atomic-scale up to 88 at%/mm with oriented grown crystals was formed in selenium-tellurium (Se-Te) semiconductor using a strong gravitational field of 1 million G level at 260 C. The lattice constants and the binding energies of Se and Te 3 electrons continuously changed along the direction of gravity accordingly, which indicated the formation of the graded band gap structure. The grown crystals showed the crystalline orientation with c-axis of hexagonal structure roughly perpendicular to the direction of gravity. It was found that the diffusion coefficient of sedimentation was larger than that of normal diffusion by more than 100 times, which suggested a different diffusion mechanism from the normal vacancy mechanism.