Structure and Electronic Properties of Te-Se Mixtures under High Pressure

概要

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X-ray diffraction and electrical resistance have been measured for amorphous and crystalline Te_<1-x>Se_x mixtures (0≤x≤1) under high pressure up to 30 GPa, and four high pressure phases of Te-Se mixtures have been observed : a monoclinic phase with 6 atoms per unit cell (M-I phase); a monoclinic phase with 4 atoms per unit cell (M-II phase) ; an orthorhombic phase ; a β-Po-type phase. It was found for the first time that the M-II phase containing 〜60at.% Se can be quenched to the atmospheric pressure. X-ray diffraction, EXAFS (extended X-ray absorption fine structure) and optical reflectivity have been measured for the pressure-quenched Te_<0.4>Se_<0.6> specimens. Pressure-quenched Te_<0.4>Se_<0.6> belongs to the space group Cm and has a puckered layer structure containing planer zigzag chains with period 3. Moreover, the superlattice structure with a unit cell size of 9 lattice constants along the b-axis was found. The EXAFS results suggest the existence of chemical short range order. We discuss the correlation between the structure and the electronic states in the high-pressure phases of Te-Se mixtures.
社団法人日本物理学会の論文
1995-12-15