Local Structure and Phase Separation in Ge sub (1-x) Sn sub x Se sub (2.5) Photoactive Glasses.

Raman scattering was used to probe the effect of tin atom substitution for germanium in GeSe sub (2.5) homogeneous glasses. Tin appears to substitute preferentially at adjacent germanium sites in catenated corner sharing tetrahedra. As the tin concentration rises, substitution will begin to occur at germanium positions in edge sharing tetrahedral sites thereby destroying those chain cross linking structures. At that point, x = 0.6, phase separation is facilitated. The use of a selenium rich composition inhibits the natural tendency for phase separation and crystallization to occur at the GeSe sub 2 composition.