INVESTIGATION OF RIGIDITY PERCOLATION, MEDIUM-RANGE STRUCTURES AND FRACTON IN MULTI-COMPOUND GLASSY SEMICONDUCTORS

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We have presented a comprehensive study of the roles of nanoscopic structural units in chalcogenide glasses in relaxation behaviors around glass transition temperature, structural changes toward crystallization, electronic structures around band-tails, and relaxation processes of photoexcited carriers.First, we have shown that the variation of Se_n (n>2) chain segments essentially determines relaxational behaviors of networks. We have also shown that the compositional dependence of resonant Raman spectra is explained by the variation in lengths of the Se_n chain and the CST chain. Second, we have found that intrinsic inhomogeneity in Ge-Ge ethan-like units, Se-Se bonds, and fragments similar to β-GeSe_2 can cause significantly different macroscopic structural changes in GeSe_2 glass. Finally, we have demonstrated that threefold-coordinated Se atoms forming Se-Se bonds play a key role in the photoinduced structural change and the dynamics of photoexcited carriers in GeSe_2 glass.