129I and 119Sn Mössbauer spectroscopy, reversibility window and nanoscale phase separation in binary GexSe1−x glasses
- 作者：P. Boolch ; P. Chen ; M. Jin ; B. Goodman ; W.J. Bresser
- 关键词：Mö ; ssbauer spectroscopy ; Raman scattering ; Modulated DSC ; Self-organization ; Nanoscale phase separation
- 刊名：Physica B
- 出版年：2007
- 期刊代码：53_09214526
- 类别：ph
- 出版时间：1 February 2007
- 卷：389
- 期：1
- 页码：18-28
- 文件大小：757 K
摘要
The molecular structure of the prototypical chalcogenide glass system—GexSe1−x in the range, has received much scrutiny over the years. These glasses have been probed by modulated DSC, Raman scattering, 119Sn absorption and 129I emission Mössbauer spectroscopy, and neutron scattering. The 129I measurements utilize 129mTe parent as a dopant in glasses, and reveal a bimodal (A, B) distribution of sites, with the site intensity ratio, IB/IA (x), tracking changes in glass structure as a function of x. At low x (<0.15) Sen-chains are stochastically cross-linked by Ge additive, and IB/IA (x) sharply declines with x. But at f16d01c60f1aacd3f" title="Click to view the MathML source">x>0.15, rigid regions nucleate at the expense of floppy ones, and the ratio IB/IA (x) reverses slope to display a global maximum in the f1c4" title="Click to view the MathML source">0.20<x<0.25 range. The latter coincides with the reversibility window usually taken as signature of self-organization of these networks. At x>0.26, these glasses enter a stressed-rigid elastic phase and in the range nanoscale phase separate into Se-rich and Ge-rich regions. The signature of the latter is saturation of IB/IA (x) at a high value of 1.5 at . 119Sn Mossbauer spectroscopy measurements independently support the picture of broken chemical order of the stoichiometric glass inferred from the 129I Mössbauer experiments. These observations using local probes are well correlated to Raman scattering, modulated differential scanning calorimetric and diffraction measurements.