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A new extended x-ray-absorption fine structure spectroscopy study of local bonding identifies for the first time significant concentrations of Ge-Ge bonds in amorphous Ge2Sb2Te5. The study provides a new understanding of the local molecular structure of this phase-change material. Application of bond constraint theory indicates that the amorphous phase is an ideal network structure in which the average number of constraints per atom equals the network dimensionality. Analysis within this framework imparts new and significant insights concerning the nature of the reversible optically driven amorphous-crystalline phase transition of Ge2Sb2Te5.

Raman spectroscopy in conjunction with near-field scanning optical microscopy is used to image Rb doped KTP within a spectral feature with high spatial resolution. We present Raman spectra as well as the first Raman images obtained in the near-field. Differences between near-field and far-field Raman measurements are discovered and discussed.

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