The structure of amorphous Ge2 Sb2 Te5 and Ge Sb2 Te4 phase-change alloys was investigated by high energy x-ray diffraction, extended x-ray-absorption fine structure, and neutron diffraction. The reverse Monte Carlo simulation technique was used to generate large scale atomic models compatible with all experimental data sets. Simulations revealed that Ge-Ge bonding is present already in Ge Sb2 Te4. Ge-Sb bonding was also found to be significant for both compositions. Within experimental uncertainties, all atomic species satisfy formal valence requirements: Ge is fourfold coordinated, Sb has three neighbors, and Te is mostly twofold coordinated. The environment of Ge atoms was investigated in detail. The predominance of Ge Te4 or Te3 Ge-Ge Te3 units in these compositions can be excluded. Instead, these alloys are characterized by a variety of local motifs.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jan 2 2008|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics