EXAFS study of amorphous Ge2Sb2Te5

Extended X-ray absorption fine structure (EXAFS) studies of sputtered amorphous pristine thin films of Ge2Sb2Te5 reveal only four of the six possible bond pairs. That is, we find no successful fit to EXAFS data showing Ge–Sb or Te–Te bonds. Furthermore, our data indicate Ge is fully four-fold coordinated (N = 4) while both Sb and Te are over-coordinated with respective N values of 3.3 and 2.4. In Ge–Sb–Te alloys we note that the difference in magnitude of the optical transmissivity between the amorphous and crystalline states of is proportional to the fraction of three-fold coordinated Te.