High-resolution x-ray photoelectron spectroscopy on oxygen-free amorphous Ge2Sb2Te5

Amorphous Ge2Sb2Te5 (a-GST) film, 100nm thick, was grown by cosputtering from GeTe and Sb2Te3 targets on a silicon wafer at room temperature. The native oxidized layer, which was formed in air and about 20nm thick measured by secondary ion mass spectroscopy, was removed by Ne+ ion sputtering for 1h with 0.6kV beam energy. Core-level spectra of the Te 3d and 4d, Sb 3d and 4d, and Ge 3d of the oxygen-free a-GST were obtained by high-resolution x-ray photoelectron spectroscopy with synchrotron radiation and compared with those from Ge and GeTe. The analysis implies that the a-GST is composed on the base of chemical states of GeTe.