Abstract
Oxygen-doped Ge 2 Sb 2 Te 5 films (denoted as Ge 2 Sb 2 Te 5 -O) with oxygen concentration in between 0 and 10.3 at. % were prepared by direct current magnetron reactive sputtering with Ge 2 Sb 2 Te 5 target. Both the crystallization temperature and activation energy of Ge 2 Sb 2 Te 5 -O films increased, while the crystalline grain size refined with oxygen concentration. For both amorphous and crystalline phases, optical band gap Eg opt increases with oxygen concentration - a similar trend as observed in resistivity measurements. X-ray diffraction results showed that the face center cubic (fcc) structure maintained even after 400°C anneal with oxygen addition in between 7.5 - 8.3 at.% - a different phenomenon from undoped Ge 2 Sb 2 Te 5 film, but with crystallinity diminished gradually with oxygen concentration. Only Sb 2 Te 3 diffraction peak was observed in the 10.3 at.% O film after 400°C anneal. In conjunction with the bonding information obtained from X-ray photoelectron spectroscopy (XPS), effects of oxygen on the microstructures, thermal properties, resistivity and stability of fcc structure are examined and the embedded mechanisms are discussed in this study. © 2008 Materials Research Society.