Sb rich Ge2Sb5Te5 materials are investigated for use as the storage medium for high-speed phase change memory (PCM).Compared with conventional Ge2Sb2Te5,Ge2Sb5Te5 films have a higher crystallisation temperature (～200℃),larger crystallisation activation energy (3.13 eV),and a better data retention ability (100.2℃ for ten years).A reversible switching between set and reset states can be realised by an electric pulse as short as 5 ns for Ge2Sb5Te5-based PCM cells,over 10 times faster than the Ge2Sb2 Te5-based one.In addition,Ge2Sb2 Te5 shows a good endurance up to 3 × 106 cycles with a resistance ratio of about three orders of magnitude.This work clearly reveals the highly promising potential of Ge2Sb5 Te5 films for applications in high-speed PCM.