Improvement of thermal stability and phase change behavior of Ge2Sb2Te5 thin films by Calcium doping

Abstract

The crystallization behaviors, thermal stabilities, and the amorphous/crystalline structures of Calcium (Ca) doped Ge2Sb2Te5 (GST) phase change films have been studied. It was found that, the thermal stability is deteriorated and two-step crystallization behavior is accelerated in GST doped with a small amount of Ca (less than 3.6 at.%), but the thermal stability is increased and two-step crystallization behavior is suppressed apparently in the more Ca-doped GST. Moreover, we found Ca does not bond with the elements of Sb and Te, implying Ca can be considered as the impurity atom in doped GST films. Together with the vacancy concept in rapid phase transition mechanism, the change of the thermal stability could be explained well in Ca-doped GST films. The Ca6.4(GST)93.6 film with moderate Ca doping, which has better thermal stability and faster phase transition speed in Ca-doped GST films, is suggested as a potential candidate material for phase change application.