Compatibility study of Ti and Ge2Sb2Te5 for phase-change memory applications

In this study, the kinetics of titanium–Ge2Sb2Te5 chalcogenide compound formation has been investigated by transmission electron microscopy, MeV helium-ion backscattering spectrometry, X-ray diffraction and secondary ion mass spectrometry. Two sets of samples have been used, one with titanium on a Ge2Sb2Te5 film and the other with a reverse structure. To induce the compound formation, isothermal experiments were carried out at various temperatures. It has been found that titanium induces the dissociation of the chalcogenide layer and the formation of TiTe2 compound. In both the samples, the growth of TiTe2 is kinetically controlled with an activation energy of 0.9±0.1 eV. In excess of titanium atoms with respect to tellurium, the dissociation of what is left in the original chalcogenide proceeds by the formation of TiGe x compound, leaving antimony and eventually germanium grains.