Investigations on phase change characteristics of Ti-doped Ge sub(2)Sb sub(2)Te sub(5) system

Ab initio calculations and experiments are both adopted to study the effects of Ti dopant on the phase change characteristics of Ge sub(2)Sb sub(2)Te sub(5). The original and Ti-doped Ge sub(2)Sb sub(2)Te sub(5) films were deposited by magnetron sputtering. The optical and structural properties were investigated by spectroscopic ellipsometry and grazing incidence diffraction methods. According to the calculation results of the density of states and optical band gap, the Ti-doped Ge sub(2)Sb sub(2)Te sub(5) has a less narrow band gap than the original one. A comparison of the theoretical and experimental results shows that Ti dopant restrains the phase transition from amorphous to cubic and eliminates that from cubic to hexagonal. Besides, the reflectivity of Ge sub(2)Sb sub(2)Te sub(5) decreases after doping the Ti element.