Investigation of the phase transition of Ge2Sb2Te5 films using internal friction method

The phase transition of Ge2Sb2Te5 has been studied by internal friction measurement. Two Q− 1 peaks were observed during the process of heating amorphous Ge2Sb2Te5 from room up to 400 °C. With a heating rate of 5.5 °C/min, the first peak (P1) is located at 180 °C and the second peak is (P2) located at 330 °C. Only the peak P1 appears when sample has been beforehand annealed at 230 °C for 1 hour. Both the peaks P1 and P2 don’t appear when sample has been beforehand annealed at 380 °C for 1 hour. The positions of P1 and P2 are both affected by the heating rate, and they follow Kissinger relation. The activation energy corresponding to the peak P1 is 1.94 ± 0.18 eV, and the activation energy corresponding to the peak P2 is 3.49 ± 0.24 eV. The isothermal annealing experiment revealed that Q− 1 monotonously decreases with time t in the process of phase change, and the internal friction Q− 1 versus time t can be represented as Q− 1(t) = Q− 1(∞) − [Q− 1(∞) − Q− 1(0)] exp (−t/τ). The characteristic time τ is affected by temperature, and lnτ increase linearly with T− 1.