Crystallization behavior caused by N doping in Ge1Sb4Te7 for PCRAM application

In this paper, we reported the effect of N doping on the crystallization behavior of Ge1Sb4Te7 thin films. It was clearly shown that the phase transition of Ge1Sb4Te7 occurred from amorphous to hexagonal state and meta-stable FCC state is shown between these phase transition processes. N doping effectively suppressed crystallization process and the crystal grain size was decreased from 21 nm to 14 nm with increasing N doping contents. N-doped film was found to have nucleation dominant crystallization process and the time demanded to start phase transition is shorter compared to un-doped film. In the case of the film deposited at 9 × 10−3 Torr without N doping, 70 ns is required for crystallization to occur at 36 mW of laser power, however, 30 ns is required in the case of N-doped film. These results are demonstrated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and static test.