Phase-change characteristics of nitrogen-doped GeSbTe films during annealing process.

The microstructures and electrical properties of nitrogen-doped GeSbTe thermally annealed in an N atmosphere were investigated. The 5.4% nitrogen-doped GeSbTe thin films showed discontinuous changes in resistance with annealing temperature, and corresponding changes in crystal structure. The phase transitions went through three states, amorphous→cubic→hexagonal, after annealing at 200 and 375 °C. No chemical compositional change occurred after 400 °C annealing. But the 20.1% nitrogen-doped GeSbTe thin films showed continuous changes in microstructure and resistance. According to XRD and TEM analyses, the hexagonal-type Ge-Sb-Te phase should be directly crystallized from the amorphous phase. Also, the SIMS and XPS spectra indicate that the oxygen in-diffusion and Sb and Te out-diffusion should have occurred simultaneously. [ABSTRACT FROM AUTHOR]