Crystallization behavior of N-doped Ge-rich GST thin films and nanostructures: An in-situ synchrotron X-ray diffraction study

Ge-rich and N-doped Ge-Sb-Te thin films and patterned structures for memory applications are investigated in situ during annealing up to 500 degrees C with a heating rate of 2 degrees C/min using synchrotron x-ray diffraction. The initial material is amorphous. Under these annealing conditions, Ge crystallization occurs at 340 degrees C and precedes the one of cubic Ge2Sb2Te5 by about 15 degrees C. In situ monitoring of diffraction allows for a quantification of crystallized quantity, grain size and elastic strain during the material transformation. Increasing N doping reduces the amount of crystallized Ge and Ge grain size. These results bring important insights into the multiphase crystallization of Ge-rich GST phase change materials for memory applications.