Influence of the adjacent layers on the crystallization kinetics of Ge2Sb2Te5 thin films

The influence of the adjacent layers (SiO2, Al, Ni, Ti, W, TiN, TiN/W) on the crystallization kinetics of Ge2Sb2Te5 thin films was investigated using the techniques based on the application of two different methods—differential scanning calorimetry and measurements of the resistivity temperature dependences. Thin films were deposited by the magnetron sputtering. The composition of the films was determined by the Auger spectroscopy and was close to Ge2Sb2Te5. X-ray diffraction was used to investigate the structure of thin films and showed that the as-deposited films were in an amorphous state, while heat treatment at 250 °C for 30 min led to the crystallization to the cubic (rock salt) phase. Effective activation energy of crystallization obtained by differential scanning calorimetry at the beginning of the crystallization was 1.8 eV and then slightly decreased to 1.7 eV at the end of the process. The values of the effective activation energy obtained from the measurements of the resistivity temperature dependences were in the range of 2.5–2.9 eV at the beginning and in the range of 2.2–3.5 eV at the end of the crystallization process. The difference in the effective activation energies of crystallization for the GST225 thin films deposited on the different sublayers is caused by the influence of the neighboring sublayers on the crystallization process. It was found that crystallization temperatures correlate with the effective activation energies and increase with their growth.