Crystallization behavior of e-beam evaporated Ga5Ge15Te80 thin films

Ga5Ge15Te80 thin films have been deposited by e-beam evaporation method. The chemical composition of the deposited films was identified using energy dispersive X-ray spectrometry. The electrical conductivity, σ of the deposited films during heating/cooling cycles was investigated in the temperatures 298–570 K. The conductivity curve showed two sudden upward trends during the first heating cycle. The first upward trend occurs in the temperature range 408–430 K and was attributed to the amorphous-to-crystalline phase transformation. While the second is in the temperature range 470–495 K, and can be attributed to the crystallization process. However, for second heating cycle the conductivity curve becomes reversible. The optical band gap of the as-deposited and annealed film at annealing temperature 423 K was determined from the recorded transmittance and reflectance spectra. The obtained results were confirmed throughout the X-ray and transmission electron microscope studies.

Research highlights
► Amorphous Ga5Ge15Te80 thin films have been prepared by e-beam evaporation technique.
► Onset of an amorphous-to-crystalline phase transformation was observed at annealing temperature 423 K for 1 h.
► The crystallization behavior has been confirmed via electrical, X-ray and electron diffraction.
► The reflectivity contrast greater than 50% in the visible range makes the material suitable for phase change optical disks.