Temperature and concentration dependent crystallization behavior of Ge₂Sb₂Te₅ phase change films: Tungsten doping effects

Tungsten-doped Ge₂Sb₂Te₅ (GSTW) semiconductor films with W concentrations of 3.2, 7.1, and 10.8%, deposited by cosputtering, have been proposed to improve the crystallization behavior of Ge₂Sb₂Te₅ (GST) phase change materials. The crystalline resistances and crystallization temperatures of GST and GSTW films have been studied using in situ temperature-dependent resistance measurements. The intrinsic crystallization mechanism from amorphous to face-centered-cubic (FCC) structure has been discovered using temperaturedependent Raman spectra from 300 K to 720 K. It was found that GSTW films exhibit a more stable cubic geometry, better thermal stability of the amorphous state and higher 10 year data retention ability than pure GST. This could be due to the substitution of Te atoms or vacancies by W atoms in the crystal lattice, which leads to disorder of the crystalline structure and inhibits further crystallization.