The crystallization behaviors of Ge2 Sb2 Te 5 and nitrogen-doped Ge2 Sb2 Te5 films, deposited by dc magnetron sputtering, were investigated using the in situ resistance measurement, X-ray diffractometry, and transmission electron microscopy (TEM). The kinetic constants were estimated using the classical Johnson-Mehl-Avrami-Kolmogrov model from the resistance measurement of Ge 2 Sb2 Te5 and nitrogen-doped Ge2 Sb2 Te5 films. The nitrogen-doped Ge2 Sb 2 Te5 showed a one-step process with the Avrami constant (n) of 1, while the Ge2 Sb2 Te5 thin film showed a two-step transformation with n of 3.6 and 1. The cross-sectional TEM revealed that the crystallizations were concentrated to the regions of 20-30 nm near the top surfaces rather than occurring throughout the films of Ge 2 Sb2 Te5 and nitrogen-doped Ge2 Sb2 Te5 films. The annealed Ge2 Sb2 Te5 showed continuous crystalline films with 20 nm grains at the surface in conjunction with the saturation of the sheet resistance, while the annealed nitrogen-doped Ge2 Sb2 Te5 showed nanocrystalline phases with 5 nm grains near the surface with a continuous decrease in sheet resistance. The crystallization of nitrogen-doped Ge 2 Sb2 Te5 was observed to be a nucleation-dominant process, while that of Ge2 Sb2 Te 5 was a growth-dominant process.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry