Structural and electrical properties of Germanium-doped Sb70Te30 eutectic thin films

Abstract Ge-doped Sb 70 Te 30 eutectic films show high potential for high transfer rate recording and non-volatile memory applications. Their potential applications are based on the difference in optical and electrical properties between the crystalline and amorphous phases. However, the structure and crystallization mechanism of such films is not yet well understood. The aim of this work is to study the amorphous-to-crystalline phase transformation mechanism in eutectic thin films of pure Sb 70 Te 30 and doped with 2, 5 and 10 at% of Ge. Results of isokinetics and isothermal annealing were carried out using various techniques: four-probe electrical, optical reflectance and X-ray measurements. The results of optical and electrical measurements of Ge doped Sb 70 Te 30 eutectic films showed that the addition of Ge increases both, the crystallization temperature and the effective activation energy of crystallization and that the mechanism of crystallization does not depend on Ge contents. In amorphous films, Ge acts as impurity center and does not affect the optical band gap value, but decreases the pre-exponential factor in the thermally activated conductivity. In crystalline films, Ge is probably incorporated into the Sb 70 Te 30 structure and Ge vacancy are responsible for p-type metallic conduction, which increases with increasing the Ge content.