Phase separation of a Ge 2 Sb 2 Te 5 alloy in the transition from an amorphous structure to crystalline structures

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vacuum, surfaces, and films, 2006-07, Vol.24 (4), p.929-933
• Main Authors: Kim, YoungKuk, Park, S. A., Baeck, J. H., Noh, M. K., Jeong, K., Cho, M.-H., Park, H. M., Lee, M. K., Jeong, E. J., Ko, D.-H., Shin, H. J.
• Format: Article
• Language: English
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.2198869

Changes in the structural and electrical properties of a Ge 2 Sb 2 Te 5 alloy thin film induced by phase transition were investigated using various analytical techniques. X-ray diffraction and scanning photoelectron microscopy showed that the phase separation occurred in a local area of the film during a phase transition when the amorphous structure was being transformed into crystalline structures. It was found that the heterogeneous distribution of Sb atoms that diffused during the phase transition accompanied the phase separation. Atomic force microscopy was used to examine the changes in surface morphology and roughness. The electrical conductance of the film was dramatically improved after the phase transition from an amorphous structure to crystalline structures as evidenced by the sheet resistance measurements. The sheet resistance changed from ∼ 10 9 to ∼ 10 2 Ω ∕ sq. during the phase transition. Differential scanning calorimetry was used to determine the exact phase transition temperature ( 160 – 170 ° C ) and the effective activation energy for the phase transition ( 2.5 ± 0.11 eV ) on the basis of Kissinger’s equation.