Crystal structure and atomic arrangement of the metastable Ge2Sb2Te5 thin films deposited on SiO2/Si substrates by sputtering method

Abstract

The Ge2Sb2Te5 thin films deposited by a sputtering method on SiO2/Si substrates were annealed through a rapid thermal annealing process and performed a high-resolution transmission electron microscopy study in order to investigate the atomic arrangement of the metastable Ge2Sb2Te5. The metastable rocksalt structure having face-centered-cubic lattice was confirmed by high-resolution transmission electron microscopy images and simulated images on the directions of < 100 >, < 110 >, and < 211 > zone axes. According to the position of Ge and Sb in the metastable rocksalt structure, the atomic distribution alters when observed in different direction and this causes change in the charge-density distribution, resulting in different images in a high-resolution transmission electron microscopy. It is expected that as the crystallization proceeds, the Ge and Sb atoms tend to position themselves on a specific plane. From this aspect, the ordered structure model of the metastable Ge2Sb2Te5 was proposed by varying the position of the Ge and Sb atoms. (C) 2005 American Institute of Physics.