Direct imaging of crystal structure and defects in metastable Ge_2Sb_2Te_5 by quantitative aberration-corrected scanning transmission electron microscopy

摘要

Knowledge about the atomic structure and vacancy distribution in phase change materials is of foremost importance in order to understand the underlying mechanism of fast reversible phase transformation. In this Letter, by combining state-of-the-art aberration-corrected scanning transmission electron microscopy with image simulations, we are able to map the local atomic structure and composition of a textured metastable Ge_2Sb_2Te_5 thin film deposited by pulsed laser deposition with excellent spatial resolution. The atomic-resolution scanning transmission electron microscopy investigations display the heterogeneous defect structure of the Ge_2Sb_2Te_5 phase. The obtained results are discussed. Highly oriented Ge_2Sb_2Te_5 thin films appear to be a promising approach for further atomic-resolution investigations of the phase change behavior of this material class.