Observation of local crystal structure and electronic states of laser-ablated Ge-Sb-Te nanoparticles for non-volatile memories

Phase-change Ge-Sb-Te (GST) nanoparticles have been synthesized in situ by a pulsed laser ablation method. Crystal formation of the GST nanoparticles was confirmed [H. R. Yoon et al., J. Non-Cryst. Solids, 351, 3430 (2005)]. Scanning and transmission electron microscopy were used to study microstructure and phase formation of the nanoparticles. Fourier transform analysis of electron micrographs exhibits the crystal structure of the GST-225. We have also measured the extended X-ray absorption fine structure of the Ge K edge in the GST nanoparticles with synchrotron radiation. Core-level spectra of Te3d, 4d, Sb3d, 4d and Ge3d of GST nanoparticles were obtained by using X-ray photoelectron spectroscopy. Our results suggest that such X-ray-based spectroscopy can be used to study the GST nanoparticles through electronic states and local structural information, these being developed for low-power non-volatile-memory applications.