We report effects of thermal annealing on the structures of Ge-Sb-Te (GST) nanoparticles synthesized by pulsed laser ablation deposition. The average diameter of the GST nanoparticles is an order of 10 nm. The as-prepared sample contains nanocrystals surrounded by an amorphous phase. Further crystallization occurs during annealing. The structures of the nanocrystals and amorphous phase were studied by electron diffraction and radial distribution function analyses. The results show that the nanoparticles annealed at 100 °C are crystalline, consisting of a mixture of face centered cubic (fcc) and hexagonal Ge2 Sb2 Te5 (dominant). In comparison, the nanoparticles annealed at 200 °C are mostly fcc. The surrounding amorphous phase has similar atomic arrangements to the previously reported amorphous GST thin films.
Bibliographical noteFunding Information:
This work was supported by Grant No. R01-2006-000-11071-0 from the Basic Research Program of the Korea Science and Engineering Foundation. Two of the authors (H.R.Y. and W.J.) are also supported by a Korea Research Foundation grant (MOEHRD and KRF-2005-041-C00165) and by a grant (Code No. 07K1501-02520) from the “Center for Nanostructured Materials Technology” under the “21st Century Frontier R&D Programs” of the Korean Ministry of Science and Technology. Electron microscopy was carried out using the facility of the Center for Microanalysis of Materials at FS-MRL, University of Illinois Urbana-Champaign, which is partially supported by DEFG02-91ER45439.