Crystalline and amorphous structures of Ge-Sb-Te nanoparticles

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 degrees C are crystalline, consisting of a mixture of face centered cubic (fcc) and hexagonal Ge2Sb2Te5 (dominant). In comparison, the nanoparticles annealed at 200 degrees C are mostly fcc. The surrounding amorphous phase has similar atomic arrangements to the previously reported amorphous GST thin films. (c) 2007 American Institute of Physics.