Figure 1

Structural characterization of epitaxial phase change materials. (a) Schematics of the crystal structures of α-GeTe, GST225, and Sb₂Te₃. The green, blue, and red circles represent Te, Ge, and Sb atoms, respectively. The arrows indicate the crystallographic directions and the letters a, b, and c the stacking sequence. The dashed lines in the right panel mark the horizontal shift of the quintuple layers in Sb₂Te₃. (b) XRD profiles of α-GeTe, GST225, and Sb₂Te₃ thin films plotted as a function of the reciprocal scattering vector Q _z . The data are vertically shifted for clarity. The sharp peaks at 2, 4 and 6 Å⁻¹ correspond to the Si(111), Si(222) and Si(333) diffraction peaks, respectively. The arrows point towards the shoulders on the right side of the α-GeTe (222) and (333) diffraction peaks and the circles indicate the broad features in the GST225 diffraction pattern. The XRD data show an obvious difference in crystal structure between the three materials.