Precession Electron Diffraction - a versatile tool for the characterization of Phase Change Materials

Precession Electron Diffraction (PED) has become a versatile tool of Transmission Electron Microscopy (TEM) for enhancing its nanoscale characterization abilities. In this contribution the advantages of PED are demonstrated on bulk samples of Phase Change Materials (PCM) with the nominal compositions Ge8Sb2Te11 and Ge8Bi2Te11. PED was applied in combination with High Resolution Transmission Electron Microscopy (HRTEM) to determine such homologous structures based on variable sequences of layered building units. The efficiency of PED can be shown by the identification of ordering which is not evident from the projection of the structure in HRTEM or by use of Selected Area Electron Diffraction (SAED). Simulations support the ability of PED for recording 3D structural information. The PED patterns of the PCM can be assigned to superstructures which exhibit specific distances between adjacent Te-Te double layers. PED was also performed to analyze the structural changes after massive irradiation of PCM crystals. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim