Atomistic structure investigation of Eu–doped ZnO nano-sponges

ZnO is a semiconductor with a wide range of applications and often the properties are modified by metal-ion doping. The distribution of dopant atoms within the ZnO crystal strongly affects the optical and magnetic properties making it crucial to describe the structure down to the atomic level. This study reveals the dopant structure and contents in Eu-doped ZnO nano-phase sponges with up to 20% EuO1.5. High-resolution STEM imaging, EELS and electron pair-distribution function (ePDF) provided atomic distances. The Eu was distributed over the ZnO:Eu crystals, but in addition, an amorphous inter-crystalline phase was observed, especially in the 20% Eu sample. The ePDF analysis revealed the presence of non-periodic Eu(III)-oxide clusters and that there were significant changes in Eu coordination between the samples, which is ascribed as due to the inter-crystalline phase. The proposed method offers a potential characterization routine for a detailed investigation of complex doped materials.