Successful application of spatial difference technique to electron energy‐loss spectroscopy studies of Mo/SrTiO3 interfaces

The electron energy-loss near-edge structure (ELNES) of Mo/SrTi0 3 interfaces has been studied using high spatial resolution electron energy-loss spectroscopy (EELS) in a dedicated scanning transmission electron microscope. Thin films of Mo with a thickness of 50 nm were grown on (001)-orientated SrTi0 3 surfaces by molecular beam epitaxy at 600 °C. High-resolution transmission electron microscopy revealed that the interfaces were atomically abrupt with the (110) M o plane parallel to the substrate surface. Ti-L 2 3 (∼460 eV), 0-K (∼ 5 3 0 eV), Sr-L 2 . 3 (∼19 50 eV) and Mo-L 2 , 3 (∼2500 eV) absorption edges were acquired by using the Gatan Enfina parallel EELS system with a CCD detector. The interface-specific components of the ELNES were extracted by employing the spatial difference method. The interfacial Ti-L 2 3 edge shifted to lower energy values and the splitting due to crystal field became less pronounced compared to bulk SrTiO 3 , which indicated that the Ti atoms at the interface were in a reduced oxidation state and that the symmetry of the Tio 6 octahedra was disturbed. No interfacial Sr-L 2 , 3 edge was observed, which may demonstrate that Sr atoms do not participate in the interfacial bonding. An evident interface-specific 0-K edge was found, which differs from that of the bulk in both position (0.8 ′ 0.2 eV positive shift) and shape. In addition, a positive shift (0.9 ′0.3 eV) occurred for the interfacial Mo-L 2 3 revealing an oxidized state of Mo at the interface. Our results indicated that at the interface SrTiO 3 was terminated with Ti0 2 . The validity of the spatial difference technique is discussed and examined by introducing subchannel drift intentionally.