@misc{LachnittDasMenonetal., author = {Lachnitt, Jan and Das, Shuvankar and Menon, Krishnakumar S. R. and Mandal, Suman and Flege, Jan Ingo}, title = {The dependence of structure on thickness of NiO(100) films on Ag(100) studied by IV-LEED}, series = {Verhandlungen der DPG}, journal = {Verhandlungen der DPG}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, abstract = {Ultrathin NiO films have prospective applications especially in heterogeneous catalysis, microelectronics, and spintronics and are thus an object of active research. The Ag(100) surface is the usual support for these films, as its cubic lattice parameter is only 2.2 \% smaller than that of NiO, which enables pseudomorphic growth at very low thicknesses. We have studied the NiO(100) surface for three thicknesses of the oxide: 2 ML on Ag(100), 20 ML on the same substrate, and a bulk single crystal. We have used intensity-voltage low-energy electron diffraction (IV-LEED) in combination with X-ray photoelectron spectroscopy (XPS) and density-functional theory (DFT) calculations. We focus on differences among the three thicknesses, mainly in terms of lattice parameters and surface defects, and our study deepens existing knowledge of the growth of ultrathin NiO films. The IV-LEED calculations have been carried out using the AQuaLEED package, which will also be briefly presented.}, language = {en} } @misc{JugovacMenteşGenuzioetal., author = {Jugovac, Matteo and Mente{\c{s}}, Tevfik Onur and Genuzio, Francesca and Lachnitt, Jan and Feyer, Vitaliy and Flege, Jan Ingo and Locatelli, Andrea}, title = {Sensitivity to crystal stacking in low-energy electron microscopy}, series = {Applied Surface Science}, volume = {566}, journal = {Applied Surface Science}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2021.150656}, abstract = {In this work we demonstrate the general characteristics of hcp and fcc stacking in low-energy electron reflectivity for transition metal surfaces, by following the restacking during homoepitaxial growth in real-time. For this purpose, the stacking of a model system, single-crystalline Ag islands during layer-by-layer growth at high temperature on O/W(110), is chosen. Multiple scattering calculations are used to model the relation between electron reflectivity and the crystal geometry. The changes in the electron reflectivity are shown to derive from the changes in the stacking sequence of the topmost surface layers. The results allow to distinguish between the hcp and fcc crystalline arrangements at a surface based on typical differences in the reflectivity curves, making the Ag results relevant for a variety of materials with hexagonal surface geometry. In particular, the multiplet structure within the first Bragg peak in the very low electron energy regime is identified with the fcc structure and thus it can be utilized as a fingerprint to determine the stacking sequence.}, language = {en} }