P. Espeter, C. Keutner, N.F. Kleimeier, P. Roese, K. Shamout, G. Wenzel, U. Berges, H. Zacharias, C. Westphal
Keywords: silicene, nanoribbon
Summary:Since the discovery of graphene much interest came up in the graphene analoga from the carbon group. One of the most famous representatives is silicene. Silicene is known to crystallize in different configurations, depending on the growth conditions, e.g. the substrate temperature during growth or the substrate. In detail, there is sheet-growth on Ag(111) or ZrB2(0001) and growth of nanoribbons on Ag(110) or Au(110). Whereas the structure of silicene sheets is already well known, the structure of silicene nanoribbons remains unclear. However, multiple different structures were suggested in literature. The suggested structure models were mostly based on theoretical simulations and scanning tunneling microscopy studies. Still, the structure is under discussion. Due to the surface sensitivity of photoelectron spectroscopy (XPS) and photoelectron diffraction (XPD) we utilized these powerful tools addressing structural and chemical issues concerning silicene nanoribbons grown on a Ag(110) substrate. First of all we will address the question of the interaction between the substrate and the silicene nanoribbons by analyzing typical XPS spectra before and after growth of the nanoribbons as these XPS spectra provide chemical information. Second, we demonstrate a structure investigation by means of photoelectron diffraction. Therefore, we will present first experimental XPD pattern of silicene nanoribbons on Ag(110) and a comparison to simulations. Within the simulations we compared a wide variety of suggested structure models in literature. All previously suggested structures covered rectangular, pentagonal, hexagonal, armchair and zig-zag terminated edges and planar, buckled and stacked planes. As a result we present a structure model which perfectly fits to the XPS and XPD data.