Abstract
Hexagonal boron nitride (h-BN) nanomesh, a two-dimensional insulating monolayer, grown onthe (111) surface of rhodium exhibits an intriguing hexagonal corrugation pattern with a latticeconstant of 3.2 nm. Despite numerous experimental and theoretical studies no quantitativeagreement has been found on some details of the adsorption geometry such as the corrugationamplitude. The issue highlights the differences in chemical and electronic environment in thestrongly bound pore regions and the weakly bound wire regions of the corrugated structure. Forreliable results it is important to probe the structure with a method that is intrinsically sensitive tothe position of the atomic cores rather than the electron density of states.In this work, we determine the corrugation of h-BN nanomesh from angle- andenergy-resolved photoelectron diffraction measurements with chemical state resolution. Bycombining the results from angle and energy scans and comparing them to multiple-scatteringsimulations true adsorbate-substrate distance can be measured with high precision, avoidingpitfalls of apparent topography observed in scanning probe techniques. Our experimental resultsgive accurate values for the peak-to-peak corrugation amplitude (0.80 Å), the bonding distance tothe substrate (2.20 Å) and the buckling of the boron and nitrogen atoms in the strongly boundpore regions (0.07 Å).These results are important for the development of theoretical methods that involve aquantitative description of van der Waals systems as required for the understanding of the physicsof two-dimensional sp2layers.
de Lima, L H