Resolving all atoms of an alkali halide via nanomodulation of the thin NaCl film surface using the Au(111) reconstruction

We investigated the local influence of the Au(111) herringbone reconstruction on the properties of thin adsorbed NaCl films using cryogenic scanning tunneling microscopy (STM) and spectroscopy. Depending on the local hcp versus fcc character of the reconstruction, NaCl adsorption gives rise to a different shift of the Au(111) surface state toward the Fermi level, in agreement with ab initio calculations. Such lateral modulation may allow for tunable nanostructuring of thin insulating films, which opens up new perspectives for molecular electronics applications. Furthermore, we demonstrate the simultaneous visualization of both the alkali and the halogen atoms in hcp regions of the NaCl/Au(111) surface using a functionalized STM tip. Ab initio calculations relate this simultaneous visualization to the larger electron density in the hcp regions.