Experimental molecular adsorption: electronic buffer effect of germanene on Al(1 1 1)

Abstract

The interaction of organic C60 molecules with germanene grown on Al(1 1 1) is investigated by experimental tools and calculations. By mean of scanning tunneling microscopy, we show that a single but disordered C60 layer is formed upon deposition in the monolayer range. Density functional theory calculations indicate that van der Waals and electrostatic interactions are present between the C60 layer and the germanene, without formation of covalent bond. Moreover, the C60 molecules are adsorbed without major crystallographic and charge modifications at the interface between germanene and the Al(1 1 1) substrate. The predicted charge transfer from the Al(1 1 1) substrate to the C60 molecules is very small, which means that the germanene layer acts as an electronic buffer between the highly electron attractor C60 molecules and the large electron reservoir Al(1 1 1). This leaves the C60 layer quite uncharged, and so preserves its electron attractor properties for further layers grown on it, in the design of new molecular sensors.