Controlling the coupling between single-molecules and dangling-bonds (DBs) on hydrogenpassivated semiconductor surfaces is of relevance from both technological and fundamental perspectives. Furthermore, DBs can be patterned on these surfaces with atomic precision by STM tip induced desorption of the hydrogen atoms from the passivated layer. This opens up the possibility to tune the properties of the molecules by contacting them with DB arrays of different complexity. With this in mind, we have investigated the interaction of a conjugated polyaromatic molecule (trinaphthylene, Y molecule) with a single-DB or a DB dimer on the hydrogenated Ge(001):H surface. Using Scanning Tunneling Microscope (STM) and Spectroscopy (STS) experiments combined with theoretical calculations, we have found significantly different results in each case. Y molecules interact weakly with the hydrogen-passivated surface, and are nearly decoupled from the substrate states. As a result, the electronic structure of the molecule positioned on the single DB is similar to the gas phase electronic structure. On the contrary, the formation of chemical bonds following the Diels-Alder addition for Y molecules attached to surface DB dimers results in a significant change of the molecular electronic structure. Our results show that the strength of the coupling between the molecule and the substrate could be tuned by creating complex arrays comprising both single and dimerized DBs.

Resumen del póster presentado a la 10th Conferencia Fuerzas y Túnel, celebrada en Girona (España) del 5 al 7 de septiembre de 2016.-- et al.

Peer reviewed