Electrostatic screening mediated by interfacial charge transfer in molecular assemblies on semiconductor substrates

Abstract

Using scanning tunneling microscopy and spectroscopy (STM, STS), we report the electronic structures of self-assembled zinc phthalocyanine (ZnPc) and hexadecafluorinated zinc phthalocyanine (F16ZnPc) monolayers on the Si(111)-B surface. We show that interfacial charge transfer occurs in the F16ZnPc monolayer, which gives rise to a pronounced spatial variation of the occupied molecular state across the molecular assembly, a feature not observed in the molecular states of the ZnPc overlayer without the presence of interfacial charge transfer. We attribute this observation to the inhomogeneous electrostatic screening of the intraorbital Coulomb interaction in molecular adsorbates arising from the substrate boron distribution. This study highlights the impact of the substrate electrostatic environment on molecular electronic structures, an essential aspect in the applications of organic and molecular electronic devices.