In-Situ Scrutiny of the Relationship between Polymorphic Phases and Properties of Self-Assembled Monolayers of a Biphenyl Based Thiol

Abstract

Two polymorphic phases of ω-(4′-methylbiphenyl-4-yl) butane-1-thiol (BP4) molecules formed on Au(111) were investigated by multidimensional atomic force microscopy, combining conductivity measurements, electrostatic characterization, friction force mapping, and normal force spectroscopy. Based on the same molecular structure but differing in molecular order, packing density, and molecular tilt, the two phases serve as a test bench to establish the structure–property relationships in self-assembled monolayers (SAMs). From a detailed analysis of the charge transport and electrostatics, the contributions of geometrical and electronic effects to the tunneling are discussed. ; This work has been supported by the Spanish Government under projects MAT2013-47869-C4-1-P and MAT2016-77852- C2-1-R (AEI/FEDER, UE) and the Generalitat de Catalunya 2014 SGR501. We acknowledge the MINECO project MAT2015-68994-REDC and the "'Severo Ochoa"' Program for Centers of Excellence in R&D (SEV-2015-0496). M. Paradinas thanks the Spanish Government for financial support through BES-2008-003588 FPI and PTA2014-09788-I fellowships. C. Munuera acknowledges financial support from the "Ramon y Cajal ́ " program RYC-2014-16626. ; Peer reviewed