Novel conjugated molecules for molecular electronics

Abstract

Two-terminal thioacetyl-protected Biphenyl-Dithiol (BPDT) and Diphenylanthracene (DPA) derivatives are synthesized. They can be easily deprotected in situ by ammonium hydroxide to dithiols used for the fabrication of self-assembled monolayers (SAMs) on gold substrates. The SAMs are characterized by Spectroscopic Ellipsometry (SE), Reflectance Fourier Transform Infrared Spectroscopy (Reflectance FT-IR), Contact Angle measurements (CA) and Atomic Force Microscopy (AFM). All these characterizations confirm that the free dithiols form SAMs on gold substrates. Conductive Atomic Force Microscope (C-AFM) was used to measure electrical properties of the Metal-SAMs-Metal junctions. The tip-SAM micro contact area is approximately 50 nm2, meaning the junction contains a small bundle of molecules (~200). Some of the SAMs possess reasonably linear I-V curves prior to the breakdown limit. Others show sigmoidal I-V curves. These SAMs are candidates for molecular electronics. These measurements show that C-AFM is a reliable method for fundamental studies of electron transfer through small numbers of molecules.