Silicon−Molecules−Metal Junctions by Transfer Printing:  Chemical Synthesis and Electrical Properties

Gold electrodes have been deposited by transfer printing (TP) on a thiol-functionalized self-assembled monolayer (SAM) on silicon substrate. A sequential chemical route is reported to incorporate thiol groups (−SH) on a preformed long alkyl chain SAM on silicon. The structural characterizations of the functionalized surfaces are described and confirm success of each chemical step (overall yield of 20%). The electrical measurements of the silicon−molecules−gold TP junctions are compared with junctions made by a classical vacuum evaporation of gold. The temperature-dependent electrical measurements show that the silicon/alkyl/Au TP junctions exhibit a purely temperature-independent tunnel behavior, while a slight temperature-dependent behavior is observed at a low bias (|V| < 0.5 V) for the junctions with evaporated Au electrodes. Admittance spectroscopy measurements confirm the better dielectric behavior of TP junctions.