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

Abstract

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.

Nanofabrication techniques of highly organized monolayers sandwiched between two electrodes for molecular electronics

“…Thus, gold electrodes are evaporated onto an elastomeric stamp and are subsequently transferred by mechanical contact onto a monolayer that contains a group with chemical affinity to gold (e.g. a thiol group) [261][262][263][264]. Liftoff assisted approaches have also been used to fabricate the top contact electrode.…”

Molecular Nanoelectronics

“…Transfer of gold is based on the affinity of this metal for thiol function -SH forming a chemical bond Au-S. Loo et al [69] have used the nTP technique to deposit gold electrodes on alkane dithiol molecules self-assembled on gold or GaAs substrates. Nanotransfer printing of gold electrodes was also deposited onto oxidized silicon surface covered by a monolayer of thiolterminated alkylsilane molecule [71,72]. Soft depositions of pre-formed metal electrodes, e.g.…”

A Detailed Description of the Chemistry of Thiol Supporting Plasma Polymer Films

“…[8][9][10] The common approach to generate TSOS is by immersion of the substrate in a solution containing molecules bearing a -SH function. [4,[11][12][13] However, this method suffers of several drawbacks. For instance, this wet chemistry route strongly depends on the substrate surface properties which could therefore reduce its applicability to some specific materials.…”

“…[3] Moreover, most of the time, the desired surface is obtained after surface preparation treatments requiring important use of solvents and long reaction time which could be detrimental from the environmental point of view. [4,12] In this context, the plasma polymerization of a thiolbased precursor appears to be a promising alternative for the generation of TSOS. Indeed, this solvent-free process presents significant advantages over the wet traditional method: one-step process, low reaction time, environmentally friendly, none or little substrate preparation, high thermal and mechanical stability of the synthesized layers.…”