Metal–Single-Molecule–Semiconductor Junctions Formed by a Radical Reaction Bridging Gold and Silicon Electrodes

Abstract

Here we report molecular films terminated with diazonium salts moieties at both ends which enables single-molecule contacts between gold and silicon electrodes at open circuit via a radical reaction. We show that the kinetics of film grafting is crystal-facet dependent, being more favourable on ⟨111⟩ than on ⟨100⟩, a finding that adds control over surface chemistry during the device fabrication. The impact of this spontaneous chemistry in single-molecule electronics is demonstrated using STM-break junction approaches by forming metal-single-moleculesemiconductor junctions between silicon and gold source and drain, electrodes. Au-C and Si-C molecule-electrode contacts result in single-molecule wires that are mechanically stable, with an average lifetime at room temperature of 1.1 s which is 30-400 % higher than that reported for conventional molecular junctions formed between gold electrodes using thiol and amine contact groups. The high stability enabled measuring current-voltage properties during the lifetime of the molecular junction. We show that current rectification, which is intrinsic to metal-semiconductor junctions, can be controlled when a single-molecule bridges the gap in the junction. The system changes from being a current-rectifier in the absence of molecular bridge to an ohmic contact when a single-molecule is covalently bonded to both silicon and gold electrodes. This study paves the way for the merging of the fields of single-molecule and silicon electronics.

Electrochemical gating enhances nearfield trapping of single metalloprotein junctions

“…In molecular electronics, different strategies have been tested to obtain durable and mechanically robust molecular junctions, including the use of different electrode materials and the inclusion or modification of anchoring groups to promote specific molecule-electrode interaction. [25][26][27] Unfortunately, these alternatives are difficult to implement in biosystems because of the implications that structural modification of biomolecules entail for their CT properties. Additionally, chemical alterations of the molecule|electrode directed at immobilising the biomolecule at the electrode may render CT-inactive molecular conformations.…”

Spontaneous S–Si bonding of alkanethiols to Si(111)–H: towards Si–molecule–Si circuits

“…[14][15][16] In the last few years, there has been increasing interest in expanding the use of SAMs in nanoelectronics from gold 8 towards semiconducting platforms including GaAs [17][18][19] and Si. [20][21][22][23][24][25] It is anticipated that combining the electrical properties of semiconductors with the chemical diversity of organic molecules, a variety of technological development can be achieved. Silicon, in particular, provides an attractive choice as an electrode because atomically at silicon substrates are commercially available, are widely used in microelectronics industry, and their electronic properties can be controlled via doping and chemical variation.…”

A post-functionalization toolbox for diazonium (electro)-grafted surfaces: review of the coupling methods

“…50,51 Recently, 3,3 0 -dimethoxy-[1,1 0 -biphenyl]-4,4 0 -bis(diazonium) was anchored to a silicon surface through selective reduction of only one of the two diazonium groups and the remaining immobilized one was used to spontaneously attach an Au STM tip. 204 The Si-molecule-Au junction showed an enhanced lifetime compared to similar architectures based on physisorbed or thiol-immobilized compounds.…”