Reduction of Gold Penetration through Phenyl-Terminated Alkyl Monolayers on Silicon

Abstract

By preparing phenyl-terminated monolayers on hydrogen-terminated silicon (111), we show that their higher surface densities in comparison with n-alkyl monolayers improves their electrical properties (lower reverse-bias currents, higher effective barrier heights, and closer-to-unity ideality factors) when contacted using either mercury drop or thermally deposited gold electrodes. Consistent with these macroscopic results, the ballistic electron emission microscopy characterization shows a significant decrease in ballistic current and higher local barrier height for the phenyl-terminated monolayers, when compared with gold | n-alkyl monolayer | silicon junctions. We propose that increased intermolecular interaction through π–π stacking of the phenyl head-groups stabilizes the monolayer structure at the buried interface and inhibits the penetration of thermally deposited gold atoms.

The rapid formation of functional monolayers on silicon under mild conditions

“…Notably, films incorporating phenyl rings and bi-functional contacts also hold considerable advantages when making top contacts in molecular devices. 81 Notes and references Fig. 5 Representative CVs (a, cycle n. 1 and cycle n. 100) and EIS and Bode plots (b and c) for ferrocene-modified DEB samples at either an applied potential E dc = E 0 0 or E dc = 0 V. The frequency range was from 100 kHz to 100 mHz.…”

Large-Area, Ensemble Molecular Electronics: Motivation and Challenges

“…223,255 In contrast, monolayers of conjugated wires with strong lateral π-stacking are more rigid and should block such penetration for the same metals deposited under identical conditions. 223,307 Pausing the evaporation after ∼0.5 nm Au deposition on thiol-terminated monolayers relaxes the interface and forms Au clusters. 257 Interestingly, these clusters behave very differently on top of a monolayer made of terthiophene-dithiol or decane-dithiol.…”

A New Route to Nondestructive Top-Contacts for Molecular Electronics on Si: Pb Evaporated on Organic Monolayers

“…Top-contact fabrication on self-assembled organic monolayers (ML) is a critical issue in molecular electronics. If evaporated onto a ML with only ∼ 1 nm thickness, the metal might penetrate through the flexible molecular array even in the absence of pinholes [1,2], creating shorts that dominate the transport characteristics (diffusion effect) [3]. Evaporated atoms may also react with the molecules, fully or partially destroying the electric properties of the ML (reaction effect).…”