Preparation of High Quality Electrical Insulator Self-Assembled Monolayers on Gold. Experimental Investigation of the Conduction Mechanism through Organic Thin Films

Abstract

Self-assembled monolayers (SAMs) form highly ordered, stable dielectrics on conductive surfaces. Being able to attach larger-area contacts in a MIM (metal-insulator-metal) diode, their electrical properties can be determined. In this paper, the electrical conduction through thiolate SAMs of different alkyl chain lengths formed on gold surfaces were studied and discussed. The influence of the headgroup with respect to the surface quality and prevention of short circuits is investigated. Phenoxy terminated alkanethiols were found to form high quality SAMs with perfect insulating properties. Synthesis of the required terminally substituted long chain thiols have been developed. The I(V) characteristics of MIM structures formed with these SAMs are measured and simulated according to theoretical tunneling models for electrical conductivity through thin organic layers. SAM based electronic devices will become especially important for future nanoscale applications, where they can serve as insulators, gate dielectric of FETs, resistors, and capacitor structures.

Molecular Self‐Assembled Monolayers and Multilayers for Organic and Unconventional Inorganic Thin‐Film Transistor Applications

“…6A) was investigated in Au-SAM-Au junctions, where the top Au electrode was deposited by cathodic deposition directly on top of the monolayer. [176] High breakdown field strengths (E B )>50 MV cm À1 were measured, and it was concluded that the terminal aromatic rings have strong p-p interactions which densify the surface, hindering the penetration of metal. Furthermore, the authors modified the typical square-well tunneling potential to fit the J-V data within the direct tunneling model, but did not investigate the J(V, T) dependence.…”

The preparation of three new partially deuterated hexadecanethiols for applications in surface chemistry

“…Johnson 11 demonstrated that in the presence of Li 2 CuCl 4 , alkyl Grignard reagents couple with only one bromide of an alkyl dibromide, with formation of the dicoupled product possible at higher temperatures and longer reaction time. Based on this and other precedents, [12][13][14] the Grignard reagent of commercially available perdeuterated bromooctane (4) was prepared and coupled to dibromooctane as the starting point for 9,9,10,10, 11,11,12,12,13,13,14,14,15,15,16,16,16-(heptadecyldeuterio)hexadecanethiol-d 17 (1, Scheme 1).…”

“…The addition of potassium thioacetate to this crude mixture produced thiolacetate 6, which was easily separated from doubly functionalized 7 by flash chromatography to yield 51% of compound 6 over two steps. The deacetylization of 6 to afford labelled thiol 1 was performed by treating the thiolacetate with one equivalent of LAH in THF for 15 min 15 producing thiol cleanly in 70% yield without disulfide contamination.…”

Oxygen Attachment on Alkanethiolate SAMs Induced by Low-Energy Electron Irradiation

“…The electron transfer is usually observed in aromatic-containing SAMs by direct tunneling, but also in aliphatic-containing SAMs. [49][50][51] It has been shown that longer chain length triggers a higher resistance to the charge transfer across the SAM. 52 Considering that the thickness of the BT SAM is of the order to the BM SAM, the electronic tunneling can explain the resistance upon >14 eV electron irradiation for short chain SAMs.…”