Ionic Liquid Based Approach for Single-Molecule Electronics with Cobalt Contacts

Abstract

An electrochemical method is presented for fabricating cobalt thin films for single-molecule electrical transport measurements. These films are electroplated in an aqueous electrolyte, but the crucial stages of electrochemical reduction to remove surface oxide and adsorption of alkane(di)thiol target molecules under electrochemical control to form self-assembled monolayers which protect the oxide-free cobalt surface are carried out in an ionic liquid. This approach yields monolayers on Co that are of comparable quality to those formed on Au by standard self-assembly protocols, as assessed by electrochemical methods and surface infrared spectroscopy. Using an adapted scanning tunneling microscopy (STM) method, we have determined the single-molecule conductance of cobalt/1,8-octanedithiol/cobalt junctions by employing a monolayer on cobalt and a cobalt STM tip in an ionic liquid environment and have compared the results with those of experiments using gold electrodes as a control. These cobalt substrates could therefore have future application in organic spintronic devices such as magnetic tunnel junctions.

Synthesis of ionic polymers by free radical polymerization using aprotic trimethylsilylmethyl‐substituted monomers

“…Mostly, free radical polymerization of vinyl‐substituted ionic monomers or ionic liquid monomers has been applied for polyelectrolyte manufacturing. Typical applications for those ionic polymers are found in gas separation membranes, water repellant surfaces, antistatic coatings, and antimicrobial surfaces …”

Fabrication of ultra-smooth and oxide-free molecule-ferromagnetic metal interfaces for applications in molecular electronics under ordinary laboratory conditions

“…Fabrication methods based on highly controlled ultra-high vacuum (UHV) environments or in situ electrochemical control are available. 4,5,[33][34][35][36] Most electrochemical techniques are based on a two-step procedure involving removal of the native oxide by electrochemical reduction, followed by immediate substrate immersion in alkanethiol containing ethanolic solutions. During transfer of the oxide free Ni surface, metal-oxides can form as the substrates are exposed to air.…”

The Importance of Electrical Impedance Spectroscopy and Equivalent Circuit Analysis on Nanoscale Molecular Electronic Devices

“…If a Nyquist plot shows an ideal semicircle shape, it attributes to a single capacitance characteristic of the junctions and one time constant, τ (where, τ = C DL × R CT ) . [ 71–73 ] In contrast, multiple semicircles indicate more than one time constants that are associated with the charge transfer process. Besides, the diameter of the semicircle is indicative of polarization resistance.…”