Scanning Tunneling Spectroscopy of Insulating Self-Assembled Monolayers on Au(111)

Abstract

Self-assembled monolayers (SAMs) of dodecanethiol (DDT), octadecanethiol (ODT), and resorcinarene C10 tetrasulfide (RC10TS) on Au(111) were characterized by scanning tunneling spectroscopy (STS) under ultrahigh vacuum conditions and evaluated as ultrathin resists. A voltage division factor η was used to parametrize the equilibrium Fermi energy level E f in terms of an applied voltage bias. Nominally symmetric tunneling (η ∼ 0.5) conditions were established by acquiring conductance spectra over a range of set point voltages. The electrical conductivity of the monolayers was observed to be dependent on both the monolayer thickness and the nature of the Au/S bonding. Leakage current densities across DDT and RC10TS SAMs on Au were estimated, with the latter comparing favorably with a 1.5-nm layer of SiO 2 on Si.

A comparative study on the deposition of Mn12single molecule magnets on the Au(111) surface

“…1a the direct deposition of suitably functionalized Mn 12 molecules via self-assembly from solution due to a strong S-Au interaction is shown. The Mn 12 solvents and Au substrates were used (see Experimental). Fig.…”

“…Single molecule magnets, like the famous Mn 12 Since the ligand shell of Mn 12 molecules can be tailored according to the needs of specific experiments or applications, 2 this material class is a favoured choice for future basic studies on quantum effects of magnetism on the molecular scale like quantum phase interference 3 and is furthermore a promising candidate for preliminary studies aiming at molecular ultrahigh density data storage devices or quantum computing applications.…”

Single-Molecule Magnets: A New Approach To Investigate the Electronic Structure of Mn12 Molecules by Scanning Tunneling Spectroscopy

“…This symmetry indicates that the electrostatic coupling between molecule and substrate is comparable to the coupling between tip and molecule. 26 In previous studies this condition was used to estimate the E F -HOMO difference, which is one-fourth of the measured energy gap width. 26 Assuming a negligible contribution from the ligands as well as from the linker molecules because of their expected conductor-like behavior in STS measurements, application of this formalism to compound 2 yields a value of 0.5 ( 0.2 eV.…”

“…26 In previous studies this condition was used to estimate the E F -HOMO difference, which is one-fourth of the measured energy gap width. 26 Assuming a negligible contribution from the ligands as well as from the linker molecules because of their expected conductor-like behavior in STS measurements, application of this formalism to compound 2 yields a value of 0.5 ( 0.2 eV. This value would be in reasonable agreement with the electronic structure found in the combined experimental and theoretical study of Mn 12 -acetate.…”

Molecular Nanoelectronics

“…With STM, the electrical "contact" occurs through the air-gap between the molecule or the molecular monolayer and the STM tip (or vacuum in case of an UHV-STM). This leads to a difficult estimate of the true conductance of the molecules [34,35]. A significant improvement has been demonstrated by Xu and Tao [36] to measure the conductance of a single molecule by repeatedly forming few thousands of Au-molecule-Au junctions.…”