Control of molecule-based transport for future molecular devices

Abstract

In this review, possibilities to modify intentionally the electronic transport properties of metal/molecule/metal devices (MMM devices) are discussed. Here especially the influence of the metal work function, the metal-molecule interface, the molecule dipole and different tunneling mechanisms are considered. A route to evaluate the effective surface work function of metal-molecule systems is given and, based on experimental results, an exemplary estimation is performed. The electron transport across different metal-molecule interfaces is characterized by relating transmission coefficients extracted from experimentally derived molecular conductances, decay constants or tunneling barrier heights. Based on the reported results the tunneling decay constant can be assumed to be suitable to characterize intrinsic molecular electron transport properties, while the nature of the metal-molecule contacts is properly described by the transmission coefficient. A clear gradation of transmission efficiencies of metal-anchoring group combinations can be given.

Probing charge transfer dynamics in self-assembled monolayers by core hole clock approach

“…Charge transport through individual molecular units, including so called "molecular wires" (MWs), is an important issue, in particular, for such frontier fields of modern science and technology as molecular and organic electronics as well as organic photovoltaics [1][2][3]. In this context, significant activity regarding the investigation of transport properties of potential MWs and prototype molecules has evolved [2,4].…”

“…Significantly, this route leads to the same final state with two holes in OV as the non-resonant Auger process (A). The latter process involves the excitation of a core electron into a continuum state (1) followed by the intershell transition (2) and the emission of UV electron (3). Note that when the bandwidth of the exciting radiation in the case of RAES is narrower than the core hole lifetime broadening of the neutral core-excited state, it is not possible to disentangle the excitation/de-excitation processes as subsequent steps, but the whole event should be considered as a one-step process with excitation and de-excitation taking place simultaneously [37].…”

Semiempirical van der Waals interactions versusab initiononlocal correlation effects in the thiophene-Cu(111) system

“…Of particular interest is the nature of the adsorbate-substrate interaction since its strength is one factor which controls the electron flow in a molecular-based device. 9,10 Among the molecule-surface systems of interest from this perspective, the thiophene (C 4 H 4 S) on a metal surface such as Cu (111) is an appealing choice since thiophene is a basic functional unit of oligothiophene used to build, for instance, a molecular field effect transistor 11 or molecular wires on the NaCl/Cu(111) system. 12 From the experimental point of view, thiophene molecules adsorbed on the Cu(111) surface have been investigated by Milligan et al, 13,14 Imanishi et al, 15 and Rousseau et al 16 In these normal incidence x-ray standing wave (NIXSW), near edge x-ray absorption fine structure (NEXAFS), and temperature programmed desorption (TPD) measurements, the focus was on the details of the ground-state geometry such as the adsorption site, the molecule-surface distance, and the tilt angle of the thiophene molecules for different coverages as well as on the corresponding adsorption energy.…”

Research Update: Molecular electronics: The single-molecule switch and transistor

“…[2][3][4][5] Measuring the conductance of an individual molecule seems at first glance a rather simple task, since one only has to apply a voltage difference across both ends of the molecule and measure the current flowing through it. The problem is that, due to the small size of the molecule, it is very hard to connect it to macroscopic electrical contacts.…”