Transport in ferrocene single molecules for terahertz applications

Abstract

The transport properties of single ferrocene molecules connected to nanoscopic gold electrodes are investigated in the framework of density functional theory (DFT) calculations using the non-equilibrium Green's function formalism. Our setup describes a molecular rotor, where one cyclopentadienyl (Cp) ring of the ferrocene molecule is fixed by the two electrodes, while the second ring is able to rotate. For small enough rotation energies the barrier between the eclipsed and staggered conformations of the ferrocene molecule ensures the functionality of a molecular oscillator. The changes in the transmission function introduced by the relative rotation angle between the two Cp rings are analyzed in both linear and non-linear bias regimes. For larger rotation energies, the device works in the spinning mode. The real time behavior of the nanomechanical device is investigated using DFT-based molecular dynamics, which shows its feasibility for applications in the terahertz regime. In the oscillating mode the natural frequencies are determined, while the spinning mode shows a remarkably reliable behavior with increasing rotation energy.

A 17 GHz molecular rectifier

“…In the present experiments, the change of frequency from 3.78 GHz to 17.8 GHz already points out the appearance of the capacitive contribution |C−C 0 |ω as a plateau in |S 11 | at low bias. Theoretical predictions suggest that an additional inductive contribution 4 (inertia related to carriers effective mass) or oscillation in S 11 due ferrocene spinning 73 should be observed in the THz range. Recently, Tan et al .…”

Theoretical Studies of the Spin-Dependent Electronic Transport Properties in Ethynyl-Terminated Ferrocene Molecular Junctions

“…Metallocene is a complex with a transition metal cation sandwiched between cyclopentadienyl (Cp) rings, and it has unpaired spin components and good chemical stability. Considering it as a possible candidate for molecular devices, the molecular junctions based on metallocene were investigated extensively through experiments and theoretical simulations [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Some spin-dependent transport properties, such as spin filtering and spin switching, were found.…”

“…The two Cp rings can be in the staggered or eclipsed conformation and rotate with low resistance about the Cp–Fe–Cp axis [ 25 , 30 , 32 ]. Nemnes et al investigated the electron transport of the FeCp 2 -based molecular junctions, in which the two FeCp 2 conformations and the different electrode–electrode distances were considered [ 30 ]. Using first-principles methods, Morari et al studied the electron-transport properties in a 1,1′-ferrocene dicarboxylic acid molecular junction.…”

“…In this work, the spin-dependent electron transport properties of ferrocene-based molecules linked to Au electrodes by the thiolated terminal ethynyl groups, as shown in Figure 1 , are investigated using the theoretical NEGF−DFT method. Although there may be some differences for the transport properties between the eclipsed and staggered conformations of the ferrocene molecule [ 30 ], the different molecular structures caused by the substitution position of the terminal ethynyl groups are considered emphatically in this work. Therefore, only the eclipsed FeCp 2 conformation is adopted for the sake of brevity.…”

Electron transport properties of fulgide-based photochromic switches

“…The ongoing scaling of electronic devices for memory and logic applications, beyond the physical limits of standard semiconductor technology, has brought into view the importance of molecular switches. [1][2][3][4][5] For this purpose, molecules with bistable states are required, generated by magnetic spin states or by changing their geometric congurations, which may be driven by heat, light, or pressure. 6,7 Photochromic molecular switches are one particular example recently investigated, both experimentally and theoretically, of promising candidates for threedimensional optical storage technologies.…”