Bias-induced orbital hybridization in diblock co-oligomer diodes

Abstract

We investigate current rectification in diblock co-oligomer diode molecules on the basis of the Su-Schrieffer-Heeger model [Phys. Rev. B 22, 2099 (1980)] combined with the nonequilibrium Green’s function formalism. The current rectification observed in experiment [M. K. Ng et al., J. Am. Chem. Soc 124, 11862 (2002)] is well explained by the mechanism of bias-induced asymmetric hybridization of molecular orbitals. The positive bias tends to delocalize molecular orbitals through the hybridization, which produces a sharp increase in current at the threshold voltage; while the negative bias enhances the mismatch of energy levels and has no effect on the hybridization and the current.

Tunnel Magnetoresistance of the Heterocyclic Molecular Junctions: A Green’s Function Approach

“…These resonance peaks are related to the eigenenergies of the individual molecules. Furthermore, we observe different molecular energy gap as we chemically change the heteroatoms in these heterocyclic molecules in accordance with experimental results [22][23][24]. Figure 3 shows the logarithmic scale of transmission function versus energy for three heterocyclic molecular junctions for P and AP configurations.…”

“…The effects of heteroatoms in the Hamiltonian of the molecule are taken to be ε S = t S = 0.125 eV, ε N = t N = 0.08 eV, and ε O = t O = 0.03 eV. These SSH parameters can reproduce the experimental band gap for the polythiophene [22], polyfuran [23], and polypyrrole [24] molecules. The tight-binding parameters for FM electrodes chosen to be ε 0 = 1 eV, t = 2.5 eV, and |J β | = 1.3 eV.…”

High rectification ratios of Fe–porphyrin molecules on Au facets

“…In parallel, intense theoretical transport calculations using non-equilibrium Green function and/or first principles density functional calculations have been carried out on simpler single chains of molecules sandwiched between the same electrode materials including s bridge [12], p bridge [13,14], various end-groups [15], and different types of asymmetric molecules [4,16,17], biased-induced orbital hybridization [18], asymmetric electrode coupling [19,20] as well as different metals for two electrodes including Au, Li, Pb, Al, Ag and Pt [6,7,21] in order to better understand the "metal/molecule" junction [2] and search for the optimized rectification.…”

Effect of geometrical torsion on the rectification properties of diblock conjugated molecular diodes

“…The molecular rectifier, as first proposed by Aviram and Ratner in 1974, 1 is among the most fundamental functional units for the future molecular nanoscale logic circuits. [2][3][4][5] Both experimental [6][7][8][9][10][11][12][13] and theoretical [14][15][16][17][18] researches have been performed in order to find suitable molecules for molecular rectifiers and to improve the rectification ratio (RR). Thanks to sophisticated experimental technologies, such as scanning tunneling microscopy (STM) 19,20 and mechanical controllable breaking junction (MCBJ), 21,22 it has been recently found many promising single-molecule diodes based on diblock co-oligomers, 4,7,10 especially the dipyrimidinyldiphenyl molecule.…”