A Dramatic Odd–Even Oscillating Behavior for the Current Rectification and Negative Differential Resistance in Carbon‐Chain‐Modified Donor–Acceptor Molecular Devices

Abstract

The donor-acceptor molecule is the only molecule that features a real intrinsic rectifi cation. However, all investigations in the last decades showed that rectifi cation behaviors of such molecules are not promising since their rectifi cation ratio is only on the order of 10. Use of carbon chains C n to serve as spacers is reported, along with attempts to modulate electrical behavior of the donor-acceptor molecule. Calculations using the fi rst-principles method show that electrical behavior is indeed altered substantively, and a particular regularity can be clearly observed, i.e., a dramatic odd-even oscillation for electronic behavior with increasing carbon-chain length n. For models with even-n carbon chains, the rectifi cation ratio is small (30), and no negative differential resistance (NDR) behavior is detected, but the rectifying performance of models with odd-n carbon chains is tremendously improved and rectifi cation ratios on the order of 50 to 400 can be achieved, alongside a large NDR. This study thus suggests that using a suitable spacer might be an effective way to signifi cantly boost electrical characteristics, including rectifying performance, of the donor-acceptor molecule.

Effect of H2O Adsorption on Negative Differential Conductance Behavior of Single Junction

“…Thus one can easily understand why the height of the transmission peaks decrease very quickly in the split process with the increase of the bias voltage. We should mention that the orbitals presented in the figure are the molecular projected self-consistent Hamiltonian (MPSH) eigenstates, which are often used to discuss the electronic transport properties of molecular junctions in literatures 7, 23 . The MPSH is the self-consistent Hamiltonian of the functional molecule including the H 2 O adsorbates with the influence of the electrode, which contains the electrode-molecule coupling effects but does not contain the Hamiltonian of the gold electrode, so the energies of the MPSH eigenstates are not perfectly consistent with the positions of the transmission peaks 7 .

Figure 4Spatial distributions of molecular orbitals for TADHA molecular junctions with one or without H 2 O adsorbate at 0.0 V, ±0.5 V and at the voltage of peak-current values, where the orbital energies relative to the Fermi level are also shown under each orbital.

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All-carbon sp-sp2 hybrid structures: Geometrical properties, current rectification and current amplification

“…This is intimately related to the localized position of a molecular state. If a molecular state is localized on the left (right) side of the molecule, which implies that this state has a strong coupling with the left (right) electrode so that this orbital level always follows the left (right) electrode under bias353637, the orbital level then moves up (down) with bias to form a straight line. However, the state localized at the one side might be sensitive to bias, this will lead to a change of the localized position of the molecular state with bias and thus to form a polygonal line or an irregular line for the shifting orbital level.…”

Electronic and magnetic properties of zigzag-edged hexagonal graphene ring nanojunctions

“…After optimization, we find that ZHGQRs remain their planar structures, the C-H bond length is 1.16-1.17 Å, and C-C bond length in the ZTG appears in a range of 1.42-1.45 Å with larger values internally than those externally. In our studies, geometric optimizations of the device region and calculations of electronic structure, transport properties, and spin magnetism are performed by using the density function theory (DFT) combined with the non-equilibrium Green's function (NEGF) method [26][27][28][29][30]. We employ Troullier-Martins norm-conserving pseudopotentials to represent the atom core and linear combinations of local atomic orbitals to expand the valence states of electrons.…”