Cai-Juan Xia

EFFECT OF TORSION ANGLE ON THE RECTIFYING PERFORMANCE IN THE DONOR-BRIDGE-ACCEPTOR SINGLE MOLECULAR DEVICE

By applying nonequilibrium Greens function formalism combined with first-principles density functional theory, we investigate the effect of torsion angle on the rectifying performance in the donor-bridge-acceptor single molecular device. The influence of HOMO–LUMO gaps and the spatial distributions of molecular orbitals on the electronic transport through the molecular device are discussed in detail. The theoretical results show that the torsion angle plays an important role in the rectifying behavior of such devices. By changing the torsion angle, namely changing the magnitude of the intermolecular coupling effect, a different rectifying behavior can be observed in these systems. The results can provide fundamental guidelines for the design of functional molecular devices to a certain extent.

THEORETICAL STUDIES OF THE RECTIFYING PERFORMANCE IN DIBLOCK MOLECULAR JUNCTIONS: THE ROLE OF THE ANCHORING GROUPS

By applying nonequilibrium Greens function formalism combined with first-principles density functional theory, we investigate the effect of different anchoring groups on the rectifying behavior in diblock molecular junctions. The spatial distributions of molecular orbitals and the influence of transmission coefficients under various external voltage biases on the electronic transport through the molecular device are discussed in detail. The results show that the anchoring groups play a significant role on the electronic transport properties. The rectifying performance in molecular junctions can be manipulated, enhanced, or suppressed by a careful consideration of the effects of the anchoring group and such modifications become crucial in optimizing the electronic transport properties of chemical structures.

A possible salicylideneanilines-based optical molecular switch induced by a reversible hydrogen transfer: an ab initio study

The electronic transport properties of the salicylideneanilines-based molecular optical switch are investigated using a nonequilibrium Greens function formalism combined with first-principles density functional theory. The molecule that comprises the switch can convert between the enol and keto tautomeric forms upon photoinduced excited state hydrogen transfer in the molecular bridge. Theoretical results show that the current through the enol form is significantly larger than that through the keto form, which realize the on and off states of the molecular switch. The physical origin of the switching behaviour is interpreted based on the spatial distributions of molecular orbitals and the HOMO-LUMO gap. Furthermore the effect of the donor/acceptor substituent on the electronic transport through the molecular device is also discussed in detail. The switching performance can be improved to some extent through the acceptor substituent.

Effect of Chemical Modifications on the Electronic Transport Properties of the Optical Molecular Switch

Using first-principles density functional theory and nonequilibrium Greens function formalism, we investigate the effect of chemical modifications on the electronic transport properties of the dihydroazulene optical molecular switch. The molecule that comprises the switch can convert between the closed and the open forms upon photoexcitation. Theoretical results show that the chemical modifications play an important role in determining the switching behavior of such molecular device. This result reflects that the current ratio can be manipulated with the careful selection of the substituents and can provide fundamental guidelines for the design of functional molecular devices.

Effect of the anchoring groups on the switching behaviour of the dihydroazulene/vinylheptafulvene molecular junction with zigzag-edged graphene nanoribbons electrodes

ABSTRACT The switching behaviour of dihydroazulene/vinylheptafulvene molecule with different anchoring groups sandwiched between two zigzag-edged graphene nanoribbons (ZGNRs) electrodes is investigated by applying nonequilibrium Greens function formalism combined with first-principles density functional theory. The calculated results show that the anchoring groups play a significant role in determining the electronic transport properties and switching behaviour of the molecular junctions. A higher current switching ratio without any oscillation can be obtained for the molecular junctions with carbon atom anchoring group, which suggests that this system has a broader application in future logic and memory devices.

The switching behaviors induced by torsion angle in a diblock co-oligomer molecule with tailoring graphene nanoribbon electrodes

By applying first-principles method based on density functional theory combined with nonequilibrium Green’s function, we investigate the effect of torsion angle on the electronic transport properties in dipyrimidinyl–diphenyl co-oligomer molecular device with tailoring graphene nanoribbon electrodes. The results show that the torsion angle plays an important role on the electronic transport properties of the molecular device. When the torsion angle rotates from 0∘ to 90∘, the molecular devices exhibit very different current–voltage characteristics which can realize the on and off states of the molecular switch.

THE ELECTRONIC TRANSPORT PROPERTIES IN NAPHTHOPYRAN-BASED OPTICAL MOLECULAR SWITCH WITH CARBON NANOTUBE ELECTRODES

By applying nonequilibrium Greens function (NEGF) formalism combined first-principles density functional theory (DFT), we investigate the electronic transport properties of optical molecular switch based on the naphthopyran molecule with two different single-walled carbon nanotube (SWCNT) electrodes. The molecule that comprises the switch can convert between the closed and open forms upon photoexcitation. Theoretical results show that these two forms exhibit very different conductance properties both in armchair and zigzag junction, which can realize the on and off states of the molecular switch. Meantime, the chirality of the SWCNT electrodes strongly affects the switching characteristics of the molecular junctions. The maximum value of on–off ratio can reach 292 at 1.6 V for the switch with zigzag SWCNT electrodes.