Rupan Preet Kaur

Augmenting Molecular Junctions with Different Transition Metal Contacts

In this research paper, the effect of the material of electrodes at the nanometer scale was elucidated towards measuring the electron transport properties of a single molecular junction comprising of anthracenedithiol molecule (ADT) stringed to two semi-infinite metallic electrodes using Extended Huckle Theory (EHT)-based semi-empirical modelling approach. The electron transport parameters i.e., I–V curves, Conductance-Voltage curves and transmission spectrum were investigated through ADT molecule by buffering it between different electrodes composed of rhodium, palladium, nickel and copper, all from transition metals series, under finite bias voltages within Keldyshs non equilibrium green function formulism (NEGF). The simulated results revealed that the copper electrodes showed maximum conduction whereas palladium showed least. The maximum conductance of 0.82 G0 and 43 μA current was exhibited by copper and thus affirmed to be the most effective electrode at nanometre scale when compared with other electrodes viz. nickel, rhodium and palladium.

Effect of gold electrode crystallographic orientations on charge transport through aromatic molecular junctions

ABSTRACT We examined the electrical conduction through single-molecular junctions comprising of anthracenedithiol molecule coupled to two gold electrodes having ⟨1,0,1⟩, ⟨1,1,0⟩ and ⟨1,1,1⟩ crystallographic orientations. Owing to this jellium model, we evaluated the values of current and conductance using non-equilibrium Greens functions combined with extended Huckel theory. This data was further interpreted in terms of transmission spectra, density of states and their molecular orbital analysis for zero bias. We evinced the oscillating conductance in all three cases, due to the oscillation of orbital energy relative to Fermi level. Our detailed analysis suggested that electrode orientation can tune the molecule–electrode coupling and hence conduction. Anthracene molecular junction with ⟨1,1,0⟩ orientation displayed favourable conduction, when compared to the other two orientations, thus can provide us an insight while designing futuristic molecular electronic devices.

First principle electron transport modeling of Be-doped organic molecular junctions

The transport properties of beryllium doped anthracene molecular junction are investigated using density functional non-equillibrium Greens function method. The equilibrium conductance of anthracene Metal-molecule-Metal (MmM) junction increases by approximately 77% by adding beryllium impurity to it. The electronic transport characteristics under both zero bias as well as finite bias are explored of such molecular junction. We observe novel attributes such as molecular rectification and NDR behavior for the molecular junction under consideration. It is found that the doping effect of Be- atom significantly changes the transport properties of aromatic molecular junction. Our findings shed light on the electron transport metrics that affect the conductance of MmM junctions within appreciable transmission limits. We firmly believe that the results deduced in this paper can be generalized for other aromatic molecular junctions as well.

AROMATIC MOLECULAR JUNCTIONS WITH INERT GASES AS ALLIGATOR CLIPS

In this research paper, we examined the effect of placing the elements of Group 0 as alligator clips with Anthracene molecule binding gold electrodes on the nanometer scale using Extended Huckle Theory (EHT) based semi-empirical model. The electron transport parameters i.e., I-V curves, Conductance-Voltage curves and transmission spectrum were investigated through Anthracene molecule by buffering it between two semi-infinite gold electrodes but via different alligator clips-Helium, Neon, Argon, Krypton, Xenon and Radon, all from Noble gas group or group-0 under finite bias voltages within Keldyshs nonequilibrium green function formalism (NEGF). The simulated results revealed that the Xenon and Radon showed maximum conduction whereas Krypton, Neon, Helium and Argon showed least. The maximum conductance of 0.62G0 and 70.4 μA current was exhibited by Xenon and thus affirmed to be the most optimal alligator clip amongst noble gases at nanometre scale.

Single-Molecule junctions based on selenol - Terminated anchor -A promising candidate for electron transport

In this paper, we perceived the effect of sulphur and selenium as anchoring groups on the nanometre scale electron transport properties of single molecular junction comprising of anthracene molecule stringed to two semi-infinite electrodes using Extended Huckel Theory (EHT) based semi-empirical model. The electron transport parameters were examined by buffering anthracene between gold electrodes and attaching sulphur and selenium one by one with gold electrodes, called molecular alligator clips, under different bias voltages. Negative differential resistance characteristics were found in the conductance-bias voltage characteristics. The simulated results discovered selenium as a better candidate in comparison to sulphur for electron transport at nanometre scale through molecular junctions.

Electrical characterization of C28 fullerene junctions formed with group 1B metal electrodes

We present an atomistic theory of electronic transport through single molecular junctions based on smallest stable fullerene molecule, C28. The electronic properties of single molecular junctions critically depend on the nature of electrode material. The two probe device is modeled by constraining C28 between two semi-infinite metal electrodes, from group 1B of periodic table, copper, silver and gold. We have highlighted the correlated phenomena of resonant conduction and current driven dynamics in molecular junctions using extendend Huckel theory in combination with non equilibrium Greens function framework. We conclude strong dependence of conductance on transmissions, which leads to oscillating conductance spectrum. An interesting interplay between conducting channels and different degrees of spatial localization and delocalization of molecular orbitals is evinced. The physical origin of current and conductance of so-formed C28 molecular junctions is discussed in detail by analysing their density of states, transmission spectra, molecular orbital analysis, rectification ratio and molecular projected self consistent Hamiltonian eigen states at different operating voltages ranging from -2V to +2V.

Charging and geometric effects on conduction through Anthracene molecular junctions

We studied the geometric effects on the charge transfer through the anthracenedithiol (ADT) molecular junction using density functional theory combined with the non-equilibrium Green’s function approach. Two major geometric aspects, bond length and bond angle, were moderated to optimize the electrical conduction. From the results established in this paper, we found that the electrical conduction can be tuned from 0.2 G0 to 0.9 G0 by varying the Au–S bond length, whereas the moderation of bonding angle assayed a minor change from 0.37 G0 to 0.47 G0. We attributed this escalating zero bias conductance to the increasing charge on the terminal sulfur atom of the ADT molecule, which increased the energy of the HOMO orbital towards Fermi level and exhibited a semi-metallic behaviour. Therefore, geometry plays a critical role in deciding the charge transport through the metal/molecule interface.

Unraveling the electrical conduction of C-40 quasi-fullerene molecular junction

In this paper, we present the state of art theoretical calculations of charge transport through quasi-fullerene molecule C40 coupled rigidly between two 3D gold electrodes by applying different electro-chemical potentials. The methodology we adopted has been based on density functional theory approach combined with Keldysh’s non-equilibrium Green’s function (NEGF) framework suggested for mesoscopic systems. The results exhibited by this molecular junction confirmed it to be highly metallic and showed prominent conduction of the order of twice of the quantum conductance, i.e., 2*G0 at zero bias. Our results are consistent with theoretical predictions in ab initiocalculations with some variants of quasi-fullerenes.

Bond length dependent transport properties of inorganic nanowire

In this research paper, we scrutinised the impact of variations in the bondlength of a Cadmium sulphide nanowire on the electron transport properties. We contemplated that if the bond length of the nanowirewas either elongatedor shortened, there was a definite impact on the electrical transport characteristics. The effect of changing bond length was observed on the values of current and conductance of the nanowire and the relative stress induced on the system under consideration. We elucidated that the bond length plays an important role in Nano meter-scale electron transport characteristics through nanowire stringed to macroscopic gold electrodes. The observed results from our findings have been plotted in terms of percentage variations in conductance as well as current for the changes brought towards elongation or shortening of the nanowire. The vital information collected through this simulation work can be significantly beneficial in molecular electronics especially as potential candidates for sensor, solar cells and bio-medical applications.