Milanpreet Kaur

ANATOMIZING ELECTRONIC TRANSPORT THROUGH SATURATED ALKANE MOLECULE WITH DISPARATE TERMINAL ELEMENTS

In this paper, we anatomized transport properties of butane belonging to the saturated alkane group (CnH2n+2) using three terminal anchor elements (nitrogen, oxygen and sulfur) in Trans configuration connected to gold electrodes, forming a two probe model. The transport properties of three variants of butane were investigated in terms of Transmission spectra, Eigenstates, I-V characteristics and differential conductance for different values of biasing voltage using Keldyshs non-equilibrium Greens function combined with semi-empirical extended Huckel theory. Amongst the three binding elements, Butane exhibited maximum charge transfer with sulfur, then with nitrogen and least with oxygen. The HOMO-LUMO gap for both nitrogen and Oxygen as terminal anchoring elements suggested that conduction was virtually impossible through Butane in particular cases. Nature of Ballistic current for butane anchored with sulfur is ideal for its applicability as nano-diode or resonant tunneling diodes (RTDs) in arena of quantum-electronics due to its strong coupling between the terminal atoms and carbon atoms of butane. The retrenching order obtained in terms of conductance is S > N > O anchored butane molecule which seemed in full confirmation with the results of Transmission spectrum and its Eigenstates and proved sulfur to be a promising binding element and can produce much better results in comparison to oxygen and nitrogen. This paper marked another step in the field of molecular electronics as the butane anchored with sulfur has characteristics in conjunction to the semiconductor junction diode.

Transport in fullerene device coupled to Cu, Ag and Au electrodes

ABSTRACT We present an ab initio approach of the electronic transport through a single molecular junction based on C20 fullerene. The electronic properties of a single molecular junction constrained within two semi-infinite metallic electrodes are largely affected by the choice of electrode material. The two-probe device formed by the mechanically control break technique has been modelled with three distinct electrode materials from group IB of the periodic table, namely copper, silver and gold. The quantum characteristics of these mechanically stable devices are obtained by utilising first-principle density functional theory together with non-equilibrium green function method. We evaluate the quantum characteristics, namely density of states, transmission spectrum, energy levels, current and conductance, which essentially determine the behaviour of a molecule linked to different electrodes. Our investigation concludes that copper, silver and gold electrode configuration in conjunction with C20 fullerene behaves as metallic, non-metallic and semi-metallic in nature, respectively.

To evince pure C24 as superconductoring mechanically controllable break junction configuration

In this paper, we expounded the superconductive nature for fullerenes, which are being explored for the molecular electronics applications. The fullerene we picked for our research work is the C24 which was then doped with popular dopants- Boron, Nitrogen and Phosphorus and the self-consistent calculations were performed in the configuration where molecule was bridged between the gold electrodes using MCBJ (Mechanically Controlled Break Junctions) technique at sub-zero temperature of 0.100K. The characteristics of these variants of doped C24were compared with that for pure C24 and the results clearly demonstrated the electrical superiority of the pure C24 over its doped counterparts for cryogenic applications of electronics. This paper would represent another mark in the field of molecular electronics that prefer carbon or organic materials as competing future in nanotechnology for military and defence applications.

Contemplating Transport Characteristics by Augmenting the Length of Molecule

In this paper, we contemplated the transport characteristics of a single molecular device junction by augmenting the length of the molecule in the scattering region. The molecules considered here belongs to class of alkanedithiols (CnH2n+2S2). Specifically, we used a tight binding semi-empirical model to compute the transport characteristics of butanedithiol, pentanedithiol, hexanedithiol and heptanedithiol connected to semi-infinite gold electrodes through thiol anchoring elements. The exploration of transport properties of considered alkanes was completed for different bias voltages within the sphere of Keldyshs Non Equilibrium Greens Function (NEGF) and Extended Huckel Theory (EHT), for studying the self-consistent steady-state solution, analyzing the out-of-equilibrium electron distribution, and the behavior of the self-consistent potential. We perceived that the current and conductance retrenches with aggravation with the increase in length of the molecule with exhibition of single electron tunneling. We observed that the coupling regime shifts from strong coupling to weak for higher order alkanedithiols and the transmission is function of evenness or oddness of the carbon atoms forming an alkane.

Proliferating miller indices of C20 fullerene device under DFT-NEGF regime

We present ab-initio scrutiny of electron transport through C20 fullerene cleaved with gold electrodes having unique set of miller orientations. The three families of miller indices {100}, {110} and {111} are considered with four exclusive device models for elucidating electronic transport under applied potential of - 2 to +2V. Thereafter, the quantum calculations employing DFT-NEGF are performed for envisaging density of states, transmission function, energy levels, molecular orbitals, charge transfer. These electronic transfer parameters lead to the study of its two electrical parameters: current and conductance. We conclude that in molecular-devices of constituted miller family {110}, HOMO-LUMO gap are inversely proportional to extent of charge carriers. While for miller devices {100} and {111}, the situation is fully contrasting with HOMO-LUMO gap being directly proportional to its charge carriers. Another important conclusion is that the gold electrodes having miller family {100} and {111} are providing equal opportunity to fullerene molecule to imply its behavior while electrodes of miller family {110} are over shadowing the performance of fullerene molecule.

Ab initio scrutiny of endohedral C20 fullerenes implanted in between gold electrodes

AbstractUsing the smallest non-classical fullerene, we investigate the impact of endohedral fullerene molecules on the quantum transport through molecular junctions, and then compared this with the pure C20-based molecular junction. By employing the density functional theory combined with the non-equilibrium Green’s function, we contemplated different electronic parameters, namely, density of states, transmission coefficient, energy levels, molecular orbitals, conduction gaps, electron density and their charge transfer. A knowledge of these physical parameters is necessary in order to calculate current and conductance computed using Landauer-Büttiker formalism. The molecule-electrode coupling influenced by endohedral molecules affects junction devices in a unique manner. We observe that the highest quantum transport is possible in an Au–N@C20–Au and Au–O@C20–Au junction device, and is even higher than that of the intrinsic C20 fullerene junction. Another notable observation is that the F@C20 molecule exhibits the least conducting nature, being even lower than that of the endohedral molecule formed by inserting the noble element, neon. Graphical abstractElectrical characteristics of Endohedral fullerene junctions

Negative differential resistance observation in complex convoluted fullerene junctions

In this work, we simulated the smallest fullerene molecule, C20 in a two-probe device model with gold electrodes. The gold electrodes comprised of (011) miller planes were carved to construct the novel geometry based four unique shapes, which were strung to fullerene molecules through mechanically controlled break junction techniques. The organized devices were later scrutinized using non-equilibrium Greens function based on the density functional theory to calculate their molecular orbitals, energy levels, charge transfers, and electrical parameters. After intense scrutiny, we concluded that five-edged and six-edged devices have the lowest and highest current-conductance values, which result from their electrode-dominating and electrode-subsidiary effects, respectively. However, an interesting observation was that the three-edged and four-edged electrodes functioned as semi-metallic in nature, allowing the C20 molecule to demonstrate its performance with the complementary effect of these electrodes in t...

Smallest fullerene-like clusters in two-probe device junctions: first principle study

ABSTRACT First principle calculations based on density functional theory are realised to investigate the electron transport of the smallest fullerene-like clusters as two-probe junction devices. The junction devices are constructed by mechanically controlled break junction techniques to ensure the maximum stability of the Be20, B20 and N20 cluster molecular junctions. We investigate the density of states, transmission spectrum, molecular orbitals, current and differential conductance characteristics at discrete bias voltages to gain insight about the various transport phenomena occurring in these nano-junctions. The results show that B20 molecule when stringed to gold electrodes works as an ideal nano-device similar to the pure C20 device and is more symmetric in its characteristic nature. However, in N20 molecular device, the conduction is negligible due to the higher atomic interactions within N20 molecule, despite the fact that it is constructed with penta-valent atoms.

The DFT-NEGF scrutiny of doped fullerene junctions

AbstractUsing the smallest non-classical fullerene, we investigate the impact of doping at the molecule–electrode interface on the electron transport of molecular junctions. This is accomplished by employing the density functional theory combined with the non-equilibrium Green’s function. We contemplate different electronic parameters, namely, density of states, transmission coefficient, energy levels, molecular orbitals, conduction gaps, electron density, and their charge transfer. The relevance of these physical parameters is obtained to calculate their electrical parameters, current, and conductance, computed from Landauer–Büttiker formalism. The molecule–electrode coupling is influenced by the nature of doping atoms and affects the junction devices in a unique course. A particular aftermath is noticed in Au-C18O2-Au device with highest ballistic transport despite the electro-negative nature of oxygen atoms. Moreover, an interesting feature is observed in Au-C18Be2-Au device with double-barrier transmission resonance and corresponding oscillating conductance. Graphical abstractThe doped C20 fullerene in molecular and device mode

Morphology pursuance in C20 fullerene molecular junction: ab initio implementation

In this paper, we implement the C20 fullerene-based molecular junction formed with two different types of geometric electrodes employing Keldysh’s non-equilibrium Green’s function formalism combined with density functional theory. The geometric electrodes with a knife and flat edges are stringed to the fullerene molecule to determine the impact of morphology in the electrode–molecule interface region. We investigate the density of states, transmission spectrum, molecular orbitals, current and differential conductance characteristics at discrete bias voltages to get the insight about various transport phenomena in these morphed fullerene junctions. The results show that current and conduction are higher in magnitude in the C20 fullerene when sandwiched between the pair of flat-edged electrodes. Thus, the flat-edged electrodes are acting as the supporting electrodes in the quantum conduction process, not overshadowing the role of molecule within a device configuration, unlike the knife-edged electrodes. Hence, the ideas and results pursued in this research paved another step in the field of “Geometronics”.