Ravinder Singh Sawhney

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.

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.

WLAN Performance Improvisation by Fine Tuning IEEE 802. 11 Parameters

Wireless networks has biggest constraint of limited bandwidth in comparison to wired networks but in spite of this constraint wireless networks are becoming popular day by day on account of their flexibility, mobility as well as inexpensive physical medium (air). Wireless local area networks (WLANs) are error-prone as well as fragile. The commuters feel annoyed when all of sudden communication cuts off and transmission of packets fails. Hence, it becomes an obligation to improve WLAN performance metrics. We investigated throughput and delay performance of WLANs using network simulation tool OPNET concentrating on the IEEE 802.11 Mac layer parameters, and suggest that Wireless LAN performance can be improved by fine tuning parameters such as fragmentation threshold, request to send (RTS) thresholds and buffer size. The main objective of this paper is buffer size manipulation to reduce load and delays, leading to performance improvement.

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.

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.

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.

MANET Link Performance Parameters using Ant Colony Optimization Approach

to-end delay of routing packets from the source to destination in a Mobile ad-hoc network is a major challenge for a large number of network scientists. This paper presents a new routing approach for mobile ad hoc networks (MANETs) which takes into consideration the Ant Colony Optimization (ACO) technique in conjunction with linear programming approach for minimizing the overall delay in networking environment. Ant colony optimization algorithms have all been inspired by a specific foraging behavior of colonies of the ants, which are able to explore the optimum route connecting the colonys nest with a source of food. It has been observed that the mean end-to-end delay of a link from the source to the destination is one of the most important metric for a MANET. The other metrics that have been considered and evaluated are utilization or efficiency of link, arrival rate and service rate with respect to link delay. The simulation tool used for our model is MATLAB 7.5.

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.

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.