Md. Shahzad Khan

Electron transport properties of a single-walled carbon nanotube in the presence of hydrogen cyanide : first-principles analysis

AbstractFirst-principles analysis based on density functional theory was performed to compute the electronic and transport properties of a single-walled carbon nanotube in the presence of hydrogen cyanide. A chiral (4,1) carbon nanotube was found to become less metallic as the number of hydrogen cyanide molecules nearby increased. When there were a sufficient number of hydrogen cyanide molecules close to the nanotube, it became semiconducting. This metallic to semiconducting transformation of the nanotube was verified by analyzing its conductance and current as a function of the number of molecules of hydrogen cyanide present. The conductivity of the carbon nanotube was very high when no hydrogen cyanide molecules were present, but decreased considerably when even just a single hydrogen cyanide molecule approached the surface of the nanotube. Graphical AbstractSWCNT based HCN sensor and its Current vs Bias voltage characteristics

Influence of Boron Substitution on Conductance of Pyridine- and Pentane-Based Molecular Single Electron Transistors: First-Principles Analysis

We have investigated the modeling of boron-substituted molecular single-electron transistor (SET), under the influence of a weak coupling regime of Coulomb blockade between source and drain metal electrodes. The SET consists of a single organic molecule (pyridine/pentane/1,2-azaborine/butylborane) placed over the dielectric, with boron (B) as a substituent. The impact of B-substitution on pyridine and pentane molecules in isolated, as well as SET, environments has been analyzed by using density functional theory-based ab initio packages Atomistix toolkit-Virtual NanoLab and Gaussian03. The performance of proposed SETs was analyzed through charging energies, total energy as a function of gate potential and charge stability diagrams. The analysis confirms that the B-substituted pentane (butylborane) and the boron-substituted pyridine (1,2-azaborine) show remarkably improved conductance in SET environment in comparison to simple pyridine and pentane molecules.

Electronic properties of a pristine and NH3/NO2 adsorbed buckled arsenene monolayer

Analogous to exfoliated 2D sheets of black phosphorene, arsenene is an atomically thin layer of the arsenic crystal. In this paper, we investigate the sensitivity of a pristine arsenene sheet for NH3 and NO2 molecules in terms of binding energy, nature of bonding, density of states and current–voltage characteristics. The calculated results based on density functional theory find that both NH3 and NO2 molecules show a significant affinity for arsenene leading to strong physisorption with significant electronic charge transfer. The calculated I–V characteristics reveal that physisorption of NH3 and NO2 induces modifications in the conductivity of pristine arsenene. Incorporation of Ge in arsenene leads to enhanced binding of NH3 and NO2 via chemisorption on arsenene.

High-Performance Single-Electron Transistor Based on Metal–Organic Complex of Thiophene: First Principle Study

The ab initio perspective based on density functional theory and nonequilibrium Green’s function for the modeling of single electron transistors (SETs) based on thiol-ended thiophene and chromium complex of thiol-ended thiophene and their functioning in the Coulomb blockade regime has been discussed. Both thiol-ended thiophene molecule and its chromium complex have been analyzed for the charge stability and conductance dependence on the gate voltage and source–drain bias. The charging energies for the isolated and SET environment for both the islands have been calculated and discussed. Also, the effect of orientation and the dielectric medium has been studied in order to increase the conductance of SET with the combination of a particular orientation and a dielectric medium. The effect of different electrodes on charge stability diagram has also been studied. The analysis shows a remarkably improved conductance for the chromium complex of thiol-ended thiophene molecule in the SET environment than the thiol-ended thiophene molecule in the SET environment resulting in a fast switching metal–organic SET.

Electronic and optical properties of functionalized zigzag ZnO nanotubes

AbstractThe present paper reports the analysis of surface decoration on the structural, electronic, and optical properties of (n,0) ZnO nanotubes, performed by means of a density function theory based ab-initio approach. Fe functionalization induced buckling in ZnO nanotubes affects its electronic and optical properties. Increase in Fe functionalization leads to better stability of ZnO nanotube and shows enhanced metallic character. The possibility of its use in optoelectronics has been analyzed in terms of dielectric constant, absorption coefficient, and refractive index. In another observation, the high sensitivity of the HCN molecule for the Fe-incorporated ZnO nanotube suggests it as a potential gas sensor. Graphical abstractHCN-adsorbed Fe-ZnO nanotube, electron difference density, and PDOS analysis of different orbitals.