Ag and Au Atoms Intercalated in Bilayer Heterostructures of Transition Metal Dichalcogenides and Graphene

The diffusive motion of metal nanoparticles Au and Ag on monolayer and between bilayer heterostructures of transition metal dichalcogenides and graphene are investigated in the framework of density functional theory. We found that the minimum energy barriers for diffusion and the possibility of cluster formation depend strongly on both the type of nanoparticle and the type of monolayers and bilayers. Moreover, the tendency to form clusters of Ag and Au can be tuned by creating various bilayers. Tunability of the diffusion characteristics of adatoms in van der Waals heterostructures holds promise for controllable growth of nanostructures.Comment: accepted, APL Ma

Quantum Transport Characteristics of Lateral pn-Junction of Single Layer TiS3

Using density functional theory and nonequilibrium Greens functions-based methods we investigated the electronic and transport properties of monolayer TiS3 pn-junction. We constructed a lateral pn-junction in monolayer TiS3 by using Li and F adatoms. An applied bias voltage caused significant variability in the electronic and transport properties of the TiS3 pn-junction. In addition, spin dependent current-voltage characteristics of the constructed TiS3 pn-junction were analyzed. Important device characteristics were found such as negative differential resistance and rectifying diode behaviors for spin-polarized currents in the TiS3 pn-junction. These prominent conduction properties of TiS3 pn-junction offer remarkable opportunities for the design of nanoelectronic devices based on a recently synthesized single-layered material

Controlling Polymer Capture and Translocation by Electrostatic Polymer-Pore Interactions

Polymer translocation experiments typically involve anionic polyelectrolytes such as DNA molecules driven through negatively charged nanopores. Quantitative modelling of polymer capture to the nanopore followed by translocation therefore necessitates the consideration of the electrostatic barrier resulting from like-charge polymer-pore interactions. To this end, in this work we couple mean-field level electrohydrodynamic equations with the Smoluchowski formalism to characterize the interplay between the electrostatic barrier, the electrophoretic drift, and the electro-osmotic liquid flow. In particular, we find that due to distinct ion density regimes where the salt screening of the drift and barrier effects occur, there exists a characteristic salt concentration maximizing the probability of barrier-limited polymer capture into the pore. We also show that in the barrier-dominated regime, the polymer translocation time increases exponentially with the membrane charge and decays exponentially fast with the pore radius and the salt concentration. These results suggest that the alteration of these parameters in the barrier-driven regime can be an efficient way to control the duration of the translocation process and facilitate more accurate measurements of the ionic current signal in the pore

hh-AlN-Mg(OH)2_{2} vdW Bilayer Heterostructure: Tuning the excitonic characteristics

Motivated by recent studies that reported the successful synthesis of monolayer Mg(OH)$_{2}$ [Suslu \textit{et al.}, Sci. Rep. \textbf{6}, 20525 (2016)] and hexagonal (\textit{h}-)AlN [Tsipas \textit{et al}., Appl. Phys. Lett. \textbf{103}, 251605 (2013)], we investigate structural, electronic, and optical properties of vertically stacked $h$-AlN and Mg(OH)$_{2}$, through \textit{ab initio} density-functional theory (DFT), many-body quasi-particle calculations within the GW approximation, and the Bethe-Salpeter equation (BSE). It is obtained that the bilayer heterostructure prefers the $AB^{\prime}$ stacking having direct band gap at the $\Gamma$ with Type-II band alignment in which the valance band maximum and conduction band minimum originate from different layer. Regarding the optical properties, the imaginary part of the dielectric function of the individual layers and hetero-bilayer are investigated. The hetero-bilayer possesses excitonic peaks which appear only after the construction of the hetero-bilayer. The lowest three exciton peaks are detailedly analyzed by means of band decomposed charge density and the oscillator strength. Furthermore, the wave function calculation shows that the first peak of the hetero-bilayer originates from spatially indirect exciton where the electron and hole localized at $h$-AlN and Mg(OH)$_{2}$, respectively, which is important for the light harvesting applications.Comment: Accepted by Physical Review

Phonon Softening and Direct to Indirect Bandgap Crossover in Strained Single Layer MoSe2

Motivated by recent experimental observations of Tongay et al. [Tongay et al., Nano Letters, 12(11), 5576 (2012)] we show how the electronic properties and Raman characteristics of single layer MoSe2 are affected by elastic biaxial strain. We found that with increasing strain: (1) the E' and E" Raman peaks (E1g and E2g in bulk) exhibit significant red shifts (up to 30 cm-1), (2) the position of the A1' peak remains at 180 cm-1 (A1g in bulk) and does not change considerably with further strain, (3) the dispersion of low energy flexural phonons crosses over from quadratic to linear and (4) the electronic band structure undergoes a direct to indirect bandgap crossover under 3% biaxial tensile strain. Thus the application of strain appears to be a promising approach for a rapid and reversible tuning of the electronic, vibrational and optical properties of single layer MoSe2 and similar MX2 dichalcogenides.Comment: http://link.aps.org/doi/10.1103/PhysRevB.87.12541

Spintronic properties of zigzag-edged triangular graphene flakes

Cataloged from PDF version of article.We investigate quantum transport properties of triangular graphene flakes with zigzag edges by using first principles calculations. Triangular graphene flakes have large magnetic moments which vary with the number of hydrogen atoms terminating its edge atoms and scale with its size. Electronic transmission and current-voltage characteristics of these flakes, when contacted with metallic electrodes, reveal spin valve and remarkable rectification features. The transition from ferromagnetic to antiferromagnetic state under bias voltage can, however, terminate the spin polarizing effects for specific flakes. Geometry and size dependent transport properties of graphene flakes may be crucial for spintronic nanodevice applications. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489919