Articles you may be interested inAb-initio calculations for a realistic sensor: A study of CO sensors based on nitrogen-rich carbon nanotubes AIP Advances 2, 032115 (2012); 10.1063/1.4739280Conductance of individual channels in a carbon nanotube field-effect transistor studied by magnetic force microscopy

No abstract

No abstract

A new compound material of 2D hydrofluorinated graphene (HFG) is demonstrated whose relative hydrogen/fluorine concentrations can be tailored between the extremes of either hydrogenated graphene (HG) and fluorinated graphene (FG). The material is fabricated through subsequent exposures to indirect hydrogen plasma and xenon difluoride (XeF2). Controlling the relative concentration in the HFG compound enables tailoring of material properties between the extremes offered by the constituent materials and in‐plane patterning produces micrometer‐scale regions with different surface properties. The utility of the technique to tailor the surface wettability, surface friction, and electrical conductivity is demonstrated. HFG compounds display wettability between the extremes of pure FG with contact angle of 95° ± 5° and pure HG with contact angle of 42° ± 2°. Similarly, the HFG surface friction may be tailored between the two extremes. Finally, the HFG electrical conductivity tunes through five orders of magnitude when transitioning from FG to HG. When combined with simulation, the electrical measurements reveal the mechanism producing the compound to be a dynamic process of adatom desorption and replacement. This study opens a new class of 2D compound materials and innovative chemical patterning with applications for atomically thin 2D circuits consisting of chemically/electrically modulated regions.

We investigate the electronic properties of bilayer MoS2 exposed to an external electric field by using first-principles calculations. It is found that a larger interlayer distance, referring to that by standard density functional theory (DFT) with respect to that by DFT with empirical dispersion corrections, makes indirect-direct band gap transition possible by electric control. We show that external electric field effectively manipulates the valence band contrast between the K- and Γ-valleys by forming built-in electric dipole fields, which realizes an indirect-direct transition before a semiconductor-metal transition happens. Our results provide a novel efficient access to tune the electronic properties of two-dimensional layered materials.

Articles you may be interested inInsight into the description of van der Waals forces for benzene adsorption on transition metal (111) Adsorption of transition-metal atoms on boron nitride nanotube: A density-functional study

Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk.

In this work, high-quality 1D van der Waals (vdW) Nb 2 Pd 3 Se 8 is synthesized, showing an excellent scalability from bulk to single-ribbon due to weakly bonded repeating unit ribbons. The calculation of electronic band structures confirmed that this novel Nb 2 Pd 3 Se 8 is a semiconducting material, displaying indirect-to-direct bandgap transition with decreasing the number of unit-ribbons from bulk to single. Field effect transistors (FETs) fabricated on the mechanically exfoliated Nb 2 Pd 3 Se 8 nanowires exhibit n-type transport characteristics at room temperature, resulting in the values for the electron mobility and I on /I off ratio of 31 cm 2 V −1 s −1 and ≈10 4 , respectively. Through transport measurements at various temperatures from room temperature down to 90 K, it is confirmed that Nb 2 Pd 3 Se 8 FETs can achieve negligible Schottky barrier height (SBH) for the Au contacts at the temperature range, displaying clear ohmic contact characteristics. Furthermore, top-gated FETs fabricated with the Al 2 O 3 dielectric layer are studied simultaneously with back-gated FETs.