As an attempt to study large systems involving weak interactions, we simulated the adsorption procedure of
the coenzyme flavin adenine dinucleotide (FAD) interacting with semiconducting (10,0) and metallic (5,5)
carbon nanotubes (CNTs) using a density functional tight binding method with the inclusion of an empirical
dispersion term in total energy. It was found that the flavin and adenine groups of FAD could be attached to
the CNT surface through π−π stacking but remain at the physisorption distance. The analysis of density of
states shows that when interacting with the (10,0) CNT the FAD contributes more components in the band
structure at the Fermi energy level, responsible for the enhancement of the semiconducting CNT electronic
mobility.
p-Type surface conductivity is a uniquely important property of hydrogen-terminated diamond surfaces. In this work, we report similar surface-dominated electrical properties in silicon nanowires (SiNWs). Significantly, we demonstrate tunable and reversible transition of p(+)-p-i-n-n(+) conductance in nominally intrinsic SiNWs via changing surface conditions, in sharp contrast to the only p-type conduction observed on diamond surfaces. On the basis of Si band energies and the electrochemical potentials of the ambient (pH value)-determined adsorbed aqueous layer, we propose an electron-transfer-dominated surface doping model, which can satisfactorily explain both diamond and silicon surface conductivity. The totality of our observations suggests that nanomaterials can be described as a core-shell structure due to their large surface-to-volume ratio. Consequently, controlling the surface or shell in the core-shell model represents a universal way to tune the properties of nanostructures, such as via surface-transfer doping, and is crucial for the development of nanostructure-based devices.
The structure and electronic properties of the ( √ 13 × √ 13)R13.9 • and (2 √ 3 × 2 √ 3)R30 • ordered phases of C 60 on the Pt(111) surface are investigated using combined dynamic low-energy electron diffraction and density functional theory (DFT) calculations. The two phases have the same local adsorption structure, while they are predicted by DFT calculations to exhibit very different electronic structures due to their different inter-C 60 orientations and distances. This result demonstrates the structural tuning of electronic properties for molecular films or junctions composed of the same materials.
Using molecular dynamics simulations, we have calculated the thermal conductivity of nitrogen-terminated silicon nanowires (SiNWs). We found that nitrogen adsorption can remarkably bring down the thermal conductivity of SiNWs. This nitrogenation-induced drop in thermal conductivity arises mainly from the phonon scattering by defects near the surface and the suppression of some vibrational modes. Our simulation results clearly demonstrate the importance of surface chemistry or functionalization in tuning the thermal conductivity, which has profound implications for thermoelectric applications of SiNWs.
We investigated the resonance and antiresonance effects in electronic transport through several-quantum-dot combinations by using the nonequilibrium Green’s function method. All distinctive quantum-dot (QD) arrangements with one to three QDs and with different architectures were studied systematically. The theoretical and numerical results show that a peak in the current-voltage spectrum can be attributed to the resonance effect, whereas a dip is due to the antiresonance effect. The results will help experimenters to better understand their electronic measurements.
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