Electronic and optical properties of hydrogenated group-IV multilayer materials.

Hydrogenated group-IV layered materials are semiconducting forms of silicene, germanene and stanene. We systematically studied the evolution of the structural, electronic and optical properties of these 2D materials as a function of the number of layers. We verify that the exfoliation energy increases upon the increase of the atomic number (Si → Sn) of the group-IV material.

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV.

Bilayer graphene on h-BN substrate: investigating the breakdown voltage and tuning the bandgap by electric field.

By performing density functional theory calculations we show that it is possible to make the electronic bandgap in bilayer graphene supported on hexagonal boron nitride (h-BN) substrates tunable. We also show that, under applied electric fields, it is possible to insert states from h-BN into the bandgap, which generate a conduction channel through the substrate making the system metallic. In addition, we verify that the breakdown voltage strongly depends on the number of h-BN layers.

Ab initio calculations of structural evolution and conductance of benzene-1,4-dithiol on gold leads.

By performing ab initio density functional theory (DFT) calculations and electronic transport simulations based on the DFT nonequilibrium Green's functions method we investigate how the conformational changes of a benzene-1,4-dithiol molecule bonded to gold affect the molecular transport as the electrodes are separated from each other. In particular we consider the full evolution of the stretching process until the junction breaking point and compare results obtained with a standard semilocal exchange and correlation functional to those computed with a self-interaction corrected method. We conclude that the inclusion of self-interaction corrections is fundamental for describing both the molecule conductance and its stability against conformational fluctuations.