Antimony selenide (Sb 2 Se 3 ) has been proposed as an alternative material for a wide range of applications; however, the electronic structure of the Sb 2 Se 3 lattice is not clearly known yet. As a consequence, there are abundant contradictory interpretations of experimental results leading to incoherent determinations of its energy band gap and the type of optical transitions. Moreover, Sb 2 Se 3 is recently being synthesized in different types of nanostructures; therefore, detailed knowledge of the bulk electronic structure is necessary to evaluate deviations due to confinement or surface effects. In this paper, we study the electronic band structure of antimony selenide using density functional theory (DFT) within the generalized gradient approximation (GGA) with GW corrections. Our calculations show that Sb 2 Se 3 has an indirect energy band gap of 1.21 eV; however, a direct transition only 0.01 eV higher than the band gap (1.22 eV) is also possible. The calculated density of states agrees well with the experiments reporting photoemission spectra.

Sub-10 nm semiconducting nanostructures are crucial for the realization of nanoscale devices. Fabrication of nanostructures at this scale with homogeneous properties is challenging. Using ab initio calculations, we show that self-standing ribbons of antimony selenide and antimony sulfide of width 1.1 nm exhibit well-defined bandgaps of 1.66 and 2.16 eV, respectively. Molecular dynamics studies show that these ribbons are stable at 500 K. The one-dimensional (1D) heterostructure of these nanoribbons (Sb(2)Se(3)/Sb(2)S(3)) along the [001] direction shows a straddling type behavior.

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Ab initio calculations show that a transverse electric field induces a homojunction across the diameter of initially semiconducting GaN single-crystal nanotubes ͑SCNTs͒ and nanowires ͑NWs͒. The homojunction arises due to the decreased energy of the electronic states in the higher potential region with respect to the energy of those states in the lower potential region under the transverse electric field. Calculations on SCNTs and NWs of different diameters and wall thicknesses show that the threshold electric field required for the semiconductor-homojunction induction increases with increasing wall thickness and decreases significantly with increasing diameter.

Using ab initio calculations, we show that atomic selenium (Se) strongly adsorbs to the outer surface of single wall carbon nanotubes (SWCNTs), converting the semiconductor nanotubes to metallic and enhancing the conductance of the metallic and semimetallic ones. Considering the ease of vaporizing and depositing selenium, due to its volatile nature and low melting point, this system could be potentially viable. Thus, selenium adsorption offers a single process for enhancing the conductance of SWCNTs regardless of their chirality making them a promising candidate for nanoscale interconnects applications.