Strain induced effects on electronic structure of semi-metallic and semiconducting tin nanowires

Semimetal nanowires are known to undergo a semimetal to semiconductor transition as a consequence of quantum confinement as their diameters are decreased. Using density functional theory calculations, the electronic structure of tin nanowires (SnNWs) under uniaxial strain within a range of -4% to +4% is investigated. It is demonstrated that a [110]-oriented semi-metallic SnNW with a diameter of ∼4.2 nm can be made either more metallic or semiconducting by the application of tensile or compressive strain, respectively. On the contrary, a [100]-oriented semi-metallic SnNW with a slightly larger diameter of ∼4.5 nm remains semiconducting with the application of either compressive or tensile strain. Carrier effective masses are calculated from the band structures; it is shown that for semimetal SnNW along [110] orientation the conduction and valence bands display near linear dispersion under both compressive and tensile strains (<3%) which leads to very small effective masses of ∼0.007m₀. We also show that strain energies and Young modulus vary with nanowire diameter and crystal orientation. The effect of alloying on the generation of tensile and compressive strains in SnNWs is also investigated.