Electronic structure tuning via surface modification in semimetallic nanowires

Abstract

Original citationSanchez-Soares, A., O'Donnell, C. and Greer, J. C. (2016) Electronic structure properties of nanowires (NWs) with diameters of 1.5 and 3 nm based on semimetallic α − Sn are investigated by employing density functional theory and perturbative GW methods. We explore the dependence of electron affinity, band structure, and band-gap values with crystallographic orientation, NW crosssectional size, and surface passivants of varying electronegativity. We consider four chemical terminations in our study: methyl (CH 3 ), hydrogen (H), hydroxyl (OH), and fluorine (F). Results suggest a high degree of elasticity of Sn-Sn bonds within the Sn NWs' cores with no significant structural variations for nanowires with different surface passivants. Direct band gaps at Brillouin-zone centers are found for most studied structures with quasiparticle corrected band-gap magnitudes ranging from 0.25 to 3.54 eV in 1.5-nm-diameter structures, indicating an exceptional range of properties for semimetal NWs below the semimetal-to-semiconductor transition. Band-gap variations induced by changes in surface passivants indicate the possibility of realizing semimetal-semiconductor interfaces in NWs with constant cross-section and crystallographic orientation, allowing the design of novel dopant-free NW-based electronic devices.

Impact of stoichiometry and strain on Ge1−x Sn x alloys from first principles calculations

“…44 The LDAcalculated 219 meV band gap in Fig. 3 is therefore likely underestimated, 85 but nonetheless, as a known underestimate of the band gap energy, strongly suggests that a direct band gap can be opened in α-Sn thin films via quantum confinement.…”

Epitaxial Stabilisation of ${\bf \mathrm{Ge_{1-x}Sn_x}}$ Alloys

“…With features in modern devices already below 10 nm and designs capable of exploiting semimetals by confinement-and surface-assisted band gap engineering already proposed, the ability to further tune band gaps by controlling alloy composition introduces another dimension of customization exploitable in nanoelectronic designs. [14][15][16][17][18][19] Fabrication of crystalline Ge 1−x Sn x alloys in the composition range predicted to exhibit semimetallic behavior when in bulk form has also been experimentally achieved. Recently, atomically flat epitaxial films grown on Ge(100) with tin content as high as x = 0.46 were reported in the literature.…”

Influence of surface stoichiometry and quantum confinement on the electronic structure of small diameter InxGa1-xAs nanowires

“…The different electronegativity of the differing surface layers leads to differing surface dipole potentials. For the III-V nanowires variation in the surface layer composition leads to band gap shifts of smaller magnitude than that found for differing surface terminations in nonpolar nanowires [27,28], but is nonetheless a significant influence on the electronic structure.…”

“…The effective masses in the III-V nanowires, as in the bulk, remain significantly lower than the effective mass at the conduction band edge for the comparable cross section [100]-oriented silicon nanowire of m*/m e =0.35. The fact that surface termination can significantly affect band gap energies is well-known for non-polar semiconductors [27] and semimetals [28]. Here it is highlighted that the breaking of periodicity in a polar nanowire can lead to either anion-or cation-rich surfaces that, in addition to the polarity induced by surface terminating species, can significantly influence nanowire electronic structure properties.…”