LOW DIMENSIONAL SEMICONDUCTING NANOSTRUCTURES: STABILITY, TRENDS AND PROMISES

Abstract

Systematic studies of low dimensional semiconducting nanostructures have been performed. In particular, silicon-germanium (SiGe) armchair type nanotubes, and both zigzag and armchair type nanoribbons were used to represent the bottom-up approach while hematite nanoribbons were used to represent the top down approach. Four high symmetric nanostructure atomic arrangements were identified. All the SiGe nanotubes and SiGe nanoribbons show definite semiconducting character and the band gaps span over large range. Zigzag SiGe nanoribbons show direct band gap nature indicating potential applications in opto-electronic devices. Standalone SiGe nanoribbons may roll into nanotubes depending on the atomic arrangement. Li adsorption on SiGe nanotubes indicated that SiGe nanotubes have potential as anode material in Li-ion battery technology when the nanotube length is over 20 Å. Most stable site for Li adsorption is Si Top site and most preferred site is Ge Top. Intrinsic puckered surface nature screen the adsorbed Li from each other and hence, increase the charge density. Hydrogen atomic adsorption increases the band gap while oxygen breaks the nanotube-wall bonds and incorporates into nanotube lattice structure. Hematite nanoribbons based on two surfaces, (110) and (104) were studied. For each surface, depending on the termination direction, it can be identified two types. Both types based on (110) surface show definite semiconducting character. One type of (104) surface based nanoribbons show surface modification while the other type obtained built-in oxygen vacancy which acquired the spin dependent transport properties and hence, possible applications in spintronics area.