title: From germanium nanowires to germanium-silicon oxide nanotubes: influence of germanium tetraiodide precursor.
abstract: Growth of semiconductor nanowires has attracted immense attention in the field of nanotechnology as nanowires are viewed as the potential basic building blocks of future electronics. The recent renewed interest in germanium as a material for nanostructures can be attributed to its higher carrier mobility and larger Bohr radius as compared to silicon. Self-assembly synthesis of germanium nanowires (GeNWs) is often obtained through a vapor-liquid-solid mechanism, which is essentially a catalytic tip-growth process. Here we demonstrate that by introducing an additional precursor, germanium tetraiodide (GeI(4)), in a conventional furnace system that produces GeNWs on silicon, tubular structures of germanium-silicon (GeSi) oxide can be obtained instead. Incorporation of GeI(4) results in passivation of the metal catalyst, preventing the occurrence of supersaturation, a prerequisite for the catalytic tip growth. We infer that passivation of the metal catalyst impedes Ge incorporation into the catalyst, leaving the catalyst rim as the only active sites for nucleation of both Si and Ge and thus resulting in the growth of GeSi oxide nanotubes via a root-growth process.
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Huang
authors.forename: Wai Kin
authors.initials: WK
authors.lastname: Chim
authors.forename: Shijie
authors.initials: S
authors.lastname: Wang
authors.forename: Sing Yang
authors.initials: SY
authors.lastname: Chiam
authors.forename: Lai Mun
authors.initials: LM
authors.lastname: Wong