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.

Nanowire and Nanocable Intrinsic Quantum Capacitances and Junction Capacitances: Results for Metal and Semiconducting Oxides

“…With the continuing current pursuit of employing nanotubes [87][88][89][90][91], nanowires [92,93] and including V 3 O 7 •H 2 O nanowires and Si/a-Si core/shells or nanocables [94], and nanocables [95] in various components from electronics (diodes, transistors, photodetectors, and photovoltaic cells) to chemistry (sensors, membranes, catalysts, batteries, fuel cells, and supercapacitors), there is little doubt that knowledge of the intrinsic quantum capacitances obtained here will be useful. That is also true for the fundamental junction capacitances found here for these nanoscopic structures.…”

Photo-sensitive Ge nanocrystal based films controlled by substrate deposition temperature

“…In the past decades, nanostructured materials have been the focus of many research groups due to their improved structural, optical and electrical properties, appropriate for various practical applications. Quantum confinement effect (QCE ) is more powerful in bulk Ge compared to Si because of Ge greater excitonic Bohr radius (approximately 24 nm in the case of Ge and about 5 nm for Si) [1,2]. Also, compared to Si, Ge has higher lattice parameter, carrier mobility and smaller energy gap, thermal conductivity or effective mass of the carriers [3].…”

SYNTHESIS AND OPTICAL PROPERTIES OF CRYSTALLINE Si1-xGexOy NANORODS

“…Furthermore, the exciton Bohr radius of Ge (24.3 nm) is much larger than that of Si (4.9 nm), which means that quantum con¯nement e®ect in Ge can be possibly achieved with larger-sized nanostructures. 8 Until now, there are only few reports on the growth of Si 1Àx Ge x O y 1D nanostructures. For § example, He et al 4 fabricated amorphous Si 1Àx Ge x O y nanowires on Au-coated silicon substrate by annealing Si 0:8 Ge 0:2 alloys in a quartz tube furnace at $ 900À1200 C in N 2 .…”

“…Ko et al 6 prepared amorphous Si 1Àx Ge x O y nanowires on Si substrate via carbothermal reduction of GeO 2 /CuO powders at 1100 C in Ar, where the growth of the nanowires was catalyzed by CuSiGe. Huang et al 8 synthesized amorphous SiGeO x nanotubes on Au-coated Si substrate by heating GeI 4 and Ge powders, respectively, in a conventional three-zone furnace system in Ar. In this work, we synthesized crystalline Si 1Àx Ge x O y nanorods on Au-coated Si substrate by heating Ge powders in a simple quartz tube furnace at $ 1000 C in Ar.…”