Metal-Catalyst-Free Growth of Silica Nanowires and Carbon Nanotubes Using Ge Nanostructures

Abstract

The use of Ge nanostructures is investigated for the metal-catalyst-free growth of silica nanowires and carbon nanotubes (CNTs). Silica nanowires with diameters of 10-50 nm and lengths of ≤ 1 µm were grown from SiGe islands, Ge dots, and Ge nanoparticles. High-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) reveal that the nanowires grow from oxide nanoparticles on the sample surface. We propose that the growth mechanism is thermal diffusion of oxide through the GeO 2 nanostructures. CNTs with diameters 0.6-2.5 nm and lengths of less than a few µm were similarly grown by chemical vapor deposition from different types of Ge nanostructures. Raman measurements show the presence of radial breathing mode peaks and the absence of the disorder induced D-band, indicating single walled CNTs with a low defect density. HRTEM images reveal that the CNTs also grow from oxide nanoparticles, comprising a mixture of GeO 2 and SiO 2

CMOS Compatible Growth of Carbon Nanotubes and Their Application in Field-Effect Transistors

“…This trend is in good agreement with the recent results of Liu et al [11] and Huang et al [12] who reported on CNT growth from oxide nanoparticles. These results suggest the following mechanism for CNT growth [16]. As GeO 2 has a melting point of 400ºC, it is likely that the nanoparticles melt during the pre-anneal at 900ºC, so that CNTs are synthesized from the Ge oxide droplets in which the carbon feedstock is dissolved.…”