Growth and characterisation of Ge Nanowires by chemical vapour deposition (original) (raw)
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Growth of Ge nanowires by chemical vapour deposition technique
Germanium, have been synthesized using chemical vapor deposition with Au nanoparticles (with size ranging from 5 nm to 30 nm) as nucleating centers (catalysts) and Germanium powders as a source for the nanowires growth. Au nanoparticles were synthesized on Si (100) by using simple and cost effective sol-gel process from HAuCl 4 as a precursor. The monodisperse, molecular-scale, singlecrystal Ge nanowires with diameters as small as 15 nm have been grown in a controllable manner. X-ray diffraction and high resolution scanning electron microscopy and X-ray photoelectron spectroscopy have been employed to characterize for their structural, morphological, and compositional properties. These nanowires are opening up unique opportunities for fundamental physics and high-performance devices also the nanowires could be used to create electronic devices for small, ultra fast computers and memories.
Heteroepitaxial Growth of Ge Nanowires on Si Substrates
International Journal of …, 2012
Electron beam evaporation has been used to prepare Ge nanowires (NWs) on top of (111) Si substrates. Despite the non-UHV growth conditions, scanning and transmission electron microscopies demonstrate that NWs are single crystal with specific crystallographic growth directions ([111], [110], and [112]). NWs are faceted, exhibiting the lower energy plans on the surface. The faceting depends on the growth direction. Moreover, the detrimental effects for Ge NWs growth of O atoms contamination are discussed. Finally, we describe how a proper preparation of the Au catalyst is able to increase the Ge NW density by a factor of 4, while heteroepitaxy and faceting features are maintained.
Oriented growth of ge nanowires with diameters below the bohr radius
2008
Highly symmetric self-organized arrays of germanium nanowires with average diameters of ∼12 (3 nm were produced by chemical vapor deposition. The nanowires grew epitaxially on the faces of single-crystal Ge microcrystals produced in the same synthesis. The epitaxial growth occurred on several crystal faces with the resultant nanowire structure varying accordingly. The (111) growth direction was found to dominate, however. High-resolution TEM images of a system consisting of the NW and the substrate on which it grew epitaxially are also reported, specifically showing the interface between the two regions, thereby elucidating the growth mechanism.
Growth of Germanium Nanowires on Silicon(111) Substrates by Molecular Beam Epitaxy
Journal of Nanoscience and Nanotechnology, 2011
Heteroepitaxial growth of Ge nanowires was carried out on Si(111) substrates by MBE. Au seeds were used as precursor for the VLS growth of the nanowires. Even if the Au droplets do not act as catalyst for the dissociation of gas, they are local preferential areas where the energetic barrier of Ge nucleation is lowered compare to the remaining non activated surface. Two sets of Au seeds were used as precursors for the VLS process. The first set have an average diameter of 125 nm and the second of 25 nm. In-situ RHEED monitoring showed a Au wetting layer between these seeds before the nanowires growth as well as at the end of the Ge nanowires growth. It means that the wetting layer acted as a surfactant from the Si(111) surface to the Ge grown layer between the nanowires. Analysis of SEM images brought the fact that the diffusion of gold from the droplets on the surface and the sidewalls of the nanowires via the Ostwald ripening is a key parameter of the growth of the nanowires.
Heteroepitaxial growth and faceting of Ge nanowires on Si (111) by electron-beam evaporation
… and Solid-State …, 2010
We demonstrated the heteroepitaxial growth of single-crystal faceted Ge nanowires ͑NWs͒ by electron-beam evaporation on top of Si͑111͒ substrates. Despite the non-ultrahigh vacuum growth conditions, scanning electron microscope and transmission electron microscope images show that NWs have specific crystallographic growth directions ͓͑111͔, ͓110͔, and ͓112͔͒ and that specific surface crystallographic planes ͕͑111͖ or ͕110͖͒ correspond to the ͓110͔ and ͓112͔ growth directions. Moreover, we studied in detail the Ge NWs structural properties. The temperature dependence of the NW length and of the frequency of each crystallographic orientation has been elucidated. Finally, the microscopic growth mechanisms have been investigated.
Fabrication of Si-Ge Nanowires
Different compositions of Si-Ge nanowires (SGNWs) have been fabricated by Vapor Liquid Solid (VLS) mechanism by using Ni as a catalyst with different SiCl4: GeCl4 ratios and temperatures respectively. The SEM results show that the SGNWs could be grown successfully vertical on the surface of the silicon with temperatures of 1000oC, 950oC, 900oC and 850oC. But for 900oC and 850oC, some of the NWs were observed to be grown as flower like structures instead of vertical. The growth rates are observed to be depending upon the ratio and the flowing times of the precursors greatly. For equal ratio of precursors (SiCl4: GeCl4=1:1) and the precursors’ flowing times of 5 min and 10 min, the growth rates of the SGNWs were observed to be around 20um/min and 30um/min respectively. The SEM results showed that the SGNWs could be grown successfully, vertical on the surface of the silicon with varying temperatures. Keywords: SiGe Nanowire, growth rate, optical characteristics.
Journal of Crystal Growth, 2011
Germanium nanowires with diameters from 10 to 70 nm and lengths up to 3 mm have been grown by Vapour-Liquid-Solid Molecular Beam Epitaxy (VLS MBE) on Ge (1 1 1), Si (0 0 1) and Si (1 1 0) substrates. The growth of nanowires was induced by gold droplets. We show that substrate temperature and germanium deposition rate, which determine surface diffusion length, are key parameters governing nanowires nucleation and growth phenomena. We also show that nanowires growth directions are independent of the strain induced by lattice mismatch.
Monolithic Growth of Ultrathin Ge Nanowires on Si(001)
Self-assembled Ge wires with a height of only 3 unit cells and a length of up to 2 micrometers were grown on Si(001) by means of a catalyst-free method based on molecular beam epitaxy. The wires grow horizontally along either the [100] or the [010] direction. On atomically flat surfaces, they exhibit a highly uniform, triangular cross section. A simple thermodynamic model accounts for the existence of a preferential base width for longitudinal expansion, in quantitative agreement with the experimental findings. Despite the absence of intentional doping, the first transistor-type devices made from single wires show low-resistive electrical contacts and single-hole transport at sub-Kelvin temperatures. In view of their exceptionally small and self-defined cross section, these Ge wires hold promise for the realization of hole systems with exotic properties and provide a new development route for silicon-based nanoelectronics.