Effect of HCl on the doping and shape control of silicon nanowires (original) (raw)
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Growth of silicon nanowires via gold/silane vapor–liquid–solid reaction
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 1997
Silicon nanowires (whiskers) have been grown on Si(111) via the vapor–liquid–solid (VLS) reaction using silane as the Si source gas and Au as the mediating solvent. The silane partial pressure and temperature ranges were 0.01–1 Torr and 320–600 °C, respectively. Growth at high partial pressure and low temperature leads to the growth of Si nanowires as thin as 10 nm. These wires are single crystals but exhibit growth defects such as bending and kinking. Lowering the silane partial pressure leads to an increase in the wire width and a reduction in the tendency to form growth defects. At low pressure, 40–100 nm wide well-formed wires have been grown at 520 °C. The VLS reaction using silane allows the growth of Si wires, which are significantly thinner than those grown previously using SiCl4.
Controlled growth of silicon nanowires synthesized via solid–liquid–solid mechanism
Science and Technology of Advanced Materials, 2005
The growth of silicon nanowires using solid-liquid-solid method is described. In this method, silicon substrates coated with a thin layer of gold were heat treated in nitrogen ambient. Gold particles started to diffuse into the silicon substrate and Au-Si alloy formed at the interface. The alloy would have molten to form liquid droplets on the substrate when temperature increases above their eutectic point, and more Si atoms diffused into these alloy droplets when heating continues. Rapid cooling of the droplet surface due to nitrogen flow into the chamber would eventually lead to the phase separation of silicon atoms from the surface of the alloy, created the nucleation and thus the growth of silicon nanowires. Controlled growth of the nanowire could be achieved by annealing the sample at 1000 8C with nitrogen flow rate set to around 1.5 l/min. The synthesized nanowires with diameter varied from 30 to 70 nm, were straight and grew along the N 2 flow. Larger amount and longer nanowires were grown when longer period of heating was applied. Nanowires with lengths more than several hundreds of micrometers were achieved by annealing the sample for 4 h. q
Nano Letters, 2006
We study the electronic and atomic structures of hydrogenated silicon nanowires (SiNWs) by changing the mean diameter, morphology, and orientation using state-of-the-art density functional calculations. Most of the SiNWs are found to have large and direct band gaps, which make them very interesting for silicon-based nano-optoelectronic devices and lasers. The band gap increases with decreasing diameter in all cases because of quantum confinement, but the scaling is dependent on the morphology of the SiNWs. For thin [112] SiNW, the calculated band gap agrees well with the recent experiments. Variation in hydrogen concentration is used to explore the sensing capabilities of different surface morphologies and the associated surface reconstructions. Further studies on p-or n-doping show bulklike modifications in the electronic structure with several advantages that can be used to design nanoscale devices of SiNWs.
Bulk synthesis of silicon nanowires using a low-temperature vapor–liquid–solid method
Applied Physics Letters, 2001
Silicon nanowires will find applications in nanoscale electronics and optoelectronics both as active and passive components. Here, we demonstrate a low-temperature vapor-liquid-solid synthesis method that uses liquid-metal solvents with low solubility for silicon and other elemental semiconductor materials. This method eliminates the usual requirement of quantum-sized droplets in order to obtain quantum-scale one-dimensional structures. Specifically, we synthesized silicon nanowires with uniform diameters distributed around 6 nm using gallium as the molten solvent, at temperatures less than 400°C in hydrogen plasma. The potential exists for bulk synthesis of silicon nanowires at temperatures significantly lower than 400°C. Gallium forms a eutectic with silicon near room temperature and offers a wide temperature range for bulk synthesis of nanowires. These properties are important for creating monodispersed one-dimensional structures capable of yielding sharp hetero-or homointerfaces.
2007
Unlike typical Au used as a catalyst for the synthesis of silicon nanowires via the vapour-liquid-solid mechanism, Cu has been found to induce a synthesis process governed by the vapour-solid-solid mechanism. Moreover, the temperature window for obtaining high-quality wires with Cu has been found to be relatively smaller than that shown by the Au: from 600 to 650 • C. However, high-resolution transmission electron microscopy analysis reveals significant new properties of the nanowires obtained. They have the peculiarity of successively switching the silicon structure from diamond to the wurtzite phase along the growth direction. This change of the crystalline structure implies that it has an important impact on the transport properties and characteristics of electronic devices. The results will be important for the future integration and application of silicon, where electrical and thermal transport properties play a significant role.
H2-assisted control growth of Si nanowires
Journal of Crystal Growth, 2003
Large-scale desired silicon nanowires without amorphous silicon oxide sheath have been synthesized by thermal chemical vapor deposition using SiH4 gas at 650°C in a flow mixture of H2 and N2, compared with the short and thick Si nanowires with amorphous SiOx coating obtained in N2. Scanning electron microscopy (SEM), Energy dispersive X-ray spectrometry (EDX) analysis, and high-resolution transmission electron microscopy
Silicon Nanowires Obtained by Low Temperature Plasma-Based Chemical Vapor Deposition
MRS Proceedings, 2012
Silicon Nanowires (Si-NWs) are obtained by vapor-liquid-solid growth using an inductively coupled chemical vapor deposition system which works at temperatures lower than 400 °C. Gold nanodots are used as metal catalyst. The selective growth of Si-NWs on the gold nanodots is obtained by controlling the contribution coming from the uncatalyzed growth on the bare Si substrate. In this way the final NW length can be controlled, and it is not influenced by the thickness of the uncatalyzed layer. The important parameter ruling the NW growth is found to be the plasma power which governs the dissociation of the Si precursor gas. Final NW lengths of 1 m are obtained at temperatures of 380 °C with a thickness of uncatalyzed layer equal to zero. Also the NW density is addressed in this work and it is optimised by increasing the gold equivalent thickness. The NW density is increased from 2.9×10 8 to 1.3×10 10 cm -2 , when the gold equivalent thickness passes from 1.8 nm to 2.2 nm.
Physical Chemistry Chemical Physics, 2012
SiNWs were grown by the vapor-liquid-solid (VLS) technique as can be found in our previous work. 16 SiNWs size and length distributions are illustrated in Fig SI-1. Hydrogen termination is conducted through HF and NH 4 F etching as explained in the references. 4,5 H-SiNWs were annealed in ambient conditions in seven distinct temperatures of 50 ˚C, 75 ˚C, 150 ˚C, 200 ˚C, 300 ˚C, 400 ˚C and 500 ˚C, each for five different time-spans: 5 min, 10 min, 20 min, 30 min and 60 min. Notice that surface contamination by organic species was constant 20±5% during annealing. This has been monitored in C1s spectra of the samples heated for 60min at each temperature. Annealing and hydrogen termination were gentle in the sense that they did not impose noticeable changes on size and orientation of SiNWs. X-ray photoelectron spectroscopy (XPS) was employed to examine impacts of each annealing stage on the thermally grown oxide amount and composition. Core level and valance band photoelectron spectra were excited by monochromatic Al Kα radiation (1487 eV) and collected by a hemispherical analyzer with adjustable overall resolutions of 0.8 to 1.2 eV. In an overall binding energy survey, samples were first scanned from 0 to 1000 eV detecting the signals for Si, C, and O. The Si2p at 98.0-105.0 eV, C1s at 282.0-287.0 eV and O1s at 520-550eV were monitored more accurately in discrete number of scans.
Silicon Nanowire Growth and Properties: A Review
Materials Express, 2011
Over the last few years silicon nanowires have come under intensive research due to their promising physical properties and potential as active materials in future electronic and optoelectronic applications. This article reviews various bottom-up growth methods of silicon nanowires. Various catalysts, including gold and other metals, as well as non-catalyst initiated growth methods are discussed in detail by comparing recipes including important parameters such as growth temperature, catalyst deposition methods, silicon nanowires diameter obtained, surface quality etc. This is expected to allow for an easier selection of a suitable growth method for a desired application. In addition, this article briefly reviews some of the developments in the field of silicon nanowire electronics and optoelectronics, including theoretical and experimental determination of charge carrier mobilities, visible photoluminescence, as well as a few recent examples of photodetectors and solar cells using silicon nanowires.
Silicon nanowires synthesis on a submicronic terminal: Structural and electrical characterization
Journal of Applied Physics, 2010
In this work, we investigate localized silicon nanowires synthesis in a room temperature-controlled silane filled chamber using submicronic resistors as heating devices. These resistors consist in circuit-connected W wires obtained, on silicon oxide substrates, by focused ion beam induced deposition ͑FIBID͒ technology. Our study demonstrates that the morphology of the synthesized nanowires is temperature and time dependent revealing a thermal gradient but also both vapor-liquid-solid and vapor-solid growth effects. Typical silicon nanowires dimensions are a length of 1-2 m and diameters of 30-40 nm. Structural characterization is performed by high resolution transmission electron microscopy using high energy electron transparent self-supported silicon nitride membranes. Electrical characteristics of FIBID-and self-connected nanowires are obtained. In both cases, they exhibit rectifying behavior.