<i>In situ</i> studies of semiconductor nanowire growth using optical reflectometry

Clement, T.; Ingole, Sarang; Ketharanathan, Sutharsan; Drucker, Jeffery; Picraux, S. T.

doi:10.1063/1.2364121

Cited by 37 publications

(34 citation statements)

References 10 publications

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“…Incubation times have indeed been measured before in other type of nanowires. 11,12 In our case, the incubation time is more likely related to the formation of holes in the oxide that host the nucleation of the nanowires. We should also add here that growth directly on a GaAs surface under the same conditions did not result into the formation of nanowires.…”

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confidence: 75%

Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

Morral

Colombo

Abstreiter

et al. 2008

Applied Physics Letters

280

272

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Molecular beam epitaxy Ga-assisted synthesis of GaAs nanowires is demonstrated. The nucleation and growth are seen to be related to the presence of a SiO 2 layer previously deposited on the GaAs wafer. The interaction of the reactive gallium with the SiO 2 pinholes induces the formation of nanocraters, found to be the key for the nucleation of the nanowires. With SiO 2 thicknesses up to 30 nm, nanocraters reach the underlying substrate, resulting into a preferential growth orientation of the nanowires. Possibly related to the formation of nanocraters, we observe an incubation period of 258 s before the nanowires growth is initiated. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2837191͔Semiconductor nanowires are believed to play a decisive role in the electronic and optoelectronic devices of the 21st century. Up to now, the synthesis of nanowires is mainly based on the vapor-liquid-solid and vapor-solid-solid mechanisms. 1,2 Common in both mechanisms is that a metal nanoparticle gathers and decomposes catalytically the precursor molecules. Supersaturation of the metal droplet follows and leads to the precipitation of a solid phase underneath the droplet in the form of a nanowire. Typically, gold is used as a catalyst. The use of such an extrinsic catalytic metal is in general not desired and some effort has been directed into finding alternatives. 3,4 Recently, catalyst-free growth has been achieved both with metal-organic chemical vapor deposition and molecular beam epitaxy ͑MBE͒. 5,6 This type of growth has always been linked to the existence of a plain or patterned SiO 2 surface, whose role has still to be clarified. To our knowledge, a detailed study on the nucleation stage of the nanowires and an analysis of the role of the SiO 2 are still missing.Nanowires were grown in a Gen-II MBE system. 2 in. GaAs wafers were sputtered with silicon dioxide; the thickness was varied between 20 and 100 nm. In order to ensure a contamination-free surface, the substrates were dipped for 2 s in a 12% HF aqueous solution, nitrogen blow dried, and were immediately after transferred in the load lock of the growth chamber. In order to desorb any remnant adsorbed molecules at the surface, the wafers were heated to 650°C for 30 min prior to growth. The synthesis was carried out at a temperature of 630°C, an arsenic As 4 partial pressure of 8 ϫ 10 −7 mbar, a Ga rate of 0.25 Å / s and under rotation of 4 rpm.We first discuss nanowires which were grown simultaneously on two different halves of GaAs substrates with the ͑001͒ and ͑111͒B orientations. After cleaning of the surface and HF dip, the two halves were still coated with a 6 nm SiO 2 thin film. Cross-sectional scanning electron microscopy ͑SEM͒ measurements of the grown nanowires are shown in Fig. 1. The micrographs clearly reveal that the nanowires mainly grow perpendicular to the substrate in the case of the ͑111͒B GaAs, and with an angle of ϳ35°in the case of the ͑001͒ GaAs. This result clearly proves the existence of a relation between the nanowire orientation and...

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confidence: 75%

Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

Morral

Colombo

Abstreiter

et al. 2008

Applied Physics Letters

280

272

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“…[8][9][10][11][12][13][14] Such a delay has also been revealed for the catalyst-induced growth of silicon and GaN NWs and attributed to the time that is necessary for the supersaturation in the catalyst to reach the critical value. [15][16][17][18][19] In contrast, for the self-induced growth of GaN NWs, the physical origin of the delay in nucleation is still open. It is the aim of this paper to cast a light on the very early stages of the nucleation phase by precisely investigating the incubation time and its evolution with the growth temperature and gallium rate by reflection high-energy electron diffraction (RHEED) measurements.…”

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confidence: 99%

Physical origin of the incubation time of self-induced GaN nanowires

Consonni

Trampert

Geelhaar

et al. 2011

Applied Physics Letters

123

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International audienceThe nucleation process of self-induced GaN nanowires grown by molecular beam epitaxy has been investigated by reflection high-energy electron diffraction measurements. It is found that stable nuclei in the form of spherical cap-shaped islands develop only after an incubation time that is strongly dependent upon the growth conditions. Its evolution with the growth temperature and gallium rate has been described within standard island nucleation theory, revealing a nucleation energy of 4.9 +/- 0.1 eV and a very small nucleus critical size. The consideration of the incubation time is critical for the control of the nanowire morphology. (C) 2011 American Institute of Physics. [doi:10.1063/1.3610964

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“…The activation of the VLS mechanism is thus prompt, thanks to the fast Si diffusion through the already liquid particle. Incubation times ranging in the order of several tens of seconds for growth of Si nanowires mediated by Au have been reported, depending of conditions such as temperature and gas phase pressure in thermal CVD processes [9,22]. The activation of the VLS mechanism with Al particles is more difficult than for Indium.…”

Section: Resultsmentioning

confidence: 99%

Alternative Catalysts For Si-Technology Compatible Growth Of Si Nanowires

et al. 2007

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The use of Au nanoparticles as catalysts for growth of Si nanowires poses fundamental reliability concerns for applications in Si semiconductor technology. In this work we show that the choice of catalysts can be broadened when the need for catalytic precursor dissociation is eliminated. However, the requirements for selective deposition in a gas phase transport ñlimited regime become stringent. When competing deposition of amorphous Si can bury the particles faster than the incubation time for VLS growth, no nanowire growth will be initiated. We show that the use of a catalyst such as In, already in a liquid form at the growth temperature, is effective. Therefore, the choice of VLS catalysts among the low melting point metals from the III, IV and V groups is suggested.

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In situ studies of semiconductor nanowire growth using optical reflectometry

Cited by 37 publications

References 10 publications

Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

Physical origin of the incubation time of self-induced GaN nanowires

Alternative Catalysts For Si-Technology Compatible Growth Of Si Nanowires

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