MOVPE growth and real structure of vertical-aligned GaAs nanowires

Bauer, Jens; Gottschalch, V.; Paetzelt, Hendrik; Wagner, G.; Fuhrmann, Bodo; Leipner, Hartmut S.

doi:10.1016/j.jcrysgro.2006.10.082

Cited by 45 publications

(59 citation statements)

References 16 publications

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“…Line tension has been identified as a potential mechanism for this adjustment. If line tension is indeed the cause, then our finding of larger contact angles for larger droplets indicates a negative value of τ , which is in agreement with separate studies 17,19,22,24 . Secondly, the contact angle influences both the crystal structure and the angle of tapering, the former due to the finding by Glas et al that WZ and ZB nucleation energies are contact angle dependent 16 , and the latter due to the potential for layers to nucleate beyond the boundary of the underlying layer, as observed experimentally (bottom of figure 3(a)).…”

Section: Methodssupporting

confidence: 93%

“…Line tension, as outlined in the introduction, is one potential cause for this relationship. As described above, it is known to affect nanodroplets and varies inversely with the radius of the solid-liquid interface, r. From equation 2, the finding that contact angle is reduced for smaller droplets indicates that τ < 0, in agreement with previous findings 17,19,22,24 .…”

Section: Methodssupporting

confidence: 89%

“…However, except for values close to zero, a positive value of τ will result in a termination of growth at a certain height, and so for steady state growth τ is usually assumed to be negative 17,19,22,24 . In (c), which is a close-up of the base of the wire shown in (a), the facet structure of the wire can be seen.…”

Section: Introductionmentioning

confidence: 99%

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Effect of catalyst diameter on vapour-liquid-solid growth of GaAs nanowires

O'Dowd

Wójtowicz

Rouvimov

et al. 2014

Journal of Applied Physics

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GaAs nanowires were grown on (111)B GaAs substrates using the vapour-liquid-solid (VLS) mechanism. The Au/Pt nanodots used to catalyse wire growth were defined lithographically and had varying diameter and separation. An in-depth statistical analysis of the resulting nanowires, which had a cone-like shape, was carried out.This revealed that there were two categories of nanowire present, with differing height and tapering angle.The bimodal nature of wire shape was found to depend critically on the diameter of the Au-Ga droplet atop the nanowire. Transmission Electron Microscopy (TEM) analysis also revealed that the density of stacking faults in the wires varied considerably between the two categories of wire. It is believed that the cause of the distinction in terms of shape and crystal structure is related to the contact angle between the droplet and the solid-liquid interface. The dependency of droplet diameter on contact angle is likely related to line-tension, which is a correction to Young's equation for the contact angle of a droplet upon a surface. The fact that contact angle may influence resulting wire structure and shape has important implications for the planning of growth conditions and the preparation of wires for use in proposed devices. a) Electronic mail: odowdbj@tcd.ie

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Section: Methodssupporting

confidence: 93%

Section: Methodssupporting

confidence: 89%

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Effect of catalyst diameter on vapour-liquid-solid growth of GaAs nanowires

O'Dowd

Wójtowicz

Rouvimov

et al. 2014

Journal of Applied Physics

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“…The lateral size limitation (<10 nm-1 mm) is realized by the wetting of a liquid nanodroplet on top of the substrate [9]. The droplet acts as a reaction vessel.…”

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confidence: 99%

GaAs nanowires grown by MOVPE

Bauer

Paetzelt

Gottschalch

et al. 2010

Physica Status Solidi (b)

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GaAs nanowire (NW) growth was studied by metal-organic vapour phase epitaxy (MOVPE). The vapour-liquid-solid (VLS) mechanism with gold-based alloy particles and the selective-area growth (SAG) mechanism on electron beam lithographically prepared SiN x /GaAs mask structures were applied. A special focus is set on thermodynamic aspects of the VLS process. The alloy particle formation and the influence of MOVPE growth parameters on the growth rate and the GaAs NW morphology are examined. Furthermore, the improvement of the real structure with particular interest on the twin formation is studied. Besides the commonly used continuous VLS growth mode also a pulsed VLS growth mode with alternating precursor supply is reported. Based on photoluminescence measurements the effect of strain in core/shell NW structures is confirmed. For the SAG mechanism the MOVPE growth parameters are determined and the real structure is described.

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“…The switchover between the two regimes is possible by tuning the V/III flux ratio. [162][163] As shown in the Figure 2.14, the growth rate dependence on nanoparticle diameter shows opposite tendency under different V/III ratios, and this is due to the changing of growth mechanisms. Through theoretical calculation, Dubrovskii 154 predicted the transition from decreasing to increasing length-diameter dependence at a certain critical diameter in the very wide-range sized Au-catalyzed nanowire growth in MBE.…”

Section: Diameter Effectmentioning

confidence: 94%

Investigation of structural characteristics of III-V semiconductor nanowires grown by molecular beam epitaxy

Zhang¹

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One-dimensional nanowires made of III-V semiconductors have attracted significant research interest in the recent decades due to their distinct physical and chemical properties that can potentially lead to a wide range of applications in nanoelectronics and optoelectronics. As a key class of III-V semiconductor nanowires, InAs nanowires have attracted special attention due to their narrow bandgap, relatively high electron mobility, and small electron effective mass, which made them a promising candidate for the applications in future optical and highfrequency electronic devices.One of the challenges in realizing these unique III-V nanowire properties in nanowire-based devices is to integrate nanowires on the nano-devices or chips with well-organized arrangement. To solve this issue, the epitaxial nanowire growth provides the uniqueness that well aligned nanowires can be grown on the chosen substrates, and by selecting substrates with particular orientations, specifically orientated nanowires can be grown. Au-assisted nanowire growth is one of the most common methods to grow epitaxial III-V nanowires via the vapor-liquid-solid (VLS) mechanism or vapor-solid-solid (VSS) mechanism.For III-V nanowires, one of the coherent problems is that the stacking faults and/or twin defects can easily be introduced in both wurtzite or zinc-blende structured nanowires due to the small energy differences between wurtzite and zinc-blende stacking sequences of their dense planes. For III-V nanowires to be practically useful, it is of significant importance to minimize the lattice defects in nanowires, and to control their crystal phase and structural quality. In this regard, in this thesis, we investigated the growth parameters on the growth behaviour, crystal phase and structural quality of III-V nanowires, particularly InAs and GaAs nanowires. By carefully tuning the growth parameters, we have successfully achieved the controlled growth of InAs and GaAs nanowires with defect-free wurtzite structure and/or zincblende structure. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School.I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis. In the meantime, I am very grateful for the staff of Centre for Microscopy and Microanalysis (CMM) at UQ, who helped me in so many ways. They are Richard IV Publications during candidature

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MOVPE growth and real structure of vertical-aligned GaAs nanowires

Cited by 45 publications

References 16 publications

Effect of catalyst diameter on vapour-liquid-solid growth of GaAs nanowires

Effect of catalyst diameter on vapour-liquid-solid growth of GaAs nanowires

GaAs nanowires grown by MOVPE

Investigation of structural characteristics of III-V semiconductor nanowires grown by molecular beam epitaxy

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