Periodically Changing Morphology of the Growth Interface in Si, Ge, and GaP Nanowires

Wen, Cheng‐Yen; Tersoff, J.; Hillerich, Karla; Reuter, M. C.; Park, Jeung Hun; Kodambaka, S.; Stach, Eric A.; Ross, Frances M.

doi:10.1103/physrevlett.107.025503

Cited by 185 publications

(295 citation statements)

References 25 publications

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“…Predominantly WZ crystal phase of the NN tops is explained by the planar growth front at β min , which allows for the triple phase line nucleation. view, 36,42,46 such growth picture fully explains the observed crystal phase trend of our GaAs NWs. For vertical NWs at β min , nucleation of two-dimensional islands occurs at the triple phase line 41 and the crystal phase is predominantly WZ, with some insertions of ZB layers.…”

supporting

confidence: 53%

“…46 If this angle is smaller than β max but larger than β min , as shown in Figure 4a, the transition between the stable contact angles β min and β max is associated with the corresponding change in geometry of the growth interface, from nonwetted vertical at β min to wetted truncated at β max . According to the current At low V/III flux ratios, the droplet volume increases by increasing the contact angle until β max .…”

mentioning

confidence: 99%

“…For vertical NWs at β min , nucleation of two-dimensional islands occurs at the triple phase line 41 and the crystal phase is predominantly WZ, with some insertions of ZB layers. For truncated growth interface at β max , islands cannot nucleate at the triple phase line 46 and the crystal phase is pure ZB.…”

mentioning

confidence: 99%

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Bistability of Contact Angle and Its Role in Achieving Quantum-Thin Self-Assisted GaAs nanowires

et al. 2017

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Achieving quantum confinement by bottom-up growth of nanowires has so far been limited to the ability of obtaining stable metal droplets of radii around 10 nm or less. This is within reach for gold-assisted growth. Because of the necessity to maintain the group III droplets during growth, direct synthesis of quantum sized structures becomes much more challenging for self-assisted III−V nanowires. In this work, we elucidate and solve the challenges that involve the synthesis of galliumassisted quantum-sized GaAs nanowires. We demonstrate the existence of two stable contact angles for the gallium droplet on top of GaAs nanowires. Contact angle around 130°fosters a continuous increase in the nanowire radius, while 90°allows for the stable growth of ultrathin tops. The experimental results are fully consistent with our model that explains the observed morphological evolution under the two different scenarios. We provide a generalized theory of self-assisted III−V nanowires that describes simultaneously the droplet shape relaxation and the NW radius evolution. Bistability of the contact angle described here should be the general phenomenon that pertains for any vapor−liquid−solid nanowires and significantly refines our picture of how nanowires grow. Overall, our results suggest a new path for obtaining ultrathin one-dimensional III−V nanostructures for studying lateral confinement of carriers. KEYWORDS: III−V semiconductors on silicon, nanowires, nanoneedles, regular arrays, self-assisted growth, droplet size engineering, crystal structure, growth modeling F undamental physical properties and applications of semiconductor nanowires (NWs) may benefit from quantum confinement due to size-dependent modulation of the density of states as well as modification of the photon energy for the allowed optical transitions.1 In GaAs, quantum confinement occurs for a size below 25 nm.2,3 In addition to quantum confinement, the optical properties can be engineered by modifying the NW shape. For example, progressively tapered nanowires have exhibited adiabatic outcoupling in the emission of quantum dots, thereby enhancing their brightness. 4 A similar design may improve the light extraction or absorption in different optoelectronic devices including light emitting diodes, solar cells, and optical biosensors.5−11 Quantum confinement in the core of radial NW heterostructures allows for the fabrication of high quality NW-based quantum dots, which are a perfect platform for delicate quantum transport experiments. 12,13 It is admittedly challenging to obtain very thin (quantumconfined) III−V NWs directly by the vapor−liquid−solid (VLS) growth technique. There are several reasons for that (see ref 14 for a review), including the Gibbs−Thomson effect of elevation of chemical potential due to the curvature of the droplet surface and difficulties in obtaining very small droplets on the substrate surface. Thin tips of VLS GaAs NWs with a stable radius down to 5 nm have previously been grown by hydride vapor phase epitaxy 15,16 (a te...

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confidence: 53%

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Bistability of Contact Angle and Its Role in Achieving Quantum-Thin Self-Assisted GaAs nanowires

et al. 2017

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“…This is expected if the nucleation takes place on an inclined facet. 27 Indeed, the interface is far from being flat, and a meniscus (or incompletely formed facet) is clearly apparent. Hemispherical gold nanoparticles are also observed by SEM at the tip of tapered NWs, particularly at the tip of the shorter ones.…”

Section: Gold Particlementioning

confidence: 99%

“…Note that a change of shape -and of facet morphology -has been observed on III-V NWs, and may even take place regularly during the growth of the NW. 27 In addition, several facets (3 in the simplest case) may form, not necessarily at the same time. For such full-sphere nanoparticles, three characteristic diameters may be considered: the measured diameter of the full sphere, 2R f ull , the diameter of the initial particle which is approximately half-sphere, 18,19 2R half , and the diameter of the contact area between the particle and the NW tip, 2R tip .…”

Section: Gold Particlementioning

confidence: 99%

Diffusion-driven growth of nanowires by low-temperature molecular beam epitaxy

Rueda-Fonseca

Orrù

Bellet-Amalric

et al. 2016

Journal of Applied Physics

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With ZnTe as an example, we use two different methods to unravel the characteristics of the growth of nanowires by gold-catalyzed molecular beam epitaxy at low temperature. In the first approach, CdTe insertions have been used as markers, and the nanowires have been characterized by scanning transmission electron microscopy, including geometrical phase analysis, and energy dispersive electron spectrometry; the second approach uses scanning electron microscopy and the statistics of the relationship between the length of the tapered nanowires and their base diameter. Axial and radial growth are quantified using a diffusionlimited model adapted to the growth conditions; analytical expressions describe well the relationship between the NW length and the total molecular flux (taking into account the orientation of the effusion cells), and the catalyst-nanowire contact area. A long incubation time is observed. This analysis allows us to assess the evolution of the diffusion lengths on the substrate and along the nanowire sidewalls, as a function of temperature and deviation from stoichiometric flux.

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Semiconducting Nanowires in Photovoltaic and Thermoelectric Energy Generation

Vastola¹,

Zhang²

2017

Nanotechnology for Energy Sustainability

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Periodically Changing Morphology of the Growth Interface in Si, Ge, and GaP Nanowires

Cited by 185 publications

References 25 publications

Bistability of Contact Angle and Its Role in Achieving Quantum-Thin Self-Assisted GaAs nanowires

Bistability of Contact Angle and Its Role in Achieving Quantum-Thin Self-Assisted GaAs nanowires

Diffusion-driven growth of nanowires by low-temperature molecular beam epitaxy

Semiconducting Nanowires in Photovoltaic and Thermoelectric Energy Generation

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