Nanoscale Footprints of Self-Running Gallium Droplets on GaAs Surface

Wu, Jiang; Wang, Zhiming M.; Li, Alvason Zhenhua; Benamara, Mourad; Li, Shibin; Salamo, Gregory J.

doi:10.1371/journal.pone.0020765

Cited by 21 publications

(15 citation statements)

References 27 publications

(42 reference statements)

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“…b). This phenomenon has been observed in the GaAs system by Wu et al . The direction of movement appears to be determined by the crystallographic anisotropy in both cases.…”

Section: Discussionsupporting

confidence: 71%

Structure and composition of non‐polar (11‐20) InGaN nanorings grown by modified droplet epitaxy

Springbett

Griffiths

Ren

et al. 2015

Physica Status Solidi (b)

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Droplets grown by modified droplet epitaxy on non‐polar (11‐20) surfaces of InGaN epilayers on GaN have been seen to be associated with underlying ring‐like structures. This work discusses droplet etching as a possible mechanism for ring formation, and droplet creeping as a possible explanation for the droplets sitting askew of the ring centre. Transmission electron microscopy (TEM) analysis shows the droplets to move along the 〈0001〉 c‐axis, and indicates that they have a very high indium content. The image shows atomic force microscopy (AFM) data of a double‐ring structure, rendered in 3D.

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“…b). This phenomenon has been observed in the GaAs system by Wu et al . The direction of movement appears to be determined by the crystallographic anisotropy in both cases.…”

Section: Discussionsupporting

confidence: 71%

Structure and composition of non‐polar (11‐20) InGaN nanorings grown by modified droplet epitaxy

Springbett

Griffiths

Ren

et al. 2015

Physica Status Solidi (b)

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“…To form ordered Ga nanodroplets in intact GaAs surfaces can be achieved by ion-beam-induced Ga migration [ 40 , 41 ]. Random motion of Ga nanodroplets can be induced by ion beam bombardment due to ion-beam-induced anisotropic mass transport and thermal fluctuation [ 41 – 43 ]. Figure 5 a shows the formation of Ga nanodroplets around a square area bombarded with 0.93-nA Ga + ion beam for 1 min.…”

Section: Resultsmentioning

confidence: 99%

Ion-Beam-Directed Self-Ordering of Ga Nanodroplets on GaAs Surfaces

Xu¹,

Wu²,

Wang³

et al. 2016

Nanoscale Res Lett

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Ordered nanodroplet arrays and aligned nanodroplet chains are fabricated using ion-beam-directed self-organization. The morphological evolution of nanodroplets formed on GaAs (100) substrates under ion beam bombardment is characterized by scanning electron microscopy and atomic force microscopy. Ordered Ga nanodroplets are self-assembled under ion beam bombardment at off-normal incidence angles. The uniformity, size, and density of Ga nanodroplets can be tuned by the incident angles of ion beam. The ion beam current also plays a critical role in the self-ordering of Ga nanodroplets, and it is found that the droplets exhibit a similar droplet size but higher density and better uniformity with increasing the ion beam current. In addition, more complex arrangements of nanodroplets are achieved via in situ patterning and ion-beam-directed migration of Ga atoms. Particularly, compared to the destructive formation of nanodroplets through direct ion beam bombardment, the controllable assembly of nanodroplets on intact surfaces can be used as templates for fabrication of ordered semiconductor nanostructures by droplet epitaxy.

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“…Gallium‐based alloys can be found in a liquid form at both room and elevated temperatures. At high temperatures (>600 °C), researchers have controlled the motion of liquid gallium arsenide via chemical decomposition of the alloy, controlling the direction of motion via surface crystallinity of the substrate . Other high‐temperature gallium alloys have been controlled and directed by surface roughness .…”

Section: Contact Angles Of Galinstan Droplets On Various Substrates mentioning

confidence: 99%

Liquid Metal Switches for Environmentally Responsive Electronics

Bilodeau

Zemlyanov

Kramer

2017

Adv Materials Inter

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providing a second system for non-mechanical liquid metal manipulation. Zhang et al. fed aluminum chips to a galinstan droplet as fuel for self-propulsion, [19] and have since developed non-contacting magnetic controls for the droplet. [20] Finally, a large category of recent research has used electricity to create relative motion and shape change in liquid metals, [21][22][23] enabling non-contacting pumps for microfluidic flow [24] and cooling, [25] self-destructive circuitry (path-destructive liquid metal droplet motion), [26] and most recently as a source for rigid-body locomotion. [27] It is well known that gallium oxidizes rapidly in normal atmospheric conditions, or in any environment with oxygen levels above 1 ppm, [11,28,29] forming a gallium oxide that has been studied in detail. [30][31][32] This oxide is solid at room temperature and forms a nanoscale stabilizing shell around liquid gallium indium alloys, enabling the liquid metal to be patterned onto, and subsequently adhere to, many different material surfaces (via a plethora of techniques). [33] If the oxide is removed, the liquid metal loses its adhesion to the substrate and will reflow under the influence of gravity (or other forces), enabling a fixed liquid metal pattern to change. In other words, oxide removal enables real-time, non-mechanical manipulation of liquid metals. This has typically been done either in nitrogen boxes (via passive oxide prevention) or in chemical etchant baths (via active oxide removal). [18,19,21,[24][25][26] Unfortunately, these methods require enclosed (air-tight or water-proof) chambers that limit the practical applications for manipulation of liquid metal circuits on the fly, as the circuits must remain inside the chamber.The two main etchants used for aqueous oxide removal are hydrochloric acid (HCl, a low-pH acid) [15,18,21,30,31,34] and sodium hydroxide (NaOH, a high-pH base). [19,21,22,[24][25][26] Both of these etchants mix readily with water and can be contained safely at high concentrations. A non-aqueous alternative for oxide removal comes through exposing the liquid metals to concentrated HCl vapor, [35][36][37][38][39] but practical applications of this are generally limited to environments that can withstand the presence of a highly corrosive gas.In this work, we demonstrate control over the surface oxide of liquid metal droplets, which in turn controls the wetting and adhesion of those drops on a substrate, using purely environmental stimuli. We compare the use of highly acidic HCl and highly alkaline NaOH (in solution) in removing the oxide to release pinned droplets. We show that although both solvent solutions result in high contact angles between the droplet and the substrate, NaOH achieves this result at a rate that is orders of magnitude faster than HCl. We further explore the use of neutral distilled water to regrow the oxide and manipulate the contact area of the liquid metal droplet on the surface, causing the droplet to readhere to the substrate. Finally, we apply this environmentally control...

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Nanoscale Footprints of Self-Running Gallium Droplets on GaAs Surface

Cited by 21 publications

References 27 publications

Structure and composition of non‐polar (11‐20) InGaN nanorings grown by modified droplet epitaxy

Structure and composition of non‐polar (11‐20) InGaN nanorings grown by modified droplet epitaxy

Ion-Beam-Directed Self-Ordering of Ga Nanodroplets on GaAs Surfaces

Liquid Metal Switches for Environmentally Responsive Electronics

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