Characterization of oxidized gallium droplets on silicon surface: An ellipsoidal droplet shape model for angle resolved X-ray photoelectron spectroscopy analysis

Čechal, Jan; Matlocha, T.; Polčák, Josef; Kolı́bal, Miroslav; Tomanec, Ondřej; Kalousek, Radek; Dub, Petr; Šikola, Tomáš

doi:10.1016/j.tsf.2008.10.011

Cited by 8 publications

(7 citation statements)

References 24 publications

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“…This doubling of the exterior shells' thickness explains the disappearance of the tin and indium, as they were no longer visible from the surface of the droplet. Though the chemical composition of gallium oxide is mainly Ga 2 O 3 , the soaked sample showed much higher amount of OH groups as evidenced from the O 1s spectra (not shown), confirming a chemical shift toward gallium hydroxide on the surface of the droplet, as expected …”

Section: Contact Angles Of Galinstan Droplets On Various Substrates supporting

confidence: 58%

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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Section: Contact Angles Of Galinstan Droplets On Various Substrates supporting

confidence: 58%

Liquid Metal Switches for Environmentally Responsive Electronics

Bilodeau

Zemlyanov

Kramer

2017

Adv Materials Inter

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“…To further corroborate these results, we have calculated the island concentrations as a function of deposition temperature, flux, and relevant activation and binding energies employing the rate equation approach 51−54 modified to account for the loss of deposited material, 29 and, subsequently, converted the obtained island concentrations and volume of the lost material into XPS intensities. 28 The procedure is described in detail in the SI.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…27 In this work, we report on our study of activation energies of relevant processes for Au and its clusters/islands on ultrathin SiO 2 and Al 2 O 3 surfaces employing X-ray photoelectron spectroscopy. As we have shown recently, this technique is capable of providing morphological information on surface confined islands 28 and on diffusion of copper atoms through SiO 2 layers. 29 Within this work, we have revealed that the temperature at which the diffusion process of Au atoms starts depends on the gold coverage rather than on the thickness and type of the employed oxide as one would suppose.…”

Section: ■ Introductionmentioning

confidence: 95%

Detachment Limited Kinetics of Gold Diffusion through Ultrathin Oxide Layers

2014

Self Cite

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Gold clusters and nanoparticles on ultrathin oxide layers are used as catalysts and represent essential parts of plasmonic and electronic devices. The stability of these nanostructures at surfaces against the diffusion of their constituents into the bulk is therefore of vital importance regarding their long-term applicability. Here, on the basis of in situ X-ray photoelectron spectroscopy measurements of gold diffusion through ultrathin oxide layers (SiO2 and Al2O3) to a Si substrate, we show that the diffusion from gold clusters/islands into the bulk is a detachment-limited process. Hence, the ultrathin oxide acts principally as a layer preventing a direct contact of metal atoms with the silicon substrate rather than a diffusion barrier. These findings contribute to a quantitative understanding of general design rules of metal/oxide structures.

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“…In our configuration, two molecular interfaces are formed, one between 1+2 on GHD and one between 1+2 and gallium oxide on gallium. The oxide 64 tunnelling barrier between gallium and the supramolecular assembly forms a blocking-layer that prevents the efficient collection of photogenerated electrons at the gallium electrode. We suggest that the resulting photoresponsive device element is hole-only, that is, photogenerated holes are readily collected at the graphene photoanode, while electrons have to tunnel to the gallium electrode.…”

Section: Discussionmentioning

confidence: 99%

Photoresponse of supramolecular self-assembled networks on graphene–diamond interfaces

Simon

Krause

et al. 2016

Nat Commun

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Nature employs self-assembly to fabricate the most complex molecularly precise machinery known to man. Heteromolecular, two-dimensional self-assembled networks provide a route to spatially organize different building blocks relative to each other, enabling synthetic molecularly precise fabrication. Here we demonstrate optoelectronic function in a near-to-monolayer molecular architecture approaching atomically defined spatial disposition of all components. The active layer consists of a self-assembled terrylene-based dye, forming a bicomponent supramolecular network with melamine. The assembly at the graphene-diamond interface shows an absorption maximum at 740 nm whereby the photoresponse can be measured with a gallium counter electrode. We find photocurrents of 0.5 nA and open-circuit voltages of 270 mV employing 19 mW cm−2 irradiation intensities at 710 nm. With an ex situ calculated contact area of 9.9 × 102 μm2, an incident photon to current efficiency of 0.6% at 710 nm is estimated, opening up intriguing possibilities in bottom-up optoelectronic device fabrication with molecular resolution.

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Characterization of oxidized gallium droplets on silicon surface: An ellipsoidal droplet shape model for angle resolved X-ray photoelectron spectroscopy analysis

Cited by 8 publications

References 24 publications

Liquid Metal Switches for Environmentally Responsive Electronics

Liquid Metal Switches for Environmentally Responsive Electronics

Detachment Limited Kinetics of Gold Diffusion through Ultrathin Oxide Layers

Photoresponse of supramolecular self-assembled networks on graphene–diamond interfaces

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