Self-Consistent Interpretation of the 2D Structure of the Liquid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Au</mml:mi><mml:mn>82</mml:mn></mml:msub><mml:msub><mml:mi>Si</mml:mi><mml:mn>18</mml:mn></mml:msub></mml:math>Surface: Bending Rigidity and the Debye-Waller Effect

Mechler, S.; Pershan, Peter S.; Yahel, Eyal; Stoltz, S. E.; Shpyrko, Oleg; Lin, Binhua; Meron, Mati; Sellner, Stefan

doi:10.1103/physrevlett.105.186101

Cited by 24 publications

(24 citation statements)

References 22 publications

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“…The upper wave-vector cutoff q max required for our observed reduction in σ (neglecting the small Φ-induced change in γ) is q max = 0:1 Å −1 . This cutoff corresponds to a bending rigidity of 100 kT, similar to that found for the solid surface bilayer on the liquid Au-Si eutectic (38). These similarities support the conclusion that the PbFBr adlayer is a 2D solid.…”

supporting

confidence: 72%

“…These σ L and σ T are substantially lower than σ T at −0.90 V, enhancing the maxima of the Rðq z Þ modulations for Φ > − 0:60 V well over the reflectivities at the same q z positions for Φ < − 0:60 V. The decrease in roughness is contrary to expectations, because thermodynamically, interfacial adsorption of a foreign species occurs when the species reduces the surface energy γ, and hence increases σ ∼ 1=γ (37). The decrease in σ found here resembles observations for the liquid/vapor interfaces of Au-Si liquid eutectic (38) and of water-supported highly compressed Langmuir films (39). In both of these systems the liquid bulk is covered by a 2D solid, the nonzero bending rigidity of which quenches shortwavelength CWs.…”

supporting

confidence: 70%

“…These similarities support the conclusion that the PbFBr adlayer is a 2D solid. A direct verification of this conclusion by X-ray diffuse scattering measurements, as done for Au-Si (38), is prohibited in our system by the high background scattering from the interface-overlying bulk electrolyte.…”

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confidence: 74%

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In situ X-ray studies of adlayer-induced crystal nucleation at the liquid–liquid interface

Elsen

Festersen

Runge

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Crystal nucleation and growth at a liquid-liquid interface is studied on the atomic scale by in situ Å-resolution X-ray scattering methods for the case of liquid Hg and an electrochemical dilute electrolyte containing Pb 2+ , F − , and Br − ions. In the regime negative of the Pb amalgamation potential Φ rp = − 0:70 V, no change is observed from the surface-layered structure of pure Hg. Upon potential-induced release of Pb 2+ from the Hg bulk at Φ > Φ rp , the formation of an intriguing interface structure is observed, comprising a well-defined 7.6-Å-thick adlayer, decorated with structurally related 3D crystallites. Both are identified by their diffraction peaks as PbFBr, preferentially aligned with theirc axis along the interface normal. X-ray reflectivity shows the adlayer to consist of a stack of five ionic layers, forming a single-unit-cellthick crystalline PbFBr precursor film, which acts as a template for the subsequent quasiepitaxial 3D crystal growth. This growth behavior is assigned to the combined action of electrostatic and shortrange chemical interactions.electrochemistry | liquid metal L iquid-liquid and liquid-gas interfaces provide exciting new possibilities for material synthesis (1, 2). Contrary to solid interfaces, which exhibit strain and stress, heterogeneities, and defects such as steps, which all strongly affect growth processes, fluid systems provide soft, defect-and stress-free interfaces. The high mobility of reagents, products, and deposited particles in liquid phases facilitates the growth process as well as the selfassembly of ordered particle arrays at the interface.A large variety of materials has been prepared via deposition at liquid-liquid interfaces, such as metals (1), oxides (3, 4), chalcogenides (5, 6), polymers (7), plasmonic materials (2), and nanoparticle catalysts of ceria (3), Pd (8, 9), and Pt (10). As demonstrated by Carim et al., deposition at liquid-liquid interfaces even allows the synthesis of group IV semiconductors such as Ge from oxide materials via a simple one-step, room-temperature electrochemical process (11). Different methods for nanoparticle manufacturing, such as deposition by reduction of metal ions (12) or electrochemical deposition (11), are available at the liquidliquid interface, allowing for particle modification and growth control via adjustment of concentration or interfacial potential.Despite the absence of long-range order, liquid interfaces provide the possibility to control the crystallinity, shape, and orientation of deposits. Examples are the growth of single-crystalline CuO and CuS films (4), the surfactant-induced oriented growth of calcite crystals (13), and the formation of pyramidal PbS crystallites with defined, high surface area facets (5). These phenomena were rationalized by energetic effects, such as the interface energies, surface charges, and specific chemical interactions, as well as by the growth kinetics. However, detailed insight into the phase formation mechanisms is generally precluded by lack of atomicscale data on the in...

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supporting

confidence: 72%

supporting

confidence: 70%

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In situ X-ray studies of adlayer-induced crystal nucleation at the liquid–liquid interface

Elsen

Festersen

Runge

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…3 for three temperatures, 635 K (LT), 695 (HT), and 720 (LL). 19,20 Note that although the Debye-Waller factor at the temperature of the LT data, which is about 300 K higher than the data for Ga that is shown in Fig. 1, should reduce the reflectivity by at nearly an order of magnitude, the peak reflectivity for Au 82 Si 18 is more than twice as intense as that of Ga.…”

mentioning

confidence: 79%

“…19,20 Reflectivity data for this alloy are shown in Fig. 3 for three temperatures, 635 K (LT), 695 (HT), and 720 (LL).…”

mentioning

confidence: 99%

Review of the highlights of X-ray studies of liquid metal surfaces

Pershan

2014

Journal of Applied Physics

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Glass transition and atomic structures in supercooled GaReview of the highlights of X-ray studies of liquid metal surfaces X-ray studies of the interface between liquid metals and their coexisting vapor are reviewed. After a brief discussion of the few elemental liquid metals for which the surface Debye-Waller effect is sufficiently weak to allow measurement, this paper will go on to discuss the various types of surface phenomena that have been observed for liquid metal alloys. These include surface adsorption, surface freezing, surface aggregation of nm size atomic clusters, and surface chemistry that leads to new 3D crystalline phases. V C 2014 AIP Publishing LLC. [http://dx

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Surface Crystallization of Liquid Au–Si and Its Impact on Catalysis

Panciera

Tersoff²,

Gamalski

et al. 2018

Advanced Materials

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is unique in forming a 2D crystalline compound at its surface, with a fixed atomic-scale thickness, over a range of temperature. While this layer has not been imaged directly, diffraction studies have established that an ordered bilayer (the low-temperature (LT) phase) exists up to 12 °C above the eutectic temperature. [2,8] (A higher temperature phase has also been detected, although its properties are less clear. [9,10] ) At present there is no straightforward explanation for this unique behavior. Ordered surface phases have been explained by surface prefreezing, [11] a phenomenon that is analogous to the wellknown surface premelting. However, an ordered prefreezing layer is expected to be present only very near the transition temperature and to have a thickness that diverges as the temperature approaches the transition temperature, both of which are inconsistent with the behavior of Au-Si. The ordered surface phase in Au-Si also cannot be explained as a solute coming out of solution and wetting the surface, as can occur in dilute Ga solutions. [6] Here, we use in situ transmission electron microscopy (TEM) to observe directly the formation of a crystalline 2D compound at the surface of liquid Au-Si. By varying both temperature and composition we find that the 2D phase can be stable over a surprisingly large range, over 150 °C, extending above and below the eutectic temperature. We develop a simple thermodynamic model that explains the wide stability range and composition dependence. Given the persistence of the surface ordering, we explore its effects on critical aspects of the behavior of Au-Si. We find that the surface layer plays a key role in the pathway of eutectic decomposition of Au-Si into solid Au + solid Si on cooling, and also that it is the root cause of the dramatic changes observed in the catalytic properties of Au-Si on cooling. We derive a strategy for controlling the presence of the surface phase as a tool in nanostructure fabrication.Surface ordering on droplets of Au-Si of different dia meters is shown in Figure 1a,b and Movie S1 in the Supporting Information. These high spatial and temporal resolution data (see the Supporting Information) were recorded by in situ heating of Si substrates decorated with Au nanoparticles, with or without exposure to the Si source gas disilane (Si 2 H 6 ). On reaching the Au-Si eutectic temperature T E = 363 °C, [12] the Au reacts with Si to form Au-Si liquid droplets. Imaging the surfaces of these droplets in profile view (Figure 1a) shows that there are two well-defined crystalline layers at the surface. The ordering can also be detected in projection over the entire droplet area in Figure 1a. In the smaller droplet shownIn situ transmission electron microscopy reveals that an atomically thin crystalline phase at the surface of liquid Au-Si is stable over an unexpectedly wide range of conditions. By measuring the surface structure as a function of liquid temperature and composition, a simple thermodynamic model is developed to explain the stability of the or...

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Self-Consistent Interpretation of the 2D Structure of the LiquidAu82Si18Surface: Bending Rigidity and the Debye-Waller Effect

Cited by 24 publications

References 22 publications

In situ X-ray studies of adlayer-induced crystal nucleation at the liquid–liquid interface

In situ X-ray studies of adlayer-induced crystal nucleation at the liquid–liquid interface

Review of the highlights of X-ray studies of liquid metal surfaces

Surface Crystallization of Liquid Au–Si and Its Impact on Catalysis

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