In Situ Determination of the Nanoscale Chemistry and Behavior of Solid-Liquid Systems

Eswara, Santhana; Howe, James M.; Muralidharan, Govindarajan

doi:10.1126/science.1146511

Cited by 61 publications

(44 citation statements)

References 23 publications

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“…However, many fundamental questions regarding the segregation behavior of solute atoms remain unanswered because of the difficulties that exist for in situ experiments to determine elemental concentrations and monitor the changes of local structure around solute atoms ahead of the growing solidification front that occurs during freezing at an atomic scale. Fortunately, Eswaramoorthy et al [3] have reported a potential method to detect the in situ redistribution of alloying elements at the nanoscale. Their experimental results showed that the maximum concentration of alloying Cu in an Al matrix was at the point a small distance away from the growth interface and that the concentration of Si gradually changes as the liquid phase transitions into a faceted Si crystal.…”

Section: Introductionmentioning

confidence: 99%

Ab initio simulation: The correlation between the local melt structure and segregation behavior of Fe, V, Ti and Si in liquid Al

Yang

Zhang

Dai

et al. 2015

Computational Materials Science

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Section: Introductionmentioning

confidence: 99%

Ab initio simulation: The correlation between the local melt structure and segregation behavior of Fe, V, Ti and Si in liquid Al

Yang

Zhang

Dai

et al. 2015

Computational Materials Science

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“…Liquid materials often exhibit medium and/or short range order, such as nanoscale structural motifs, clustering, or local ordering at the level of the atomic coordination spheres. Describing this local order of soft matter systems and supercritical fluids in particular is crucial for understanding the origins of their material properties [9][10][11][12][13][14]. …”

mentioning

confidence: 99%

Structural Evolution of Supercritical CO₂across the Frenkel Line

Bolmatov

Zav’yalov

Gao

et al. 2014

J. Phys. Chem. Lett.

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The supercritical state is currently viewed as uniform and homogeneous on the pressuretemperature phase diagram in terms of physical properties. Here, we study structural properties of the supercritical carbon dioxide, and discover the existence of persistent medium-range order correlations which make supercritical carbon dioxide non-uniform and heterogeneous on an intermediate length scale, a result not hitherto anticipated. We report on the carbon dioxide heterogeneity shell structure where, in the first shell, both carbon and oxygen atoms experience gas-like type interactions with short range order correlations, while within the second shell oxygen atoms essentially exhibit liquid-like type of interactions with medium range order correlations due to localisation of transverse-like phonon packets. We show that the local order heterogeneity remains in the three phase-like equilibrium within very wide temperature range. Importantly, we highlight a catalytic role of atoms inside the nearest neighbor heterogeneity shell in providing a mechanism for diffusion in the supercritical carbon dioxide on an intermediate length scale. Finally, we discuss important implications for answering the intriguing question whether Venus may have had carbon dioxide oceans and urge for an experimental detection of this persistent local order heterogeneity.PACS numbers: 05.20. Jj,5.70.Fh, 05.70.+a Unlike the long-range order of ideal crystalline structures, local order is an intrinsic characteristic of soft matter materials and often serves as the key to the tuning of their properties and their possible applications [1][2][3][4][5][6][7][8]. Liquid materials often exhibit medium and/or short range order, such as nanoscale structural motifs, clustering, or local ordering at the level of the atomic coordination spheres. Describing this local order of soft matter systems and supercritical fluids in particular is crucial for understanding the origins of their material properties [9][10][11][12][13][14].

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“…[12][13][14][15] Metalcatalyzed VLS growth of semiconductor nanowires proceeds by the precipitation of semiconductor material out of metal-semiconductor eutectic melt droplets, which are supersaturated by ceaseless exposure to gas-phase semiconductor reactants above the eutectic temperature. [8][9][10] More recent works have demonstrated that semiconductor nanowires can also be grown via a VSS growth mechanism below the eutectic temperature, at which the catalysts may exist in the form of solid solution or compound(s) of metal-semiconductor.…”

mentioning

confidence: 99%

Metal‐Catalyzed Growth of Semiconductor Nanostructures Without Solubility and Diffusivity Constraints

Wang

Phillipp

et al. 2010

Advanced Materials

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Semiconductor nanostructures have attracted tremendous interest in recent years due to their numerous potential applications, for example, in nanoelectronics, [ 1 ] fl exible electronics, [ 2 ] photonics, [ 3 ] sensors, [ 4 ] and in energy harvesting [ 5 , 6 ] and storage [ 7 ] devices. Semiconductor nanostructures are produced mainly by metal-catalyzed growth via vapor-liquid-solid (VLS) [8][9][10] and vapor-solid-solid (VSS) [11][12][13][14] mechanisms, requiring substantial solubility and diffusivity of the semiconductor in the catalyst and thus high growth temperatures. The present study reveals, using in situ heating electron microscopy, that metal-catalyzed growth of semiconductor nanostructures can be realized without these constraints, thereby enabling strikingly low growth temperatures. The growth mechanism has been unraveled at the atomic scale for the Al-catalyzed growth of Si nanostructures at 150 ° C. Growth starts with wetting of high-angle grain boundaries (GBs) in the Al catalyst, by Si in its amorphous form, and continues by nucleation and growth of nanostructured crystalline Si (c-Si) in the template as precisely defi ned by the Al grain boundary network. The disclosed mechanism breaks solubility and diffusivity limits that have hitherto dictated selection of metal catalysts and growth temperatures and thereby opens new perspectives for direct fabrication of nanostructure devices on heat-sensitive substrates.The fundamental understanding of the metal-catalyzed growth mechanisms has been advanced by recent developments of in situ heating electron microscopy techniques. [12][13][14][15] Metalcatalyzed VLS growth of semiconductor nanowires proceeds by the precipitation of semiconductor material out of metal-semiconductor eutectic melt droplets, which are supersaturated by ceaseless exposure to gas-phase semiconductor reactants above the eutectic temperature. [8][9][10] More recent works have demonstrated that semiconductor nanowires can also be grown via a VSS growth mechanism below the eutectic temperature, at which the catalysts may exist in the form of solid solution or compound(s) of metal-semiconductor. [11][12][13][14] The growth of crystalline semiconductors as a thin fi lm can be realized also via supersaturation of a metal fi lm at suffi ciently high temperatures (about 500 ° C). [ 16 , 17 ] Such conventional metal-catalyzed growth processes require signifi cant solubility and suffi cient diffusivity of the semiconductor atoms in the bulk of the (liquid or solid) metal catalyst. Due to such constraints, the selection of an appropriate metal catalyst, as well as the growth temperature, has been strictly constrained in accordance with the corresponding equilibrium phase diagrams. [ 9-11 , 14 ] High processing temperatures (500 ° C or higher) are typically needed. Gold, which possesses high solubility of Si and Ge at relatively low eutectic temperatures, [ 18 ] has been the most commonly used catalyst, even though Au contamination is highly detrimental to device performances. [ 10 , 19 ] ...

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In Situ Determination of the Nanoscale Chemistry and Behavior of Solid-Liquid Systems

Cited by 61 publications

References 23 publications

Ab initio simulation: The correlation between the local melt structure and segregation behavior of Fe, V, Ti and Si in liquid Al

Ab initio simulation: The correlation between the local melt structure and segregation behavior of Fe, V, Ti and Si in liquid Al

Structural Evolution of Supercritical CO₂across the Frenkel Line

Metal‐Catalyzed Growth of Semiconductor Nanostructures Without Solubility and Diffusivity Constraints

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In Situ Determination of the Nanoscale Chemistry and Behavior of Solid-Liquid Systems

Cited by 61 publications

References 23 publications

Ab initio simulation: The correlation between the local melt structure and segregation behavior of Fe, V, Ti and Si in liquid Al

Ab initio simulation: The correlation between the local melt structure and segregation behavior of Fe, V, Ti and Si in liquid Al

Structural Evolution of Supercritical CO2across the Frenkel Line

Metal‐Catalyzed Growth of Semiconductor Nanostructures Without Solubility and Diffusivity Constraints

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Structural Evolution of Supercritical CO₂across the Frenkel Line