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34 results on '"Reuter, Mark C."'

2. Interface dynamics and crystal phase switching in GaAs nanowires

Author

Jacobsson, Daniel, Panciera, Federico, Tersoff, Jerry, Reuter, Mark C., Lehmann, Sebastian, Hofmann, Stephan, Dick, Kimberly A., and Ross, Frances M.

Subjects
Crystals -- Growth -- Structure, Gallium arsenide semiconductors -- Design and construction -- Properties -- Analysis, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Controlled formation of non-equilibrium crystal structures is one of the most important challenges in crystal growth. Catalytically grown nanowires are ideal systems for studying the fundamental physics of phase selection, and could lead to new electronic applications based on the engineering of crystal phases. Here we image gallium arsenide (GaAs) nanowires during growth as they switch between phases as a result of varying growth conditions. We find clear differences between the growth dynamics of the phases, including differences in interface morphology, step flow and catalyst geometry. We explain these differences, and the phase selection, using a model that relates the catalyst volume, the contact angle at the trijunction (the point at which solid, liquid and vapour meet) and the nucleation site of each new layer of GaAs. This model allows us to predict the conditions under which each phase should be observed, and use these predictions to design GaAs heterostructures. These results could apply to phase selection in other nanowire systems., Many materials can grow in multiple (meta)stable crystal structures, and phase selection is one of the most fundamental problems in materials science. However, the selection process is difficult to access [...]

Published
2016
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4. Catalytically mediated epitaxy of 3D semiconductors on van der Waals substrates

Author

Periwal, Priyanka, Thomsen, Joachim Dahl, Reidy, Kate, Varnavides, Georgios, Zakharov, Dmitri N., Gignac, Lynne, Reuter, Mark C., Booth, Timothy J., Hofmann, Stephan, Ross, Frances M., Periwal, Priyanka, Thomsen, Joachim Dahl, Reidy, Kate, Varnavides, Georgios, Zakharov, Dmitri N., Gignac, Lynne, Reuter, Mark C., Booth, Timothy J., Hofmann, Stephan, and Ross, Frances M.

Abstract

The formation of well-controlled interfaces between materials of different structure and bonding is a key requirement when developing new devices and functionalities. Of particular importance are epitaxial or low defect density interfaces between two-dimensional materials and three-dimensional semiconductors or metals, where an interfacial structure influences electrical conductivity in field effect and optoelectronic devices, charge transfer for spintronics and catalysis, and proximity-induced superconductivity. Epitaxy and hence well-defined interfacial structure has been demonstrated for several metals on van der Waals-bonded substrates. Semiconductor epitaxy on such substrates has been harder to control, for example during chemical vapor deposition of Si and Ge on graphene. Here, we demonstrate a catalytically mediated heteroepitaxy approach to achieve epitaxial growth of three-dimensional semiconductors such as Ge and Si on van der Waals-bonded materials such as graphene and hexagonal boron nitride. Epitaxy is "transferred" from the substrate to semiconductor nanocrystals via solid metal nanocrystals that readily align on the substrate and catalyze the formation of aligned nuclei of the semiconductor.In situtransmission electron microscopy allows us to elucidate the reaction pathway for this process and to show that solid metal nanocrystals can catalyze semiconductor growth at a significantly lower temperature than direct chemical vapor deposition or deposition mediated by liquid catalyst droplets. We discuss Ge and Si growth as a model system to explore the details of such hetero-interfacing and its applicability to a broader range of materials.

Published
2020

9. Strategies To Control Morphology in Hybrid Group III-V/Group IV Heterostructure Nanowires

Author

Hillerich, Karla, Dick, Kimberly A., Wen, Cheng-Yen, Reuter, Mark C., Kodambaka, Suneel, and Ross, Frances M.

Subjects
Nanowires, heterostructures, group IV/group III-V, interlayers, in situ TEM, morphology, CVD, SILICON NANOWIRES, GROWTH, TRANSISTORS, GOLD, Nanoscience and Nanotechnology
Abstract

By combining in situ and ex situ transmission electron microscopy measurements, we examine the factors that control the morphology of "hybrid" nanowires that include group III-V and group IV materials. We focus on one materials pair, GaP/Si, for which we use a wide range of growth parameters. We show through video imaging that nanowire morphology depends on growth conditions, but that a general pattern emerges where either single kinks or inclined defects form some distance after the heterointerface. We show that pure Si nanowires can be made to exhibit the same kinks and defects by changing their droplet volume. From this we derive a model where droplet geometry drives growth morphology and discuss optimization strategies. We finally discuss morphology control for material pairs where the second material kinks immediately at the heterointerface and show that an interlayer between segments can enable the growth of unkinked hybrid nanowires.

Published
2013

10. Controlling the Growth of Si/Ge Nanowires and Heterojunctions Using Silver-Gold Alloy Catalysts

Author

Chou, Yi-Chia, Wen, Cheng-Yen, Reuter, Mark C., Su, Dong, Stach, Eric A., and Ross, Frances M.

Subjects
nanowire growth, Si/Ge heterojunctions, AgAu alloys, vapor-solid-solid growth, in situ transmission electron microscopy, LIQUID-SOLID MECHANISM, SILICON NANOWIRES, CRYSTAL GROWTH, LEDGE-FLOW, ABRUPTNESS, KINETICS, Nanoscience and Nanotechnology
Abstract

We describe a new catalyst for group IV nanowire heterostructures, based on alloying Ag with Au, that combines the ability to control catalyst phase and nanowire structure with good environmental stability. Compared to other alloy catalysts, we show a higher oxidation resistance of AgAu and more consistent crystal shapes and catalyst/nanowire orientation relationships during growth. We show that AgAu catalysts are also stable against diffusion during growth, making them capable of forming long nanowires with uniform diameters. Furthermore, we demonstrate the growth of compositionally abrupt Si/Ge heterojunctions with good reproducibility and yield, switching individual nanowires between vapor-liquid-solid and vapor-solid-solid growth to optimize growth rates by control of the catalyst state. The stability and properties of AgAu catalysts potentially open up a promising and practical route toward control of group IV heterostructure nanowires.

Published
2012

27. Strain and Stability of Ultrathin Ge Layers in Si/Ge/Si Axial Heterojunction Nanowires.

Author

Cheng-Yen Wen, Reuter, Mark C., Dong Su, Stach, Eric A., and Ross, Frances M.

Subjects
*STRAINS & stresses (Mechanics), *STABILITY (Mechanics), *GERMANIUM, *HETEROJUNCTIONS, *NANOWIRES, *BAND gaps
Abstract

The formation of abrupt Si/Ge heterointerfaces in nanowires presents useful possibilities for bandgap engineering. We grow Si nanowires containing thick Ge layers and sub-1 nm thick Ge "quantum wells" and measure the interfacial strain fields using geometric phase analysis. Narrow Ge layers show radial compressive strains of several percent, while stress at the Si/Ge interface causes lattice rotation. High strains can be achieved in these heterostructures, but we show that they are unstable to interdiffusion. [ABSTRACT FROM AUTHOR]

Published
2015
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31. In Situ Growth of Si Nanowires Using Transmission Electron Microscopy

Author

Chou, Chia, Wen, Yen, Reuter, Mark C, Stach, Eric A., and Ross, Frances M

Abstract

We discuss the use of the alloy catalyst AgAu to grow silicon nanowires and Si/Ge heterojunctions. Nanoscale particles of the catalyst with compositions Ag:Au varying from 2:1 to 1:2 can be fabricated and used to form Si nanowires with high crystal quality, and SiGe interfaces that are close to atomically abrupt. In situ experiments in the TEM are essential for investigating the mechanisms of growth with these alloy catalysts. We describe the relationship between growth kinetics and catalyst state, as well as the environmental stability of the alloy catalysts.

Published
2013

34. Realization of a linear germanium nanowire p-n junction.

Author

Tutuc E, Appenzeller J, Reuter MC, and Guha S

Subjects
Electric Impedance, Electrochemistry methods, Electromagnetic Fields, Equipment Design, Equipment Failure Analysis, Molecular Conformation, Particle Size, Crystallization methods, Electrochemistry instrumentation, Germanium chemistry, Microelectrodes, Nanotubes chemistry, Nanotubes ultrastructure, Semiconductors
Abstract

Germanium nanowires grown by chemical vapor deposition exhibit a peculiar dopant incorporation mechanism. The dopant atoms, such as boron and phosphorus, get incorporated through the wire surface, a mechanism which limits the doping modulation along the wire length, and therefore the fabrication of more elaborate structures that combine both n- and p-type doping. Using a novel device design that circumvents these constraints, we demonstrate here a linear Ge nanowire p-n junction.

Published
2006
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