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Core–shell Ge/GeSn nanowires provide a route to dislocation-free single crystal germanium-tin alloys with desirable light emission properties because the Ge core acts as an elastically compliant substrate during misfitting GeSn shell growth. However, the uniformity of tin incorporation during reduced pressure chemical vapor deposition may be limited by the kinetics of mass transfer to the shell during GeSn growth. The balance between Sn precursor flux and available surfaces for GeSn nucleation and growth determines whether defects are formed and their type. On the one hand, when the Sn precursor delivery is insufficient, local variations in Sn arrival rate at the nanowire surfaces during GeSn growth produce asymmetries in shell growth that induce wire bending. This inhomogeneous elastic dilatation due to the varying composition occurs via deposition of Sn-poor regions on some of the {112} sidewall facets of the nanowires. On the other hand, when the available nanowire surface area is insufficient to accommodate the arriving Sn precursor flux, Sn-rich precipitate formation results. Between these two extremes, there exists a regime of growth conditions and nanowire densities that permits defect-free GeSn shell growth.
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The mechanism of controlled integration of ZnO nanowires using pulsed-laser-induced chemical deposition
Laser-induced chemical deposition is an economical “grow-in-place” approach to produce functional materials. The lack of precise control over the component density and other properties hinders the development of the method towards an efficient nanomanufacturing technology. In this paper, we provide a mechanism of direct pulsed-laser integration of ZnO nanowire seeding and growth on silicon wafers toward controlled density. Investigation of laser-induced ZnO nucleation directly deposited on a substrate suggested that the coverage percentage of nucleus particles was a function of instantly available area, supplementing the classical nucleation theory for confined area deposition. A processing window was found in which ZnO nanowires only grew from the early deposited nucleated particles as seeds. A study on ZnO nanowire growth showed that the process became transport limited over time, which was important for density-controlled nanowire growth integrated on nucleated seeds. The proposed mechanism provided guidance to integrate nanomaterials using laser-induced chemical deposition with a controlled density and morphology.
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- Award ID(s):
- 1663214
- PAR ID:
- 10092249
- Date Published:
- Journal Name:
- Nanoscale
- Volume:
- 11
- Issue:
- 6
- ISSN:
- 2040-3364
- Page Range / eLocation ID:
- 2617 to 2623
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c8nr06890a
