The critical growth velocity for planar-to-faceted interfaces transformation in SiGe crystals

Yang, Xinbo; Fujiwara, Kozo; Абросимов, Н. В.; Gotoh, Raira; Nozawa, Jun; Koizumi, Hideaki; Kwasniewski, Albert; Uda, Satoshi

doi:10.1063/1.3698336

Cited by 13 publications

(11 citation statements)

References 21 publications

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“…The critical velocity was observed to be greater for the fibres with smaller (10 μm) cores. This diameter is less than the facet lengths observed in two-dimensional recrystallization of SiGe31, and this suggests that the planar growth front may be stabilized by capillarity effects48. In both the large and small diameter fibres, increasing the germanium content in the fibres from 6 at% to 40 at% with a fixed temperature gradient resulted in a significant decrease in the critical growth velocity, consistent with the Tiller formulation.…”

Section: Discussionmentioning

confidence: 51%

“…In addition, in an alloy system, non-uniform composition could lead to excess scattering due to the refractive index variations. Rapid thermal annealing and related techniques28 have been used to crystallize insulator-encapsulated alloy thin2930 and thick31 films, and similar processing has been shown to improve overall crystallinity of semiconductor core fibres32. Laser processing, for which the fibre geometry is particularly well suited, as established in the case of conventional glass fibres333435, combines a small heat zone and large thermal gradients with fine motion and temperature control.…”

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confidence: 99%

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Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

et al. 2016

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Glass fibres with silicon cores have emerged as a versatile platform for all-optical processing, sensing and microscale optoelectronic devices. Using SiGe in the core extends the accessible wavelength range and potential optical functionality because the bandgap and optical properties can be tuned by changing the composition. However, silicon and germanium segregate unevenly during non-equilibrium solidification, presenting new fabrication challenges, and requiring detailed studies of the alloy crystallization dynamics in the fibre geometry. We report the fabrication of SiGe-core optical fibres, and the use of CO 2 laser irradiation to heat the glass cladding and recrystallize the core, improving optical transmission. We observe the ramifications of the classic models of solidification at the microscale, and demonstrate suppression of constitutional undercooling at high solidification velocities. Tailoring the recrystallization conditions allows formation of long single crystals with uniform composition, as well as fabrication of compositional microstructures, such as gratings, within the fibre core.

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Section: Discussionmentioning

confidence: 51%

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confidence: 99%

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

et al. 2016

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“…Naively, directional solidification of SiGe in a strong thermal gradient could lead to Janus morphologies. However, it is well known that germanium rejection in the liquid tends to create strong compositional gradients driving constitutional supercooling of the alloy, leading to growth of dendritic or cellular morphologies (17,18,(21)(22)(23)(24). Therefore, in practice, stable solidification front propagation and Janus morphologies are difficult to achieve.…”

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confidence: 99%

Confined in-fiber solidification and structural control of silicon and silicon−germanium microparticles

Gumennik

Levy

Grena

et al. 2017

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

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Crystallization of microdroplets of molten alloys could, in principle, present a number of possible morphological outcomes, depending on the symmetry of the propagating solidification front and its velocity, such as axial or spherically symmetric species segregation. However, because of thermal or constitutional supercooling, resulting droplets often only display dendritic morphologies. Here we report on the crystallization of alloyed droplets of controlled micrometer dimensions comprising silicon and germanium, leading to a number of surprising outcomes. We first produce an array of silicon−germanium particles embedded in silica, through capillary breakup of an alloy-core silica-cladding fiber. Heating and subsequent controlled cooling of individual particles with a two-wavelength laser setup allows us to realize two different morphologies, the first being a silicon−germanium compositionally segregated Janus particle oriented with respect to the illumination axis and the second being a sphere made of dendrites of germanium in silicon. Gigapascal-level compressive stresses are measured within pure silicon solidified in silica as a direct consequence of volume-constrained solidification of a material undergoing anomalous expansion. The ability to generate microspheres with controlled morphology and unusual stresses could pave the way toward advanced integrated in-fiber electronic or optoelectronic devices. multimaterial fibers | microparticles | confined solidification | silicon−germanium spheres | stressed silicon C ontrolling the microstructure or state of stress of microparticles and nanoparticles is often key to attaining the desired properties for a specific application (1-5); however, the ability to do so is strongly limited by the synthesis method. For instance, nonspherically symmetric distributions of inorganic materials are difficult to achieve from bottom-up approaches (4-7). Likewise, controlling the state of stress or strain of semiconductor particles is challenging in unconstrained nucleation-and-growth synthesis methods. However, Janus particles of silicon−germanium (SiGe) could potentially find applications as microswimmers or nanoswimmers owing to asymmetric absorption properties (8), as well as in infrared photodetectors or solar cells for increased infrared absorption (9). Stressed silicon particles, on the other hand, could be used for bandgap tunability in photonic or optoelectronic devices (10-12).In the past few years, thermally drawn multimaterial fibers have emerged as a unique platform for top-down scalable fabrication of microparticles to nanoparticles over a broad range of materials, through controlled in-fiber capillary breakup of the fiber components (13-15). In the case of polymers or chalcogenide glasses, structural control of the particle can be achieved by constructing complex cores at the preform level, which is later broken up in the fiber state to form structured particles (13). However, in the case of traditional semiconductor materials such as silicon and germanium, the same...

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“…[130,131] The interface instability in laser-annealed Ge-rich SiGe alloys is even more severe because the critical speed for stable solidification drops when the Ge content increases. [132] To prevent cellular and dendritic solidification in SiGe thin films, either low solidification speeds or high temperature gradients at the liquid/solid interface must be ensured during directional solidification. However, solidification speeds (<10 μm s À1 ) for stable growth are too low to be practical in terms of process time.…”

Section: Laser-driven Phase Segregation In Sige Alloy Thin Films With Uniform Compositionmentioning

confidence: 99%

Laser Thermal Processing of Group IV Semiconductors for Integrated Photonic Systems

Aktaş

Peacock

2021

Advanced Photonics Research

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In the quest to expand the functionality and capacity of group IV semiconductor photonic systems, new materials and production methods are constantly being explored. In particular, flexible fabrication and postprocessing approaches that are compatible with different materials and allow for tuning of the components and systems are of great interest. Within this research area, laser thermal processing has emerged as an indispensable tool that can be applied to enhance and/or modify the material, structural, electrical and optical properties of group IV elemental and compound semiconductors at various stages of the production process. Herein, the recent progress made in the application of laser processing techniques to develop integrated semiconductor systems in both fiber‐ and planar‐based platforms is evaluated. Laser processing has allowed for the production of semiconductor waveguides with high crystallinity in the core and low optical losses, as well as postfabrication trimming of device characteristics and direct writing of tunable strain and composition profiles for bandgap engineering and optical waveguiding. For each platform, the current challenges and opportunities for the future development of laser‐processed integrated semiconductor photonic systems are presented.

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The critical growth velocity for planar-to-faceted interfaces transformation in SiGe crystals

Cited by 13 publications

References 21 publications

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

Confined in-fiber solidification and structural control of silicon and silicon−germanium microparticles

Laser Thermal Processing of Group IV Semiconductors for Integrated Photonic Systems

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