Confined In-Fiber Solidification And Structural Control Of Silicon And Silicon-Germanium Microparticles

Keywords

Confined solidification silicon-germanium spheres; Microparticles; Multimaterial fibers; Stressed silicon

Abstract

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.

Publication Date

7-11-2017

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Volume

114

Issue

28

Number of Pages

7240-7245

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1073/pnas.1707778114

Socpus ID

85023191903 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85023191903

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