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Block Copolymer Self-Assembly-Directed and Transient Laser Heating-Enabled Nanostructures toward Phononic and Photonic Quantum Materials.

Authors
  • Yu, Fei1, 2
  • Zhang, Qi1
  • Thedford, R Paxton1, 3
  • Singer, Andrej1
  • Smilgies, Detlef-M3, 4
  • Thompson, Michael O1
  • Wiesner, Ulrich B1
  • 1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States. , (United States)
  • 2 Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States. , (United States)
  • 3 Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States. , (United States)
  • 4 Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14853, United States. , (United States)
Type
Published Article
Journal
ACS Nano
Publisher
American Chemical Society
Publication Date
Aug 24, 2020
Identifiers
DOI: 10.1021/acsnano.0c03150
PMID: 32790333
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Three-dimensional (3D) periodic ordering of silicon (Si), an inorganic semiconductor, on the mesoscale was achieved by combining block copolymer (BCP) self-assembly (SA) based mesoporous alternating gyroidal network formation with nonequilibrium transient laser heating. 3D continuous and periodically ordered alternating gyroidal mesoporous carbon thin-film networks were prepared from spin coating, SA under solvent vapor annealing (SVA), and thermal processing of mixtures of a triblock terpolymer with resorcinol resols. The resulting mesoporous thin films, acting as structure-directing templates, were backfilled with amorphous silicon (a-Si). Nanosecond excimer laser heating led to transient Si melts conformally filling the template pores and subsequent Si crystallization. The ordered mesostructure of the organic polymer-derived templates was kept intact, despite being thermally unstable at the high temperatures around the Si melting point (MP), leading to high pattern transfer fidelity. As evidenced by a combination of grazing incidence small-angle X-ray scattering (GISAXS) and scanning electron microscopy (SEM), after template removal, the crystalline Si (c-Si) inherited the inverse network topology of the 3D mesoporous thin-film templates, but with reduced F222 space group symmetry (D2 point group symmetry) from compression of the cubic alternating gyroid lattice. Structures with this reduced symmetry have been proposed as photonic and phononic materials exhibiting topologically protected Weyl points, adding to the emerging field of BCP SA-directed quantum materials promising advanced physics and materials properties.

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