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Electronic Melting of Silicon in Nanostructures using X-ray Forbidden Bragg Reflections

Robinson, Ian; Yang, David; Wu, Longlong; Kim, Hyunjung; Ha, Sung Soo; Choi, Sungwook; Song, Changyong; ... Kim, Sunam; + view all (2025) Electronic Melting of Silicon in Nanostructures using X-ray Forbidden Bragg Reflections. Journal of Electronic Materials , 54 (7) 10.1007/s11664-025-11781-2. Green open access

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Abstract

We carried out a short beamtime at the Pohang Accelerator Laboratory x-ray Free Electron Laser to perform a pump-probe (PP) laser excitation diffraction experiment on the silicon (222) forbidden Bragg peak. To limit the x-ray penetration, we used a “device layer” silicon film wafer bonded to a silicon substrate. The sample, specially fabricated by MEMC Electronic Materials, had a Si(100) substrate bonded to a 170 nm Si(100) film rotated at 45° for crystallographic isolation. A second sample was reactive-ion-etched down to 52 nm thickness. In the silicon lattice, the covalent bonds are seen exclusively at the 222 reflection. Upon laser excitation, these electrons are expected to be excited to the valence band on femtosecond electronic time scales. The Si(222) reflection is therefore expected to be extinguished on this fast time scale, while the electron–phonon coupled acoustic response is determined by the lattice dynamics. The latter is determined by the speed of sound over the device thickness, which is in the mid-picosecond range.

Type: Article
Title: Electronic Melting of Silicon in Nanostructures using X-ray Forbidden Bragg Reflections
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1007/s11664-025-11781-2
Publisher version: https://doi.org/10.1007/s11664-025-11781-2
Language: English
Additional information: © 2025 Springer Nature. This article is licensed under a Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).
Keywords: Laser excitation, silicon, valence electrons, forbidden reflections, non-thermal melting
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: https://discovery.ucl.ac.uk/id/eprint/10210831
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